Wrong master cylinder - should I worry?

[RaeRae1]

Originally Posted by bobss396

You must have an incompatible piece of hardware somewhere. The calipers are fine if they match up, they only have one moving part and that year Cougar really had no other option for calipers, so if they fit, they're right.

So, between your power booster, master cylinder and proportioning valve, something is "not exactly". I always had my power boosters and masters rebuilt so I always got "mine" back. I had my '68 Mustang with the Kelsey Hayes disc brake set up done that way.

The bitchy thing about Cougars and other Mercury products is that if you don't get the EXACT match up with parts, you'll have headaches like yours. Often enough, parts were specific for ONE year only and that's it.

Do you still have your old power booster and master? If so, shell out a few $$ and get them rebuilt. If not, try to get some NOS parts that still have the Ford/Mercury part numbers on them. You may even find them aftermarket if you hit upon the right source. Is there a club in your area that might be able to help?

I'm also not sold that you have the correct proportioning valve. This alone would be the basis of your woes.

Bob

I agree - I know it is just one thing that isn't playing well with the others. As a last ditch effort I am going to put back in the old prop valve (this has been rebuilt and has new seals), remove the adjustable prop valve, and do a little concentrating on the rear drums (ie - make certain they are clean and get new shoes). The wheel cylinders and springs are all new. After that, she gets put away or sent away to a pro shop in hopes they can figure out the piece that doesn't play.

I do have my old MC, in fact we took it apart, cleaned it up well, and put it in just to see what would happen, and it reacted the same with the new and the old MC's).

The booster was sent back to the place where we got the new one from (West Coast Cougar Classics) for the deposit. I suppose I could call him and see if he still has it but I doubt it.

Thank you so very much for all of your help on this Bob. Your input has been what has kept me going and not giving up.

[bobss396]

You can do the rear shoes if you want, just make sure they are adjusted and (the long shoe goes to the rear) about equal to each other. This will give you a better pedal. That's why the pedal will come up with a couple of pumps, which has nothing to do with air in the system. It will help overall.

Install the original proportioning valve and take out the adjustable one, just to simplify the equation. For laughs, see what the depth of the recess (for the rod) is in the old one, measure it and write it down for now. You can compare it later when you get up the nerve to take the "new" one out again.

Maybe your booster manufacturer can double check to see that you have the right part for the disc brake application. I doubt he'd have yours around still.

I don't mind helping you out, the problem is intriguing. I'd like to see you get it solved eventually. I've played with old Cougars (the car type), Mustangs, Fairlanes and Falcons quite a bit and never ran into something like you got there.

We'll get to the bottom of this yet!

Bob

[RaeRae1]

hahaha... just an FYI - took the cougar out for a quick ride on halloween - the push rod is out too far. The brakes started to seize pretty bad by the time we limped it back into the driveway. Guess what I'm going to be doing tonight! hahahahahahahahaha.... Oh well, at least we know where "too far" is!

Interesting though, I replaced the check valve and now the pedal seems to want to grab or work well at the top end of the pedal and then fades????? Have to fix the push rod and take it out again so I can get a better idea of what it is doing now.

[bobss396]

Hooray, something happened! You HAD to force it to get something out of it, now you KNOW where too far is. I agree that now you have to back the rod off a tad.

You do understand what happened, the brake fluid heats up and expands, locking up the brakes due to having insufficient free play. Go with an 1/8" to start.

I think you're close to a solution and it will be a totally different animal once you fine tune the rod. If you haven't done it, check the rear brake adjustment as this will help the pedal height.

Bob

[RaeRae1]

Update on the brake saga of SATAN'S COUGAR

Ok, so I adjusted the push rod back about 1/8 inch and then proceeded to check the back brakes, just in case there might be something amiss, or contamination or whatever. Well..... Bwahahahahahaha! Here is what we found when we took off the drum.



Yep - the pad is actually BROKEN. There is an extra piece that was floating around in there - hmmmm. Think this could have been an issue????? Keep in mind, we had these brakes completely apart and put in new wheel cylinders and springs etc - why we didn't get new shoes I don't know, but the old ones looked ok with pretty decent wear life on them. There was no damage to them when we had them apart the first time.

Either we have some of the worst brake luck in the world, or this car is just another Christine in the making.

I think with the properly adjusted push rod, the new check valve, the new booster, the PROPER MC, the leaky line fixed at the prop valve, new pads, new shoes, new calipers, new lines, new wheel cylinders and another bleed - I might just have it......


Yeah - I'm not holding my breath, but I am hopeful.

[bobss396]

I can't see the picture at work, but my guess is that a piece of the brake shoe lining broke off. Old shoes get brittle and often a corner breaks off from taking the drum off and on.

Slap a new set of shoes on, adjust them up (do not bleed it, quit while you're ahead!!) and go for a ride.

Bob

[RaeRae1]

Originally Posted by bobss396

I can't see the picture at work, but my guess is that a piece of the brake shoe lining broke off. Old shoes get brittle and often a corner breaks off from taking the drum off and on.

Slap a new set of shoes on, adjust them up (do not bleed it, quit while you're ahead!!) and go for a ride.

Bob

Well Bob, As usual you were right on. Yes, a piece had broken off. We have put on new shoes and I took it for a ride.

The brakes are still not right but they have "changed" through all of this. What I get now is a stiff pedal when the car is of (rock solid). A soft pedal when the car is on -which feels normal. What it does do however, is gives a good grab for the very first second when you hit the pedal, then it "fades" and you have to increase the pressure on the pedal until the brakes fully engage. If you drive for a bit without using the brake, it does the "grab first touch and fade" thing. If you continue to use the brakes, the first grab seems to go away and the brakes become progressively more difficult to get to engage.

My thoughts now are leaning toward vacuum - either the booster (which is new, but could possibly be defective), or just a bad vacuum somewhere.

Any thoughts? I know it can be really tough when you can't actually feel the pedal but I am hoping from the description you might have an idea.

Thanks again Bob.

[MagicRat]

Originally Posted by RaeRae1

My thoughts now are leaning toward vacuum - either the booster (which is new, but could possibly be defective), or just a bad vacuum somewhere.

I agree, that sounds like a vacuum supply problem.

In my experience, a few things can cause this. If the vacuum line going to the booster is under-sized, or if there is an under-sized fitting, a kink in the line or any other kind of partial obstruction or leak, your vacuum booster will 'fade away' exactly as you describe.

Also the vacuum source needs to be the manifold vacuum (the one that sucks most at idle) not the ported (distributor) vacuum.

If there is no obvious obstruction, install a vacuum gauge on the vacuum line for the brakes. Tee it in if you have to, and measure the vacuum strength that the brakes are getting. It should be at least 18 inches of vacuum at idle. It will drop as you step on the gas, that's normal...... any less vacuum can cause a problem like you describe. Poor vacuum can be a result of improper valve timing, leaking intake valves or a radical aftermarket camshaft.

If all this checks out then it may be a bad booster.

[RaeRae1]

Originally Posted by MagicRat

I agree, that sounds like a vacuum supply problem.

In my experience, a few things can cause this. If the vacuum line going to the booster is under-sized, or if there is an under-sized fitting, a kink in the line or any other kind of partial obstruction or leak, your vacuum booster will 'fade away' exactly as you describe.

Also the vacuum source needs to be the manifold vacuum (the one that sucks most at idle) not the ported (distributor) vacuum.

If there is no obvious obstruction, install a vacuum gauge on the vacuum line for the brakes. Tee it in if you have to, and measure the vacuum strength that the brakes are getting. It should be at least 18 inches of vacuum at idle. It will drop as you step on the gas, that's normal...... any less vacuum can cause a problem like you describe. Poor vacuum can be a result of improper valve timing, leaking intake valves or a radical aftermarket camshaft.

If all this checks out then it may be a bad booster.

Thanks MagicRat! I have the vacuum diagram (yeah, spaghetti bowl of tubes ACK!) and plan on tracing them as best I can. I will see about picking up a vacuum gauge (or I might be able to use the one from my self bleed kit, have to read the instructions again). I Also plan on replacing most of the lines since the rubber is old and it won't cost much to replace. A vacuum issue seems in line with the fact that my hidden headlight covers aren't really closing on their own any more either and that is run by vacuum as well. I couldn't find any hoses that seemed to be kinked or missing but I have not really delved into it deep yet.

I am hoping it is a hose because I am pretty sure the valve timing is ok, I'm not getting any ticking or knocking and the engine is running smooth and strong.

[bobss396]

The acid test for a bad booster is: With the car off, pump the pedal until you exhaust all the vacuum in the booster, it should be very hard at that time. With your foot on the brake pedal, start the car. The pedal should drop very noticeably. That means the booster is probably good or has no gross leak.

To really rule out the booster, unplug the vacuum line and plug it, you really have no brake booster. Now go for a ride. If the hydraulics are really good, it will stop but you have to use more force. It should be consistent though.

Aside from that, go with what te MagicRat suggests.

Bob

[joe68]

well i been reading with you guys, and was wondering if you made any headway?

[RaeRae1]

Originally Posted by joe68

well i been reading with you guys, and was wondering if you made any headway?

Not yet Joe. Planning on attacking the vacuum hoses this weekend. Gotta fix my DD first (stupid water pump went out ). I'll let you know what I find. Be a nice little B-day present to me if I could actually get if fixed this weekend

[RaeRae1]

Just a quick update. I plugged off the headlight vacuum hose and tried it again. The brakes are better. Still not quite right but I think they are good enough to pass inspection. I plan on tweeking it more and putting on the vacuum tester, just haven't been motivated as of late. I am just elated that I was able to get it out, drive it around and feel like I could actually feel like the brakes are safe.

Thanks to everyone for their help.

A special thanks Bob and Magic Rat for you unending confidence and fantastic help/suggestions. I owe you big time!

[MustangMarty]

Couple Of tips for you:
Hook up a T with the vacuum gauge going inside and watch it when you hit the brakes, if it gets less that 15 or so you may have a blockage or booster may be bad.
Just beacause a part is new or rebuilt doesnt mean its good. I have had bad luck with rebuilt master cyls, Buy a New one. Rebuilt boosters are bad too sometimes.
Cheap or glazed brake pads will cause or magnify your problem, Use the Hawk street compound pads from summit, pep boys. They're great.
And the most likely - Check if your front calipers are reversed - Left will fit on the right side and vice-versa, but you will never be able to bleed correctly. Look at the bleeder valves, should be at the uppermost point on the caliper cylinder. Also brakes must be bled with vehicle level. Good luck!

[RaeRae1]

Originally Posted by MustangMarty

Couple Of tips for you:
Hook up a T with the vacuum gauge going inside and watch it when you hit the brakes, if it gets less that 15 or so you may have a blockage or booster may be bad.
Just beacause a part is new or rebuilt doesnt mean its good. I have had bad luck with rebuilt master cyls, Buy a New one. Rebuilt boosters are bad too sometimes.
Cheap or glazed brake pads will cause or magnify your problem, Use the Hawk street compound pads from summit, pep boys. They're great.
And the most likely - Check if your front calipers are reversed - Left will fit on the right side and vice-versa, but you will never be able to bleed correctly. Look at the bleeder valves, should be at the uppermost point on the caliper cylinder. Also brakes must be bled with vehicle level. Good luck!

Thanks MustangMarty. I'll keep that in mind. I know the front calipers are not reversed. We have gone over that one a few times. I'm pretty sure it is vacuum at this point. It has been pretty bad weather here as of late so she is stuck in the garage, plus I have been working a lot on my DD right now so, as soon as I have that cleared up, and the weather again turns nice, I will once again be ravaging this site for help.