sebTeggy

Hey guys, I'll be replacing my brake master cylinder soon.

I recently replaced my rear brakes (pushed the piston in properly, loosened the valve) and have a few questions. Im replacing it because I have a spongy pedal and its been like this for over a year.

1. The pedal gets spongy only after diving for a while (heated fluid)
2. On hot days its really really bad, especially while idling on an uphill
3. When the car is at Op Temp, and if I slam on the brake, the idle will rise. Something to do with my prop valve or booster?
4. If it is my prop valve or booster, could this be the reason my pedal is spongy? I already bled all the brakes in the proper sequence and no luck.
5. When I replaced my rear brakes, I heard dragging from the pads/rotor. Even with the wheel jacked I could rotate it effortlessly but there was still dragging. How do I adjust this? Is this the booster adjustment?
6. Should I empty all the fluid out of all the lines, bench bleed the new MC, then bleed each caliper one by one RR FL RL FR?

Thanks!

mark@silbernage

#3 makes me think that the booster is leaking air - and speeding the idle by allowing more into the intake.

It's wise to fix the things you know aren't right first (just like dealing with codes) before spending time and money trying to find other things. Often, when you fix the known problem others disappear as well - and save you a lot of grief.

Anyone else find the 'stomp on brake to raise idle' a bit suspicious?

Mark

10psiLsEf2

mines doing the same thing sinking pedal and when i hit brakes idle comes up!

i dont wana jump at the master cylinder just yet!


IM IN FOR THE RESULTS

sebTeggy

Okay honda tech, I'll look around my booster. I can disconnect the MC from the boosted without fluid going anywhere correct? I'll look around and check my tolerances. Also any tips on how to check for thisstuff?

Is the booster just supposed to keep a vacuum? There is no fluid inside right? Between the master cylinder and firewall, I have no idea what goes on in there lol

TheRealTegger

The rising-idle does sound like a leaky booster. There's a seal and filter at the pushrod that prevents air from entering. It can wear or get damaged. Engine running, get down in the driver's footwell and push the pedal hard with your HAND. Do you hear hissing from under the dash? If so, then the booster is leaking. No cure other than replacement, as far as I know.

It just holds vacuum. The reason you have a giant cake-pan between the firewall and the MC is because that's how big the rubber diaphragm needs to be in order to multiply the engine's vacuum effort so as to make the pedal easier to push.

As for your spongy pedal, that's normally due to any of these things:
1) seized moving-parts at/in the caliper
2) air in the lines
3) hoses expanding with pressure
4) aftermarket pads
5) rust on the caliper/pad parts
6) aftermarket MC seals too soft
It takes skill and experience to do brakes properly; there's more involved than just swapping parts.

I have a page on replacing the Master Cylinder, if you'd like to look through that:
http://www.tegger.com/hondafaq/maste...ace/index.html
This is a 2nd Gen Integra, of course.

By the way, DO NOT drain the lines of fluid!!!!!! You will cause yourself tons of extra work by introducing enormous amounts of air into the system.

TinterJeff

I had just replaced my master cylinder also, had same problem when I replaced it, fixed my problem but.

sebTeggy

Read the service manual, and this is what it said:

BRAKE BOOSTER INSPECTION

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 master cylinder, 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 vary, the booster or the 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 vary while depressed for 30 seconds, the vacuum booster is OK. If the pedal rises, the booster is faulty
2. With the engine stopped, depress the brake pedal several times using normal pressure. When the pedal is first depressed, it should be low. On consecutive applications, the pedal height should gradually rise. If the pedal position 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 a vacuum available. If no vacuum is available, the check valve is not working correctly. Replace the check valve and retest.

END TEST



I'm going to go outside and try this right now lol. Hope this helps anyone