Air system leak ?

[Fester's Quest]

Hi all, my festy is having afew issues that i think could be related to an air leak but i'm not sure where to look.

problem #1 the brake pedal usually moves too far down while stopping. it feels similar to the symptoms of a bad brake master cylinder but different because it still stops ok as long as you apply enough pressure to the brake pedal. It also works better if you pump the brakes once before stopping. This leads me to believe that there could be a leak in the air system causing the brake booster to not work properly.

problem #2 the car has an irregular idle / idle bounce that generally occurs in the 600 to 800 rpm range. also leading me to believe that there's a leak in the air system.

where should i look if this is indeed an air leak ? Is there supposed to be a check valve in the hose that connects the intake manifold to the brake booster ? because mine doesn't have one and i know most cars do.

[FestYboy]

what year?

can you apply the brake pedal, lift ever so slightly and then push it to the floor? from your description, it sounds like a bad master cylinder.

yes there is a checkvalve between the intake manifold and booster though you may not see it as it's usually burried in the hose, feel for a slight bulge and that's where it is.

[Fester's Quest]

Thank you !!!

it's a 91 L base model

i'm going to check the hose for a valve and test the brake pedal tonight. i'll update my results soon.

[Fester's Quest]

I tested the brake pedal by depressing it, slowly raising it, and then depressing it again. the pedal never sinks all the way to the floor.

I felt around the hose and i did find that there was a very slight raised spot right before the hose starts to bend on the brake booster side of the hose. the spot is also somewhat harder than the rest of the hose so i believe the check valve is present in the hose.

[mckabe]

Turn the car off and pump the pedal. If it gets stiff at the top your master cylinder is good if not you either have air in your brake lines or your master cylinder is bad. If the led gets stiff hold it as you start the car, if the brake booster is in check the pedal will move closer to the floor.
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[WmWatt]

Any change in the brake fluid level in the master cyclinder reservoir?

[Fester's Quest]

I just tested it. When pumping the brakes with the engine off, the pedal doesn't sink to the floor and it doesn't build pressure and stay at the top either, it always goes the the same location, about an inch and a half from all the way to the floor.

While keeping pressure on the pedal and then starting the engine, the pedal moved down a little bit, but not much, about an inch.

There's no brake fluid leaking out either.

[FestYboy]

sounds like air in the line (would be accompanied by a spungy pedal).

or

more likely: you're rear drums are out of adjustment causing you to have excessive pedal travel do to excessive shoe clearance.

[mckabe]

Sounds like air in a line to me as well. The pedal should get hard when car is off and you pump it. Or master cylinder.

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[Fester's Quest]

i probably just need to bleed my brakes right ?

I recently replaced the passenger wheel drum and when i did, it changed the steering wheel's position while driving straight down the road. it was straight but now it's off, leading me to believe that the car was aligned with a bad wheel drum on the right side.