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Brake booster issue?

  • Thread starter Thread starter ebk06
  • Start date Start date Mar 11, 2010
E

ebk06

Member
Feb 23, 2007
113
12
18
Mar 11, 2010
#1
  • Mar 11, 2010
  • #1
Well after replacing my headers a month ago I started having an issue. When I would start coming to a stop the car would drop in rpms. The issue slowly go worse and worse to where now if I have to slam on the brakes the car dies. After pulling codes I replaced my tps and saw a vacuum line on the egr valve came off. With those fixed I still have the stalling problem and actually the car will die if i press the brakes hard when im stopped with the transmission in neutral.

Now I have gone through the surge idle check list and didnt come up with anything. Ive done both KOER and KOEO tests and nothing comes up. I do still need to check the voltage on my alternator but dont feel this is the issue. Also all my vacuum lines and sensors were replaced about 2-3 years ago and honestly Ive probably only put 10k-12k on the car since then. I did recheck all the vacuum lines and replaced the ones going to the charcoal canister but everything else looks fine.

I did notice I was getting a hissing noise inside the car that got louder as the brakes were applied but its seems to have gone away. When the noise was noticable though i never had any braking issues. Now im really thinking its the brake booster causing the issues or maybe the check valve on the booster is clogged. But has anyone heard of the booster causing the car to die? Is simply pulling the vacuum line to the booster and stepping on the brakes to see if it dies a good way to check for a bad booster? Im just pretty frustrated after spending the last few weeks slowly checking everything i could think of.....
 

MustangLX-5.0

Founding Member
Dec 2, 2000
856
7
38
Lehigh Acres Fla.
Mar 11, 2010
#2
  • Mar 11, 2010
  • #2
Bad check valve in BB perhap. I had the same hissing noise come out of my old BB. Sometimes it went away for awhile, but if it hit the brakes hard, or just tapped the pedal a tiny bit, it would start hissing. It was making the engine run like *****. It was also contributing to an over rich condition.

With the car off, step on the brake a couple times to get all vacuum out. Now pull the hose off the booster and plug the hose with a rubber cap or something. Start it up. I'll bet you it runs a lot better. You won't be able to recreate the problem with the vac line off. I highly doubt it has anything to do with the MC. Replace the booster, and your good to go.

Do you have a setup that would demand more vac to other devices? I heard on certain setups that either using and electronic booster or adding a vac storage canister can help.
 
E

ebk06

Member
Feb 23, 2007
113
12
18
Mar 11, 2010
#3
  • Mar 11, 2010
  • #3
Thanks ill give that a shot. No the car is basically a stock '87 5.0. A friend suggested a vac canister but with it being stock I'd like to get the issue resolved incase some mods down the road demand a canister.
 
E

ebk06

Member
Feb 23, 2007
113
12
18
Mar 16, 2010
#4
  • Mar 16, 2010
  • #4
So I finally had a chance to pull the line off the brake pooster last night. I capped the vacuum tree and mashed on the brakes and the car didnt drop in rpms or die. I hooked the line back up and mashed the brakes and it died. So Im assuming this does mean the brake booster is bad.
 
S

Sicarius428

Active Member
Jan 6, 2004
2,085
5
49
Mar 16, 2010
#5
  • Mar 16, 2010
  • #5
Sounds like your BB is bad then. Time for an upgrade... hehe
Kevin
 
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