Honda CRX Si Brake Woes

[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.

[darthmonkeyIT]

@ Xian - Just did the front wheel bearings. Didn't know the current state so I changed them out before the start of this season.

@ Bob Roth I was thinking about trying some new pads. I have a new set of Carbotech XP10's to start the season. I have been pleased with them so far and don't want to change something before I know if have it fixed. A new feeling might be misconstrued as something still wrong. I might try something new after I have the problem fixed.

Its a 90' CRX Si so it came with vented front rotors and four wheel disc. I haven't seen much uneven wear. For the most part its just lack of force and a soft pedal feel. The pedal firms up at the bottom but the travel has no feeling. With that said I am looking to order some Centric Cryo's off Tire Rack (http://www.tirerack.com/brakes/brake...0&autoModClar=). Currently use Brembo blanks because they were easy to find and $$$. Was going to buy two of these Centric's and see how they feel.

[Matt93SE]

When you're bleeding your brakes, how are you doing it? I've found with Nissans you almost have to have two people to get the air out of the system.

[darthmonkeyIT]

When you're bleeding your brakes, how are you doing it? I've found with Nissans you almost have to have two people to get the air out of the system.

I use two people. One person at a caliper the other in the car. We pump the pedal three time to build pressure in the system then the person at the caliper cracks the line. We have a modified mason jar with a exhaust port and a inlet tube port for bleeding brakes that we put over the bleeder screw.

Once the major outrush of fluid is done, we seal back up the bleeder screw and then release the pedal. Rinse repeat.

We have used a pressure bleeder on the system before but the pressure bleeder seems to have difficulty moving air out of the system. Especially at the master.

[chuck baader]

You are throwing money away...see post # 1,4,7,8,9,11.Chuck

[darthmonkeyIT]

You are throwing money away...see post # 1,4,7,8,9,11.Chuck

Haven't thrown any more away since i started this post.

Currently determining where to order the booster from. HPD was out so I am looking at a rebuild. Pretty much A-1 Cardone from all the auto guys or a third party HPD recommended I speak with.

[rice_classic]

Currently determining where to order the booster from. HPD was out so I am looking at a rebuild. Pretty much A-1 Cardone from all the auto guys or a third party HPD recommended I speak with.

If I were you and I'm not, here's how I would go about it by addressing the whole damn system:

1: Address Booster. Either replace bad vacuum line or replace booster and in that process it might be worth bench bleeding the MC.

2: STOP disposing of your brake fluid when bleeding (unless it's OLD and USED). If you're bleeding and bleeding and bleeding you're essentially throwing away unused, good fluid. Just catch it in a clean container as it leaves the caliper and put it back in the MC.

2a: Buy the Stainless Steel speed bleeders and follow their instructions closely. They should be the 10x1.25 size. They work great. I replaced my MC, 4 bleeder valves (Speed bleeders) and 1 caliper. With the speed bleeders (and reusing the new fluid after it left the caliper), I was able to bleed each corner, by myself, 12 times with half a can of ATE. Rock solid pedal. PS: Most people complain about Speed Bleeders for 2 reason: 1: they introduce air and 2: they strip. On 1: they don't introduce air if you read the instructions because it is stated that after a lot of use they need to be removed, threads cleaned, thread sealer reapplied and then baked int he oven for 10 minutes and reinstalled. 2: The don't need to be tightened by the incredible hulk. Also the SS ones are a bit stronger in case your crew person has a habit of over tightening. Also, bleed your brakes with new pads installed! That helps me considerably as the pedal will feel firmer at the top of its stroke when the system if free of air because the piston doesn't have to move as far so you'll have a better feel of when you've completed your task.

3: Rotors and Pads. I've been running the cheap China rotors and the are awful however my co-racer has run the expensive Cryo stuff with no improved value. They lasted no differently and performed no differently then a good Centric Premium or a good Brembo Blank. I wouldn't waste the $$ on the cryo as a 9.5" rotor, cryo or not, isn't going to have a long lifespan. You can do your own cost benefit analysis here.

4: Brake ducts. Not only is is good for braking but it will also lengthen the life of the hub and bearing. The trick is routing and of all the things I've tried in the past this works best for me: Instead of just cooling the inside blade of the rotor it blows air at the center of things including the hub.



5: It is possible that you boiled fluid. If you're something off the shelf you might want to consider a higher temp fluid like ATE Super Blue or Motul 600.

6: During race weekends I will flip my pads in the caliper (so the inside is now the outside pad). This evens out taper and increases the life of the pads as well. (won't help you in this initial soft pedal dilemma).


I still believe that it's your booster or vacuum to your booster. Good luck!

[darthmonkeyIT]

If I were you and I'm not, here's how I would go about it by addressing the whole damn system:

1: Address Booster. Either replace bad vacuum line or replace booster and in that process it might be worth bench bleeding the MC.

2: STOP disposing of your brake fluid when bleeding (unless it's OLD and USED). If you're bleeding and bleeding and bleeding you're essentially throwing away unused, good fluid. Just catch it in a clean container as it leaves the caliper and put it back in the MC.

2a: Buy the Stainless Steel speed bleeders and follow their instructions closely. They should be the 10x1.25 size. They work great. I replaced my MC, 4 bleeder valves (Speed bleeders) and 1 caliper. With the speed bleeders (and reusing the new fluid after it left the caliper), I was able to bleed each corner, by myself, 12 times with half a can of ATE. Rock solid pedal. PS: Most people complain about Speed Bleeders for 2 reason: 1: they introduce air and 2: they strip. On 1: they don't introduce air if you read the instructions because it is stated that after a lot of use they need to be removed, threads cleaned, thread sealer reapplied and then baked int he oven for 10 minutes and reinstalled. 2: The don't need to be tightened by the incredible hulk. Also the SS ones are a bit stronger in case your crew person has a habit of over tightening. Also, bleed your brakes with new pads installed! That helps me considerably as the pedal will feel firmer at the top of its stroke when the system if free of air because the piston doesn't have to move as far so you'll have a better feel of when you've completed your task.

3: Rotors and Pads. I've been running the cheap China rotors and the are awful however my co-racer has run the expensive Cryo stuff with no improved value. They lasted no differently and performed no differently then a good Centric Premium or a good Brembo Blank. I wouldn't waste the $$ on the cryo as a 9.5" rotor, cryo or not, isn't going to have a long lifespan. You can do your own cost benefit analysis here.

4: Brake ducts. Not only is is good for braking but it will also lengthen the life of the hub and bearing. The trick is routing and of all the things I've tried in the past this works best for me: Instead of just cooling the inside blade of the rotor it blows air at the center of things including the hub.



5: It is possible that you boiled fluid. If you're something off the shelf you might want to consider a higher temp fluid like ATE Super Blue or Motul 600.

6: During race weekends I will flip my pads in the caliper (so the inside is now the outside pad). This evens out taper and increases the life of the pads as well. (won't help you in this initial soft pedal dilemma).


I still believe that it's your booster or vacuum to your booster. Good luck!

Awesome info! Thank you! I have ordered a new booster and currently run ATE Super Blue/2000 fluid.

As rotors go thanks for the tip about the types. I had a feeling changing rotors types wasn't going to make much of a difference verse getting more cooling to the brakes.

The tip about bleeding with full pads is interesting. I had not thought about that.

I am also ordering some high temp brake duct along with some aluminum plate to build larger air deflectors. I am looking into how to route the ducting so it has some durability and just doesn't fall apart after 10 laps.

[pavis]

agree with majority. replace the booster. similar problems in my crx. problem now solved.

[USGUYS]

I don't think anyone mentioned rear wheel bearings. Just like the front, if they are loose they cause the rear brake pads to be kicked back too much. This causes a long or soft pedal too. It is the first thing we look at if the pedal gets long. Never had a booster failure.

[darthmonkeyIT]

I don't think anyone mentioned rear wheel bearings. Just like the front, if they are loose they cause the rear brake pads to be kicked back too much. This causes a long or soft pedal too. It is the first thing we look at if the pedal gets long. Never had a booster failure.

Would a rear wheel bearing still cause a soft pedal with the car stationary? I do not notice a difference between the pedal feel while driving verse the pedal feel up on jack stands in the pits.

[almracing]

Late to chime in here... definitely add cooling ducts. It is common for the calipers/pads to heat up quite a bit and especially when they are worn past 1/2 way. My experience is that when the pads are new I get a nice strong high pedal throughout a race. When they get less than 1/2 thickness, the pedal is longer and gets soft coming out of high braking areas.

[Tom Blaney]

I agree with what Anthony mentioned. We would usually have to change pads when they got down to half thickness, and the pedal would firm up. Sort of the cost of doing business I suspect.

If you need to get a set of brake ducts for the 88-91 CRX/Civic and Integra let me know I still have the template and can make them in a few days. If you want other car formats I just need to get a set of struts, calipers and rotors as a model and will be returned with the finished ducts.

[darthmonkeyIT]

Booster replaced and the system feels much better. Pressure prior to booster replacement was arund 900 psi at the front caliper on a single push. Pumped made it to 1400 but bled off slowly at around 50 psi a second until around 1100. New booster is 1200 to 1300 psi on a single press up to 1400 pumped and the pedal feels lots better.

Test day tonight at gingerman to see how the system is working.

Thanks everyone! I will post with test results tomorrow.

[darthmonkeyIT]

Well really trying night. I ended up mis judging the booster adjustment at the pedal and the brakes seized on me lap one. I thought there was enough pedal free-play but apprently I was wrong. My 1 to 5 mm five finger gauge gauge failed me.

At this point I know what I need to do to fix the booster adjustment. Disappointed in that I destroyed a set of brake pads as a result and now have to be concerned with how much damage the heat may have done to other things. Mainly concerned with the front wheel bearings. I replaced them this year but I know heat is the enemey there.

Based on the caliper discoloration the brakes got REALLY hot. With the brakes seized against the rotor it also just soaked into the rotor. Hind sight being 20-20 I should have just disconnected the booster line to get the car free and why I didn't think of this I don't know.

So overall very embarrassed in myself. I checked the system and still got it wrong. Learned some valuable brakes lessons though:

1. Drive the car for a longer duration after brake testing. A few stop and start test is not adequate. Few laps around the neighborhood in the future.

2. Use some old or junk pads when testing new brake work to avoid destroying still good pads.

3. Carry a adjustable crescent wrench in the car. I would have been able to pop off the booster line with it easily and been able to get under way again.

I will now be replacing the rotors with new and have the ones currently on the car turned to be used as back-ups. The wheel bearing is a unsettling feeling. The duration of the heat on was 1 minute or so of starting to seize with 5 minutes of locked up system. Following my return to the pit box I put cooling fans on the system. Was able to work on it 10 minutes later. I don't know if a single major heat cycle can destroy the bearing grease or not.

[Eagle7]

Been there, done that. Maybe not as tight as yours. Started to feel it at 1/2 lap at Mid-Ohio. Was able to make it back to pit lane using heavy throttle. Rolled fine when it cooled. Scratched head, then repeated next session. Finished the weekend without issue after just a pedal height adjustment.

[Xian]

Yep, did the same thing in my CRX... made it half a lap around Roebling Road (took the emergency road back to the paddock). This'll put some serious heat into the system but I highly doubt you heat soaked the bearings enough to cook anything. In fact, I'm betting that they weren't anywhere near as hot as the temps you see after 30 min on track. Think about it, tou mention that you could work on the system 10 min after parking the car. Think you could do the same just as quickly after a race?

Christian

[darthmonkeyIT]

Took the front system apart of the weekend. I did a lot less damage then I thought. The system did not get super hot. The brake pads are a little cooked and the rotors contact surface isn't to happy but overall not bad.

The right front caliper dust boot was iffy so replaced the piston seals on both front calipers. Ended up rubber banding a piece of siran wrap to the master cylinder from the advice of a friend to keep the fluid in. Worked like a charm. Only lost the fluid in the calipers. Bled the system through some after reassembly and it feels good again.

Ended up turning the booster piston two full turns to get to pedal slop. It was hard to tell early on since the clevis pin also had some slop in it which was consuming some of the pedal travel.

The only concern I have is that the pedal travel and stiffness feels good. the system works well as far as stopping power. But the pedal feels like I hit a hard stop at the base of the travel. the pedal travels right up until a abrupt stop that almost feels mechanical. I am wondering if my booster adjustment was to much but the pedal travel is not terrible. The pads on the car are practically new thickness though so once they wear in some more I will be able to tell more. Something I just have to watch.

[darthmonkeyIT]

Tested this past Tuesday at Gingerman. Brakes felt great compared to what they were end of last season. I could actually get the front end to pitch down and load up and I didn't feel like I was on roller skates at the end of straights. System has enough power not that I locked up the front end going into 1 which I haven't been able to do in a while. This was using the brake pads and rotors that I seized up with last week. I will be putting new rotors and pads on for this weekend.

Thanks everyone! Really appears to have been the booster.

Now I just need to find my balls again. Tuesday they were somewhere in turn 6-7 combination or turn 11; Grattan I have feeling they will be in turn 1, 3, or 8.