gearhead313

Originally posted on CB7tuner.com:

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">Just finished up a full 5 lug conversion, new pads, rotors, calipers, SS brake lines. Got it all done, went to bleed it, no problems, seemed to get all the air out... Well after it was finished, we had a crappy pedal. It didn't really pump up, but stayed mooshy the whole time. So, since it wasn't that great before the 5 lug swap, we concluded that the master cylinder was bad.

So tonight, just a little while ago we get a new 1" master cylinder installed, bench bleed, brake bleed... Same Fing thing, soft pedal. We bleed it a good while after, used almost a whole quart of fluid. The fluid is brand new at the calipers and i have good pressure.

I cannot for the life of me figure out why we can't get a good pedal. This is a 92 ex car, so we already had discs in the back, so no proportioning valve should have been needed. It is an abs car though. Does something need done with the abs? it seems like it passes it right up when we bleed it with no problems.

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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">I've bench blead the MC, then installed it and blead it with the car off first. it didn't do anything, so i did it once i believe with the car running. no difference.

I have no idea how you bleed the abs, from what i understand you need a factory honda tool to bleed it were you can activate the abs manually. It doesn't appear to be abs, but if anyone knows how to shadetree bleed it, then im all up for that.</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">We worked on it a little more tonight. Exchanged the MC for a new one and it got worse.

I read through some of my factory service manuals laying around and you do need a special honda tool to bleed the abs. It plugs in under the pass. seat and simulates an abs stop. while you run the tool, your supposed to have some one holding the brakes on. I was able to run solenoids and hte pump and actually got some frothy fluid out of it. But its still a crappy pedal.

I dont know what else there is to do. I've done everything, i've bleed it 80 times... there has to be something im missing.
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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">What sucks is that the new MC never bled enough to get to where the old one was... that really aggrivates me.


Everything is tight. I've checked all the connections a couple times over now. I can try at least tightening everything one more time. I'd have to clean everything off and mash the pedal to see if i get any fluid. If there really is any, its extremely minuet.. which i dont think will cause this problem.

We have driven it, burning the pads in etc. Two times we went out was normal driving. I want to say the rotor temps were around 180f, 110r. The next time I had my buddy really work them and he came in with 450f and like 150r.. so it would seem that the rears arn't getting the pressure. I've heard its supposed to be within 20% of eachother? I'm not positive on that.

So maybe its the rears.. which maybe its the abs modulator that has the prop valve in it? Thats a big job to change... especially since everything else abs related seems to be working. Ideas?</TD></TR></TABLE>

So to date, we have new calipers, brackets, slide pins, HONDA oem master cylinder, pads, stainless lines, rotors, abs modulator.

It seems that the front brakes are working. On a test drive, you can lock the fronts up at will, but the backs seem to be just along for the ride.

One interesting factor is that one rear caliper piston seems to be returning instead of staying out once you pump the brakes up. It will move out, then suck back in... I did this with the caliper removed even. When at rest, you can grab the caliper and move it back and forth on the slide pins about 1/2".. way to much. The pedal is low now b/c its taking up that slack.

If this is all correct and im moving it the right direction, I need to know why the calipers arn't staying out in the back. I've changed the rear calipers to new ones and exchanged them twice now. What might be next is reverse pressure bleeding the entire system as well as adjusting the e-brake cable out all the way up at the lever.

If anyone has heard or can shed some light on this, I would be so greatly appriciative. Thanks so much for reading!

F23Coupe

Did you check for leaks in the brake lines (not in the SS lines but in the main hard lines) to the rear brakes? You can probably get a pressure gauge and see if the pressure is low right before it gets to the caliper. I don't have pressure specs on your car but that's one way to know that you have a leak somewhere. You can also measure the pressure in the front calipers too, to make sure that your front brakes are getting sufficient pressure even if you finaly got the pedal to where you want it.

gearhead313

I've never actually measured the pressure. Say that the pressure to the back is low, then what does that mean in your opinion?

I looked all over for leaks and didn't find any. There might have been one or two spots that still had wetness, but it didnt look like a leak. I've gone around and tightend all my connections at least once and didn't notice anything at the hard lines

F23Coupe

If your hard lines are ok, I'd check the SS lines and then the caliper itself. The SS lines are hard to tell if there's a leak since the braided lines do a good job protecting the teflon tubing beneath it. But it sure sounds like a leak. When you jab the brakes, the piston will push out but when there's a leak somewhere, the caliper is receding because the pressure can't keep the piston from pushing against the brake fluid. Maybe there's a leak by the master cylinder. But you want to take some brake pressure readings to get a feel for any differential pressures between the left and right of the rear calipers and front to rear calipers. It's a good starting point. It's sort of like finding out electrical faults like shorts and ground failures in an electrical circuit. It's best to diagnose by using readings rather than replace parts and hope that you have all the good parts installed.

I forgot to ask you this, but when you bleed the rear brakes, did the fluid pump out pretty consistently and normal? There's a small chance that there's a clog or build-up before the rear brakes.

gearhead313

The brake pressure gauge is on order, so we'll see if that reveals anything.


I'll go over the car again, but it doesn't seem to be loosing fluid. Everything is brand new, so if something is leaking I will not be happy!!


I also ordered the junction under the master cylinder, where a normal non-abs car has its prop vavle. The pressures in the rear were not quite as strong as the fronts when we bled them, but thats not necessarily that odd. Another reason I would like to try reverse pressure bleeding to try to pump whatever might be in there out.

JimBlake

Did you ever figure out the rear piston sucking back in? I'd concentrate on that.

I don't know '92 calipers very well, but look for something like an anti-rattle spring that's installed wrong. On my '01 Saab (just for example) the anti-rattle spring can be positioned to the wrong side of the sliding part of the caliper and it'll do exactly what you're describing.

Similar to the spring above, maybe it's something screwed up with the internal auto-adjust mechanism for the handbrake. That stuff might be capable of pulling the piston back in. ??

Whatever the reason, it's certainly not normal for the piston to suck back in. I think that's the reason for your problem, rather than air in the lines.

gearhead313

I agree with you in that the caliper is the problem. I dont know saabs that well, but will take a guess that they are fairly similar to these calipers. They need screwed back in when you change pads, not just compressed. The ebrake lever is on a screw type mechanism that screws out the piston to engage the brakes, then returns when you release it.

This is the closest picture i can find of it:




Maybe later I can take a video of what it does.


Either way, I still wonder if the ebrake needs adjusted... but yet the pressures still seem to be low.

I did get the brake pressure gauge in today, so i'll report on what I get.

JimBlake

The Saab spring is different, & there's no handbrake on it. I'm guessing your rear caliper doesn't even have an external wire spring over near the pads?

Is that your caliper, all clean & shiny & brand new? Seems strange that it would be screwed up?

The handbrake auto-adjuster is completely inside the caliper, kinda like a ratcheting jackscrew. When it operates, it doesn't actually spin the piston, only spins some internal parts that you can't see.
Try this...
Don't spin the pistons all the way in to make room for pads. Only spin them in just enough so the new pads fit without dragging. That way the auto-adjuster isn't miles away from its proper position.

gearhead313

No sorry, that is just similar to what the setup is like. When i get the car back in, i'll snap a pic of it. They are brand new calipers.

I think i remember trying to screw them back out, but couldn't get them in the right spot (it was between notches), so it was either in too far, or too tight to were you couldn't get the caliper on.

We are going to mess with it tomorrow (sat.) and see what we come up with.

JimBlake

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gearhead313 &raquo;</TD></TR><TR><TD CLASS="quote">I think i remember trying to screw them back out, but couldn't get them in the right spot (it was between notches), so it was either in too far, or too tight to were you couldn't get the caliper on.</TD></TR></TABLE>That's typical. So at least it wasn't turned in way too far.
I'm running out of ideas...

gearhead313

ya, so am i!


It has to be something that was overlooked, but I dont know what else to check. I'm to the point where I'd like new eyes to look at it, maybe the dealer if they are willing to work with me.