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This guide describes how to quickly and easily replace your car's brake pipes and hoses. It specifically relates to the Mercedes E-Class (W210), but the technique can be used for any car. Replacing your brake pipes is not hard, but it does take some time and does require special (although cheap) tools. These procedures are not without risk so please ensure you have read this disclaimer (click here)
Replacing brake pipes is easy, but it can be a costly business if you don't do it yourself. For example a Mercedes dealer will charge you up to £1200 to replace your rear brake pipes or lines, and an independent garage will charge you up to £450 for the same job. However, even if you have to buy all the special tools and equipment you can do the same job for less than £60. If you already have the special tools then the same job will cost you about £25 and 4-6 hours of work.
So why does it cost so much at a dealers? Well, it all comes down to what you replace your brake pipes with - copper brake lines or original steel brake pipes. If you use steel brake pipes then you need to disassemble and drop the car's subframe, as steel cannot be threaded into place like copper. This takes time and time of course means money. Then there is the cost of the parts, copper brake line is around £10 for 7m or 25ft, OEM steel brake lines can be up to £70 a pipe.
Should you use OEM steel brake lines or copper brake pipes?
So should you use the original manufacturer's steel brake pipes - they're expensive, but are they any better than copper? Amazingly, no they're not better than copper. Your original (and expensive) steel brake pipes are the real cheap and nasty option! You'll hear stories like "oh copper brake pipes burst under the pressure of modern brake servos", but this is simply not true. It is true that in a few countries the use of "pure" copper brake lines is illegal, this is because if not properly installed they could work harden and eventually crack (this reasoning never made sense to me because steel lines rust and burst which surely is just as bad?). These countries use kunifer instead, which is a copper alloy and looks very similar (so similar in fact that some people still refer to it as just "copper brake pipe"!). Either way, copper (pure or as a kunifer alloy) has been used for years in servo assisted braking. It will not burst under brake pressure (your rubber brake seals in your calipers would burst before the copper pipe). In fact copper was the material of choice for brake lines until prefabrication became the name of the manufacturing game, and that's the reason they now use steel - Prefabrication! Copper is expensive, too soft and bendy to prefabricate and without extensive prefabrication manufacturing costs would rise. Manufacturers use steel brake pipes to keep the cost down, pure and simple - steel is the cheap and nasty option. If you go to an independent garage your rusty steel brake pipes will probably be replaced with copper ones - they don't rust and they're easy to put into the car without stripping it down. The only down side to copper is that it work hardens (becomes brittle if bent repeatedly), but all you need to do to prevent this is make sure it's well supported by car's body clamps/clips so it cannot repeatedly flex. When compared to rust, work hardening is a minor price to pay. So my advice is unless you have a darn good reason, always use copper brake pipes if you need to renew them. Sure, go for kunifer if you want or have to, but unless you are using it on a track day car you won't notice the difference. I have classic cars that have been running on unsupported (by modern standards) "pure" copper brake pipes for more than 30 years and I have never had even one pipe crack (and yes, I used to race one of them).
But will a professional do a better job than you can ?
Maybe, but probably not. Replacing brake pipes is time consuming but not difficult. In fact most garages I know give it to the trainee mechanic as you do not require any experience and it can be unpleasant. So in all probability the guy replacing your brake pipes could have less experience than you - OK, yes the job will be checked by a experienced professional once finished, but if you're really that worried simply book your car in for a 15 min check after you have completed the job with the garage - most won't even charge you! However, this "check" is easy and I would do it yourself as it is simply a case of "is everything secure and is any brake fluid leaking out under pressure? ".
Do you really need to replace your brake pipes ?
If your brake pipes look like the photo then you probably need to replace them. However, recently my car failed the MOT due to rusty brake pipes and brake hose ferrules. This was a surprise for two reasons; (1) There had been no advisory on last year's MOT and (2) I had only just bought the car and had thoroughly checked it over only a few months previously. However, the golden rule is never to question the "MOT man" (especially as I know him so well) - so there was nothing for it but to rip out the brake lines and replace everything. Once I'd got the old brake pipes out I cleaned them up to properly inspect them. As expected they were perfectly sound, just the plastic film cracking and some surface rust with some light pitting. So if you're in the same situation as me with a failed MOT, before you go ahead and replace the brake pipes try cleaning them up in situ - check them carefully, but they could be fine. A wire brush and some Waxoyl may be all you need to do.
IMPORTANT: Safety First (Please Read!)
Working on brakes is potentially dangerous both during and after the repair:
Brake fluid is corrosive and will damage paint work and your skin. Wipe any up immediately if it is spilt. It is not as bad as some people think (I've accidentally squirted it in my eyes and I was fine), but have some water handy to douse yourself if you have an accident with it (e.g. eyes). Basically treat it like household bleach and you'll be fine. Always wear barrier cream and nitryl gloves and have some rags handy to mop up. You can leave it on your hands for quite some time during a repair, but it will eventually make them red and itchy.
When you have completed work always use the triple check rule: (1) check the work you've done in situ (2) road test and then check the work you've done again (3) finally re-check the work you've done after driving 50 miles. This is particularly important with brakes.
As you will be pulling apart the brake system you will need to bleed it. You may as well do all those extra servicing jobs at the same time, as this will stop you having to pull the system apart at a later date and bleed it again. So I really would recommend you:
(1) Replace your brake hoses at the same time as these items are only lifed for around 5 years.
(2) Carry out a complete flush and renewal of your brake fluid. Don't just bleed the brake system until there are no air bubbles in it, but run it through until all the old fluid is replaced. You should be doing this ever 2 years in any case, so why not do it now?
(3) Also you may as well take the opportunity to restore, de-rust and paint your calipers. If you do this make sure you use caliper paint and only paint the outside surfaces, never the rubber seals, pistons or where the brake pads slide in and out.
(4) Replace any brake pads that are close to wearing out.
Tools and Equipment
Getting the right result without spending hours or skinning your knuckles is all about having the right stuff handy. What you need for this job is:
- Axle stands (the exact number will depend on which brake pipe you are replacing)
- 1 Jack (at least)
- Socket set or spanners
- Flare spanner set or at least an 11mm and a 14mm for the E-Class (£4 each and essential)
- Pipe bender (£15 and essential do not bend brake pipes through 180 degrees by hand)
- Pipe cutter (not essential but cheap at £3 and the best way to do a good job)
- Pipe flarer kit (£15 and essential)
- Wire brush
- Penetrating oil (WD40 or similar)
- Tape (duct tape or masking tape)
- wipes and a pan/bucket for spilt brake fluid
- small pencil torch or similar
- 4 x pairs of male and female brake pipe fittings (50p each, not essential)
- copper brake pipe (about £10 per 25ft, or even less if you can get it on trade)
- Brake fluid (Dot 4 for the Mercedes E-Class W210)
- Brake bleeding kit (as low as £5 but the Gunson Easi-Bleed at £20 is excellent)
- 5 Gallons of Home Brew
- Decent stereo
Which Brake Pipe Flaring Tool? Imperial and Metric Brake Pipe Flares
Brake pipe flares are the way in which the end of your brake pipe is "flared" out to joint the next brake fitment, they do not relate to the type of fitment itself. In cars built after about 1960 you will only ever find double SAE (imperial) or single DIN (metric) flares. Almost every modern European car will now use the metric single DIN flare (except some 'classic' Land Rovers and Jaguars). SAE flares tend to only be used on American cars, but slowly even these are being standardised on the improved DIN fitment. Metric and imperial flares are interchangeable with metric or imperial brake pipes, for example you can safely use a metric flare on an imperial brake pipe. What matters is that you use the correct flare for your fitment, luckily this is easy as you cannot fail to tell these two types of flare apart. The metric Din looks like a bubble, but the imperial SAE looks like a cocktail glass (see photo to left). When you remove your old brake pipes have a look at the flare on the end of them (it'll almost certainly be DIN) and only use that type of flare. On the Mercedes the flare was as expected a DIN/ISO single bubble on a 4.75mm standard brake pipe, as a result the (even more) standard 3/16 inch (or 4.7625mm!) imperial brake pipe can be used as a replacement (which is of course why 4.75mm was chosen as the standard metric pipe diameter to allow them to be interchangeable!). As an aside, imperial SAE and DIN metric flares will seal well against each other if you are using copper brake pipe, and this is the technique used to create the "Brake Pipe End Caps" in the next section. However, do not mix and match like this for any part that is going to be left on the car permanently. Almost all brake flaring tools (brake flarers) will do SAE and DIN, but you need to make sure that you have one or buy one that covers both these standards. While all brake flaring tools will work with "pure" copper pipe, only the expensive tools tend to work with kunifer copper pipes. If you are going to replace your brake pipes with kunifer, make sure your flarer specifically mentions that it works with this material as it is much harder. Tools that work with kunifer tend to be around £100, while those that only work with copper are much cheaper at about £15.
Helpful tools you can make - Brake pipe end caps
These are very simple to make and take only minutes to fabricate. One of the problems with working on brake pipes is that as soon as you disconnect them they start to drip brake fluid which makes the job messy and unpleasant. Also, you need to be very careful to keep pipe ends clean as if you get dirt in the pipes your braking system will become spongy. I restore classic cars so there were times I needed to remove and seal up a system for a few weeks, but I always had to drain it because of these issues. Many years ago I thought of a simple way to solve this problem - just make a set of male and female brake pipe end caps (see photo)! These bolt onto the ends of brake pipes and seal them preventing fluid loss and keeping them clean. They are also very helpful when threading new pipes into position without getting dirt into their ends. To make them you need your brake flaring kit, some male and female fitments, a soldering iron and some solder. Simply cut some short lengths of pipe (about 1 inch long) and flare one end with the flarer (single flare for male fitments, double flare for female - your flarer will come with instructions for this). Now slip on the fitment and finally seal the un-flared end with solder so the pipe is sealed. Clean them well and you're done - simple! To use your end caps, just screw the appropriate end cap onto the brake pipe you've disconnected and it will seal it completely and easily. You can leave brake systems sealed like this for very long periods without them dripping and without having to worry about dirt or water getting into the system. Believe me, you will not regret having a set of brake pipe end caps in your toolbox.
MAIN PROCEDURE: How to replace brake pipes or brake lines
This procedure describes how to replace brake lines on your car with copper or kunifer brake pipes. If you want to replace your brake lines with steel, you will need to drop the whole subframe rather than follow this simple procedure. Anyway, this procedure specifically relates to the Mercedes E-Class W210, but the general approach is applicable to any vehicle. Please ensure you have read the information in the above sections and that you have the correct tools available.
Familiarise yourself with the route of the brake pipe you are going to replace (see photo to the left). The photo also shows the locations of the rear brake line pipe-to-body fixings. The front fixings are not shown as these can easily be seen from above. If you are replacing rear brake pipes I would strongly recommend that you have some spare Type 4 black screw nuts shown in the photo as these often break on removal - they are available very cheaply from your dealer. I would also recommend that you buy some 8mm black rubber petrol hose as this can be cut up and slit to make spare Type 5 fixings. Working on brakes is potentially dangerous both during and after the repair - always use the triple check rule: (1) check the work you've done in situ (2) road test and then check the work you've done (3) finally re-check the work you've done after driving 50 miles. The triple check rule particularly applies to bolts if you have removed any calipers. Garages and dealers can't use the triple check rule, they can only double check, which is one good reason I always work on brakes myself and I've never let them (or anyone else) near the braking systems on any of my cars.
Step 1 - Get the car off the ground
Before you jack up the car loosen the wheel nuts a little on the wheels you are going to remove, then jack the car up, support it and take the wheels off. Depending on which brake line you are replacing you may or may not need to get the car completely off the ground and supported on axle stands. If you only need to replace a front brake line then you can get away with just jacking up the front of the car and making the front two wheels accessible. However, you will need to get all four wheels off the ground and accessible if you need to replace a rear brake pipe. That said, bleeding brakes is simpler and quicker if all four wheels are off the ground and accessible, so for the reasons given in the recommendations section of this guide, if possible I'd always get the car completely off the ground anyway. Click here for a guide that tells you how to safely jack up and support your Mercedes with either 2 or 4 wheels off the ground.
Step 2 - Prepare the old brake pipe for removal
First locate the rear fitment of the brake pipe you will be replacing - this is where the brake pipe terminates in a fitting with the rubber brake hose that goes into your brake caliper. It ill be found under the wheel arch on the side of the wall (see photo to right). These fitments are notorious for welding themselves together - this is where the penetrating oil (WD40 or similar) and flare spanners come in. For the moment just spray it with penetrating oil and leave it alone to work in. If you're replacing the brake hose as well then spray the brake hose ferrule at the caliper, but be careful to prevent any oil getting on your brake pads. While you're about it also spray the bleed nipple on the caliper with penetrating oil.
Have a look at the photo to the left and familiarise yourself with the location of the brake fluid reservoir and junction box. The brake pipes on junction box are labeled (HR, VR, HL, VL) see the photo at the start of this section for how these relate to the brake pipes. Starting at the front of the car, lift the bonnet, unscrew the brake fluid reservoir cap and place a rubber glove over it before screwing it back down to form an air tight seal. This will reduce fluid loss when you unscrew the brake pipe fittings.
Now get your brake pipe end caps (see here for how to make them), old rags and a jam jar handy. Using a flare spanner (do not use a standard spanner or you may round off the nut), unscrew the brake pipe you will be removing from the junction box. Place the brake pipe ends into the jam jar to catch any fluid and seal the hole in the junction box with a male brake pipe end cap. Finally seal the end of the brake pipe with a female brake pipe end cap and make sure you clean up any spilt brake fluid with rags immediately as it is very corrosive.
Next if you are working on the rear pipes, you need to get under the car and remove the rear section of the underguard tray beneath the engine/transmission (see photo to left). The Mercedes E-Class has 3 trays in total that work together like the shell of an armadillo. The front and middle trays can be left in place, although it is easier if they are removed too (especially if you drop something from the top of the engine!). The trays all unbolt from the chassis in the following order: back, then middle, then front tray. With the tray removed you should be able to see all the brake pipe to body fixings and gain access to them.
OK, take another look at the brake pipe routing schematic in the photo on the right. Note the position of the types of boy fixings and, if you are replacing a rear brake, note the position of the fixings shown in the photo. Some fixings are of the simple clip type and can be sprung simply by pulling the brake pipe away from the fixing (Type 1 and 3), some have to be levered open before the brake pipes can be sprung lose (Type 2), some can be removed after you have the brake pipe out (Type 5) and some on the rear pipes are held in by a screw bolt fixing (Type 4). Locate all these fixings and release the brake pipe from them along its length. Work methodically from front to back and be very sure every one that needs to be opened is found and the brake pipe released from it.
Finally, you need to remove and seal the rear fixing of the brake pipe, the penetrating oil should now have done it's work and if you are lucky it will not be welded together anymore. However, often you don't get this lucky, and be aware that your brake pipe may snap at the fitting so make sure there is a basin under it to catch any stray drips of brake fluid and some rags. Also make sure you have a male and female brake pipe end cap handy to seal the brake hose and pipe once it is removed. Always use a flare spanner for undoing the fitments at the brake pipe end of the fitting, as they will be very tight and an ordinary spanner is likely to round off the nut making it impossible to remove without grinding it out. Support the brake hose end of the fitment with an ordinary spanner to stop it rotating, there is a flat cut into the cylindrical steel ferrule of the brake hose for you to do this (see photo to left). Now undo the brake pipe from the brake hose and then seal both with brake pipe end caps. Congratulations your brake pipe is now ready to be removed
Step 3 - Remove the old brake pipe
Removing the old brake pipes should now be easy - the key is to try not to break them as they are full of fluid. You'll need to bend them to get them, out but don't worry they'll bend a lot before they break even if very rusty. If you are removing a front brake pipe then you should have enough access that the job is trivial. For rear brake pipes the job is a little harder.
Removing a rear brake pipe needs to be planned. On right hand drive cars the near-side is easier to remove than the off-side (driver's side), but neither is truly difficult to remove as a single item if planned. There is enough clearance to get the brake pipe above the subframe (see photo to right) and the old pipes will bend quite a large amount without breaking. The order you should plan to remove them is as follows:
(1) Working at the front of the car, bend and manoeuvre the brake pipe down through the engine bay and onto the ground under the car. Position it so that it can easily be pushed out as a single piece between the front wheels of the car as you release it from the rear subframe.
(2) Working at the back of the car, start by releasing the brake pipe from around the suspension and springs in the wheel arch (you will need to bend it a bit). Push it back under the car and above the subframe.
(3) Working under the rear of the car, first work the brake pipe free from the recess in the middle of the floorpan where there is a sharp 90 degree bend so it doesn't get caught during removal. Now at the back of the car, bend and manoeuvre the brake pipe over the subframe. If you are working on the longer pipe that runs to the off-side wheel arch you will need to bend and work it round the frame. As you pull the brake pipe over the subframe, the other end of the brake pipe can be pushed out between the front wheels (that is why you positioned it there).
(4) Once you have the full length of brake pipe on the ground and fully released, just push it out between the front wheels and remove it.
Step 4 - Prepare the new brake pipe
The usual method for preparing a pipe is to make the key bends in the new pipe (using the old pipe as a template) before you fit it into the car. You can probably get away with pre-bending the pipe on the front brake pipes, but I'd really recommend you do not pre-bend the pipe if you are replacing the rear brake pipes or you will never get it over the subframe. Either way, you'll be amazed how forgiving copper brake pipe is, it's easy to thread and bend into place, just don't overdo and make sure you use a brake pipe bender on the really sharp bends or the pipe will collapse and kink.
Whether you pre-bend or not, the first step is to always seal the new pipe so that dirt will not get into it while you fit it. The easiest way to do this is to place the fitment and flare the end of one end in the brake pipe (ready to be attached to the car), but to leave the other end un-flared and sealed with tape. This allows you to thread the brake pipe into place and then bend it, without having to worry about getting it exactly the right length. Personally I leave my brake pipe rolled, fabricate the fitment, add a brake pipe end cap to seal it then seal the pipe end with tape. I then unroll it as I fit it. Once fitted you can then cut the other end, flare it and be sure of an exact fit. See the photo to the left for what I mean. If you are fitting two brake pipes at the same time, a good tip is to use different colour tapes to seal them so you can identify which is which.
Step 5 - Fit the new brake pipe
Fitting new brake lines is easier than removing old ones, but there are a few rules to follow:
(1) Make sure that the pipe does not rub against any the chassis or other parts. You can usually achieve this by careful bending, but if you can't just place a Type 5 body fixing anywhere it is likely to rub against a metal part.
(2) Ensure that all body fixings are closed and hold the pipe securely to the car.
(3) Lubricate the brake pipe fitments with brake fluid or a very small amount of copper grease before tightening them to the brake hose or junction box. If you do use copper grease be very, very careful to only get it on the threads, not into the pipe. The "correct" way of lubricating brake fitments is with brake fluid (never anything else because of contamination). However, I have tried both brake fluid and copper grease over the years - brake fluid works well for about 3 years then the pipes bond to the fitments (not good!), but copper grease has never caused me any issues unless I've accidentally allowed it to contaminate the pipes. So personally, I'd recommend doing it the "incorrect" way and carefully use a bit of copper grease.
Fitting a front brake pipe will not cause you any difficulty so I will not waste time explaining it. However, if you are replacing rear brake lines then you do need to follow a procedure. Start at the front of the car above the engine and slowly unwind and thread the brake pipe down through the engine bay fitment end first (not taped up end first!). Don't bend it yet, keep it straight, but be careful to follow the path of the original brake line (don't get it the wrong side of any water pipes etc.). Keep feeding it through under the car until the end reaches the ground beneath the rear subframe. At this point, don't feed any more pipe through, but step back from the engine and straighten the rest of the pipe out in front of the car. Now working under the car at the rear you should be able to pull the pipe through and feed it up over the subframe, following the path of the original brake line and threading it around obstacles until it pops out under the rear wheel arch. Feed through a bit more than you need, so you have space to bend it to attach to the brake hose (see photo to right).
Before bending anything, check the pipe is all in the right place and roughly following the original brake line path (again don't get it the wrong side of any parts of the frame). Now working from the rear forwards, start to make the bends in the pipe. Start with the brake hose to brake pipe bend (you will need a brake pipe bender for this one) and when complete, make the bends around the rear spring before tightening the fitment to the brake hose to make it secure. Now it is just a case of working backwards from the rear of the car to the front making bends and fastening the pipe into the body fixings as you go. When you reach the junction box at the front, make the final bend before measuring and cutting the pipe (see photo to left). Do the final flare fitment and bolt it down into the junction box - congratulations you have fitted the pipe!
Step 6 - Bleed the brakes
Bleeding the brakes removes all the air from the system. If any air bubbles are left in the brake lines your brakes will not work properly and will feel spongy when you press the brake pedal. Bleeding is a simple procedure that involves forcing brake fluid through the system from front to back while you open and close every bleed nipple (remove their rubber dust covers first!) on each caliper in sequence to let the air get pushed out (see photo to left). The sequence for bleeding always starts with the longest brake pipe run and works to the shortest. This sequence ensures air bubbles do not get trapped in the lines. You can use the old method of pressing the brake pedal to force fluid through, while there is a one-way valve placed over the bleed nipple to stop air being sucked back up into the lines. However, you do risk scoring your brake master cylinder using this method by forcing down further than it would normally go into old dirty deposits. If you score it, it may leak and you will need a replacement (expensive!). I would therefore recommend using a pressure bleeding system like Gunson Easee-Bleed, they're cheap, effective and far more easy to use.
You need to bleed the pipes in sequence as shown in the photo to the right. If you are also flushing the brake system with new fluid, you will find that new fluid is paler and clearer than old fluid so you should be able to tell as soon as the new fluid starts to come through. There are special colourants you can put in brake fluid to help you tell when you have flushed the system, but they are expensive and not really required. Anyway, connect up your brake bleeding kit and have a jam jar and some rags handy. Work your way around the car, bleeding each brake in sequence by opening the nipple, letting fluid flow out and then closing it before moving on to the next wheel. Continue bleeding a nipple until you cannot see any bubbles being expelled from it. If you're flushing the system then continue until you start to see the new fluid flow out of the nipple and down the pipe. Once you have completed the sequence, carefully depress the brake pedal in the car 5 or 6 times, then go back around and bleed each brake nipple again in sequence. If no more air bubbles are expelled, then you have completed the brake bleeding operation.
Step 7 - Finishing up (The Triple Check)
The Triple Check is really important for safety so please make sure you complete it:
Check 1 - Recheck everything in-situ. Before you put the wheels back on and lower the car to the ground you need to check everything you replaced in situ - this includes clips, pipes, bolts and screws. You need to make sure that none of the brake pipe fittings is leaking and that everything is tightened to the correct torque especially if you removed any calipers to paint them. Start by depressing the brake pedal in the car and seeing if it feels spongy. If it does then you still have air in the system and need to bleed the brakes again. If everything is ok, then depress the brake pedal again with as much pressure as you can. Hold it down for at least 20 seconds. Now work your way around the whole car and check every brake pipe fitment isn't leaking. If any are leaking then tighten them up and recheck them again by pressing and holding the brake pedal. Finally work your way around and under the car checking every brake pipe, fixing and bolt you disturbed. If everything is secure then put the wheels back on the car and lower it to the ground.
Check 2 - Recheck everything after a short test drive. Take the car for a drive, first gently test your brakes and then choose somewhere safe and try an emergency stop. Take the car back home, jack up each corner in turn (safely!) and repeat the procedure in Check 1. If everything is OK proceed to the final check (Check 3).
Check 3 - Recheck everything after you have driven 50 miles. Drive the car normally, but do not take it on any long journeys yet. After you have completed around 50 miles in it you need to carry out the final checks. As before, jack up each corner in turn (safely!) and repeat the procedure in Check 1. If everything is OK then .... Congratulations! You have completed the triple check and successfully replaced your own brake pipes! Grab a brew you deserve it!
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