76 Scout TSM disc brake issues

B

bvscout

New member
I've got a 76 scoutii/345v8/Holley 2210/torqueflite/4x4, that I'm haveing some brake issues with that I've run out of ideas on. This is the third Scout I've owned (69 800a,78 scoutii). I've done brakes on several cars before, including replacing about 6-7 mc's and several calipers and drum brake setups, so this isn't my first time.
I have a 6-year old TSM rear disk brake conversion (78 el dorado parking brake calipers), that had been working great since I installed it. I did notice that the right parking brake never really engaged properly, but other than that the brakes always felt solid and stops were nice and straight. I had also replace the mc and booster with new/rebuilt 'stock' units from my local kragen at that time (and steel braded brake lines)
about 2-months ago, I started noticing my brake warning light flashing on, whenever I hit the brakes. The warning light would flash more and more often over a period of time, but never stayed on. I read in some of the four wheel disc conversion forums on-line, that an 'out of adjustment' rear parking brake caliper might cause this, so I tried to ratchet out the right rear caliper with the parking brake lever, but it seemed to have no effect.
I ordered and installed a new replacement rear caliper, and adjusted up the parking brake without a problem. I bled the brakes, but the brake warning light came on and stayed on no matter what I did. I then noticed that I was leaking brake fluid from the 'rubber' plug on the original pv2 combination valve. After reading on line, that I might want to convert to the pv4 (disc/disc) combination valve, I decided to order a new brass one from a hot-rod supply, and use that instead. I also installed a new(not rebuilt) brakebest disc/disc mc I picked up from my local o'reilly(kragen) (mc250010) which was supposed to be for 74 corvette w/power disc brakes. I did bench bleed the new mc before installing it, and then bled the entire system. But, the brake warning light still came on, when I hit the brakes, and the peddle felt low and squishy. I tried bleeding the brakes two more times, and ran about 2 quarts of new fluid through the system with no bubbles, but the brake warning light still comes on when I hit the brakes, and the pedal still feels low. If I pump the brakes 2-3 times the warning light will go out, and the pedal firms up , but as soon as I let it sit for a few seconds, the warning light comes on again as soon as I hit the brakes,until I pump the pedal.
I've checked the whole system again, to make sure there aren't any leaks anywhere, and I'm just out of ideas.
Btw - when I bled the brakes, even though I have speed bleeders on all four calipers, I had someone else pump the brakes, so I could watch for bubbles in the clear tube I had attached the the bleed nipples.

Any ideas?

Regards - bryan
 
Well lots of guys have problems with Scout II brakes because there is a little button you need to pull (or is it push?) on the proportioning valve right under the mc. Once you do that and bleed the brakes I think will end your problem. Hth!
 
eagle-Mark said:
well lots of guys have problems with Scout II brakes because there is a little button you need to pull (or is it push?) on the proportioning valve right under the mc. Once you do that and bleed the brakes I think will end your problem. Hth!
Click to expand...

Thanks for the response.
The pv4 combination valve doesn't have the little button on the front like the original pv2 did, other than that, the two valves look identical. The difference between the pv2 and the pv4, is that the pv2 is specifically for a disc/drum setup, and the pv4 is for disc/disc. My understanding is that the button on the front of the pv2, is part of the front brake delay valve to keep the front disc brakes from locking, before the rear brakes.

Thanks anyway.
 
Darn! I tried... Now that I reread your post I just don't know? And I am a fairly experianced mechanic, professionslly trained in 77, but just a gear head since 79... I'm stumped, if you are bleeding properly I am stumped!
 
eagle-Mark said:
darn! I tried... Now that I reread your post I just don't know? And I am a fairly experianced mechanic, professionslly trained in 77, but just a gear head since 79... I'm stumped, if you are bleeding properly I am stumped!
Click to expand...

Thanks for trying...

But like I stated above, this TSM conversion worked great for about 5-years without any issues. At that time, I had all new calipers & disks (front and back) as well as a new/replacement mc and booster. The only thing that was original was the combination valve, which has now been replace with the pv4

is it possible, I need a residual pressure valve for the rear el dorado calipers?
Everything I've read seems to indicate, I now have the optimal set-up for the TSM conversion.
Btw - I've only put about 5-6k miles on my Scout in the last 5-years, since it is used primarily for skiing, camping, and fishing trips, and the occasional run to home depot;-).
 
Wellllllllllllllll, I don't know, but from what your saying it was fine. Now you got a brake light on and spongee pedal? I just don't know? Hope someone else will chime in with an idea. Only thing I could think of at this point is your master cylinder went bad.
 
eagle-Mark said:
wellllllllllllllll, I don't know, but from what your saying it was fine. Now you got a brake light on and spongee pedal? I just don't know? Hope someone else will chime in with an idea. Only thing I could think of at this point is your master cylinder went bad.
Click to expand...

My first thoughts were either air in the line or a leak some where, but I've gone through all that. I'm leaning toward a bad mc, but I have never had a 'brand new' mc that was bad before. I'm just trying to figure out if there is something I May have missed, before I remove the new mc, and exchange it for another, and start the whole bleeding process again. I'd really hate to do that and end up with the same situation.:nonod: I have seen this situation in the past when bleeding a brake system with an 'old' original mc. During bleeding, the piston seals get chewed up on the 'corrosion lip' that build up in the mc bores after a few years of use, and the bleeding process pushes the pistons past the lip. But that would not be the case with a brand new mc.
 
I thought I'd post an update on my brake issues.
After running out of ideas, I concluded the issue must be the new brake mc I installed, so I returned the mc to my local kragen, and they exchanged it for another new mc (under warranty). While I had the mc off I also rechecked the length of the booster push rod, by checking it's depth inseted into the new mc.
I bench bled the new mc on the Scout (much easier than trying to do it on the workbench, and much more effective), I hooked it up, and the brakes seemed to be better.
I then went through the the normal bleeding procedure starting at the rear rt side, and finishing on the left front.
Guess what??? - it still has the same problem:icon_crying:
like before, there are no detectable leaks, and there was no bubbles in the brake fluid.
The brake warning light still comes on as soon as I touch the brakes, but will go out as soon as I pump them, and the pedal still doesn't seem as firm as it should be. I'm just about ready to throw in the towel and just disconnect the brake warning light switch.

Any other suggestions?
Do I need to add a 'check valve' between the pv4 and the rear brakes?
 
I never did follow up with the solution to this problem, so I thought I better 'close the loop'.
Here's what the problem was:

the automatic brake adjuster on one one of the rear 'el dorado' calipers was not working, and so the piston travel in that caliper had to travel a much longer distance than it should, which made the brake pedal feel spongy. The auto adjuster is supposed to ratchet the caliper piston out every time you engage the parking brake via the parking brake cable, and the lever arm on the caliper.

After I replace the 'bad' rear caliper, everything started working fine:) oh and the parking brake holds the Scout on a hill now!
 
Thanks for the update. I did this very same conversion on a '90 Bronco years back. Never really got it to work fully. Since scrapped it and sold the 8.8 rear-end to a Jeep guy about 7 years ago.

Currently I'm running a d-44 under my 73 Scout with the tera brake kit. Which is a take off of the Ford explorer rear disk brakes
 
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