Tips on flushing brake system.

[Z51JEFF]

I would like to put a set of braided brake lines on my car as well as flush the system but have never dealt with an ABS system before,any tips?Also I would like to use a non corrosive brake fluid if thats possible.Thanks.

[Hib Halverson]

How to address bleeding the EBCM or EBTCM during the process of flushing the car's brakes depends on the model year.

Complete instructions for the process are in the Factory Service Manual, but if you perfer not to acquire the FSM, post your model year.

There is no such thing as a "corrosive brake fluid".

Most brake fluid is hygroscopic and over time moisture develops in the fluid. If the fluid's moisture content gets very high, rust can develop inside the braking system. In fact, that's one of several reasons why periodic flushing is required.

The only brake fluid which is not hygroscopic is DOT 5-rated, silicone-based brake fluid, but do not use DOT 5 fluid in a ZR-1. It is not compatible with the car's ABS.

[Karl]

Originally Posted by Hib Halverson

How to address bleeding the EBCM or EBTCM during the process of flushing the car's brakes depends on the model year.

Complete instructions for the process are in the Factory Service Manual, but if you perfer not to acquire the FSM, post your model year.

There is no such thing as a "corrosive brake fluid".

Most brake fluid is hygroscopic and over time moisture develops in the fluid. If the fluid's moisture content gets very high, rust can develop inside the braking system. In fact, that's one of several reasons why periodic flushing is required.

The only brake fluid which is not hygroscopic is DOT 5-rated, silicone-based brake fluid, but do not use DOT 5 fluid in a ZR-1. It is not compatible with the car's ABS.

Mine is a 1992 Hib. What is the correct process? Pull the fuse and relay from the abs and flush away?

Thanks!

[Z51JEFF]

Thanks for the replies,I should have been more specific in my request.What I meant by corrosive was something that wont eat paint but considering my only options are DOT 3-4 Im limited to what I can use.My cars a 91.Im just going to do what I can,a little of the old fluid wont hurt a thing.

[Hib Halverson]

Originally Posted by Karl

Mine is a 1992 Hib. What is the correct process? (snip)

Great question.

I use a modified version of what's in the service manual.

First thing I do is suck all the fluid out of the master cylinder reservoir with my MityVac. I suck out all the fluid such that there is just a tiny bit of fluid left in each of the master cylinder's inlets. Then, I remove the reservoir, wash it out with brake clean, reinstall it and fill it with new brake fluid.

Then, I install my pressure bleeder.

I bleed the master and the master cylinder ABS prime pipe per the FSM. The bleeder for prime pipe is on the EBTCM which is in the well behind the driver seat.

Next, I go to the farthest bleeder from the master cylinder, open the fitting and let it run into my bleed container until the fluid runs clean. I do the same thing for the other three, LR, RF, LF.

Then I road test and if the pedal doesn't feel right, I'll bleed per the FSM, again.

Keep in mind that while you can use a scan tester to command the EBTCM to run an auto test, the auto test simply duplicates the self-test regimen the ABS goes though each time you key-up then drive 7-mph or faster, so if you think there's air in the EBTCM which won't come out unless the ABS activates, just drive the car on a short road test which includes one or more shut offs and key-ups then drive, again sequences.

Then, take the car back to the shop and bleed the brakes, again.

Originally Posted by Z51JEFF

Thanks for the replies,I should have been more specific in my request.What I meant by corrosive was something that wont eat paint but considering my only options are DOT 3-4 Im limited to what I can use.My cars a 91.Im just going to do what I can,a little of the old fluid wont hurt a thing.

There is no DOT 3, 4 or 5.1 brake fluid which will not damage paint. The only brake fluid which is "paint friendly" is DOT 5 and it cannot be used in a ZR-1's brake system.

[5ABI VT]

I used a motiv on my m3 and it was fine but I had to finish off with the old friend-pump method. I just bought a reverse bleeder and am going to try that for the brakes

[Z51JEFF]

Thanks for all the tips guys,just now digging into this.I can honestly say I think brake fluid to the auto enthusiast has got to be the equivalent of Ebola to the health care profession,once you crack open the system every single drop has to be accounted for.Ive got pictures of the car basically in a plastic cocoon.

[Hib Halverson]

Originally Posted by 5ABI VT

I used a motiv on my m3 and it was fine but I had to finish off with the old friend-pump method. I just bought a reverse bleeder and am going to try that for the brakes

A reverse bleeder (i.e.: Phoenix Systems V12) might work ok on an M3, but think carefully about using a reverse bleeder on a C4 with Bosch ABS 2S.

C4 ZR-1 EBCMs and EBTCMs have internal screens to trap debris flowing in the normal direction but may lack screens to trap debris flowing in reverse.

I'd want to be confident I was not going to flush contaminants backwards through the EBCM or EBTCM before I'd deploy a reverse bleeder.

Maybe contact Phoenix Systems and ask about it.

[mike100]

I have the abs module for my tech1a scanner but it does not work/ communicate with my abs controller. Anyhow, I have bled my brakes two or 3 times in the last 4 years and the fluid remains clean and low moisture content. The second best way to get the old fluid out of the ABS valving and circuitry would be to actually cycle the system on a wet road and then briefly re-bleed the system in the near future. this is what I have done. There may also be a small amount of natural purge during the self check that occurs after every start when the car reaches 4 mph.

I'm not losing any sleep over it.

[KJL]

Off of the Wilwood web site:

"Wilwood does not recommend using DOT 5 fluid in any racing applications. DOT 5 fluid is not hygroscopic, so as moisture enters the system, it is not absorbed by the fluid, and results in beads of moisture moving through the brake line, collecting in the calipers. It is not uncommon to have caliper temperatures exceed 200 degrees F, and at 212 degrees F, this collected moisture will boil causing vapor lock and system failure. Additionally, DOT 5 fluid is highly compressible due to aeration and foaming under normal braking conditions, providing a spongy brake feel."

Stay away from DOT 5 ....period. Use DOT 4 for best temperature protection.