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Discussion Starter #1
I installed 4-whl discs on a friends '66 FJ-45 a month ago.He has put about 75 to a 100 miles on it since, with no problems until now.
He was running down I-5 Sat. and hit the brakes, and the rear disc calipers locked up solid on him. <IMG SRC="smilies/eek.gif" border="0">
He was doing 75 or so,and skidded to a stop with smoke pouring out the rear brakes. NOT GOOD <IMG SRC="smilies/frown.gif" border="0">
Some background:
Here's the setup I installed
Toy mini knuckle-out front discs
TSM kit rear
Wilwood prop. valve(on rears)
'82 4-whl disc Supra 15/16" Master
'85 Toy mini booster
Wardens booster adapter and pushrod ext.
SSBC braided SS rear lines
Step 1
I thought the pushrod might be too long,so I shortened it up.
Took a test drive,and after about 30 hard stops,I was able to make the rears seize up again.They locked up tight on the rotors and would not release until I bled off pressure at the bleeder valve on one cal.Both rear calipers released then.
Step 2
I thought I might have gotten a bad or incorrect residual valve in the rear section of the master, so I replaced the valve with one that I had punched out (no residual pressure in the lines now)
Took it out today and the bitch locked up after about 30 stops again <IMG SRC="smilies/crybaby2.gif" border="0">
Step 3
I ordered a new (reman)master cyl. today and will try it tomorrow.

Can anybody think of anything I might have overlooked????
Just the rears are locking up
Prop. valve is adjusted correctly.
The brakes work great until the F-up,good pedal feel etc.

They seem to want to seize up on a "Panic stop"
When they seize,I still have a normal,firm pedal.
Could I have incorrectly adjusted the pushrod???
I adjusted it by "Feel" I reached up under the dash and jiggled it to mahe sure it was not engaging the piston.
Is there a better way? <IMG SRC="smilies/confused.gif" border="0"> <IMG SRC="smilies/confused.gif" border="0">

Thanks for the help.
Bill

[ 08-14-2001: Message edited by: Kaiser Bill ]
 

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Hi there Bill. Hope you guys had fun at Rimrock. We had fun fishing.
I want to say proportioning valve, but do you have a line lock on there at all> That is what it is doing.Where the calipers new with the kit or reman? Prop valves arent a one way valve anyway. So is the rotor the right one for the caliper, could the piston in the caliper be overextending itself out the bore, cocking and jamming until the pressure is released?It has to be something either locking the single rear line or a problem that both calipers share alike.Anyway enough guessing good luck I hope I was some help... <IMG SRC="smilies/smile.gif" border="0"> <IMG SRC="smilies/smile.gif" border="0">
 

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Discussion Starter #3
Hi Shawn <IMG SRC="smilies/biggrin.gif" border="0">
Rimrock was good.One roll over,two snapped drivelines,one flat,lots of dents,and a few almost-engine fires.Just a normal day wheelin!!!

I don't have a linelock installed.
the calipers are Re-mans but I'm pretty sure they are good.
the rotor is the correct one for the kit.
It's off a '91 1/2 ton chev.
I've been trying to get a hold of Skip at TSM, but they're on vacation.

Those are all good things to check out.
Thanks! <IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0">
 

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If the pushrod or the booster rod are too tight fluid pressure will build up in the lines and cause the calipers to seize. The master cylinder has to return fully to relieve this pressure. The fact that the rears are the only ones that lock might indicate that you aren't quite balanced (front to rear) yet. Do you also have the stock rear prop valve in line? I needed both after trying with just a Wilwood adjustable valve, the rears still locked up first. No residual valves are needed on disks unless the master cylinder is below the calipers, as in some street rods and race applications.

HTH,
Mike
 

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Discussion Starter #5
SpaceGhost,
Are you saying that since my Front/Rear Bias is off,thats why the rears are locking first?
I should say "seizing" I guess.
I can get all 4 whls to skid on pavement,but the rears do lock first on gravel or dirt.

I'll try backing off on the pushrod somemore,but I already have an airgap with the pedal released,should'nt this be enough? <IMG SRC="smilies/confused.gif" border="0">
 

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Originally posted by Kaiser Bill:
<STRONG>SpaceGhost,
Are you saying that since my Front/Rear Bias is off,thats why the rears are locking first?
I should say "seizing" I guess.
I can get all 4 whls to skid on pavement,but the rears do lock first on gravel or dirt.

I'll try backing off on the pushrod somemore,but I already have an airgap with the pedal released,should'nt this be enough? <IMG SRC="smilies/confused.gif" border="0"></STRONG>
First off I understood your original post to say that you had removed the residual valve. Some masters have this in the outlet and others have a bushing (fitting) that contains the residual valve and it also reduces the line size to 10mm x 1mm. The symptoms you are describing are exactly that of a drum brake residual valve that is still in the circuit. I would first off make sure that this is removed! Not doubting you, just worthy of note.

Based on that, what I was hoping to convey was that the rear are siezing "first" as a result of the front/rear bias or lack of enough proportioning. I'm only guessing that if you could continue to drive the fronts would be locking up shortly thereafter. Might be able to confirm this with the front jacked up to see if the fronts are dragging. The bias is not the cause of the seizing, just the reason the backs are most obvious.

There is an adjustable rod that is part of the booster that may be too tight. Assuming you have backed the pedal pushrod out until there is play or daylight you need to seperate the booster and master and back that one off also. A clue will be if the master starts to seperate when you back the bolts off like it under compression. Maybe you could drive it until the backs seize and then loosen the master bolts and see if they free up? Then adjust the rod in until there is some play.

As far as the backs seizing first, I had to install a stock prop valve and an adjustable one to get the bias balanced. The test is best done on loose gravel or downhill where you can watch that the rears don't lock up first. On a dry street at 30 mph with 35" tires it is difficult to be certain what's happening.

I had read all kinds of posts about going to rear and 4 wheel disks before I started on mine. Since I had manual, single circuit drums all around (68) I did not have a stock prop valve and most of the posts were about converting a disk front Cruiser to 4 wheel disks. These all had the stock prop valve and I "now" assume that everyone just added the adjustable valve. I also have seen and read of people that leave the residual valve in and don't report any trouble with it. Seems that different combinations give different results under different types of use.

Hope this set you free!
Mike
 

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Discussion Starter #7
SpaceGhost,
Thanks for the reply, that is some good info and was well thought out.I didn't think about the other adjustment on the inner pushrod.

I think I found the problem.BAD WILWOOD PROP VALVE <IMG SRC="smilies/eek.gif" border="0">
I decided to see if I could isolate the pressure buildup,so I went out on a test drive and got the rears to seize up again.

Instead of releasing the pressure at the rear calipers,this time I tried at the master.
No pressure and the rears didn't unlock.That meant the master was working right.
Next I tried at the outlet side of the prop. valve and, presto they released.
Thats the only prop valve on the rig,being a '66, it was like yours and didn't come with another stock one.
I called Skip at TSM and he told me that he has seen 4 or 5 of these Wilwood valves go bad in the past.
Wilwood won't admit to a problem but I guess they don't want to be subject to any liability.
I'll get a new one in a few days and hopefully it will solve the problem.
Thanks for the help. <IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/blender.gif" border="0">
 
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