DIY: E53 X5 Siphon Pump with Improved O-ring and Teflon Wrap
 

DIY: E53 X5 Siphon Pump with Improved O-ring and Teflon Wrap

- This is strictly maintenance as I don't want to be stranded by failed Siphon Pump.
My 2006 X5 runs fine down to Fuel Tank YELLOW light but I did this as preventive maintenance.

- If you don't want to do this job then:
1. Use Test #6 to periodically monitor the Siphon Pump function.
2. On very long trips, keep fuel above 40% at all time. This is b/c when the
Siphon Pump fails, the Right tank will go dry when fuel is less than 32L or so.
By keeping tank above 40% at all time, you are safe on very long trips.

- Special thanks to andrewwynn for being the pioneer of the E53 X5
Fuel Tank Design and Siphon Pump DIY.

- I put everything in this thread so it is easier for others.

- IMPORTANT threads...

---> E53 X5 Fuel Tank Design and Function by andrewwynn:
https://xoutpost.com/bmw-sav-forums/...stic-help.html

---> E53 X5 Siphon Pump Repair by andrewwynn:
https://xoutpost.com/bmw-sav-forums/...iy-repair.html


PARTS/TOOLS:

- Search ebay for PN 16116761645, but don't buy the factory O-ring.
Instead look for the listing with "Improved E53 X5 Siphon Pump O-ring".
This Improved O-ring is much better than factory O-ring b/c it is THICKER!

- Fuel Pump Removal Tool. I like OEMTOOLS 25156, about $18-$20 on ebay.

- Small hose clamp.

https://xoutpost.com/attachments/x5-e53-forum/74643-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-01.jpg



PROCEDURE:

1. Read the above DIYs by andrewwynn first!
Work outside with a low fuel tank, ideally less than 10L.
Open both REAR doors to vent fume.
Hit the center console switch to turn OFF the interior lights, to prevent draining battery.

* Remember the Siphon Pump assembly is not meant for rebuild like this, so you have to be creative when prying things apart etc. Proceed with CAUTION...


2. Lift the FRONT of the seat bottom upward and prop it up.
If you want to remove the seat from the car, then undo the 16-mm bolt
holding the middle seatbelt. I see no need to remove the 16-mm bolt.

3. Remove the four (4) 10-mm nuts, then remove the metal cover.

4. Remove the factory Oetiker clamp (during re-assembly, use a new small
clamp), and squeeze the sides of the connector to d/c the connector.
Use a right-angle pair of pliers, ROTATE the hose a bit to unseat it, then
GENTLY lift it upward. Do NOT break the plastic nipple.
If you break the plastic nipple, search forum for the repair using a brass barb fitting!


https://xoutpost.com/attachments/x5-e53-forum/74644-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-02.jpg


https://xoutpost.com/attachments/x5-e53-forum/74645-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-03.jpg


https://xoutpost.com/attachments/x5-e53-forum/74646-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-04.jpg


https://xoutpost.com/attachments/x5-e53-forum/74647-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-05.jpg



5. The White Plastic Collar slides along the rubber seal during factory installation.
So pry it UPWARD on all sides slowly, spray a bit of lubricant such as WD-40
to make it easier to slide upward.


https://xoutpost.com/attachments/x5-e53-forum/74648-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-06.jpg


6. NOTE that the design is:

Return Fuel (I think it is about 20-30 psi) ---> Plastic Nipple ---> "Coupler"
---> Two (2) black pipes to drive 2 separate "Suction Foot" devices.

The COUPLER:
- On top is the O-ring.
- On the lower part, it is a press-fit seal (not ideal but adequate for this).
The idea is to use "Improved O-ring", which is thicker and fits tighter for the
UPPER part of the Coupler and Teflon for the LOWER part of the Coupler.


https://xoutpost.com/attachments/x5-e53-forum/74649-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-07.jpg



7. To separate the Coupler from the Lid: press on the 2 tabs with a small screwdriver, then use a larger screwdriver to GENTLY pry it out.
- Remember that this was designed from factory for "single use" (i.e. "get a
new Siphon Pump if this fails") and not for rebuild like this DIY.

8. Once separated, you can see that:
---> The floater can theoretically get stuck at > 1/4, mine worked fine, but in
order to avoid that, I bent the floater a bit as shown to avoid the floater from
hitting the side of the fuel tank.
This is the part I don't understand: some people (car from factory ant not
repaired previously) had the floater stuck at 40%, causing stalling b/c people
think they have 40% of fuel, when in fact, they ran out of fuel.


https://xoutpost.com/attachments/x5-e53-forum/74650-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-08.jpg



9. The next step is OPTIONAL bc/ prying this apart is NOT easy with one person.
Basically wrapping Teflon to the LOWER part of the Coupler to prevent any
leak. However, the factory design is probably good enough with a "press-fit"
seal. Since I don't want to do this job again, I followed the advice by
andrewwynn to wrap it with Teflon.

- Prying this part apart is NOT fun, if you have a second person as helper, it
is better b/c you have to use small screwdriver to push the small tabs inward
while prying the fittings apart.
Work SLOWLY and METHODICALLY to pry it apart. You don't want to break it.
If you break this, time for new Siphon Pump!
Again this step #9 is Optional!

10. Install the new and Improved O-ring. I apply some engine oil on the
O-ring and it is a nice and tight fit (factory O-ring is a loose fit).


https://xoutpost.com/attachments/x5-e53-forum/74651-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-09.jpg


https://xoutpost.com/attachments/x5-e53-forum/74652-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-10.jpg






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Part II...
 

11. Since andrewwynn said you need to apply a zip tie as shown to prevent movement,
I did the same thing as advised, although I doubt it makes a difference.
Anyway, a zip tie does NOT hurt.


https://xoutpost.com/attachments/x5-e53-forum/74653-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-11.jpg


https://xoutpost.com/attachments/x5-e53-forum/74654-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-12.jpg



12. During re-assembly note:
a. Oil the Plastic Flange, Seal so it slides well.
b. New small clamp for the return hose (place the metal lock ring in place first!).
c. When you tighten the Metal Lock Ring properly, the factory glue will line up.
Better: mark with sharpie from the beginning, this way you know where things should line up.
d. Don't forget the connector!
e. If you drop any debris, leaves etc. remove them from the fuel tank.

BEST is to vacuum the Lid are BEFORE opening the Lid!


13. Replace the metal cover, big grommet rubber seal (above metal cover), then rear seat bottom.
- Make sure you pull the all 3 seatbelt buckles through.


https://xoutpost.com/attachments/x5-e53-forum/74655-diy-e53-x5-siphon-pump-improved-o-ring-teflon-wrap-e53-fuel-pump-13.jpg



14. Now test drive with about 1/2 tank and use "Test #6" to see when it drops below 32L.
- Make sure the RIGHT tank always have anywhere between 2L-5L.
- Note that when fuel is below 30L or so, during right/left turns or deceleration/acceleration, the fuel level on the RIGHT side will vary widely,
but during cruise, they remain stable.

That is all boys and girls. Hopefully you don't get stranded with the improved O-ring...





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I plan on doing this tomorrow since I have to order a new intake manifold gasket. Gotta make sure of that downtime! Did you use PTFE or Gasoline Rated Teflon Tape? Will keep it from dissolving.

Also. What are you calling an improved o ring? I ordered the OEM one from BAVAuto. Simple 2x22 o ring.

DIY: E53 X5 Siphon Pump with Improved O-ring and Teflon Wrap
 

The zip tie, not the o-ring is the actual fix. The failure happens because the o-ring is not held square not because the o-ring is too small or somehow wears out.

There is nothing in the original design to hold the o-ring square. It's far more important to solve the twist of the seating surface than use a thicker o-ring. Time and pressure will win just like geology.

https://uploads.tapatalk-cdn.com/201...718b1ef828.png
This photo shows the problem. The blue lines are parallel and where the bottom part should be. The red line shows where it is. The seal fails because nothing in the design holds the right side of the o-ring seal up. It's held only on one side it's like wearing one suspender of course your pants will fall down on one side.

EDIT: this photo just is a representative of HOW it fails I think that this picture was taken during disassembly on a unit that I believe hasn't actually failed yet (hence the indifference on the importance of the zip tie). It's a better representative photo than any I have as I already had mine either apart or from the wrong side to show the failure mode.

The zip tie forces the left side down forcing the right side up. It has to be a wide enough zip tie to touch the bottom part when assembled.

The other solution I recommend is to drill a 7/64 hole outside of the high pressure zone of the o-ring and install a 3mm stainless screw that's even better than the zip tie but the zip tie is instant.

Also after about 3-4000 hours on my car the second seal was leaking significantly but just drip drip drip not spraying like the open o-ring. There is no actual seal. The factory design has a plastic to plastic flare that will absolutely fail. In my case the female side was 0.2 mm larger diameter and has no choice but to leak.

The teflon wrap is a quick fix the better fix is to add an o-ring groove and add an o-ring, that said the teflon will eliminate the gap and reset the clock for a long time.

Nice complete step by step I only took the critical steps photos it'll be a lot easier for somebody to follow this new recipe.

The only other tips I could think of off hand are these:

Run the car with the electric pump unplugged to drain the fuel lines

A bent metal bar and a big vice grip will substitute for the proper tool to open the monster nut, other options I've used when I've misplaced my tool I made: lock a small vice grips on opposite sides and use a long rod between the two: it's
Better to use even pressure than try to use a hammer and chisel method that only puts pressure on one side

I wet the seal with gas v oil I figure that way it will evaporate and be rubber to plastic seal no oil left over

Not specifically mentioned above but the photo shows: the seal around the sender unit will typically come out with the unit leaving most to believe it should be on the unit when installing but that is impossible. You must remove the seal and install into the tank first (shown in the photo but I didn't see the description). Wet the ID of the big seal (I'm wearing surgical gloves when I do this so I just dip my fingers in the gas tank and wet the seal with gas)

Have a fresh roll of paper towels handy to soak up any fuel and "dispose of properly" (by which I mean burn them in a safe container): liquid fuel will safely burn; evaporated gas that reaches the proper stoichiometric* ratio will explode! Eg much safer to burn a soaked rag than risk it evaporating into an explosive situation.

I did the first two fuel pump repairs with the seat in the car but with impact tools it's so easy to remove the 16mm bolt and there is twice the elbow room with the seat out I now remove the seat bottom from the car when doing this job it's worth it for the extra room but totally not necessary. I've just had the seat fall on me enough times I've retired the leave the seat in method.

*Thank you MythBusters for teaching me that word.

Great post!

Thanks andrewwynn,

The photo you posted above should NOT be used to show your point.
That photo I took is when I pried the Coupler out.
It was halfway out so it is NOT an in-situ photo of factory setup!

I am very convinced the root cause is either:
A. O-ring shrinking with time.
B. The one-way valve (Plastic+Spring) momentarily seized,
pressure builds up and blows the O-ring outward...

Just some theories...


BTW, I think one can remove the Plastic+Spring combo (I did not) w/o any issues. This is an over-engineered part.

270_BMW,

The improved O-ring is thicker.
I used it and love it.
It is a tight fit and almost impossible to blow out under pressure.
Remember O-ring usually blows out because it is "under-sized" for the gap it tries to seal, or bc the pressure is too high for the design.

Another thought as to root cause...

The fuel pressure regulator is built into the fuel filter.
I wonder if or when the FPR fails, does it allow too much fuel
pressure in the return line to rise let's say from 20-25 psi
(does anyone know the normal fuel pressure in a return line?)
to the 45-55 psi range (which is normal operating range),
causing seal blowout?

For every problem, there must be a cause...

Could you provide a link or description for the improved one? I’m curious of the size.

DIY: E53 X5 Siphon Pump with Improved O-ring and Teflon Wrap
 

Thought a link was in the start post.

1.2-1.3 bar if memory serves. It's in my detailed fuel system thread. I think it's about 15-18psi. It will of course vary over the life of the electric pump as the pump weakens.

As far as the cause it's oversight on the designers part that didn't hold the o-ring from both sides.

If the fpr fails there is a relief valve to dump the extra fuel directly to the right tank. It's labeled on my fuel system thread

DIY: E53 X5 Siphon Pump with Improved O-ring and Teflon Wrap
 

Thanks for the feedback I thought that photo looked partly disassembled but it works perfectly to showcase the issue because it's exaggerated somewhat. I've updated my post to make it clear.

I didn't take a picture from the correct angle to show the problem mine is already fixed by the time I snapped the shot.

https://uploads.tapatalk-cdn.com/201...b3aee9348e.png

This photo shows the o-ring pushed out of the seat. In both mine and wife's case the photo marked up with the blue and red lines perfectly showcases the issue though it was a little tighter.

Neither A nor B is correct. Both my wife's and my car had the same exact problem where the o-ring writhed out after the part twisted like shown (by chance) as shown in the photo above.

B is not accurate because there is a pressure relief valve to deal with back pressure and dump over pressure to the right side tank

The problem could be exacerbated by the o-ring being smaller than it could have been but without movement of the plastics the o-ring would be lifetime.

Even though I applied the zip tie, I don't think it is the solution.

When I removed the siphon pump, mine was intact with intact O-ring, zero issues. Everything aligned perfectly from factory.

I still think the O-ring shrinks with time, allowing it to bow under pressure.
When I disassembled the Coupler, the part slides out easily, telling me that O-ring has reduced in size. It should have been tighter when sliding it out.

Anyway, the new O-ring is much better, a tight fit.

The one-way valve is over engineered, if you remove the one-way valve can be removed without issues.

I understand that you did a lot of pioneering work in the fuel siphon pump issue, kudos to you. But I don't think anyone here knows for sure the EXACT cause of failure...

Everything here is conjecture...

DIY: E53 X5 Siphon Pump with Improved O-ring and Teflon Wrap
 

What I'm saying is that yours just didn't fail yet. It's great if one can catch this issue before it fails because it's so simple to prevent it from happening. The o-ring will never come out of its seat until there is enough room for it to do so. You didn't see It because yours didn't fail. Sadly I didn't take a pic from the best angle to show why I'm absolutely certain that regardless of other valid email examples of what can help the problem along, that without the tilting of the seat of the o-ring this o-ring failure would be non-existent.

It's best if somebody can catch it before it failed because then fish a zip tie though without even disassembly and you are done. For a non-pro I wouldn't even recommend messing with the other "seal" that will only drip when it fails.

Simple engineering and geometry plus laws of physics dictate why I'm making my claims. There is a 1" cross section with 18psi pushing down about 1" from the fulcrum. 18 in · lb of torque applied to a plastic part for 4000 hours is apparently enough to bend it enough to get the o-ring close to where it will squeeze out of the seat.

Very possibly a toward the thinner side of spec on the o-ring cs or fatter opening on the plastic part or a spike in pressure will be a contributor to the failure it's rarely just one thing. My contention is that in spite of any of the other contributor factors it will simply not ever fail if the o-ring seat is always square.

You could overcome the problem with a fatter o-ring but it's unnecessary since the primary issue is the not square seat of the o-ring.

The fatter o-ring fit makes a lot of sense and you are more correct than it sounded like I was suggesting only it was not the o-ring that shunk it was the plastic that grew: case in point the other non-seal "seal". I measured that the outer part was a full 0.2mm larger than the inner part and that is without the intense pressure of an o-ring pushing on it for 17 years in my case. I am willing to bet the outer part has grown at least half a mm making a chubbier oring make more sense than the OE spec that will work just fine in my opinion, the fatter cs option will work fine-er.

Actually I think that part is critical. I think it's job is to make sure the siphon jets go only from left to right.

Her is what I mean: when the car is pitched up or down one siphon jet will be sucking air and may not produce any voiume maybe it's job is to make sure there isn't reverse flow going in a circle from back to front of the left tank.

This is absolutely a guess. I can't even remember the direction of flow on the thing I just remember it's a very soft spring that would "suggest" the direction of flow. Maybe more to keep the siphon jet lines primed when the car is off? The seal is plastic to plastic it's not going to hold forever more of a suggestion, perhaps to prevent damage to the siphon head in the case of overpressure from the FPR?

This is a very timely review of this system for me as I have a replacement pump ready to install into my 113K mile E53 4.4i

I ran Test 6 on a 20 mile highway drive today and say right tank levels in cruise rang8ng about 2.0 liters to 3.8 liters. During some braking and turns I saw as low as 0.5 liters and was pretty freaked out but all kept running fine and the right tank numbers recovered.

I currently have about 26 liters total in test 6 and started my trip with about 30 liters.

I’ll be opening up the left side of the tank to evaluate my siphon jet pump but wanted to get an opinion on whether my current test 6 values show anything amiss in the Jet pump.

Thanks in advance to you guys who have dug deep into this system and provided excellent photos of the areas involved.

Mike

The right side should hover close to 1.4L once the left gets below about 28L. If on level ground the right side starts to drop it means the siphon jet or not keeping up with the gas being consumed from the right side "well" and the siphon jet needs addressing.

The value will vary wildly when cornering or braking/acceleration.

Example: a hard right turn will slosh a bunch of fuel out of the well to the left side. You can make a hard right and once you go to level constant speed, the right side will be lower like 0.9 and slowly build back up to "1.4"

You should be able to drive down to year six of 000 for the left and 014 on the right with no problem. At that point you have 5L of gas left. At 000 000L there is about 3.6L in the tank about 3L you could actually consume.

When my siphon jet was leaking I noticed that the right side would hover at 0.9 for a good while then start to drop while the left side had 18-20L. That's the exact symptom of leaking siphon jet. The good news is that the right side has a good 10-15 miles once the right side drops below 1L on test 6.

Thanks Andrew, that's very helpful.

Mike

semcoinc,

- The above tests are EXACTLY what I had in my 2006 X5 when fuel is below 32L. And that is normal as my siphon pump worked perfectly before I did the preventive maintenance.

- I just did the experiment the other day, the YELLOW warning light comes on when there is about 10L in the LEFT tank.

- As andrewwwynn pointed out in other threads, I am redrawing the fuel tanks so you can see. It is just descriptive drawing for the ideas (not to scale).

- First photo shows the real tank shapes. NOTE that the 5L well, where the fuel pump sits, is EXCLUDED from the level sensor calculation, so this 5L well is somewhat "sacred".

- The 2nd photo shows my understanding of the cross-section, as if you look directly from the FRONT of the car.

- Now you can see why when you turn R or L, accelerate or decelerate, the level sensor moves up and down, either by the swaying motion or the turns/braking etc. (without liquid moving it) or by liquid sloshing over the right side moving the R level sensor...

- The important lessons are:

1. The 5L pump well is "sacred".

2. Calculation is done via 2 level sensors and the sum is reported to the instrument cluster.

3. Fuel Level Sensor issue: sometimes the gauge shows 40% but the car dies from lack of gas. This happens either because:
a. The level sensor is stuck in the 40% position.
b. The resistor (the level sensor works by varying the resistor Ohm values) is kaput and reports an Ohm values consistent with "stuck at 40%", no matter where the mechanical float is...

4. If your car dies and you suspect failed siphon pump, try to jack the left side up (drive it up on a curb so the left side is up on the curb), this should slosh about 5-6L to the right side, allowing you to get to the nearby gas station. Or do a hard left turn lol...

Hope this helps...


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DIY: E53 X5 Siphon Pump with Improved O-ring and Teflon Wrap
 

That's a great depiction of the tank and how it works. 10,000% better than BMWs own since they copied the page from the sedan which does not have the pit and they drew the left and right lobes the same size and symmetrical.

A minor difference is that the right gauge will actually read about 1.4L of the 5L pit so the unlisted "sacred" amount meant to keep the pump always submerged is about 3.6L

I would have flipped the drawing to have right on the right side but see you drew to match the photos taken from the front.

If you catch yourself as you are about to run out of gas from a failed siphon jet you can make a hard left turn (with any luck a U-turn to a gas station you just passed) I bumped into several threads where people mentioned success with this trick in sedans while doing my fuel system research.

This trick or the one to Jack the left side will likely not work on the X5 however, because as the o-ring seal fails, it still will siphon some gas it just relies on the depth of the fuel to help that's why some people run out of gas at 30 miles to empty some people run out at 75 like when happened to me. The wear level of the electric pump comes into play as well: stronger electric pump will push more fuel volume and pressure back to the siphon and will work longer with the leak.

The other problem is you don't get to use all the emergency gas you put in: anything over 5L will spill info the left lobe of the tank and the pump will suck out more than you consume and send it over to the left side so you can't drive very far with the siphon jet failed and a boost of 2gal from a plastic can of gas. (eg though 2 gal should get you 30-40 miles it might only get you 5-10. )

One last thing: test six works when the car is on not running so if you do stall while driving you can perform test six to confirm a siphon jet vs electric pump failure. If both sides have plenty of gas eg 402153 expect fuel pump failure. If you see 254000 it's a sure sign of siphon jet failure. If indicating siphon jet failure you don't need a tow just 5L of gas to drive to a near station where you can add more than 30L to flood to the right lobe. Then do the fix above and it'll be good until the elec pump fails.

- Used regular household plumbing White Teflon Tape.

- I did an experiment: White Teflon (household plumbing) tape inside a jar containing gasoline. Two (2) weeks later, zero issues, tape is still intact.
So I am not worried. I will report this experiment result in another 3-4 months.

- See photo of experiment...

- The Improved O-ring is a tight fit, very good O-ring, better than factory O-ring.


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What a good job doing experiment. I did my experiment inside my fuel tank was much harder to check up on later. I used fastape brand and it was perfect after about 5-6 months in the car.

Good explanation.

So the ziptie holds nothing together, just serves as a spacer to keep the joint aligned/square?

Seems BMW could have done this right and added another release clip to the right side so it can't fall down/bend.

Yes bad design it's only held up from one side.

- I did the zip tie thingy but I do not think it is essential at all. I personally think the O-ring is undersized, allowing it to protrude under pressure.

- The improved O-ring, you can tell it fits tightly and should be good for a long time, with or without the zip tie thingy.

- Even without the zip tie, you cannot wiggle the couple b/c it is held by 2 separate tabs.

- On the other hand, the zip tie does not hurt, just a placebo effect b/c it is not proven. I did it anyway.

@cn90; you just didn't see it when failed: the plastic deforms over time, one side opens up enough for the o-ring to squeeze out. True with a fatter o-ring that might not happen but only one of the clips holding the joint together does anything. I reassembled mine without the zip tie and it was immediately twisted which is why I added the zip tie. The zip tie keeps the joint perfectly straight. I clearly had more hours on mine and wife's siphon jet than you did.

If somebody catches this before failure all they need to do is add the zip tie and it will prevent the o-ring from popping out even with the thinner stock o-ring.

Great write up I'll mention again. ∞ more detailed than mine. I think I already edited my thread to say "go over there to the better thread"

really nice DIY! I just might have to pick up one of those fuel pump tools for a rainy day

I did this repair pre-emptively yesterday on my 2001 3.0i with 196k miles. Had no problems before or after, and things were in good shape when I found them. Some details:

I used a hammer and block of wood to undo the ring holding the cover on, rather than getting a special tool. Marked with a sharpie beforehand, so when reinstalling, I made it exactly the same. Only needed about 15 degrees of rotation before I could spin it off by hand.

Something I did not find clear in the instructions ... when removing the main assembly, I disconnected the two clip-retained sub-assemblies, leaving them in the tank. I initially had tried to remove it all, and don't know how that would have worked. I basically tried to do as little as possible, especially since this was a pre-emptive repair. Reminded of the saying, "If it ain't broke, fix it until it is." :D

I left that valve, and the seal that AndrewWynn tuned up with Teflon tape alone. BTW, my interpretation of the Teflon debate is that Teflon will not be a problem in gasoline, but many Teflon tapes are not actually made of Teflon, so there's a chance of a problem = not worth it for something that may not even be needed.

My o-ring was in fine shape, but I replaced. Details on sizing:
BMW seems to say this is a 22x2 (ID x thickness) o-ring.
Mine measured as 23x2, probably stretched a little in all those years.
I tried using a couple of o-rings from a Viton kit I recently bought at Hazard Fraught:
20.22 x 3.53 was way too big to fit.
18.72 x 2.62 fit OK, but was maybe stretching the o-ring a little too much, so ...

The head gasket kit I bought a couple of years ago included two 21x2.5 o-rings for the VANOS solenoids. I ended up leaving the solenoids in place (since they seemed welded in place and would not be too difficult to access if they ever did leak), but saved the o-rings. Using one of those seemed like a perfect fit. 0.5mm thicker than the original made it tighter, but not difficult to install. Happy with that solution.

I read the full discussion on using the zip tie, concluded it was worth doing, and did it in less time than it took to type this sentence. In case anyone needs this number, the thickness of the zip tie I used was 9/64" and it was a pretty perfect fit. Installation was easy and I still don't fully know what the assembly looks like. Just fed the zip tie in the gap and it routed around easily so I could finish the installation. And unlike the Teflon tape repair, I don't think there is any chance the zip tie would cause a problem.

Overall, things seemed really well built throughout. Plastic did not seem brittle, things came apart and went together pretty easily. I was having no problems at 196k miles and 19 years, so hopefully most people never have a problem with this pump.

A while ago, my gauge was sticking at about 11 gallons (as verified by Ibus app) and would not go below that level. I almost got stranded on a long trip by not realizing it in time but as luck would have it I realized that I could not possibly be getting near 500 mile range pulling a nearly 4000# trailer. :dunno:

It turns out that the driver side level sensor was sticking and if I gave a few dood whacks on the top of the cap housing it would fall and go to the proper level.

I did the o-ring swap to the bigger one when I changed out the level sensor.

Mike

I thought my float was maybe turning vertical and getting struck that way but I'm pretty sure in my case it's electrical. I cleaned the contact wiper once when it was reading like 35L high and it worked right to zero for a good while.

Then one day I noticed my DTE got to about 37 miles and just hovered there. Pulled up the test six and it showed less than 1L on the right side meaning the left is bone dry.

I'm still reviewing this thread from top to bottom but while I'm in the middle of it and thinking of it I wanted to throw this out there since you were testing white teflon tape. The yellow teflon tape is made for use with petroleum products. The white, according to code, is for use with water, in general.


Great thread so far!

I used fastape. It's gray and made with actual Teflon. That said I've also tested branded white Teflon in gas without issue I just prefer the gray because it's 2-3x as thick and also has a "teletale" when it's working: it turns black when compressed. You can do a test fit and if it's still gray you didn't use enough.

Does anyone have any suggestions for the better oring if it's not available on ebay anymore? I can find the item with a google search (on ebay), but it says "currently sold out". Been watching it for a few weeks now.

ebay.com/p/22025216173

I found mine at my local Ace Hardware for 99 cents. It was late in the day so I bought a couple.

You bought a random o-ring to work better than the OEM one? What specs were you looking for...? was it the 22x2.5mm? Is that it? Does material matter? (sorry, I'm not exactly a gearhead)

It wasn’t random. I had the original blown out one, some precise digital calipers and did some measurements OD and ID. Based on that, there were three choices and one works perfectly.

Here are my notes from when I did it on my 2001 back in 2020. Tells exactly what worked (for me: 21mm ID x 2.5mm thickness = 26mm OD) and what did not work. Every half millimeter counts. It would be good to have a few choices unless you are sure you know what you will need.

The removed original o-ring seemed to be 23mm ID x 2mm thickness = 27mm OD.

I believe BMW spec is 22x2, so maybe mine stretched.

Replaced with one of the two spare o-rings from the engine work. I think it was for the VANOS solenoid. Measured 21mm ID x 2.5mm thickness = 26mm OD.

Slightly thicker seemed to achieve the desired improvement. A little silicone grease to aid reinstallation made it easy.

Initially tried and failed to use some Viton o-rings from a set bought at Harbor Freight. Biggest one: A2311 = 20.22mm ID x 3.53 mm thickness was way too big to fit. Tried A116 = 18.72mm x 2.62mm. That fit OK, but was maybe stretching the o-ring a little too much, so I used the VANOS leftover.

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In summary, the thickness was the critical dimension, since it needs to fit, and you want it snug enough to provide some structural support. I found 2.0mm to be too thin, about 2.5mm or 2.62mm to be just right, and 3.53mm to be too fat. The overall inner diameter is not so critical, as long as it is not too big. If too small, it can stretch a little.

I would not use "Teflon" tape without doing my own long term test on a shelf in a jar with gasoline, not knowing exactly what is in that tape other than PTFE.

Thank you @andrewwynn and @cn90 for this write up. Another e53 saved from starvation.......