I ask here because the probem seemed to arise after I started autocrossing my car. My master cylinder started bypassing rather abruptly after my second autocross. 500 bucks later I had a brand new one. That was about six months ago, and now it feels like it is starting to bypass again (the pedal feels a little soggy when I apply light pressure to it). Granted I haven't autocrossed since the end of October but still, I'm wondering if there is a connection.

Car is a '96 Integra GS-R with 59,000 miles on it

Any Honda drivers, expecially Integra drivers, have you had MC problems? This is starting to look like a glaring flaw in an otherwise bulletproof car



[Modified by Angry Joe, 11:37 PM 2/9/2003]

 

We had to replace the MC in our car. The pedal felt like the system needed a bleed. Turned out to be the seals going.

FWIW, I remember reading that if you bottom out the pedal when bleeding, you are damaging the MC.

 

Exactly what happened to me.

I had the work done by the dealer so I don't know if the new one was bled correctly. But since I think that problem arises from junk accumulating in the un-used portion of the cylinder, I don't think it would be the cause of the second failure since it was new. I also had not had the system bled recently before the first failure.

 

by soggy do you mean it sinks when you put constnat pressure on the pedal? if its just spongy, thats not necessarily the master cylinder.

 

ot? what are the causes of increased brake pedal travel?

 

When is the last time you bleed your brakes? Could it be they just need a good bleed? How old is the fluid?

My original MC lasted thru 79k street miles & 3 years of track duty. I honestly can't remember what exactly the symptons were when ours went bad. We narrowed it down by doing the bleeding. I thought it might be a bad booster but the symptons didn't change with the engine running or engine speed. We had to call my engine builder from the track.

 

brake testing procedure.

http://www.binghamtonlife.com/manual...s/91-19-16.jpg

 

I guess I could have looked it up in the Helms but I am honestly just too lazy.

 

If I apply very light pressure to the pedal it starts to sink to the floor. Heavier pressure results in more resistance. It's very subtle right now but I suspect it may get worse.

Its very possible the first failure was caused by old fluid since I hadn't bled the brakes since I bought the car used. That wouldn't expain this instance, however since it's only been around six thousand miles since the the new one went in.


[Modified by Angry Joe, 12:46 AM 2/10/2003]

 

ok, but the sinking can be due to other leaks. brake problems suck, its tuff to get behind the wheel of a car you dont have full confidence in the brakes. i tihnk you can buy rebuild kits to fix the seals as well. but have you checked the calipers?

 

If you went to the dealer & got it repaired last time, it should be warrentied for 1 year. Make sure that is the problem before going there though.

Since I couldn't read the page that Tyson's link sent me too, I dug out the Helms.
On the MC, all it says is to check for leaks. The brake booster list a functional test & a leak test.

Functional Test:
1) with the engine stopped, depress the brake pedal several times, then depress the pedal hard and hold that pressure for 15 seconds. If the pedal sinks, the MC, brake line or a brake caliper is faulty.
2) Start the engine with the pedal depressed. If the pedal sinks slightly, the vacuum booster is working. If the pedal height does not vaer, the booster or check valve is faulty.
Leak Test:
1) Depress the brake pedal with the engine running, then stop the engine. If the pedal height does not very wheile depressed for 30 seconds, the vacuum booster is OK. If the pedal rises, the booster is faulty.
CAUTION: do not try to disassemble the booster. Replace the booster assembly with a new one.
2) With the engien stopped, depress the brake pedal several times using normal pressure. When the pedal is first depressed, it should be low. On consecutive applications, pedal height should gradually rise. If the pedal postion does not vary, check the booster check valve.
Check Valve Test:
1) Disconnect the brake booster vacuum hose at the booster.
2) Start the engine and let it idle. There should be vacuum available. If no vacuum is available, the check valve is not working correctly. Replace the check valve and retest.

 

I first noticed a slight pull to the right under straight line braking accompanied by slightly more brake dust on the right wheel. At first I thought it was the caliper getting suck so I rebuild the 2 front calipers. But the pulling and more dust on right wheel still persist.

I did the MC test stated on the helms manual and it checks out ok. I was going crazy trying to diagnose the problem. I narrowed it down to the ABS unit or the MC. I borrowed a 7/8MC from a 99 Si to replace my 15/16 MC on my civic EX so far it seemed to cure it.

Charleston

 

Get an LHT MC brace. I had the same problems on my Type R for 18 months. Installing a MC brace made by LHT really really made a BIG difference.

Search the ITR forum for "LHT"

 

There are different comninations, but brake pedal travel usually doesn't change unless you changed something. A smaller diameter MC piston will allow more overall pressure per a given input force, but but the smaller piston must travel further to do so. Leaks can also cause pedal travel to increase, but usually pedal feel is what drastically changes between setups. The compliance of the hydraulic system is often the culprit, and that deals with piston sizes, and strength of lines etc.