I have a 89 crx and did a rear disk brake conversion. When I drove it with my stock brake booster and master cylinder it worked fine but the pedal was mushy. So i put in an integra brake booster and master cylinder. I bled the brakes and took it out for a test drive. Everything was great; pedal was firm. As I was coming back the pedal got alot firmer and I noticed that it felt like my car was alot heavier. Needless to say, the front brake we locked on. I got home with red hot disks and smoke. I have no idea what caused this cause if the brake booster shaft needed to be adjusted, wouldn't that lock up all 4 disks? Any help would be much appreciated!

 

i dont know if id would cause a problem but did u change to a 4040 proportioning valve???

 

yes i did that.

 

more info: the brake booster is from a 4 door 93 integra. the master cylinder is from a coupe. I had to change the master cylinder out cause the rear line had a different sized thread for the brake line. I did notice that when putting the coupe MC on I had to use pressure to bolt it down when the 4 door MC just slid on the shaft with out any problem.

 

M/C should just slide on with no pressure. Pull M/C and rod in Booster. Compare with stock one. it sounds like the one you have is longer causing M/C to be applied partially (depending on length) at all times. With the 40/40 valve it is applying to all brakes. Check it out and update.

 

yea thats what I was thinking. I am going to go to the junk yard and get that integra brake line so that I can use the original MC that came on that brake booster. is it possible to change out the rod?

 

Yeah it is. Just remove M/C and pull rod out of booster.

 

Is the rod connected to the brake pedal? AKA does the rod go all the way through the booster?

 

ok update. got in my car and the brakes weren't locked up anymore. It drove just like yesterday. went good for 15 minutes then the pedal got firmer and firmer as the brakes got more and more locked up. Here's my solution. Put the stock booster and mc back on... and sell the car haha

 

Oh and i went back to the junkyard and looked at the integra that i pulled the mc and booster off of and its' a abs integra... i'm almost positive that that is the problem.

 

Nope.
It makes no difference if you use an ABS or non-ABS booster/MC.

 

did you install the check valve properly?

check your booster if its working properly.

http://www.norcalcrx.org/tyson/pics/braketest.jpg

 

Why is the rear (of M/C) brake line threads bigger than the front? Is it because it came off a 4 door integra?

 

The check valve is working fine. I put the stock one back on. I'm done with messing with it. Idk why i tried to fix something that wasn't broken...

 

why dont you stay with your stock booster and install a 91 Crx SI master cylinder

 

No. That line is bigger just because you used it from that year Integra.

I used a 1" 1998 ITR MC and Booster (up for sale if anyone cares).
It was from an ABS car, but the thread were the same as the Civic.
Only difference was that one of the lines came off the other side of the MC so it required some easy, yet careful, bending of the hard line.

 

Thats what I didn't

 

I like that idea alot. the 91 is bigger right?