Hi,
I have a totally stock 2005 evolution. I have been using the brake very aggressively over the weekend. On Saturday, I noticed the brake pedal went very spongy and the brake power was greatly reduced. I thought may be mositure got in my brake system, and cooked my brake fluid. So I bleed the brake fluid with ATE superblue which is DOT 4. The brake pads are fine. On Sunday, the spongy feeling can back and again I lost brake power. This time, when I pumped the brake once, then brake. The spongy feeling went a away momentarily. Also when the car is still, if I put my feet on the brake pedal with just the weight of my leg, the brake pedal will sink down very slowly. Someone told me that it is a sign of leaking brake cycliner. Have anyone experienced this? Or can anyone shed light on this problem.

Thanks alot.

Jim

 

Looks like it's time to check all bleed nipples, brake lines, ABS unit and master cyclinder for leaks. Do this just to be safe.

Does that brake power loss come right after any turns or does it happen any time?

 

Mayhem,
The brake power loss happens any time. I don't think it is over heating brake fluid. Today after the overnight, the break pedal is still feel soft and still sinks with weight of my leg. I plan to have to take it to the dealer for a check up. I want to gather as much as information before I go in.

Jim

 

There are two bleeders per caliper, one inside, one outside. Did you find both?

 

I did bleed both. I bleed the inside ones first then the outsides.

 

Same thing happened to me with the stock brakes. You must be driving fast and braking late and hard. I did.

Same thing happened EVEN after we installed customized air ducts to the stock brembos at out last race at Laguna Seca. After 5 laps of FAST and HARD braking!!!

We've solved our braking problems since. Call Mueller at Road Race Chassis if you wanna upgrade and solve the problem.

IMHO the stock brembos work great but only for a handful or so of hot laps.

 

Does "any time" include with the engine off? How confident are you that you really bled the brakes correctly? Some persuasion with a rubber mallet can help "unstick" air bubbles. But then it did this before you touched anything at all, right?

Anyway, double-check everything you've touched: caliper pistons, bleeder screws, banjo bolts, flare nuts to make sure they're not leaking. Pump the brakes a lot and check the level in the reservoir. If all the fluid is staying in the system then maybe it's a bad seal in the master cylinder. If the pedal drops only with the engine on I'm guessing (really, I'm guessing!) that might indicate the EBF or ABS.

Dave

 

Air bubbles in the lines will cause the pedal to pump up, i.e. -- pump pedal 2-3 times if the first pump goes down further than the second or third then there’s air in the line. If it doesn’t pump up there’s no air in the system.

The pedal slowly going down with the weight of your leg is most likely the master cylinder leaking internally back past the seals = need to replace it. Slight chance that there could be something wrong (internal leak) in the ABS valveing.

 

Thanks for the good information guys.

Autoxevo, sorry to sound very ignorant, but I am new to the sport. "pump the pedal" means press down the brake pedal, right? should I do this with car moving or still? If still, should I leave the engine running or off? and, what do you mean by "pump up" ?

Jim

 

No problem, I'll try to explain it better Do it with the car still and eng turned off. Push the brake pedal down 3-4 times (this will remove all the vacuum assist in the booster)

Wait about 5 seconds

Now the test;
Push the brake pedal down 3 times as far as you can, not as hard as you can, just pretend your braking hard, due this within 3-4 seconds (As soon as the pedal gets hard let it up, as soon as you let it up, push it back down, should take 3-4 seconds to push the pedal 3 times).

Now, the last 3 times you just pushed on the pedal it should have stopped/got hard at the same distance down. If the first push went down further towards the floor than the second or third push then there’s air in the system ("pump up"), but if they all were at a same consistent level then there’s no air in the system. Basically just pay attention to how far the pedal goes down on the first push and compare it to the second push down (should go down the same distance)

Its really a feel thing, if you want to do the test again wait about 5 seconds between tests (this allows the air to expand again, if there is any)

Here’s a good write up on bleeding brakes on an Evo http://www.joe250.com/cars/evo/brakebleed.htm

Hope that helps, I may not be the best at explaining, so feel free to ask for clarification

 

Thank for the clear explaination, autoxevo. I will use your method to check my brakes.

Jim