89PhoneixREX

Hello All,

Been lurking in these forums for years but until now never had a reason to post. Just want to say up front, LOTS of good info here and solid answers, so thanks for all the help so far.

We just purchased our 4th REX (89 Si) in the last 10 years, all have been great cars and this one is no exception, however I have been chasing a problem for about 2 weeks and think I have it narrowed down but want some opinions before I embark on what is a pain in the @$$ operation.

REX's symptoms:

Hot Brakes after short (About 20 minutes) drive.
Mild to moderate humming (Most noticeable when slowing down)
Hard pedal to go with hot brakes
Front left brake is the afflicted brake

Fixes already done:

New Calipers
New Rotors
New Pads
Bled brakes MULTIPLE times.
Checked the booster using home method.

The humming leads me to believe it is a bad front wheel bearing, however details on the net are sketchy at best as to if this can cause hot brakes and hard pedal. My opinion is that heat from the bad bearing is boiling the brake fluid on the front left causing the caliper to expand and drag brakes (Causing more heat and more boiling till eventually I get hard pedal and I'm sure if I kept driving after that I would get brake locked).

BUT, before I tear this knuckle off I wanted to get some opinions about other options, cause honestly I hate pulling wheel bearings, they suck on this car.

What do you guys think?

JamesS

Does you wheel get hot as well?

My brother's S2000 had bad wheel bearings - had no brake issues, but I noticed his wheels would get hot to the touch.

If you know the wheel bearings haven't been replaced on your car, it wouldn't hurt to do so because of its age. I'd do the suspension bushings while at it as well.

89PhoneixREX

By the time I get hard pedal the rims are so hot they are too hot to touch.

Also, above 70mph on the interstate starts vibration that is unmanageable.

I'm almost 100% at this point that its that damn bearing.

CRX-Kid11

tires chopped? could be chopped causing the humming noise also, plus if they are wearing faster then the balence would go out faster as well, as far as brakes when u did new calipers did you service the slides? can the pads move freely in caliper brackets, ive seen slides so dirty and corroded that pads would not move at all and had to use a hammer to remove, do the wheel bearings have any movement? if u could drive vehicle on a lift using a stethoscope place on each steering knuckle youd would be able to tell quickly what bearing is causing noise

89PhoneixREX

Well, the pads are tight in there, that never occurred to me, The slide bolts are brand new (on the side that's heating up). But yeah it took some work to push the pads in (I double checked part numbers to be sure). I think I know what your getting at. So lets assume they are tight in there, heat will only make them tighter, and as such expand, jamming the pad in its slide grooves correct? And its a vicious cycle from there, more heat=more expansion = more rubbing = more heat. And when it gets high enough boiled brake fluid will pop the caliper applying even more pressure.

Right?

Define chopped, never heard that term before (I'm old).

In addition I jacked the car tonight and attempted to wiggle the tire looking for bearing play... No movement as far as I could tell, this slide solution sounds like it may be the culprit.

OneBadTurboCRV

I am old too and I can assure you the saying "chopped" tires has been around as long as I can remember. It refers to the tread of the tires being cut up... if you run your hand over it it will not be smooth, but rather raised edges and smooth edges. If your brakes were hanging up you would surely have a severly blued rotor. Just look at the hub- is it blued? The wheel bearing can be bad but have no play in it. It can also be changed with moderately common hand tools, a press is preferred.

Spug

I would go ahead and change the brake hose on that corner as well. However unlikely, the hose could be collapsed and hold pressure even after taking pressure off the pedal.

Might be an excuse to get SS lines for all four corners?


When we say "old".........how old are we talking? Internet old, or OLD? I'm kind of old as well.

89PhoneixREX

Old like >35

And I've never heard the term chopped nor seen it on a tire. But I get the concept and no they aren't chopped. I might grab some new lines here today on the way back from work.

Spug

Meh, I'm only 30, lol. I've never had my tread chopped up, but I've had it wear oddly uneven so it looked like /l/l/l/l/l

OneBadTurboCRV

Since we are all sharing, I am >60... My son used to be on here a lot but now I just do it because I am bored... anyways...

"Spug" what you are describing sounds like "chopping"... (AKA "cupping")



^^^ Generic picture but should help with visualization...

Spug

Yup, that's definitely what it looks like

89PhoneixREX

So my very observant son pointed something out. He mention the "cool" color that the old rotor was... I wasn't paying attention when I swapped them I was rightly pissed by the time I was to replacing rotors.

The color? A very nice shade of blue.

So I know its not a stuck caliper, or a wheel bearing that did this, it must be something in the pressure system for the brakes. I'm gonna roll with an earlier suggestion of flex lines and if that doesn't solve it then were going to the brake proportion valve.

Suggestions?

OneBadTurboCRV

I would go in that order - but be aware I have seen the hardlines themselves be a culprit. If you must - start taking things off while working your way to the master cylinder. Check flow by lightly pressing on the brake pedal. If you see one line flows greater than the other keep going until you find the problem and replace everything downstream. While this is time consuming it (to me) is the most effective.

89PhoneixREX

So the flex line is off and honestly it doesn't seem to be the issue, it seems to me that the lines are getting good flow out to the caliper, but not enough suction back. I imagine this could only be one of two culprits... The proportion valve or the master cylinder push rod setting...

If its the proportion valve then its stuck in the outgoing position and for some reason is not allowing flow back to the master cylinder, if its the push rod then its not retracting far enough to provide the required suction to pull in the fluid out of the caliper... problem is, how to tell which one it is...

The only other thing I can think of is the banjo bolt on this line... I'm seriously considering cheating and just as a test using the passenger side line on the drivers side to see if that's the issue. (as a test only, not permanently). Something is not allowing reverse flow, but were running out of suspects...

89PhoneixREX

So I get the right side pulled a part and it dawns on me "How well did I check the right rotor?" so I went and grabbed it and sure enough the inside was a nice shade of blue. So no reason to pull the other line. I reassembled it all, and bled, and bled and bled and bled. Now the left is working great and the right seems to stick just a minor bit, I'm wondering if this whole mess is just a really bad break job done by the po and then handed off to me when he couldn't fix it...

Anyways I just zipped around my neighborhood and slammed on the brakes every so many feet seeing if I could get hard pedal out of it... no hard pedal and rims are cool when I get home, think I might have this one licked, though I'm still not sure how I did it...

89PhoneixREX

The saga continues... The fronts began dragging again the next day...

So while poking around checking parts I notice a slight amount of brake fluid near the booster, trace this back to the master cylinder and yell AH HA! Replace the master cylinder and...

NO LUCK

So here is where we are...

New Rotors
New Pads
System Bled more times than I can count
New Master Cylinder
New Front flex hoses
Push rod adjustment checked

So I'm gonna have to say that it is most likely the hardest part to find and the most expensive, the ******g Prop valve. I say this because after the master cylinder replacement I bled, and when I bled the front brakes they pushed fluid out as soon as I cracked the the bleeders (Not a ton, but wasn't a drip so I think they had pressure applied).

So my new question is, what Prop valves can be used? I'm pretty sure 3040 is stock, but those are discontinued and near impossible to find (180.00 to 300.00 new). So can I used a 2040, or a 4040 (I doubt this one highly)? Or does anyone have a sure fire way to clean and attempt rebuild of the old one?

Suggestions are welcome cause 300.00 for one valve is B******T.

And yes I want to do rear teg brake conversion BUT that one cant be snuck past the wife till AT LEAST next month, and I need this car back on the road asap.

So lets hear it, give her your best shot.

89PhoneixREX

So some testing tonight showed a couple things.

As far as the prop valve goes it seems good. I hooked a bleed kit up to it and sure enough fluid will pass from one port to another both ways (Couldn't really test the rear port but those brakes are not experiencing issues).

With the bleeder (and pump gun) hooked to the brake side and the MC side hooked to the Prop valve it seemed that fluid passed easily through the valve, but would get to a point where no more would go in ( we didn't pump too hard just enough to get a bit of resistance), When pressure is released, the fluid flows back through the valve in to the pump gun as would be expected.

I'm at a loss. I can only look one direction now, and that is Push rod adjustment... It there any way to tell if this is bad without a special 300.00 dollar tool? (It seemed good, no contact when installing the MC as far as could be seen).

89PhoneixREX

I've had requests to keep this thread updated so here we go.

Problem (For those just joining us):

Front brakes drag after short period of operation, eventually leading to brake lock up. It seems the brakes are keeping pressure applied and friction from Pad/rotor contact is heating them causing expansion (which causes even more heat due to further caliper pressure) and then lock up/or smoking burning brakes. Car feels like its pulling another car behind it.

Tested/Replaced items:

Disks (R)
Pads (R)
Flex Lines (R)
Master Cylinder (R)
Prop Valve (T) Appears Working Properly
Brakes Bled 7 times now (No issues seen)

None of these items solved the issue. Then today we had some progress, using Sage Mechanics CRX brake write up I began by adjusting the pedal height, this appears to have GREATLY improved the situation though not completely solved it. It is my opinion at this time that brake height and push rod adjustment are the issue and as such I will be adjusting the push rod this afternoon and hopefully be throwing a SOLVED at this thread later today.

galbal

I've been there before.. My front brakes did the same. i've had to take off the calipers, push the pistons out, and clean the pistons side of rust. The side of the pistons were rusted so they couldnt go back to their places into the caliper.

After I've taken apart both sides and cleaned both pistons with sandpaper, everything was fine.

U might have the same problem I've had...