Brake Booster Seal?

[reluctantmechanic]

Getting a hiss, or better, a slight buzz when I step on the brakes (01 4cyl solara, auto, 170k)...dealership said brake booster needed to be replaced (700bucks).

Been reading that the likely culprit is the seal between the master cylinder, and the brake booster..

Anyone ever do this job, or know where I can find a replacement sea?

Thanks!

[Chris Crash]

Does the pedal get squishy? If you have the car on and hold your foot on it, will it go down too far?

[SilverSoarer]

Originally Posted by reluctantmechanic

Getting a hiss, or better, a slight buzz when I step on the brakes (01 4cyl solara, auto, 170k)...dealership said brake booster needed to be replaced (700bucks).

Been reading that the likely culprit is the seal between the master cylinder, and the brake booster..

Anyone ever do this job, or know where I can find a replacement sea?

Thanks!

You can try a junkyard or NAPA brake boosters.

[73sport]

First Isolate?

With E-brake on, car idle, stick your head under the dash and press on the brake pedal. If you hear a hiss clearly, than I'd say you need a new booster.

If there is doubt, have a helper push the pedal while you listen from the engine bay. This one you have the engine running and then kill (to kill the noise) and have a helper push the pedal right after the engine noise stops. Listen to the booster area. You might use a paper towel tube to the ear to hear this at the base of the master cylinder.

If it leaks under the dash = booster
If it leaks under the hood = $6 bucks and your fixed with a seal and pulling the MC and bleeding the brakes.

Edit: don't forget to check the one way valve!

[reluctantmechanic]

Originally Posted by 73sport

First Isolate?

With E-brake on, car idle, stick your head under the dash and press on the brake pedal. If you hear a hiss clearly, than I'd say you need a new booster.

If there is doubt, have a helper push the pedal while you listen from the engine bay. This one you have the engine running and then kill (to kill the noise) and have a helper push the pedal right after the engine noise stops. Listen to the booster area. You might use a paper towel tube to the ear to hear this at the base of the master cylinder.

If it leaks under the dash = booster
If it leaks under the hood = $6 bucks and your fixed with a seal and pulling the MC and bleeding the brakes.

Edit: don't forget to check the one way valve!

73sport, thanks for your answer - very helpful.

Here's what I observed. Can hear a very light hiss under the dash - much more pronounced hiss directly at the MC/Booster...I used a stethoscope, and it very clearly seems to be leaking under the MC.

Going to try the seal first...in the haynes manual (and when I look at the car), I can see there is a gasket between the mc and booster - I'm guessing my seal is under that, on the booster side?

Thanks again for the help - times are very tight, and if I don't have to spend the money, that would be great

[73sport]

Originally Posted by reluctantmechanic

73sport, thanks for your answer - very helpful.

Here's what I observed. Can hear a very light hiss under the dash - much more pronounced hiss directly at the MC/Booster...I used a stethoscope, and it very clearly seems to be leaking under the MC.

Going to try the seal first...in the haynes manual (and when I look at the car), I can see there is a gasket between the mc and booster - I'm guessing my seal is under that, on the booster side?

Thanks again for the help - times are very tight, and if I don't have to spend the money, that would be great

Sorry, this is one of the few times where a tube would help more than a stethoscope!

Two things:
If the seal by the master cylinder is torn up, look for rust, damage, pliar marks. It needs to be smooooooooth so it doesn't tear up the seal. Like super smooooooooooth!


Also:
** I can not confirm this, but that seal must have the correct grease to prevent wear but all
I could find was this which calls it "LITHIUM SOAP BASE GLYCOL" *** but usually this is for places directly exposed and used in brake fluid. This area is not, but this grease should be OK. Just don;t use normal petroleum grease or the seal will double in size!


Yoda test:

BRAKE BOOSTER OPERATIONAL TEST
1. OPERATING CHECK
(a) Depress the brake pedal several times with the engine off and check that there is no change in the pedal reserve distance.
(b) Depress the brake pedal and start the engine. If the pedal goes down slightly, operation is normal.

2. AIR TIGHTNESS CHECK
(a) Start the engine and stop it after 1 or 2 minutes. Depress the brake pedal several times slowly. If the pedal goes down farthest the 1 st time, but gradually rises after the 2nd or 3rd time, the booster is air tight.
(b) Depress the brake pedal while the engine is running, and stop the engine with the pedal depressed. If there is no change in the pedal reverse travel after holding the pedal for 30 seconds, the booster is air tight.

[dudutzu]

hey guys
so here is my situation, when I shut off the car I can hear an air leak from the brake master cylinder/booster area(while listening from the engine bay area, lasts like 10 seconds at the most), followed the steps above and everything seems to be ok except the 2.b after like 5 seconds later after I shut the car off the pedal comes up( it pushes my foot up) I assume that means it failed the test and it isnt air tight
does that mean the seal between the master and booster is bad?
reluctantmechanic - did you fix your issue?
thanx

[reluctantmechanic]

Originally Posted by dudutzu

hey guys
reluctantmechanic - did you fix your issue?
thanx

I did. I took the booster and master cyl from a lower mileage camry and just swapped it out. Noise went away.

[KILLA CAMfuzed]

^I'm selling a perfectly functioning brake booster and master cylinder in this thread: GEN 4-4.5 Camry/Gen 1-1.5 Solara OEM Part CLEARANCE - Must GO!