Honda CRX Si Brake Woes

darthmonkeyIT

darthmonkeyIT

New member
Hello! Have a very annoying brake problem and I am running out of diagnostic or repair ideas to alleviate it. Looking for some fresh outlooks on the problem.

Last June I ran a test day at Gingerman Raceway which went great. Car felt awesome…until around 1 PM when the brakes went spongy and it felt like I had cooked a caliper. I pulled into pits, parked the car, and began working on diagnosing the problem. The left front brake was smoking from burn off which I had never seen before so my mind went immediately to overheating.

I pulled off the left and right front wheels and allowed the brakes to cool for a bit before bleeding fluid out of them. I got some air out of both front lines and called it good to see how the system felt. Got back out there and the brakes ended up still feeling crummy. Brought it back in and did some more work to no avail.

So fast forward to today. The brake pedal has long travel (practically to the floor), feels very soft (no modulation), and the braking force feels greatly reduced. Generally feels like I am on a roller skate when I brake and I can’t get the front end to pitch down on a car weighted 60% front with maxed out rebound control on the front shocks and minimum rebound on the rear shocks. This makes it very difficult to drive in race trim because I have no idea how my brakes are going to act.

So far here is what I have tried:

  • Master Cylinder (4 of them so far)
  • New Carbotech XP10 brake pads (Temporarily alleviated the issue when at new size. Quickly went back to spongy in one session)
  • Bleeding, bleeding, bleeding (5 liter cans or more of ATE super blue/2000 trying to get the air out along with bleeding rear T joint, brake bias, master cylinder, and using a pressure bleeder)
  • New stainless steel brake hoses
  • New SSBC Brake Bias
  • Removed and tested Brake Booster (brake booster checked fine)
  • Adjusted brake booster pedal travel
The symptoms generally didn’t get better and sometimes got worse as a result. I just dismantled the entire system to replace the brake hoses, brake bias, and rear T along with a new master cylinder. The pedal still feels very soft. I have yet to be able to test how the brake force feels. I need new brake pads on the front at this point.

Theories I am considering at this point:

  • Air trapped somewhere in the system that is not moving
  • Air is being drawn back into the system without a fluid leak (doesn’t seem to get worse as I drive so don’t believe this is the case)
  • Brake booster needs replaced (none of the symptoms seem to be brake booster though)
  • New front rotors of a different brand (Currently use Brembo blanks. Considering Centric Cryo’s or buy Brembo’s and having them cryoed. Mostly for possible brake force issue. Concerned I annealed my current rotors based on burning up a set of brake pads very fast at Mid O last September)
  • Firewall flex (do not see anything flex while having someone else operate the brakes but I have considered it)
  • Replace Calipers (calipers are Autozone replacements from December 2010 and have not exhibited any problems)
  • Change fluid type (Brakes seemed to work fine with it prior to the issue so not convinced this is an issue)

Any ideas would be greatly appreciated. I am running out of ways to address the problem if it continues to be an issue short of pulling everything out (hard lines and all) and pitching it for new.

Thank you!
 
I would replace calipers if you still have problems after replacing booster. And absolutely change rotors to fresh ones. I've cooker rotors on my truck where even new pads didn't work. No need to go to all that fancy treatments though. The car is light enough that the problem is somewhere else
 
1stGenBoy said:
Drum or discs on the rear? The early cars came with drums that some people still use.
Click to expand...

Rear discs.

Replacing the booster really fixed it? Hrm guess I should look into getting a replacement booster. What a pain to get that thing in and out though. @.@

Just doesn't seem like a booster failure mode. Always thought the booster would either not work and the pedal is very stiff or work so well that the brakes will just lock up if ya touch the pedal. Wasn't aware there could be a in between failure mode.
 
definately replace the booster and rotors, don't try to diagnose any more until you have done so and have seen if it worked. car parts don't always play by the rules.

Also check to see that the rear caliper pistons are turned out to minimize the gap between the pads and rotor when sitting. just turn them counterclockwise in 180 degree increments and test fit, stop and go back one when you cant get them over the rotor. lots of sloppy brakes start here.
 
Ditto on my DA. Brakes got worse and worse over a year, threw parts at it. Finally after replacing the booster AND getting it adjusted properly, did my brakes finally work well again. If you were at the 2010 ARRC, you remember my battle, which resulted in a DNS.
 
First thing I thought of, when reading your list was "the booster". They are funny beasts. And even if it's NOT the booster, at this point in it's life, it's a liability, and should be replaced.

One way to tell if it's the calipers or drum cylinders (if equipped) is to take the lines off and screw on 'caps". Eliminate them from the equation. IF things get solid, attach them one at a time, and you'll find your issue.

If it's still soft, then unscrew the lines from the master cyl, and block it's openings. If it gets solid, you have issues in the lines, prop valve, or dist blocks.

Since you've done so much sleuthing, I might just start straight away by plugging the MC lines to eliminate the whole system downstream to prove it's in the MC booster system.

If it's still soft, then it's in the master, or the booster.
 
lateapex911 said:
First thing I thought of, when reading your list was "the booster". They are funny beasts. And even if it's NOT the booster, at this point in it's life, it's a liability, and should be replaced.

One way to tell if it's the calipers or drum cylinders (if equipped) is to take the lines off and screw on 'caps". Eliminate them from the equation. IF things get solid, attach them one at a time, and you'll find your issue.

If it's still soft, then unscrew the lines from the master cyl, and block it's openings. If it gets solid, you have issues in the lines, prop valve, or dist blocks.

Since you've done so much sleuthing, I might just start straight away by plugging the MC lines to eliminate the whole system downstream to prove it's in the MC booster system.

If it's still soft, then it's in the master, or the booster.
Click to expand...

Great idea. Didn't think to plug off parts of the system to narrow down the problem.

As I thought about it more yesterday the booster is making more sense. The pedal comes up nice and feels great with the car off. Couple pumps and I have a nice solid pedal. After I turn the car on though the pedal feels gets soft and even with pumping I can't get it to feel "good".

I will also check the rear brake calipers. The pistons threads on the rear are still in place so the system should be adjusting the piston but that doesn't mean it isn't a little loose in the back.

I have done a lot of research into this trying to find people with similar issues. Found a lot of people with similar problems but rarely saw anyone recommending replacing the booster. I feel fairly confident replacing the booster with the feedback I got here. Thanks a lot guys. :023:
 
Parts question: Where should I look to buy a brake booster?

I looked them up on Rock Auto and they have AC Delco rebuilds for around $80. Rebuilds can be dicey though especially if you don't know where it came from. I am a member of HPD but I have not looked yet to see how much one from HPD would be.

Any recommendations?

Also looking to try some new front rotors. Anyone have experience with Centric Cryos? They have them on Tire Rack and was interested in swapping to them from the un-cryo'ed Brembo's I am running now.
 
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Make sure it's available on HPD. It's the first choice for many looking at NEW quality OEM.

Cyros are definitely heavier, will hold more heat in and in general wear slower.
 
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. ;)
 
Matt93SE said:
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. ;)
Click to expand...

All four bleeder screws are still pointing up. :023:

I have removed the calipers to check the sliders. Everything seems to be in working order with the calipers.
 
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.
 
Tom Blaney said:
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.
Click to expand...

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. :rolleyes: 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.
 
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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
 
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