What noise does a leaking Brake Booster make?

[Ian Anderson]

I was out in the car this evening and running well (New gearshift system and wheels all aligned correctly with correct springs and what a difference - thanks Brian)

But when getting to a slow speed on the brakes (10 mph ish) it sounds like an air pump is running (farting) - perhaps the noise is there all the time but this thing is to loud to hear anything.

Never tried the brakes hard so cannot say if one end locks up too early.

Also when I have my foot on the brakes the engine tends to splutter and die - it will idle better with no brake pedal.

Is this symptoms of a booster leak?

So if one of the boosters is leaking what noise should I hear?

Sorry never had one of these go faulty before.

Cheers
Ian

 

[Rob]

Hi Ian,
Listen for what sounds like a vacuum leak. If at idle with foot on brake, the engine sputters and stalls, it sure sounds like you have a vacuum leak in the booster diaphram. Need to determine where the booster inlet vents from.... if under the dash, then stick your head under there, if external have someone push the pedal for you so be there so you can hear if the vent makes noise. The smallest movement of the input/output shaft will crack the booster off its seal, then if there is a leak in the diaphram, you will hear the engine vacuum hissing.

The booster functions off of vacuum, but doesn't draw any air in from the vent side accept for the volume that is needed on the back side of the diaphram as it moves forward and aft in the drum. If that makes any sense...

Hope this helps.

 

[Howard Jones]

Do you have 1 or 2 boosters? GTD style?

If one, find a nice safe spot and disconnect booster vaccum source. Plug it on the engine side and try it again. Be aware that the car might not stop as well so do this test at low speed <10mph with a lot of run off room. The engine should run better if the booster is a vacuum leak. The engine stumble under brakeing might also be a carb issue. Check float level. Fuel pressure. reset idle higher, etc.

If two, try them one at a time. Also, check to see if you have the same drop off in brake performance on each with same peddle force. There will be some difference due to ballance front to rear but at this low of a speed I don't think there will be much.

You can also try to pull a vacuum, suck on it, THE BOOSTER MAN ! on the side that goes to the engine. It should not allow air in as you suck on it. Ya, I know all about dirt maybe a little gas fumes, etc. etc. You'll be fine, trust me.

These are the free things to try. The kind I like. You can also have the booster checked with a proper vacuum booster checker.

 

[Ian Anderson]

Thanks guys

I'll try the disconnect and suck and also try plugging the manifold and driving

The car is Efi so shouldn't be a surge problem (Running through swirl pot too)

The Tilton pedal set up is very close to usable without boosters so I'll see how the brakes feel and perhaps run without them.

Does running without vacuum hurt the boosters in any way? time is tight and the Stoneleigh show is on this weekend!

cheers
Ian