Very hard brakes

[Alfonso Gomez]

​

Almost 2 years ago I had to replace my 87 Coupe's brake booster. The car would not stop and there was a loud hissing sound when the brake pedal was depressed. The mechanic at the shop tested the car and determined I needed a new booster. So, in it went. The car was fine until I got a code 34 last week. Together with the crappy performance, surging, rough idle, etc., I noticed that it was an effort to stop the car.
The pedal was very hard but if I pressed very hard, the car would stop. Let me explain its behavior: the pedal was hard initially. When I kept pressing the pedal it "loosened up" and moved downward a little and it felt like before the problem.
I changed the MAF relays, cleared the code 34 and the car started working OK, except the idle is a bit high and surges from time to time. Like its 600-700 RPM's, climbs to 1,200 RPM's, then goes back to 600.
I doubt the code 34 problem has anything to do with the brakes, but who knows?
I made this test: started the engine, let it idle in PARK. Then I pressed the brake pedal and it was very hard, but has no hissing. When the pedal moves downward, it does not have the hissing sound. I shut the engine and disconnected the vacuum hose from the booster and blew in it. The air passed freely, so there are no obstructions. (I could feel the air go into the plenum).
Then, I blew into the booster thru the check valve but the air did not pass, which I expect is correct. I then tried to suck air thru the check valve (like the vacuum tube would do with the engine running), and air did pass. So, I must conclude that the booster is working properly, or am I wrong?
Anything I should check before going to the shop and throw more money at it?
This is my daily driver and my right foot hurts from the force needed to stop this car.
PLEASE HELP!!!!!!!!
Thank you.

 

[Ken]

It's not only going to be tough trying to diagnose this problem, but I would be also be concerned about providing my guesses and perhaps incorrect information, which could lead to a safety hazard. Brakes are nothing to be guessing about; you better know for sure that the brakes are functioning properly.

No matter what feedback you get in these forums, myself, I would take it to a reputable brake-knowledgeable mechanic.

 

[G Winter]

I would not drive it till you have that fixed. You could get into a situation that you need full brakes and you do not have them. They could also fail completely with no warning . This problem could be power booster, master cyl. proportioning valve or even stuck calipers. Have you notice large amounts of brake dust on the wheels ? If you are not familiar with braking systems head to a good shop. Good luck , I hope it don't empty your saving account to get it fixed.


I reread your post and having drivability problems could point to the booster . you might not hear a small vacume leak and it could be enough to effect the oxygen sensor which in turn would effect the ECM's ability to control the fuel mixture. Try starting the engine. pull the hose off the booster and plug it. If the booster is leaking the engine might run better with the hose plugged.

 

[Ken]

I would not drive it till you have that fixed. You could get into a situation that you need full brakes and you do not have them.

I foolishly let a minor problem on my Barracuda brakes go unrepaired for too long back in the late seventies.

This beautiful car ...

Went to this attempted restoration...

It was never concluded.

 

[AdvancedAutoCC]

Do the smart thing.....

Check for an obvious vacuum leak to the booster and for any vacuum leaks. If you find none, take it to a professional ASAP. Brakes are nothing to fool around with, or to gator-arm. :nono


When you step on the brake pedal, your life is in your foots hands.

 

[tyrel]

Even if there were a vacuum leak, the brake pedal should not be as hard as described. The brakes still work without the booster. I suspect there is more than one problem, the first one being the master cylinder. As for the surging, that could be any number of things: fuel pump, fuel filter, fuel pressure regulator, IAC valve, a clog in one of the vacuum lines (or a vacuum leak), the throttle body needs cleaning, the TPS, battery cables, or maybe even the ECM. A bad battery or a dying alternator can cause all kinds of problems too. I would take a top-down approach and test every component starting with the battery and working my way around the engine.

 

[AdvancedAutoCC]

Even if there were a vacuum leak, the brake pedal should not be as hard as described. The brakes still work without the booster. I suspect there is more than one problem, the first one being the master cylinder. As for the surging, that could be any number of things: fuel pump, fuel filter, fuel pressure regulator, IAC valve, a clog in one of the vacuum lines (or a vacuum leak), the throttle body needs cleaning, the TPS, battery cables, or maybe even the ECM. A bad battery or a dying alternator can cause all kinds of problems too. I would take a top-down approach and test every component starting with the battery and working my way around the engine.

Not to disagree, well..yes to disagree to a point here: The brake booster provides power assist and when the booster either loses vacuum or has a mechanical internal fault, it causes a hard brake pedal. Yes the system still functions, but with MUCH greater pedal effort. Have you ever had a car stall out on you, and you hit the brakes? The first hit is ok, but if you hit them again, it takes a lot more effort to stop the car... that's due to the loss of power assist, due to loss of a vacuum source to the booster. There could be trouble with the master cylinder, but usually those problems manifest themselves as low and/or spongy feeling brakes. From the sound of it, loss of power assist is my first bet, but it's hard to diagnose any trouble without having the car in front of me.
You could be correct in there being more than one fault (C4's are notorious for this), but the original intent of my particular response is this: IF you do not have the knowledge, skills, facilities, you can do greater damage to both yourself and your car than if you take it to a professional (note, I didn't say take it to BillyBob down at the local "graje" here), who does have the necessary skills, facilities and knowledge. I have personally seen the results of the average car enthusiast who has gotten in over his head, and brakes are nothing to muck around with.

And the single most overlooked item in the fuel system is the one that usually causes the most driveability complaints....the fuel filter. I tell my customers to change their filters every 10,000 miles at the minimum, more often if their fuel source is questionable. Not to say this isn't the problem, but filters are cheap, and to gator-arm there is false economy. Anyway, I hope this clarifies things.

 

[Alfonso Gomez]

Tried this today: started the engine. Let it idle for a couple of minutes until it warmed up. Engine RPM's are 600. When I press the brakes, RPM's go up to about 750-800
This tells me there has to be somethig wrong with the only brake component connected to a vacuum source: the booster.
Somebody told me to check the ABS system. I said: it does not have ABS because the unit died almost 3 years ago and it was too expensive to replace. So the unit was removed and the lines that come out from the master cylinder now connect to a manifold. From that manifold the lines go to the wheels. That person told me: that's your problem because the ABS unit "helps" the booster do its job. No ABS will damage your booster. Since the guy is well-intentioned I did not tell him to stuff it. Anyway, he is a door-and-window installer, not a mechanic.:L

 

[vigman]

Getting boosted

Ok... your ABS has been pulled.. who made the manifold.. and how does it function?

When the ABS died & you did this mod.. did the pedal effort " feel " correct ( assuming the booster was OK at this point?)

I saw your other post about the brake booster for 164.00.. that looks OK to me.

And interesting thought.. you were having a code 34 issue... and now your booster is not so good... were you leaking fluid out of the back of the master cylinder on to the MAF relays?

If the car surges idle.. it indicates that there could be a vacuume leak...

At this point ( if it were my car ) I would take the time to locate a good used ABS system.. change the master..change the vac booster & and bleed the system..

My .02

Vig~

 

[vigman]

ABS on E bay

Just FYI

http://cgi.ebay.com/ebaymotors/ws/e...tem=7950757325&category=33560&sspagename=WDVW