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Old 10-15-2019, 12:09 AM
Join Date: Jun 2014
Location: Omaha, NE
Posts: 1,584
cn90 is on a distinguished road
DIY: 2006 BMW E53 X5 3.0i Brake Line Replacement

DIY: 2006 BMW E53 X5 3.0i Brake Line Replacement

- Searching forums, info on brake line (metal line) repair is scattered with bits and pieces all over the place.
I am doing this to consolidate all PNs, Special Tool, local Auto Parts store info in one place the help others.

- Although this is written for 2006 BMW E53 X5 3.0i with 130K miles,
you can use this technique for any car.


1. Basic tool: 8-mm, 10-mm socket. Screwdriver to remove rivets (pry the center pin outward to remove the plastic rivet).

---> Strongly recommend Flare wrenches: 11-mm (O'Reilly line is 11 mm), 12-mm (Advance Auto line is 12-mm), and 15mm.
Best is to buy a set of metric flare wrenches.

2. Bending Tool about $8 at Harbor Freight.
This tool is a MUST to bend the line.
Pay attention which way to bend it, you have one chance to bend the line correctly!

3. Special Tool: this is an interesting topic.
Most local autoparts store do NOT sell or loan BUBBLE Flare tool.
O'Reilly and Advance Auto loan the DOUBLE Flare tool only.

- Although some youtube videos say you can use DOUBLE flare tool to make BUBBLE flare, it will be a hit-and-miss issue.
I strongly recommend using the correct Bubble Flare tool.

- Neiko 20657A ISO Bubble Flare Tool, about $23 online (amazon etc.), this is the exact same tool as the OTC 4504
(about $33 online).
Search for the reviews on amazon, a lot of good tricks there.
I really like the Neiko tool, please read on for tricks to keep the tool last longer.

4. Brake Fluid: I use DOT4 brake fluid from O'Reilly Auto. The brand is
"BrakeBest", probably made by Valvoline (just a guess).
I have had good experience with this brake fluid for 10 years.
I bought 1 qt, which is plenty for this job.

5. Expanding Rivet PN is 51118174185, about 35 cents/each. Local dealer wanted 75 cents each.
I bought from local dealer b/c shipping cost adds up to the same amount.

6. O'Reilly and Advance Auto sells metal brake line: either steel or NiCopp
(NiCopp is 2-3 times the price of steel).
Since the car came with steel, I used steel but next time probably NiCopp
as this is easier to flare and to bend.
But steel is OK too.

This is my list of purchase. You may need longer line if your rusted
section is longer:
* Two (2) 30-inch lines, with the bolts included.
* Two (2) extra 8-inch lines for different purposes: to practice and to get the extra bolts.

* Four (4) BUBBLE FLARE metric unions.
- O'Reilly carries the UNION made by "American Grease Stick" (or AGS).
The BLU8B (Zinc) is for ISO Bubble Flare type.
"BLU" = ? perhaps stands for "Blue"
"8" = their type of Union.
"B" = Bubble.
Although the thread is M10 x 1.0, the outside of the nut is 1/2" type! You can use 13-mm wrench if you don't have the 1/2-inch wrench.
The 1/2-inch wrench is better for counter-hold.

- Make sure you have an extra car, bicycle or Uber in case you screw up and need to go to the parts store.

- Common screw-ups:
a. Forget to insert the bolt before making flare.
b. Forget to place the bolt at the flare BEFORE bending the line.

- The factory line is 4.75 mm (which means the O.D. = 4.75 mm, I.D. = about 2 mm).
You can use 3/16-inch (or 4.7625 mm) line at local auto parts store
and this will be fine.

- Material: Steel vs Ni-Copp. Search forum for the debate between the two types. O'Reilly Auto Parts carries both types pre-flared with the bolts.

- The bolt that comes with the metal line: factory is M10 x 1.0.
Make sure you get the bubble flare type with M10 x 1.0 bolts.
Do NOT buy the bubble flare line with "Standard SAE bolts".

- Note that for two (2) REAR brake lines, BMW used different unions
M12 vs M10 to prevent confusion in the factory assembly line. But
both pipes are the same with O.D. = 4.75 mm.


1. The brake bleeding procedure. You can do 2-man vs 1-man.
I built an ATE cap a long time ago to be used with an air compressor
set at 10 psi.
- This has worked great for me for > 15 years.
- Detail on how to make the ATE cap is below:


---> You can also buy the similar bleeding cap at FCPEuro (CTA # 7092 for $15).

2. To prevent brake fluid loss, there are 2 tricks:
* Use a rubber glove and rubber band and somehow make a tight seal at the reservoir cap.
* Use a wood stick about 26" long and wedge it against the SW and brake pedal.
Note that I use shop towel for cushion to prevent damage to the SW leather.

3. The plastic cover: I lost counts of quantity!
- The 8-mm screws (qty = ? 11 or so).
- The 10-mm screws: about qty= 5-6 or so.
- The expanding rivets (qty = 6 or so).

- I drilled a few holes (3/4" hole) this way I can rinse this area during warm days > 32F in the winter to prevent corrosion.

4. Search forum and youtube for difference of: SINGLE Flare, DOUBLE Flare and BUBBLE Flare.

- Most Euro cars use BUBBLE Flare type.

- Before you flare any line, SLOW DOWN and make sure you INSTALL the bolt before making the Flare.
- Same thing with bending line: make sure the bolt sits at the BUBBLE flare before bending the line. I learned it the hard way!

- Clamp the side near the tube first.
Then tighten the other nut.
Attached Images
1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT

Last edited by cn90; 10-15-2019 at 10:04 PM.
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Old 10-15-2019, 12:13 AM
Join Date: Jun 2014
Location: Omaha, NE
Posts: 1,584
cn90 is on a distinguished road
- The Neiko wing nut broke after a few use.
Went to Lowes hardware and bought some M8 x 1.25 bolts and nuts.
The Lowes nuts are much better than the wing nuts from Neiko.
See photos for detail.

- Soon or later the serrated or threaded portion of the tool will strip
due to the force from making bubble flare. Toward the end, the tube just
slides in the tool, making it useless.
If anyone has any trick to make it alive again, please let the rest of us know.

In retrospect, if I had used the Lowes nut to start with, the grip is tight
and I did not destroy the clamp serrated edges, which rendered the tool useless.
So yes, get the nuts at Lowes way before the job.

- Technique:
* Clean cut is a must.
* Deburr the inside (I use the wood drill bit shown). I use my hand to deburr. Do NOT use an electric drill here.
* The chamfer: use a file and chamfer the outside to 45 degrees.
* Before installation, blow inside the tube to make sure no bugs, debris are inside.
* Use a drop of oil wherever there is friction (on the tool bolt threads x 3, and on the 4.75-mm adapter where it contacts the pipe).
* When making the flare, make sure the tool is as straight as possible.
Attached Images
1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT

Last edited by cn90; 10-15-2019 at 12:24 AM.
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Old 10-15-2019, 12:15 AM
Join Date: Jun 2014
Location: Omaha, NE
Posts: 1,584
cn90 is on a distinguished road
5. Create some extra slack in the factory line, this way if you screw up the first flare, you have a 2nd or 3rd chance for another flare.
THEN get the new line, bend it to shape and make flare to meet the factory line. This way if you screw up the new line, simply go to the store to buy another line for $5-$6.
You rather have excess line than too short.
Excess line (after everything is done) can be gently turned to create a slight "S" shape to reduce slack to minimize tension.

6. During installation of union: finger-tight and turn a bit, leaving a bit of room for further tightening if there is a leak. I use a bit of anti-seize on the nuts.

After everything is bolted back, I pressurize the line to 10 psi.
- Saw leak at 2 separate places. Tightened the nut a bit more.
---> Then bone-dry.

The sealing effect is accomplished by the bubble flare (hard metal by steel)
against the softer metal in the Union (Zinc or Brass I don't know).

- Whatever you do, do NOT allow the reservoir to run dry.

- Test drive around the neighborhood at low-speed 10-15 mph.
Make sure your Parking Brake works in case!

- Then do a few "panic stops".

- Bring the car home and inspect for any leak.

- Leave the plastic cover off for a few weeks to allow you to
inspect your work.

- I posted on separate thread on how to prevent future corrosion.
Follow that thread here:

PS: That is all it is not difficult but tedious. As mentioned, good tool and technique is important. ALWAYS make sure the bolt is in place BEFORE
making the flare or bend.

If I do this again, I'd buy a few extra 4.75-mm adaptors (about $7/each on line) in case the pin breaks. In my case, the pin broke after making about 15 flares (some from practicing and some on car flares).

Interestingly, even after the pin broke off from the 4.75-mm adapter, I could still make good flare, as long as the tool is centered.

Anyway, making flare requires patience, some finesse and patience.

That is all boys and girls, not difficult as long as you are SLOW and METHODICAL.
Attached Images
1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT

Last edited by cn90; 10-15-2019 at 12:43 AM.
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Old 10-15-2019, 01:23 AM
andrewwynn's Avatar
Join Date: Jun 2015
Location: Racine, WI
Posts: 10,343
andrewwynn will become famous soon enough
DIY: 2006 BMW E53 X5 3.0i Brake Line Replacement

Good stuff.

See my photo album from when I did mine. I figured out a way to make a perfect clone of the previous line.

Put the old one in the 1/4 bender slot. Put the new in the 3/16. Tape as you go along. See the pics.


One thing I'll add: get some crow foot flare sockets! Get a branded set not harbor fright [sic]. Get both metric and sae. Often rust changes the size enough to matter and if I remember correctly and oddly enough, the factory 10mm fittings used a 7/16 and 5/8" wrench so strange.
2011 E70 N55 (me)
2012 E70 N63 (wife)

Last edited by andrewwynn; 10-15-2019 at 01:29 AM.
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Old 10-15-2019, 12:11 PM
Join Date: Oct 2010
Location: Atlanta
Posts: 154
sgrice is on a distinguished road
Wow - this is amazing!!

Thank you so much for all the great information, photos, discussion, etc. Really great work.
2010 e70 35d- now driven by son #2
2005 e53 3.0 - now driven by son #1
2021 G05 45e PHEV - now driven by me
2008 ML320 CDI - driven by wife
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Old 10-15-2019, 06:14 PM
Join Date: Jun 2014
Location: Omaha, NE
Posts: 1,584
cn90 is on a distinguished road
- Glad I can be of help. It took me a long time to gather all information, lines/unions info, played with the flare tools, learned from my mistakes. This way future DIYers do not have to make the same mistake.

I forgot to mention this:

- After installation, most of the leaks can be stopped by loosening the bolt, then tighten it again.

- On the rare occasion of persistent leak, you can use a washer (finishing washers carpenters use to install cabinets) per the thread below:


- Or conical washer 2GF-3 (80 cents each online etc.)

- When you think about it, engine oil drain bolt has a copper washer for sealing purpose. So, when you deal with leak on bubble flare, most likely it is from imperfection of the mating surface. This is why you keep the mating surface clean and smooth. If it is rough, you can sand it a bit.

- So the idea of a washer to help with sealing is not new. In fact, per the threads above, they use it on aircraft lines.

- Anyway, photos of the cabinet trim washers and conical washer 2GF-3 in case you need it to seal difficult leaks...
Attached Images
1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT
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Old 08-29-2020, 01:10 PM
Join Date: Jun 2014
Location: Omaha, NE
Posts: 1,584
cn90 is on a distinguished road

I am the original poster, did this repair in Oct. 2019, about 11 months later, bone-dry, all is good!
1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT
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Old 07-20-2021, 02:20 PM
Join Date: Jun 2014
Location: Omaha, NE
Posts: 1,584
cn90 is on a distinguished road
- Almost 2 yrs since I fixed this, so far so good.

- A related question for the gurus, since the Neiko tool is above-average (it did the job for me), someone told me the dedicated tool such as
Titan 51535 (US $38.00) is better? Can someone give feedback on this dedicated tool?

- Although the listing says "Double Flare", the review/comment section clearly said it can be used as "Bubble Flare"
(since Bubble Flare is half-way through the Double Flare process)...


- This is what it looks like...

Attached Images
1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT
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Old 07-20-2021, 04:48 PM
Join Date: Jan 2013
Location: Finland
Posts: 1,294
Clavurion is on a distinguished road
I used this quite similar tool on my project and it worked like a charm.

E39 530dA -02 M-Sport Messing metallic
E53 X5 3.0dA -06 Sport Stratus grey
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Old 07-22-2021, 06:49 PM
Join Date: Jun 2014
Location: Omaha, NE
Posts: 1,584
cn90 is on a distinguished road
Food for thoughts...

I just inspected my 1998 528i with 186K miles.

Midwest winter with salt etc., but I wash my chassis every Spring around April-May or so.

- To undo the plastic clip: gently remove the center pin first...
- One 10-mm nut...
- Just remove a few clips and the 10-mm nut just enough for inspection.

For the most part, the brake pipes are in good shape! I'd say 90% good, except for a few areas of very minor break in the coating with very very minor surface rust...

So, this is good bc I don't have to replace the brake pipes, a job I know exactly what to do but I hate it lol.

Back to the E53, definitely something wrong with these pipes from factory. Or the fact that the E53 pipes are hidden under the plastic shield completely. Versus the E39 (5-series) has the plastic shield open at the aft side, allow rain water or garden hose water to rinse it clean.

This is why we don't see too many corrosion pipes on the E39 5-series...

Anyway, photo of my 1998 528i with 186K miles...

Attached Images
1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT
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