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

[andrewwynn]

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.

[Scott ZHP]

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.

[andrewwynn]

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

[cn90]

- 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.

[andrewwynn]

@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"

[richardb]

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

[oldskewel]

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."

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.

[semcoinc]

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.

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

[andrewwynn]

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.

[absolutezero273c]

Originally Posted by cn90

- 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.

---

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!