High brake pedal effort despite new booster and master cylinder.

[jlinde]

My 93 Eldorado needs some extra effort to stop. I have put in a new master cylinder and brake booster

but that did not make any difference. I also bleed the brakes and the pedal feels OK and firm when there is no vacum from booster and when the engine is started it will sink an inch or so when it is depressed. The brakes are definitely a little better in reverse. I have studied the shop manual and it talkes about glazed pads but I could not see anything special - maybe the rotors look a little bit more brown in color compared to other discs ( a Mustang 88 GT and a 94 Pontiac Trans Sport are the ones that I have to compare with- my 94 STS is stored at some other place for the summer).

I do not know what kind of pads that I have as I put them on 5 years ago. The high effort has been more pronounced the last year.

I have followed he discussion about pads but I have not got any idea what my problem can be.

/Jan L.

[Ranger]

Did you bench bleed the master cylinder before installation?

[Ed Hall]

From what I understand, the harder the brake pad material, the harder the brake pressure is going to be. You might try some brake pads made with softer material such as the organic variety. They won't last as long but they'll require less braking pressure and your rotors will also last longer.

[BodybyFisher]

Check for collapsed/swollen brake hoses

[wotmode]

Hard to say without getting a feel for it. Does the car stop as well as before, just requires more effort? Or can you push as hard as you want and just won't stop as well as before? The reason I ask is because a car should be able to stop in the same distance with or without power assist. The only difference is how hard you push. You need to figure out if it is an assist problem, or an issue with hydraulics, pads, etc.. I would test vacuum to your booster. Test the flow through the check valve also. It's probably OK, but it is free and easy to check. Test with a gauge(using your finger can lead to a false "pass"). You should get 17 - 19" of vacuum instantly. If it gradually builds, there is a restriction. Look at the inside surface of your rotors. At the dealer I work at, I can't count how many rotors I've seen look perfect on the outside with nearly all rust on the inside. If all looks OK, I would buy premium grade semi-metallic pads(Some will disagree, but properly installed the premium don't dust or squeak and the stopping power is awesome)

[catmendo]

Check for collapsed/swollen brake hoses

very good point, et al ...

and, i have heard of brake lines, that looked fine, but were corrupted on the inside and

had like a broken away flap of rubber that impeded the fluids flow ...

if those lines, are the original lines, i would consider doing, what i would call, a real brake job ...

[catmendo]

"I have put in a new master cylinder and brake booster" ...

parts store cr*p or the real deal ???

[jlinde]

I replaced the booster because I thought the original booster was faulty (I did that on my

Mustang 88 GT with expected result) and at the same time I replaced the master cylinder.

They were both A1Cardone remanufactured parts from Rockauto. I have a good experience

of their parts except some engine mounts which are reman. in India and it has happened to me two times that I got two front instead of front and rear. Anyhow I am convinced that there were

nothing wrong with the original booster and cylinder -can be good for the future to have them on the shelf. My 50000 mile Eldorado TC passed the inspection without a problem and when I said to the inspector that I thought the brakes needed too much effort he did not agree and said that the brakes were OK.

I did the vacuum test and it seems relatively OK but I will do one more bleeding with a helper-

I have done it now with a vacuum pump but with a helper I think that it can be figured out if

there is some restriction as you said. The restrictions cannot be in just one wheel as they were

all even at the inspection.

I have done many brake jobs during my nearly 50 years with cars but this feels peculiar.

/Jan L

[jackc]

I have done many brake jobs during my nearly 50 years with cars but this feels peculiar.

For what its worth - I'd say the same thing about my 93 ETC. The brakes feel more "coasty" than "grabby", and seem to require more pedal pressure than I'd like.

When I bought the car, the rotors were glazed (which I later learned was due to the ISC causing a runaway condition that overheated the brakes). New pads and turning the rotors helped - though not as much as I'd hoped. But then the ISC stuck again and I again overheated the brakes, putting me back where I started.

Also FWIW - I had it in the dealer recently and they said they thought the brakes were ok and recalled that there may have been something odd about the 93 brakes. I didn't really buy it, but that's what they said.

[BodybyFisher]

I would check the hoses, maybe some sort of contaminant swelled them. There are hoses in the front and back. It does sound like you are not getting enough power assist. Did the fluid look very dark when you bleed the lines?

[BodybyFisher]

I have been thinking about this. You have a 93, if during its long life the brake system ever absorbed moisture, the brake tubing could have rusted from the inside sort of like plak. This could have narrowed the tubing causing your pedal pressure not to be able to apply sufficient pressure to the calipers.

Given that you have replaced the brake booster and master cylinder you have eliminated a lack of power assist, that is unless something is wrong with the new power booster, but assume that it is OK for the time being.

That means that something is preventing hydraulic pressure from reaching the calipers. If your rotors are always black/or discolored from heat it would mean to me that you are not getting stopping pressure on the rotors and they are overheating from the increased friction from the increased length of time it takes to stop. I would check the lines for blockage from any source, the proportional valve, assuming there is one for proper function or blockage, the rubber hoses. I have heard of the hoses swelling inside thereby decreasing flow. If I am not mistaken, the ABS unit was responsible for problems on the early cars and needed replacing, the Alante comes to mind.. Do some research on that.. maybe there is a bulletin, etc. Ill bet Logan would be able to help here.

Do the rear rotors appear to be a different color from the front rotors? If your front hoses were shot, your rear would pick up more of the load than its designed to and your braking would be poor.

That you said you replaced your pads 5 years ago means that you either have a very light foot on the brake pedal or it is not driven a lot, neither of which is a good thing.

I would look into this because if your tubing has a blockage, the increased pressure in the line before the blockage could burst a line (call me Mr. Safety, but it seems like a logical thought)

[BodybyFisher]

I have been thinking about this and found this info

When you start looking at your old brakes, it is strongly recommended that the individual owner seriously take a close look at the entire system, including hard lines, rubber lines and cylinders for decay and corrosion. After more than 30 or more years, no matter how good it looks, it probably isn't as good as it seems. The steel lines corrode and the rubber swells shut. Also, standard DOT brake fluid absorbs moisture and causes internal parts to rust. Check it closely. I suggest that after rebuilding your brakes and flushing out your brake system you consider using at least the synthetic DOT 4 fluid. Even better is the more expensive (in the short run) Silicon DOT 5 fluid which does not absorb moisture and corrode

[jlinde]

I will make a real bleeding procedure in the near future. When I bled the rear calipers yesterday

the brake liquid was quite black. I have been out testing today and the brakes can be nearly OK for a while but kind of inconsistant and spongy feeling BUT when the engine is not running and the vacuum has dissappeared after depressing the pedal a couple of times the pedal is real hard or firm and cannot be moved more than the 2 inches that the manual says.

Anyhow the feeling is also that the brakes are kind of slow to work and also slow to release which

of course as you say BodybyFisher points to some kind of restriction or ? can it be that

faulty/glazed pads/rotors requires such a high pressure from booster that it also takes a little extra time to release? This week I will also receive a pair of new front rotors and as I have a set of

old relatively nice pads I can test with those.

I have also bought a Tech1 tool on Ebay and that will give me some opportunities to play

-I do not know yet if it also has the setup to bleed the abs on the 93 Eldorado. I bought it mainly

to work with a 94 Trans Sport where it is needed both for engine and abs and I like to fix the problems

myself (hopefully).

/Jan L

[BodybyFisher]

Check this

http://www.babcox.com/editorial/cm/cm20119.htm

[BodybyFisher]

See this also

http://forums.club4ag.com/zerothread?id=17...p;postid=170458

[KHE]

I suggest that after rebuilding your brakes and flushing out your brake system you consider using at least the synthetic DOT 4 fluid. Even better is the more expensive (in the short run) Silicon DOT 5 fluid which does not absorb moisture and corrode

I would be absolutely sure that the DOT 4 or 5 fluid was compatible with the rubber components in the brake system. All that's really required is a flush with fresh DOT 3 fluid every 10 years/100,000 miles.

[BodybyFisher]

I suggest that after rebuilding your brakes and flushing out your brake system you consider using at least the synthetic DOT 4 fluid. Even better is the more expensive (in the short run) Silicon DOT 5 fluid which does not absorb moisture and corrode

I would be absolutely sure that the DOT 4 or 5 fluid was compatible with the rubber components in the brake system. All that's really required is a flush with fresh DOT 3 fluid every 10 years/100,000 miles.

I agree Kevin, I copied that from a web site and my intent in posting that clip was about the moisture and internal rust that can occur. I saw that statement but did not squelch it, good pick up.. Thanks

By the way Kevin, what do you think is causing this problem

[JimD]

.... All that's really required is a flush with fresh DOT 3 fluid every 10 years/100,000 miles.

Make that every 2 years for my cars.

[KHE]

I suggest that after rebuilding your brakes and flushing out your brake system you consider using at least the synthetic DOT 4 fluid. Even better is the more expensive (in the short run) Silicon DOT 5 fluid which does not absorb moisture and corrode

I would be absolutely sure that the DOT 4 or 5 fluid was compatible with the rubber components in the brake system. All that's really required is a flush with fresh DOT 3 fluid every 10 years/100,000 miles.

By the way Kevin, what do you think is causing this problem

Not sure. If the rubber hoses are not ballooning out, I would make sure the parking brake is adjusted properly. There is some interaction with the parking brake adjustment and brake effort. If the rear brakes do not have the proper initial adjustment, they won't be doing their proper share of braking.