Honda CRX Si Brake Woes

[Matt93SE]

REALLY stupid Q.. did you ever remove the calipers from the car?
If so, did you reinstall them on the correct side?
If you installed them backwards, the bleeders are now at the bottom, and you have a huge air bubble at the top of the caliper that will never go away. spongy brakes till the cows come home, but everything else looks right and works.

If that's your problem, you don't have to say that was it. just tell everyone rebuilding the calipers or a new booster solved the problem.

[darthmonkeyIT]

REALLY stupid Q.. did you ever remove the calipers from the car?
If so, did you reinstall them on the correct side?
If you installed them backwards, the bleeders are now at the bottom, and you have a huge air bubble at the top of the caliper that will never go away. spongy brakes till the cows come home, but everything else looks right and works.

If that's your problem, you don't have to say that was it. just tell everyone rebuilding the calipers or a new booster solved the problem.

All four bleeder screws are still pointing up.

I have removed the calipers to check the sliders. Everything seems to be in working order with the calipers.

[Tom Blaney]

I suggest a couple possible solutions:
First: Make sure that if you have a one way valve going to the brake booster from the intake manifold that it is working properly. A soft pedal can sometime be caused by the booster pressure being sucked back out by the intake vacuum.
Second: If it was a rear disc upgrade from rear drums than make sure the proportioning valve is the correct year match
Third: If you don't have brake cooling ducts (either trick or a simple hose) make them, try and direct as much air to the center of the rotor
Forth: You might be boiling the brake fluid (which creates steam albeit minute) but it is still air. Make sure you use Dot 4 or higher and don't use the bottle again once you open it. Once the seal is broken, the fluid will absorb moisture(some will contradict this but it is true).
Fifth: Replace brake system parts with the very best you can buy, there are cheap rotors available from parts stores that are poor quality, and if they get hot they warp, which will kick back the pads so each time you have to use the brakes you have to pump the pedal.
Sixth: Bleed the brakes every weekend, making sure that you don't have any air seep back in the system from the bleeder catch bottle etc.

Those are my suggestions, hope it helps.

[darthmonkeyIT]

I suggest a couple possible solutions:
First: Make sure that if you have a one way valve going to the brake booster from the intake manifold that it is working properly. A soft pedal can sometime be caused by the booster pressure being sucked back out by the intake vacuum.
Second: If it was a rear disc upgrade from rear drums than make sure the proportioning valve is the correct year match
Third: If you don't have brake cooling ducts (either trick or a simple hose) make them, try and direct as much air to the center of the rotor
Forth: You might be boiling the brake fluid (which creates steam albeit minute) but it is still air. Make sure you use Dot 4 or higher and don't use the bottle again once you open it. Once the seal is broken, the fluid will absorb moisture(some will contradict this but it is true).
Fifth: Replace brake system parts with the very best you can buy, there are cheap rotors available from parts stores that are poor quality, and if they get hot they warp, which will kick back the pads so each time you have to use the brakes you have to pump the pedal.
Sixth: Bleed the brakes every weekend, making sure that you don't have any air seep back in the system from the bleeder catch bottle etc.

Those are my suggestions, hope it helps.

Ya I have some heat issues up front. Need to get some more ducting there. Currently have air deflectors on the pillars but really need something more. It is difficult to find the space around the wheel though. Still working on that. Wheel lock can rub the side wall which is only a concern in pits but with a 2.5" tube I lose even more than just wheel lock. Routing down and around concerns me since if I have a "excursion" I would probably lose all the ducting to the grass. The symptoms though stick around even after a fresh bleed and with the car cool. So at that point heat hasn't done anything.

I was concerned with the brake hoses since they were probably 4+ years old stainless steel braided lines and have heard generally to change those every 2 years. Was afraid the Teflon lining may have fatigued allowing for expansion in the Teflon line under pressure. I have since changed those.

I bleed brake fluid generally at least once a day on a weekend if not after each session (especially in late summer). The stuff I am using (ATE Super Blue DOT 4) is rated to 540 degrees F. Seems to hold up well based on running a one hour enduro last year at Mid O in July. Also read up a lot on ATE and have heard it absorbs water at a better rate than some of the others I have been debating about changing to Motul 600 based on posts on this forum.

The car is a stock Si so the brakes were originally disc all four corners. I do not believe the stock prop valve is still in place though. The car was a built into a race car off the Honda production line and had a Tilton piston brake bias to the rear when I got it. Not positive if the prop valve stays in the car when you have changed to something like a adjustable brake bias. Forgive my ignorance on this, just not really 100% on if its still there or not. I have since removed the Tilton piston bias (Like to trap air bubbles at the base of the piston when almost fully disengaged and was a pain to bleed) and changed to a screw type SSBC.

Thanks for the advice Tom! Really good points to look for.

Edit: Oh and HPD is out of boosters. Will need to go to the rebuild market for one.

[Xian]

Something else that I don't think has been mentioned is front wheel bearing and hubs... as they start to go, they can give you a long pedal. I doubt this is the case since you'd likely have had a catastrophic failure by now. Something else to potentially look at are the sliders themselves. They can wear and introduce slop into the system and exacerbate poor feel.

Christian

[Bob Roth]

If you are getting a hard pedal with engine off, I think everything is fine on the hydraulic side. If there is travel, I wonder about caliper flex.
Sometimes you can psych yourself out by feeling mushyness while not driving with the engine on when in fact to put that much force when rolling you would be locked up. Another thing, if the pads are not wearing square, which is common in a 2nd gen crx, I wonder how much distortion there is when the pad is not sitting square on the cylinder.

Also, have you tried another pad, Hawk blues for example.

[Bob Roth]

A couple more thoughts. If you replaced the Master Cyl, did you get a '91 cylinder. If your car was built in 88 - 89, it had drums and a smaller master cyl. This is my recollection (so confirm it) but I think the '88 drum cylinder is marked 1 3/4 where the '91 disc master is marked 1 7/8. If you ise a drum master on a car with rear disks, you will get a long pedal.

Also, be aware that a CRX does not have very big rotors and you can't just abuse the brakes. If you compare your pads and brakes (ps, does your car have '91 fronts or '88 fronts because the '88 fron pads are smaller than the '91) to '92 series civics and other cars, Honda really put potatoe chips up there for front rotors. Bottom line is there is not a lot of mass on a CRX rotor to take heat. If you are really standing on your brakes lap after lap, I would not rule out that you are getting your rotors really hot and boiling fluid or melting pads, especially if you are seeing smoking calipers after a session.

[sackdz]

Can anyone lend any tips on pushrod adjustment without the Honda tool? I think I can get close with vernier calipers, but its such a pain in the ass to get to the booster I only want to do it once.

Thx
Ed

[darthmonkeyIT]

Can anyone lend any tips on pushrod adjustment without the Honda tool? I think I can get close with vernier calipers, but its such a pain in the ass to get to the booster I only want to do it once.

Thx
Ed

The stock nut on the booster is a real pain. It is actually a 12 pt nut which requires cutting a slot in a 14 mm wrench to be able to get around the nut. This makes the 14 mm box end very weak in relative terms. Further still the 17 mm square behind it is half size so a full 17 mm crescent won’t fit and still allow another wrench.

If you put a flashlight on it as well you may see some yellow torque stripe paint on the nut-square. That paint on mine had seeped into the thread interface and locked them closed pretty good. When we took the booster out, locked it down in a vice, and put a torque wrench on it for kicks it took roughly 100 ft-lbs to break it free. We were never going to get that much force on it inside the car with a chopped open box end.

If you really want to try though from inside the car buy a 14 mm box end and chop a slot in it to fit around the rod and over the nut. For the skinny wrench I bought a 17 mm bicycle cone wrench – 1/8” thick steel wrench. Caution it does hurt applying pressure to that skinny wrench if you really have to push on it.

For us it was ultimately easier to remove the booster and get the nut-square broken free. When you remove the booster you can take off the 14 mm 12 pt nut and replace it with a 17 mm standard hex nut. This makes adjusting in the car a lot easier because now you can use a standard 17 mm open end and the 17 mm cone wrench. It also gets rid of paint and years of grime locking them together.

The pedal slop measurement – make sure the slop you feel has resistance. The pedal will slop a bit prior to engaging the booster rod which is not part of the booster gap measurement. Make sure the slop you are measuring is the booster slop and not the pedal slop.