Brakes locking up

Matt,

Your brakes are dragging because the caliper pistons are not moving freely, therefore the calipers require rebuilding. The rubber seals between the pistons and their bores get old & hard, the pistons themselves will develop rings of dirt, gum etc on their outer surface, and the bores can collect "splooge" in their bottoms.

Your friend on the DTBB, George

How difficult do you think it would be for a complete novice like myself to apply a rebuild kit?

Matt, So many Pantera owners upgrade their brakes.....that means there are a lot of stock calipers out there. I bought a pair of fronts and rears off ebay for less than $100. I figured if I ever had a problem, I would have the parts to get me out of it.........I guess after looking at them they should be rebuilt before installing. I have seen rebuilt kits sell for $20. I am sure PI has them. You can do it!! If you can take them off...you have the skill to rebuild!!

Matt I have a pair of the original rear calipers that were used for emergency brakes on my car. I replaced them with a new E Brake system. I rebuilt them and as far as I know they work fine. If you are interested please email me at charlesbuthala@yahoo.com
P.S. what exactly is SPLOOGE?

quote:

Originally posted by Matt Bradley:
How difficult do you think it would be for a complete novice like myself to apply a rebuild kit?

Matt,

I don't know what your experience & mechanical aptitude are like, so its hard to answer that question.

I would rather err on the side of safety and tell you it would be best to do the job with the aid of an experienced friend OR let a pro do the work. The brakes are a very important system, something you don't want to fail while you're operating your car.

You have to be able to remove & re-install the caliper pistons without damaging them, and ignore any advice given to hone the bores. Also, only use brake fluid or brake parts cleaner, lint free rags, etc.

Your friend on the DTBB, George

quote:

Originally posted by cab:
P.S. what exactly is SPLOOGE?

Ha, ha, ha, ha......

It's the stuff Matt is going to find inside the bores of his 30 year old calipers!

It's the stuff that drips out of the end of a 2 cycle motorcycles exhaust system.

Splooge is stuff that doesn't belong wherever it's at; and its sticky, gummy, messy, almost impossible to remove. Its normally the byproduct of a lubricant. Oil or grease that has been beguiled by the dark side of the force.

Your freind on the DTBB, George

Splooge, not to be confused with spooge.

Jeff
6559

quote:

Originally posted by jeff6559:
Splooge, not to be confused with spooge.
Jeff 6559

It shouldn't be confused with STOOGE either!

I'll bet you weren't expecting a grammer lesson when you logged onto the PIBB today, where you?

George ..... lol......

Thanks for the responses. I guess I'm going to have to figure out if I want to tackle it myself, or pay someone to do it.

All brake calipers have been rebuilt now. Just been waiting for a sunny day for to see if the problem came back. It did.

I just got back from picking the Pantera up at a shop (installed my new oil pan and get the AC going again). When I went to pick it up, it was sitting out in the nice warm sun (this often itself would heat the brakes up and cause that braking problem). Sure enough, it didn't take long coming home to feel the brake engagement become higher and higher. And when coming to a stop light, depressing on the clutch all the way, you could feel the brakes calipers engaging, not letting it roll totally free. And this is with it, what, 75 degrees out? It's going to get worse when it really gets warm. Aaaarrgh!

Any guesses now?

quote:

Could my master cylinder be a problem, even after verifying it's correct length?

How did you 'verify' length?

I have been told the easiest way to do this is to unbolt the MC - leave the lines attached - so it can pull off the booster. If pushing it back to the booster finds resistance, that is you are pushing against the MC spring, then the rod is too long. It should allow the MC to seat in place without tension. Tension means the piston is already moving in the bore, and when things heat up, it may move even more - likely dragging the caliper pads, heating things up even more, dragging the pads more as the heat increases,etc.

Is this how you checked the MC pushrod length?

Larry

From what I understand this syndrome is caused by the master cylinder piston not returning all the way to the back of the master cylinder and is usually caused by the adjustable push rod between the booster and master length being too long. It usually has to be off quite a bit so that the piston covers the brake fluid intake/vent holes that feed down into the piston. With the holes covered and the brake fluid expands from heat the only place the fluid can expand is to the caliper pistons, moves them and cleverly applies the brakes. When everything cools of the brakes relax. Larry is correct in that you should be able to tell if the rod is too long by unbolting the master from the booster. If the rod is too short then there will be too much free play in the pedal before the brakes start.

Mike

wow, sounds almost exactly what i have been dealing with. it appears that the length of the push rod is quite critical.

being away from working on autos for 25+ years, i had long forgotten everything that i once knew about braking systems so i found the following website to be of great help (please forgive my transgression in looking at a honda website, i promise to do penance) specifically at the end of part 5 is a description of what may well be occuring to cause the brake lock-up. to aid in understanding, the article has very descriptive diagrams of what occurs in the master during a braking cycle.

hope it helps.

nazgul

This same thing was happening to someone a few years ago in Las Vegas. I suggested loosening the nuts that hold the master to the booster and slipping a couple of coins in between the back of the master and the booster then snug the nuts and drive it to see what happened. He did this and came back saying it was now working fine. I told him to shorten the push rod when he got home and as far as I know that solved his problem. It is a quick and easy way to check for overlength push rod.

I had the same problem after a long restoration. I was stumped for a while. It's more than likely being caused by your brake booster and the diaphram aging. Simply shorten the rod in the master cylinder and the problem will be resolved. I spoke with Dennis Quella about it and within 15 seconds of the discussion he told me it was common and shortening the MC rod (even shorter than the specified length), will address the problem. In my case he was correct. -No problems since. Use common sense when you do this and cautiously shake down your brake system. If you are uncomfortable with this, as others have suggested, hire it done.

K

It's been over a year since the pushrod length was checked, I'll reinvestigate this. How it was checked before was done by a fellow club member who knows much more about this stuff than I. He checked by using some putty, and said it looked fine. I'll report back once that has been checked. Thanks everyone.

quote:

Originally posted by www.PanteraPlace.com:
From what I understand this syndrome is caused by the master cylinder piston not returning all the way to the back of the master cylinder.

Mike

Mike that would be my gues as well. Had this happen to an airplane I was flying last year. Took a little to trouble shoot it as we have 4-master cyl (2 each side). We taxied out and everything seemed fine. As I rolled down the runway it seemed fine right up till rotation. Just as I rotated (at 110knots or 126mph) I felt the left wheel dragging. I knew it wasn't right. Flew around and did the maintenance test we needed to do then brought it back. Touch down seemed fine. as I turned off the runway, left wheel was really dragging. Came to a stop just off the runway at the maintenance area. Got out of the airplane and left brake was cherry red. We stood there with fire extinguisher. It ignighted after about 3 min. Spent the next 10 min putting out the fire each time it lit with a dry chemical extinguisher.

Turned out one of the master cyl was not returning 100%. It dragged a little but not enough to feel until we gained real speed. That was the key!!!! As the pad built head, drag increased which created more heat!!!! You didn't feel it in the taxi or even on the take off roll but as heat built up it became a cascading situation.

We have left master cyl and right master cyl. We have master cyl for pilot and co pilot. This situation was a master on the left side. I think the question would be is it all the brakes or just one? If it drags on more then one brake deffinantly the master cyl. If it is just one brake ten maybe the caliper.

Gary

What is the consensus on what the MC pushrod length should be?

I take it adjusting this won't result in having to bleed the brakes again?

Bleeding not again necessary.

Length is not a number, it is what is determined to be proper for your car. As posted earlier, loosen MC from booster, pull a bit away, then push back to booster. Rod should not cause any resistance to get the MC to seat on the booster. If you have to depress the MC spring, rod is too long. Adjust as necessary until correct.

Larry

Ok, I'm stumped. I got the MC off, but I don't see inside there where I'm supposed to adjust anything. I guess I thought I'd see a place in there to use a screwdriver or something, but I don't. I pushed on the green thing, it didn't move.

Then see the black lining around the green thing--see where it doesn't continue, where there is a gap in completing the circle? Problem?

A closer look...

You are looking in the wrong direction. The pushrod is behind the adapter plate that is attached to the booster. The pushrod presses on an adapter piece in the center of the adapter plate.


What you want to do is slowly move the master up to the front of the adapter plate and see if the piece inside the adapter contacts the back of the master piston (the green part) before the flange of the master contacts the adapter plate. You do this by feel because you cannot see the parts making contact. If the master piston moves you can feel the resistance. When you take the adapter plate off to adjust the push rod be careful not to damage the rubber donut seal on the booster.

You can also measure the two distances to see if there is a gap.

Mike

The black part you can see is the retaining clip that stops the green bit from coming out.
It looks just fine.

Ok, I feel a little stpuid here, but everyone kept talking about the MC pushrod, but it's really the booster's it seems. I'll hit it again after work.

Good to know the retaining clip is normal too.

Thanks!

Well my pushrod setting turned out rather well. I was scrambling to do all of this to make the a big drive with the Ferrari folks yesterday. I screwed the acorn nut on the pushrod back as far as it would go, which was only 1.5-2 turns. I could still see some thread left to turn against, but I think it's just old and grimy, and probably needs a good shot of WD-40 to loosen it up. The brakes themselves worked great on the whole trip, and they got a good hard workout yesterday, with no problems--UNTIL I went to leave the restaurant. From sitting in the hot sun, without any air to breeze past them, they were clamping down a little. The good part was that 5mins into the drive back home, it went away, as the air cooled them off, and had no problems the rest of the way. So it still looks like the pushrod needs to be adjusted a tad more. But it's already worlds better. Thanks to everyone helping me in my novice ways.

Did it have any pre-load when you assembled it and if so how much?

Mike

Mike, I have no idea what pre-load is.

quote:

Mike, I have no idea what pre-load is.

Was there tension - meaning rod is trying to push "the green thing" - when you put the MC up to the adapter? Tension would mean the rod is still too long.

There should be none.

No, before the adjustment, the two were not connecting with the existing brake issue.

Yes, I'm back...with the same issue. By now I have flushed and bled all the brake fluid (twice), rebuilt all the calipers (they were in good shape actually), and have now replaced the master cylinder. I've also adjusted the pushrod back as much as it will go. And I've had the front rotors resurfaced because they were quite blue and nasty from this issue. The problem is still there. It's driving me crazy. The only two things left that I can think of are replacing the booster (which the mechanic tells is fine), or putting in new brake lines (which are steel, and bleed clear).

Does anyone have any idea what the problem could be? I've spent a lot of money and time chasing this, and I've gotten nowhere.

Sounds like you have pretty much replaced everything; except the proportioning valve. This may be faulty, putting more pressure to the affected area of the brakes.

I'm pretty much stabbing in the dark -- food for thought.

last year, this same problem drove me to drink a lot more than normal for a while.

check to see that more than one brake is locking up, if it is just one wheel-then its the brake caliper, if it's more than one wheel locking up at the same time then it is a component that the wheels share. I cannot see why you need to replace lines or rebleed.

i suspect that you have a push rod length problem, just like i did, even if i screwed the adjusting rod all the in, the brakes still locked up, until they cooled down-and that is the key to the diagnosis.

i temporarily replaced the adjusting screw and it's locking nut with a cut down bolt and ground down nut so that i could get a substantially shorter push rod (grind the bolt end round so it does not score the "green thing"). If i recall correctly, the end result was a push rod about 1/4 inch shorter than originally. either try this or the "quarter" spacers as described earlier in this thread.

good luck

nazgul

This could be a thought, don't laugh.
If the wheel bearings are average, it could allow the disc to wobble around rubbing on the pads.

Just a thought.

Mmmmm....I read back through the thread and you have fixed or replaced just about everything.

You mention it happens when just parked in the sun, so here's my stab in the dark...Do you have an aftermarket Master Cylinder with an adapter plate to the booster?

Some vendors use a plastic bushing in the aluminum adapter to guide the actuating rod. When things heat up in the front trunk, the hole in the bushing closes up and the bushing squeezes down on the rod, holding it in position. This is a documented issue that has numerous occurences and the fix is as simple as reaming out the bushing for greater clearance.

quote:

Originally posted by DeMopuar:
Sounds like you have pretty much replaced everything; except the proportioning valve.

I put in a gutted proportion valve too.

quote:

Originally posted by nazgul:
i temporarily replaced the adjusting screw and it's locking nut with a cut down bolt and ground down nut so that i could get a substantially shorter push rod

That nut comes off? I thought it was permanent, and could only be moved back and forth a little.

Julian, yes I'm running a system with the adapter plate. I don't see any bushing in it though. Appears to be just a metal spacer, and the master cylinder goes through it, to mate up withe the booster.

I had the same problem 3 weeks ago, original master cylinder was defective. Very illusive problem if you think 30+ year old MC should be OK(I did) MC seemed intermittent so I replaced it and no longer use a proportioning valve.

Mark, I don't have a setup to get underneath the car to take pictures of everything. But it is a basic stock setup--stock calipers, with braided stainless steel lines, using a gutted proportion valve, new master cylinder (using the Ford setup with spacer), etc.

I'm at a complete loss.

in your june 10 posting you said "don't see any bushing" there should be a rubber bushing (dust cover) or rubber guide to keep the actuating rod straight and in line, otherwise it could move around a bit, if it moves around, it may not return all the way, and not totally release the pressure in the brake system.

i understand how frustrating this is, i went through it!!

a great source to understand how the master cylinder works is http://www.tegger.com/hondafaq/mastercylinderreplace/howworks.html

i tried to attach a photo of the rubber bushing on the push rod but the file size was too big, i don't know how to get around that problem.

as an aside, any chance that there maybe a vacuum leak on the booster, any sucking noise from any of the vacuum hoses???

nazgul

quote:

My stock brakes (seems like both fronts at this point, possibly back end, can't tell) are engaging on their own, to the point where if I'm driving and put it in neutral, it will come to a stop.

I would be courious to find out what the problem ended up to be. One thing to look at would the the emergency brake assy at the rear end. I did have an issue a couple of times where I was having the same symptoms as you but found out that the e brake was not releasing all the way, I thought it was but was still engaged just enough that when things warmed up..... whut a drag.

Angelo