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 > Technical Articles: / BMW E36 3-Series (1992-1999) >
BMW Brake Line Replacement

Pelican Technical Article:

BMW Brake Line Replacement


4 hours4 hrs






11mm flare wrench, 11mm open end wrench, 9mm flare wrench, 14mm flare wrench, 13mm open end wrench, 14mm open end wrench, 17mm socket and driver, 8mm socket, floor jack and four jack stands, pressure bleeder, BMW OEM DOT4 brake fluid, paper towels,

Applicable Models:

BMW E30 318i Coupe/Conv (1984-92)
BMW E30 318i Sedan (1984-92)
BMW E30 318is Coupe (1984-92)
BMW E30 325 Coupe (1986-88)
BMW E30 325 Sedan (1986-88)
BMW E30 325e/es/is/iX Coupe (1984-93)
BMW E30 325e/i/iX Sedan (1984-93)
BMW E30 325i Coupe/Conv (1984-93)
BMW E36 318i Convertible (1992-99)
BMW E36 318i Sedan (1992-99)
BMW E36 318is Coupe (1992-99)
BMW E36 318ti Hatchback (1992-99)
BMW E36 323i Convertible (1998-99)
BMW E36 323is Coupe (1998-99)
BMW E36 325i Convertible (1992-95)
BMW E36 325i Sedan (1992-95)
BMW E36 325is Coupe (1992-95)
BMW E36 328i Convertible (1996-99)
BMW E36 328i Sedan (1996-99)
BMW E36 328is Coupe (1996-99)

Parts Required:

Front and rear flexible stainless steel brake lines

Performance Gain:

Brakes that again stop sure, straight, short and true

Complementary Modification:

Replace all brake pads and bleed brakes
101 Performance Projects for Your BMW 3 Series

This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.

One of the most popular projects for the BMW 3 Series cars is replacing the flexible brake lines that run from the main chassis of the car to the A-arms and trailer arms. These lines are made out of rubber and, over time, tend to break down and corrode. Carefully inspect the rubber lines every 10,000 miles or so. They can exhibit strange characteristics, such as bubbling and expanding, prior to actually bursting. Failure of these lines is a very bad thing, as you will instantly lose pressure in one-half of your braking system.

Faulty brake lines in the front of your BMW can also cause steering problems when braking. Bad hoses can cause a car to dart from side to side when braking. Bad hoses may also allow pressure to build up in the caliper, but sometimes do not release this pressure properly when the pedal is released.

To replace the lines, first elevate the car (see Project 1). Then remove the wheels from each side of the vehicle for easier access the brake lines. To prevent a large amount of brake fluid from leaking out, push the brake pedal down just to the point of engagement and block it there. You will lose less brake fluid, and less air will enter the system.

Now it's time to disconnect the brake lines. Have paper towels handy, as some brake fluid will leak out of the lines. Brake fluid is perhaps the most dangerous fluid to your car, as any amount spilled on the paint will permanently mar it. If you do get some on the paint, make sure you blot it--don't wipe it off. Your hands may also be contaminated with brake fluid, so don't touch the paint on the car.

The brake lines themselves can be very difficult to remove. The goal of this job is to remove the lines without damaging anything else. In this case, the easiest pieces to damage (besides your paint) are the hard steel brake lines that connect to the flexible rubber lines. These lines have relatively soft fittings on each end and often become deformed and stripped when removed. The key to success is to use a flare-nut wrench. This wrench is designed for jobs like this, in which the fittings are soft and might be heavily corroded. The flared end of the wrench hugs the fitting and prevents it from stripping. Use only this type of wrench, as it is very easy to damage the fittings using a regular crescent wrench.

The fitting is supposed to turn and rotate on the end of the line, but sometimes it becomes too corroded to break free and can get stuck to the hard line. When this happens, the fitting and the line will usually twist together, breaking the line in half. Thus, be careful when removing this fitting to make sure you do not twist the line.

If you do damage the hard line or strip the fitting, the replacement line might be a special-order part that will have to be shipped in from Germany. You can usually find the correct length of line at an auto parts store, but then you would have to bend it into shape--a very difficult process that usually requires a few special tools. The moral of this project, and really this entire book, is that you should use the right tool for the job (in this case, the flare-nut wrench).

After you have disconnected the flexible rubber line from the hard metal line, you can remove it from the car. At the chassis end, the lines are attached using spring clips. Sometimes, depending upon the angle, these clips can be difficult to remove. With a good pair of Vise-Grips, though, they can usually be pulled off the car.

Installation of the new lines is straightforward and easy. Before you attach them, make sure you have the correct ones for your car. There are a few different types, and a few different lengths, so make sure the ones you are putting on match the length and fittings of those you just removed. If the line you install is too short, it may stretch and break when your car goes over a bump.

When it comes to replacing brake lines, many people install braided stainless-steel lines on their cars. Rumor has it the stainless-steel sheath keeps the rubber inner line from expanding under pressure and actually delivers better performance than the standard lines. While this reasoning sounds good at first, it's mostly hype. Stainless-steel braided lines are usually made of the same rubber underneath and are simply protected by the outside sheath. Even if the sheath were tight and strong enough to prevent the lines from expanding, it wouldn't make a difference in braking. If the lines expand a little, the resulting pressure exerted at the caliper will be virtually the same.

Still, I recommend braided stainless-steel lines for your car because the outside sheath does protect the lines from dirt, grime, rocks, small animals, and anything you might run over.

Another point to consider is the label of "DOT" (Department of Transportation) certification. The original rubber lines were required to be certified under a certain set of specifications dictated by the DOT for use on U.S. highways. Often, braided stainless-steel lines are aftermarket components that are not DOT-certified and subsequently are listed "for off-road use only." In reality, these lines are more than adequate for use on your car, and any concern over their use is not really necessary.

However, for those who want to be absolutely sure and certified, there are manufacturers who make DOT-certified stainless steel lines, but they're usually more expensive than the noncertified ones. (Both types are available at

If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.

Figure 1

Old rubber brake lines are often responsible for poor brake performance. As the car ages, the rubber begins to break down and can clog the lines, restricting the amount of pressure getting to the calipers. Renew the brake lines if they are old or if you are having problems with your brakes. The arrow points to the flexible brake line on the rear of the car that needs to be replaced.

Figure 2

A required tool is the flare-nut wrench that fully wraps around the brake line. If you use a standard wrench, there is a high chance you'll round off the corners, permanently damaging the hard brake lines. These fittings are not very strong, and will become stripped if you don't use a flare-nut wrench. If the fitting becomes stripped, the line needs to be replaced (usually a special-order part from Germany). Also, make sure the fitting is turning (blue arrow), not the line itself (yellow arrow). It is very easy to twist off the ends of the hard lines when the fitting binds.

Figure 3

New stainless-steel lines are identical in size and length to the original ones that shipped with the car. Stainless-steel lines have a protective coating on the outside that prevents the elements from attacking them as easily. However, the stainless-steel sheath doesn't allow you to inspect the rubber inside for significant deterioration. Some of the aftermarket lines are made out of Teflon (or have Teflon components) to increase their durability.

Comments and Suggestions:
vince Comments: I am replacing the ancient rubber brake hoses on my 1990 325i e30 with the steel braided set PLB-323-106D. Is it recommended to use any type of lock-tite or anti-seize on the threads when installing if so, what would you recommend? Or is it best to just clean the threads if so, what to clean with / what not to clean with?
March 10, 2017
  Followup from the Pelican Staff: No threadlocker is needed. You can use brake cleaner spray and a wire brush to clean the threads. Ne sure to plug the brake line before cleaning to prevent debris from entering the hydraulic system. - Nick at Pelican Parts  
Handgunner Comments: What is the fitting size for these braided lines, AN-03 or 04?
January 13, 2017
  Followup from the Pelican Staff: I'm not 100% sure, it may vary. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
Bigsean Comments: Okay, I cannot get the brass nut to turn off of the rubber brake line. What is the plan B method of removing the rubber brake line from the metal brake line? Can I hold the rubber brake line at the metal fitting and turn it while holding the brass fitting tight/stable?
September 22, 2016
  Followup from the Pelican Staff: Vise grips to separate them, then replace anything that is damaged. - Nick at Pelican Parts  
Bigsean Comments: I ordered a set of braided brake hose lines from Pelican to replace the old lines on my E36 1994 325 sedan. How do you put the rubber grommet that holds the hose onto the strut onto the new hoses? Are the grommets split to make installation possible? Are new grommets available?
September 21, 2016
  Followup from the Pelican Staff: Some lines come with the grommets installed and some do not. I haven't installed a set without them. I imagine there is a a grommet or mount available to get them attached. - Nick at Pelican Parts  
paranoia Comments: Hi thank you for such great way of showing how change many parts on bmw : i like to know how i can make my brakes be harder sorry for English what i mean that I have changed the lines as you indicated here without loosing much fluid than i did not have choice but conecting first to wheel section than to body. So im guessing that as there is air left inside the brake pedal goes righ to flow than i feel braks basically the pedal is very loos how i can fix that ? Thank you
August 14, 2015
  Followup from the Pelican Staff: What vehicle are you working on? If the pedal is soft and all the brake lines are sealed, try bleeding the brakes again. - Nick at Pelican Parts  
kyle Comments: Hi,
Just replaced both of the soft brake lines in the front on my 96 328i. The driver side line had a small leak at the hardline fitting, passenger was just old. With the new soft line installed it began to leak again. I emery clothed the line and tried cleaning up the fitting but no luck, so i put a little amount of teflon on the fitting and put it back together, It has created a better seal but i don't know if it will hold.
Is teflon tape ok to use to get a better seal or will the dot4 brake fluid eat away the teflon?
July 26, 2015
  Followup from the Pelican Staff: No, teflon tape is not a good idea. The flare of line may be faulty. I would suggest replacing the section of line that is leaking. - Nick at Pelican Parts  
Vin Comments: Hi ,
I am looking to change all my brake hoses soon. Is their a particular order to follow. E.g rear brake hoses first then front brake hoses? Thanks Vin
June 24, 2015
  Followup from the Pelican Staff: Not really. The order is important when bleeding. Start where ever you like when replacing. - Nick at Pelican Parts  
DriftHQGMW Comments: I'm upgrading all the line in the car to ss front to back and bypassing the abs but I don't have a clue what fittings come from the master.
April 19, 2015
  Followup from the Pelican Staff: What vehicle are you working on? - Nick at Pelican Parts  
Micallef Comments: Great article - My four wheels jam solid when the engine is turned on and warmed up. This happens even without stepping on the brakes at all. I rebuilt the booster, installed new master cylinder and front brake lines to the calipers but not the rears replaced all fluids and bled. It worked for a few minutes but then on the second attempt engine on the symptoms still persist - all 4 wheels jammed with engine warm. No pentosin leaks. Am I overlooking something fundamental? The car is a 1991 E31 850. Many thanks
March 3, 2015
  Followup from the Pelican Staff: If you loosen the brake lines at the master cylinder, do the wheels become free? - Nick at Pelican Parts  
KA Comments: Hi, there's a small yellowish almost transparent oily doesn't seem like engine oil leak on the front of the car near the radiator more to the side of the passenger, could this be brake fluid? Brake rotors and pads were changed a couple of days ago including the regular fluid change and an alignment was recently done. I've also been experiencing a whining noise before stopping after brakes have warmed. Brakes doesn't seem to have lost any performance at all. Could this all be related and if it's any of the hoses, what do you think it is? Car is a European 92' 325i E36.
August 11, 2014
  Followup from the Pelican Staff: Could be power steering fluid. - Nick at Pelican Parts  
Mguy Comments: Hey I came here to find out more about the actual fittings. Looking to do a hydro on my e36 M. Hydro says 7/16 in, 3/8 out cylinder and M10x1 brake line fittings. I think I get the 7/16 and 3/8. But what does M10x1 mean?
April 30, 2014
  Followup from the Pelican Staff: M10/1 means 10mm bolt thread size with a 1mm thread pitch. - Nick at Pelican Parts  
Jacob Comments: I have broken my Master cylinder 3 times, I have no clue why it's breaking.. 2/3 the O ring snapped n half and the other time the master cylinder completely broke..... Could it because of a pressure problem?
April 13, 2014
  Followup from the Pelican Staff: Pressure, unlikely. I would check for an alignment problem, or something making contact with the master cylinder. - Nick at Pelican Parts  
wins Comments: Hi I have temperamental brake stick on my front rightside drivers/offside caliper with the usual heating, brake dust symptons. Have had friends suggest new caliper, but looking on forums such as these maybe try the hose lines first. My question is as it is now an then would it def be more aimed towards the brake lines or possibly the pin within the caliper needing to be sanded down?
January 3, 2014
  Followup from the Pelican Staff: If you can get it to stick all the time you can narrow it down by cracking the line to relieve pressure. If you crack the bleeder or line (at the caliper) and the caliper releases, it is the hose. - Nick at Pelican Parts  
ortho Comments: Could you clarify: "...push the brake pedal down just to the point of engagement and block it there." What does block it there mean? Put a weight on the pedal to hold the pedal down?
first time changing brake lines
October 21, 2013
  Followup from the Pelican Staff: What exactly are you trying to do?
- Nick at Pelican Parts
vladv Comments: Hello.

Whats thread sizes of female and male fittings of bmw brake hoses?
September 1, 2013
  Followup from the Pelican Staff: The thread sizes are going to be metric they might vary by year and model, Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.

- Nick at Pelican Parts
John Comments: Like Nelson, I have a caliper that sticks. Paid for a whole new brake job calipers, rotors, pads, but still had problems with the sticking caliper. Plenty of dust on that wheel compared to other wheels. Also having serious steering wheel shimmy after driving in traffic for maybe 20 minutes - possibly because stuck caliper is grabbing rotor eventually goes away. Now I will be replacing brake lines first, then seeing if the issue is solved. Need to replace caliper again because it is probably seized/fried. Great article...thanks a bunch for posting and for all comments!
July 11, 2013
  Followup from the Pelican Staff: be sure to replace the brake hoses if they are in question. A collapsed hose can cause a caliper to stick. - Nick at Pelican Parts  
Traviss Comments: You have a leak travis...
May 31, 2013
  Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help. - Nick at Pelican Parts  
Travis Comments: My brake pedal goes to the floor when I brake. It only happens when I brake noramlly, then release, then lightly brake again. like sitting in traffic. I have bled the brakes allready and inspected for leaks. No leaks found and the vacuum lines are all ok also. Is this a master cylinder issue? or ... thoughts? Thanks.
March 17, 2012
  Followup from the Pelican Staff: Clamp off all four brake hoses, if the pedal drops then you have a bad master cylinder. if not then check the calipers pads and slides, check the wheel bearings for play, and make sure the brakes are properly bled.
- Nick at Pelican Parts
eztuner12 Comments: Hi Wayne
Would by any chance swapping from the OEM rubber brake lines to a DOT-certified stainless steel lines will increase braking performance in any aspect?
Thx for the answer.
May 26, 2011
  Followup from the Pelican Staff: The brake pedal will feel a little stiffer because the lines have less flex in them.
- Nick at Pelican Parts
Ryan Comments: Great article. I'm currently replacing my lines on the e28 with a set of SS lines. And while I may be missing the obvious here, why are their six lines in the set? It seems that the long male-female lines are for the front, while the short male-female lines are for the rear. What's the application for the short male-male pair of hoses?
March 16, 2011
  Followup from the Pelican Staff: Rear on some cars have 4 lines, 2 from the caliper to the hard line on the control arm and 2 from the control arm to the chassis. - Wayne at Pelican Parts  
wally Comments: What about the mid-lines coming out of the ABS module in the engine compartment, usually on the passenger side behind the heat shielding? Do these two rubber hoses also need to be replaced at the same time as the hoses for the four corners? Looking at diagrams it seems they lead to the hard lines going to the rear-wheel brakes but my worry is whether I'll need to have a BMW dealer flush the ABS module if I change these two out myself. Or will I be okay provided I make sure to flush out all of the hard line when I do my rear brakes? The Pelican site treats these two as special-order items, and the pricing is not cheap.
February 14, 2011
  Followup from the Pelican Staff: The lines that connect to the ABS module are typically not an issue. The hoses that take the most abuse are the ones that connect the chassis to the movable parts of the suspension. - Wayne at Pelican Parts  
nelson Comments: I have a caliper that keeps sticking. I replaced it and it still sticks. I found this article. I have been told not to and to replace the lines. I can't the the piston to release, so I am assuming there isn't any backflow in the lines. I don't get the caliper jam until the car is on and the brake pump is working. When the car is off everything is fine after I release the pressure from the bleed valve. Will replacing the line solve my problem?
February 1, 2011
  Followup from the Pelican Staff: I think so. The rubber lines can break down and get thin. Then when you step on them, they expand. When you release, the contract back up and constrict, and it can almost be like a one-way valve. This is common on older cars (like 40-50 years old), less so on more modern cars, but it can indeed happen. I would replace the brake lines first, as that would be the easiest solution, I would think. - Wayne at Pelican Parts  
Stu Comments: Hi,
I am replacing my hardlines and hoses from the master cylinder back to the caliper. The hardlines go above the gas tank on either side. Do I have to fully remove the gas tank to put the lines in or can I lower the tank enough without removing any hoses from the gas tank? Thanks, Stu
July 24, 2010
  Followup from the Pelican Staff: I think it depends upon which car you have, there are different types of routing for the lines. In general, I'm guessing it would be easiest just to remove the tank. - Wayne at Pelican Parts  

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