Need Maintenance Advice...:(

[LostCause]

Over the last couple of days, every time I use the brake pedal I hear a hissing sound. When the engine is at idle, applying the brakes occasionally causes it to stumble and risk stalling out. When I'm driving extremely slow and at idle, the power brakes will die, leaving me unassisted.

I don't think this is a very big safety risk simply because I rarely use my brakes anyways and I'm confident in my ability to stop the car manually, but it is something I obviously want to take care of. The check engine light came on today (as I was applying the brakes), so I definately need to take care of this soon...especially before emissions testing.

I'm almost certain my brake booster is dying, but I'm not 100% sure. I'm assuming my engine is stumbling because the booster is trying to pull to much vacuum, which drains excess power from the idling engine. I can find a new booster online for ~$140, but I figure a mechanic is going to want $400-500+.

For those more mechanically inclined, is this something I could tackle on my own? I have a pretty solid understanding of car components/function, but I have essentially zero experience tinkering under the hood. The brake booster seems pretty accessible, but I figure I'll have to drain the brakes...which I'm nervous to do.

On a scale of 1-10, what would you say the difficulty is? Should I attempt the fix or would it be better to let a professional handle the problem? Biking to school is looking more enticing every day...

- LostCause

[meemooer]

check the hose going to the brake booster first. Should be about 1/2 inch round, going along the firewall, from the back side of the intake. It could be cracked, and that's a cheap fix.

[Red]

Yeah check the vacuum hose first, although if it was the source of your leak you would have an high idle speed as well. You could do it though in your driveway.

[LostCause]

Thanks, I really appreciate the help. If only the beer option was available...

I'm still kind of stumped why the engine would stumble when the brakes are on at low speed. At this point, I'm more worried about my engine dying on me than having power brakes. It looks like I'll be working on a solution tomorrow, as the stumbling is getting worse. I've never driven so carefully/gracefully in my life.

I checked the brake booster as best I could, but I could only find one 1/2" rubber pipe (ID ~1/4" I assume) that came off the assembly. While it is old and stiff, I couldn't feel any cracking along its length. I'm assuming that's the vacuum line as:

1.) It's the only large hose coming off of the booster
2.) It routes to a T-line that has a hose running off to the manifold
3.) I'm 99.99% sure the tube isn't on the interior side of the firewall (didn't check)

Here's a quick MS Paint graphic, which hopefully will do until I can borrow a camera tomorrow. The image is head on:


Does anyone know the tools I'll need? Also, does anyone know who makes OEM Ford Service Manuals? I know Helms does for Honda, but I couldn't find theirs for my car...

Service Manual
Torque Wrench
Sockets/Wrenches
Jack/Stands
Brake Bleeder Pump
Brake Booster
New Hoses?

...and some way of turning the CE light off.

- LostCause

[meemooer]

i know autozone will turn off the check/clear the code. Plus i'm sure they have the chilton manual for your car.
Another thing i thought of is, there might be a "oneway" check valve in the vacuum lines. Just trying to think back 4 years ago when i had brake problems on a street/strip car i had. I had a radical cam, which produced low vac, and my brakes sucked, and it too would almost kill the engine. So i bought a vacuum canister, hooked it up the opposite way and the brakes were overly stiff, flipped it around, and the brakes were great like before the rebuild.

IDK thinking out loud to see if i hear something else

[Coyote X]

unhooking the battery for 30 minutes always worked for me to clear the codes.

You could possibly plug the line going to the booster so it is disabled. The brakes will suck and not work as good without a lot of effort but that will let you drive without worrying about the car dying when hitting the brakes.

I can't remember much from my old 93 tbird but I am pretty sure you can take the master cylinder off the booster and there is enough brake line length to get it out of the way without unhooking them. Then you can get the booster off and slip it out from behind it and replace it with a good one. I think the bolts holding it are inside and you will need to fight under the dash for room to work but I still think it could be done over a weekend easy.

[dremd]

If your Booster is going bad, check for brake fluid leaks, the majority of boosters I've seen fail had leaking master cylinders associated with the failure. I assume that the leaking brake fluid degrades the rubber diaphragm.


Disconnecting Battery only works on Some cars . . ..

Booster CAN be a pain to change out.. Take a look at it. Typically there are 4 bolts through the Firewall, the actuator rod attached to the pedal, and of course the master cylinder / brake lines.

Best way to check for vacuum leaks is either with a can of either, or a propane torch (BOTH NOT LIT) when you spray the leak you idle will smooth out, and you'll know where the issue lies.

There is also a test procedure for boosters. I can't remember it exactley, but essentialy.

With engine off "Pump" brakes up till the pedal is SUPER hard.
Start engine with foot on pedal
Pedal should SINK to the Floor
If it does not you have a booster issue/ HUGE vac leak.

I'd do the Either check for vacuume leaks first.

Good luck

[Johnny Mullet]

I have replaced a few boosters in my career and 90% of them required a master cylinder replacement due to fluid leaking into the booster.