Brakes from hell

[XXL]

I've been battling "bad brakes" on the Wallet Eater for years. The various issues I've had may not actually be related, but it feels like there's a fundamental problem somewhere. I don't drive the truck much (less than 1500 per year on average), but have recently been driving it more.

Some background-- the truck is a '69 that I converted to 73+ disc/71-72 drums on the rear (axle swap). Over the years, I have replaced EVERYTHING. Let me repeat that... E V E R Y T H I N G . A few years ago, I moved to Kugel underdash brake setup, and went with a Corvette (C4, IIRC) remote reservoir master, 7" dual diaphragm booster, and billet remote reservoir. What I recently learned is that, apparently, during that swap, the shop doing the work "disappeared" my stock 73+ prop valve... because it sure ain't there now .

The original problem was that I couldn't keep pedal pressure without a few pumps, but 4 or more bleedings-- bench, 2-man, and pressure bleeding never solved the issue. At the advise of a shop that is now (not necessarily because of this issue) on my feces list, we swapped out the 7/8" Corvette remote reservoir setup for a 73+ 1 1/8" local reservoir unit. That's been on the truck for about 9 months, and I've come to love with mediocre brakes.

However, recently, while rockrln was doing some work on the truck, the right front caliper decided to freeze up. It froze in a "touching" state, and so it didn't stop the truck from rolling, but at speed, because of the friction, caused a pretty bad wobble. Note: this came out of nowhere, and I secretly believe Kevin used the truck in a local demolition derby one weekend, thus causing the issue *i keed, i keed*. He replaced the caliper and all is back to mediocrity. Kevin described it as "fluid, but no pressure" coming out of the calipers when he bled them after the swap. That's a pretty good descriptor for the performance of the mediocre brakes. I'd have to stand every ounce of my weight to get the back brakes to lock up, and even then, I don't think they would. But it may well be that the back brakes are the only ones slowing me down. That would explain the mediocre performance and possibly the locked up caliper that really just stuck in position due to non-use, and then got hot from the friction, where it locked up for real.

So, I've got fluid (and no air) coming out of the front, so the pedal is pushing the mc, which is pushing fluid to the calipers. And multiple mc's haven't changed this fact... why am I not getting pressure?

Discuss.

[ebfabman]

restriction in line somewhere???

[ebfabman]

Oh, sorry I should read the complete post before a reply........


Ok well the lady in the rear to the left of the woman in blue seem to be looking at the breast of the woman seated to her left. While no one seems to notice, I think the guy in the brown suit, 2nd from right, knows something. I'll study the picture more and get back...........

[lolife99]

Do you have an adjustable porportioning valve and/or residual check valves in the lines?

[ebfabman]

"..we swapped out the 7/8" Corvette remote reservoir setup for a 73+ 1 1/8" local reservoir unit..." Do you mean these to be the m/c bore sizes? Do still have to "pump them up" even after going to the 1 1/8 m/c?

[XXL]

Originally Posted by ebfabman

"..we swapped out the 7/8" Corvette remote reservoir setup for a 73+ 1 1/8" local reservoir unit..." Do you mean these to be the m/c bore sizes? Do still have to "pump them up" even after going to the 1 1/8 m/c?

Yes, mc bore. No, to still pumping them up. I was kind or rambling about the various problems it has had over the years. The current mc (1 1/8) does not need pumping up, but there is, IMO, more pedal movement than it should have before any braking begines (I'm guessing here... maybe a couple of inches of play).

[ebfabman]

This..""fluid, but no pressure" situation.....how does the peddle feel when the bleeder valves are open....does it go to the floor with no resistance, or does it feel like maybe the bleeder valves are only slightly open requiring "pressure " to get to the floor when bleeding?

[westofb]

When you say everything, does this mean lines and rubber hoses to the calipers/ brakes as well? I have experienced problems in the past where the rubber lines to the calipers looked good from the outside (no cracks or chaffing), but the inner lining had swollen, causing restrictions to the calipers (low pressure) and causing on caliper to stay slightly under pressure causing it to drag on the rotor as you descibed above.

[Rokcrln]

Yes lines are new as well. One thought I had is what if the push rod is to long and pushing the master a bit when no brakes are being applied. I know this will cause a problem but I don't remember what problem
But as stated the rears are stopping the vehicle and not the front. The front has fluid flow but I feel no real psi at all. Oh and I came in second in the derby!

Kevin
LFD Inc.

[ebfabman]

Have the metal lines for the fronts been replaced also??? Any way to measure the pressure at the m/c, then at the calipers?

[XXL]

Originally Posted by westofb

When you say everything, does this mean...

Everything, as in if you were to install brakes on your house. First you have nothing. Then you have everything. Note... this transformation of parts has been over time (but not much mileage).

Originally Posted by ebfabman

Any way to measure the pressure at the m/c, then at the calipers?

That's what I was thinking... some kind of thread-on barometer that would take the place of the caliper to measure incoming pressure. It's just a gut feeling, but I don't think there's some dramatic pressure drop from mc to booster... since that would require a line blockage of some sort, which... if you think about it, wouldn't affect pressure so much as volume (when you pinch the garden hose, you get more pressure, less volume). Hmmm... maybe the front lines are too big??? What size should they be for disc?

[smashingchuck]

Two questions:

Have you verified that the bell crank is actually pushing the master cylinder piston all the way through travel, and what prop valve are you running now?

I'm assuming that the master cylinder has been bench bled.

[cparman]

The truck has to have a prop valve. What size steel lines are on the truck? There should be 3/16 lines to the front, and 1/4 to the rear. I am buyin the 1 1/8 master cylinder, the fact that you say that you need to pump the pedal a few times to get a decent pedal, would make me point to the need of a prop valve, or a 10 LB residual vale for the rear brakes. Drum brakes need a bit of residual pressure to make them respond the pedal application. 10lb residual vales are usually used when the master cylinder is located LOWER that the brake calipers/wheel cylinders. NOW the stupid questions:

rear brakes are adjusted properly?
does the truck have a posi? Posi's will make you think the brakes are dragging, when they really are not.
MY $.02 is the need of a prop vale, and make sure the steel line size is correct

[XXL]

Originally Posted by cparman

The truck has to have a prop valve. What size steel lines are on the truck? There should be 3/16 lines to the front, and 1/4 to the rear. I am buyin the 1 1/8 master cylinder, the fact that you say that you need to pump the pedal a few times to get a decent pedal, would make me point to the need of a prop valve, or a 10 LB residual vale for the rear brakes. Drum brakes need a bit of residual pressure to make them respond the pedal application. 10lb residual vales are usually used when the master cylinder is located LOWER that the brake calipers/wheel cylinders.

A prop valve doesn't add... it only subtracts. And so, without it, I currently have full pressure on the front and full pressure on the back. And the backs don't lock up. So, while I agree, I should work a prop valve back into the setup, I don't believe that's the problem. Also, while it may not be clear in my previous posts... I DO NOT have to pump the brakes to get pressure. That's what I used to have to do before changing the mc.

Re line size, the front lines are the oldest of the new parts, and so I don't remember... but I really think they're 3/16" to the tee on the left frame rail. I'll measure them tonight to be sure.

I wouldn't think there is a need for residual valve. The booster is at stock height and it gets solid vacuum from 'stock cammed' motor.

[cparman]

So you say you have a full pedal, and also have good pressure from the bleeders when trying to bleed the brakes??
The pedal is hard to push, as in no power assist?
If I remember correctly your truck is an L6
Do you have 17" of vacuum at idle with the engine running?

[ebfabman]

Just a thought...is it even possible to have the line reversed at some point in the system?

[Rokcrln]

Originally Posted by cparman

So you say you have a full pedal, and also have good pressure from the bleeders when trying to bleed the brakes??
The pedal is hard to push, as in no power assist?
If I remember correctly your truck is an L6
Do you have 17" of vacuum at idle with the engine running?

Yes he has an L6 with 21" at idle to the booster.

Originally Posted by ebfabman

Just a thought...is it even possible to have the line reversed at some point in the system?

This is possible but I did not check when it was here. But now that I think about it when I replaced the front caliper I think I had to fill the front bowl. But then again I was on my back under the dash looking through a mirror so not sure

Kevin
LFD Inc.

[smashingchuck]

Originally Posted by ebfabman

Just a thought...is it even possible to have the line reversed at some point in the system?

Originally Posted by Rokcrln

This is possible but I did not check when it was here. But now that I think about it when I replaced the front caliper I think I had to fill the front bowl. But then again I was on my back under the dash looking through a mirror so not sure

err... reversed? How do you reverse a brake line?

[XXL]

I haven't had a chance to measure because I'm using the Wallet Eater as my dd right now while the normal dd is getting a giant snail installed.