Hard peddle, little stopping power

ronmc1954

ronmc1954

Member
On my 74 Scout II 345, d44s, front disk, rear drums: the problem is I seem to have little stopping power. It stops alright but I can't lock'm up, even on gravel. I put new shoes and brake springs and drums in the rear and manually adjusted for a slight drag. The front disks have not been touched but look good.
On gravel, I tried to lock them up and only the pass rear slid, a little, I can stand on the peddle so there is something there. On pavement I can stop but I can't lock them up.

The mc has never run low on fluid so air should not be an issue.

This prob seems to have occured after it has been sitting for a month getting a face lift.

The vboost apears to be working also, if I press the peddle the start the engine the peddle goes down and just the opposite when I shut it off.

Any ideas? I have read most of the posts here. It seems like something is sticking, wheel cylinder or proportioning valve?

Ron
 
My opinion without actually being there ron...

Ya gotta blockage in the wet side of the hydraulics. I see this all the time on rigs that have an "unknown" brake system and have been allowed to sit without the bakes being activated.

My suggestion, since you have done such a wonderful job in bringing the rig to life, is a complete brake job. Open all the plumbing connections and then check each run for liquid flow at each point. And...verify that the rear soft hoses are not "balloning" due to internal rot.

Pull apart both rear wheel cylinders and either rebuild if not corroded beyond limits, or replace.

You can carefully dismantle the junction/proportioning valve and clean out also and re-center the spool valve if it's "stuck". Or simply replace it with either a fresh oem valve, or shitcan it altogether and put adjustable valve in the rear brake circuit only. You will give up the "warning" light but who cares??? That's a nanny-state device anyway. We had hydraulic brakes for well over 50 years without the gummint telling us to check the brakes or put air in tires!
 
Hey michael; good info in your reply. Thanks for your coment on the restore. I know the rotors/pads and the shoes and drums are good. Not so sure about the wheel cylinders. But since my problem affects all four and I have a hard peddle I think I will start at the proportioning valve. I will have to bleed everything after that anyway. So my thought is, as you said a blockage in the wet side, I will confirm fluid flow when I bleed and hopefully then I can confirm that the calipers and wheel cylinders work.
Does that sound like a good way to proceed?
One other bit of info, I checked the 75's propotioning valve and the little pin or rod that I have read about will not move (by hand) but will on the 74, is that an indication of a stuck proportioning valve?
Anyway if it cools off a little more I will pull it in the shop and work on it tonight, about 95f right now, makes me sweat just looking outside:icon_smile:

ron
 
ronmc1954 said:
hey michael; good info in your reply. Thanks for your coment on the restore. I know the rotors/pads and the shoes and drums are good. Not so sure about the wheel cylinders. But since my problem affects all four and I have a hard peddle I think I will start at the proportioning valve. I will have to bleed everything after that anyway. So my thought is, as you said a blockage in the wet side, I will confirm fluid flow when I bleed and hopefully then I can confirm that the calipers and wheel cylinders work.
Does that sound like a good way to proceed?
One other bit of info, I checked the 75's propotioning valve and the little pin or rod that I have read about will not move (by hand) but will on the 74, is that an indication of a stuck proportioning valve?
Anyway if it cools off a little more I will pull it in the shop and work on it tonight, about 95f right now, makes me sweat just looking outside:icon_smile:

ron
Click to expand...

Yes, check each component on the wet side for flow! Circuit by circuit!

The "bleeder button" you describe should move when a force of 25>38psi is applied to "compress" it. It should be held in the "depressed" position throughout the entire bleeding operation and then released to it's "normal" state.

Not all Scout II platforms use the same setup though, with some brake sets, the proportioning effect is achieved through the use of different size front caliper pistons vs. Rear brake wheel cylinder diameters. I think you have a service manual set for sii so ya need to review the various brake system scenarios described in the brake section.
 
Ok here is what I found:
with the wife depressing the brake pedal the bleeder button moved out then back in, so the proportioning valve is not stuck (anymore)
I opened each bleeder valve, one at a time, and had fluid flow at each which looked fairly clean. I did not have enough fluid to flush but I will do that later.
I re-adjusted the rear brakes, took about 6 clicks each.
Then tested, 3 wheels locked up the pass front did not. Also one rear wheel cylinder has a different size bleeder on it so one has been changed.
It does work alot better than it did and I really did not do anything. I does look like a brake overhaul is in order.
Thanks for the guidance michael

ron
 
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