Ok, here's the problem. I swaped my drum brakes off my 91 Civic Si HB for CRX Si disk brakes. I also put on a brake booster and master cylinder from a 90-93 Integra. In the process of doing all this I had to drain the brake fluid and then refill the new master cylinder. I have bleed the brakes SEVERAL times in the correct wheel order. But still; after about 200 miles, the brake peddle starts to get hard and will evenutally come to the point where it cannot be pushed down at all. When this happens, one of the brakes (just the front driver so far) is slightly applied making the car undrivable. If i go through and bleed the brakes again the problem is solved for about another 200 miles, then it starts right back up agian. I have made sure that all the fittings are tight and the bleed bolts are securly tightened.

Do you guys have any idea what could be causing this and/or what I should check on? I need to get this fixed!

Thank you

 

Well if it was air in the brakes it would be soft not hard. Me thinks you might have a bad master cylinder. But possibly have a bad felx line to the wheel that seems to have the brakes grabbing, they can swell internally holding presure, or you may have inadvertantly smashed or kinked a line when you replacved the master cylinder I would take a second close look at that. If you find nothing when the brakes have gotten hard crack the bleader screw on the brake in question. if fluid shoots out of it you have a restriction in the line. with the car sitting there it should have no pressure on it.

 

sounds to me the master cylinder its going bye bye

 

You replaced your brake booster. It needs to be adjusted. Its not releasing air. When it doesn't release the air its keeping pressure on the master cyclinder. The fix is.....Where the brake booster goes onto your brake pedal under the dash there is a u-bracket with a threaded bolt running thru it, turn the bolt so that it is going futher into the u bracket or you may have to use the bolt on the brake booster which is about a inch futher away. Its not the master cylinder its the booster just needing adj I had the same problem a few months ago. Also to make a quick check about air being trapped in the brake booster. Under the hood you know the check valve that is on the brake booster VIA a hose. Its a white thing with a E and a arrow pointing towards the engine. Unhook it on the side closest to the brake booster you should hear it releasing air. If that is so presto thats tha man adj the brake booster with the adjusting rod....


[Modified by zCivic, 9:50 AM 6/21/2002]

 

Yeah, thanks guys, now that I think about it, when putting the booster in, I did move that bracket to make it fit. So am I to understand that I need to adjust it; screwing the bracket in towards the booster? Because it seems that if I were to do that, it would just pull my brake peddle down...and if it goes down too far, it gets pulled away from the brake light switch.

So just to clarify, which way do I need to adjust the brakcet (or the bolt)?

 

no out away from the booster. If you turn it into the booster it will hold more pressure. Turn it so the adjusting rod pulls away from the master cyclinder....

 

Yep... It's the master cylinder... had a friend with the same problem, but he ended up replacing his whole brake system and it kept doing the same thing... then he replaced the master cylinder and the problem went away... 1000 bucks later almost.. he went through 2 sets of Green Stuff pads in the process also.. in only 2 days!

 

The brake booster is totally different from the master cylinder. The master cylinder bolts to the brake booster... Telling him its the master cylinder is not complectly or partly correct....not trying to be a *** but if the master cylinder was bad it would leak and be empty.... not full and locking up the brakes...... I ran in to the same situation and they all said it was the master replaced it that wasn't the problem, had to replace booster and ran in to his same problem.....

 

Not necessarily... I had the exact problem as his, and once I swapped the MC it was fine.

 

AHHHHHHHHH it locked up on me again on the way home from work!!!

I think it may be the booster not releasing pressure becuase when it locked up, if I pushed down the brake pedal all the way to the floor, it would release and be okay again till the next stop light. This is a pain in the *** and it needs to be fixed!!!

I'll try adjusting the booster first becuase that is pretty easy and doesn't involve draining brake fluid. If that doesn't fix the problem I'll go grab another master cylinder and probably brake booster too, becuase I can get them cheap. Hopfully that will fix it.

When adjusting the booster....how would I know when it is adjusted correctly?? Is it just trial and error or is there some method of checking?

Thanks for the help!


[Modified by 91civ, 5:43 AM 6/22/2002]

 

Pretty much trial and error but thats how I work there may be a better way but I dunno it yet. When you drive there locking up and you have to let it sit for a while and then they loosen up right? Because it sounds just like my problem. When they lock up again just unhook the check valve and see if it relieves the pressure.

 

ok... i think i fixed this. surprisingly it appears to be just a bad caliper. I'm still watching it, but so far it appears to be fixed. YaY!

Thanks for all the help guys