Brake Booster Testing & Strange pedal feel Issues? - Alfa Romeo Bulletin Board & Forums
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post #1 of 3 (permalink) Old 04-22-2019, 11:48 AM Thread Starter
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Brake Booster Testing & Strange pedal feel Issues?

I have a '66 GTV with single circuit brakes and a Bendix Brake booster.

The previous owner fitted brake master cylinders similar to the Alfaholics under pedal box setup, girling master cylinders etc.

I then have Brembo Aluminum Calipers from a 75/Milano.

Anyway, brakes work quite well but i've always wondered whether the brake servo is all good.

I get inconsitent pedal feel, sometimes the brakes are there sometimes they feel like the pads are not "there" and or the pedal changes pressure/pulses a bit.

I've taken of the rubber hose from the bottom of the servo and it's dry, I've also tried dipping a cable tie into the vaccuum port to see if any oil is in the servo, also seems dry.

Anyway, I think the servo is probably ok but maybe my calipers and or setup are in some way a bit odd.

Has anyone come across this sort of strange pedal feel before?

I found one thread on an Aussie forum about strange pedal feel that sounds similar??

https://www.alfaclubvic.org.au/forum...?topic=16759.0

Angus
1966 Giulia Sprint GT Veloce- Twin Spark Converted
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post #2 of 3 (permalink) Old 04-22-2019, 05:14 PM
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What happens when you disconnect the vacuum line and drive it?
(Plug/tape up the line so the engine doesn't suck extra fresh air in, and remember that you will have to push the pedal a lot harder to make the car stop.)
If the problem disappears when you do this, it points to the booster failing internally and needing a rebuild. Main rubber perforated or air valve sticking.
No change? Unlikely to be the booster.
A sticky one-way valve at the manifold is another possible culprit.
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post #3 of 3 (permalink) Old 04-23-2019, 04:11 AM Thread Starter
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Thank you Ranz.

Embarrassingly this looks my own fault!

I went to check my one way return valve and there isn't one.

My car has a twin spark and a couple of years ago I converted to throttle bodies and aftermarket EFI, so I got rid of the standard 75 Plenum, I left the one way return valve attached to that!

And with my new AHM manifold I tee's straight in with no check valve!

I'm a donut! I've ordered an inline check valve now!

Hopefully that sorts it, might also apply a mild vacuum to the diaphragm using my mityvac to see if it holds a vacuum and is all good!

That funny brake feel thanks to me omitting a 5 part!

Angus
1966 Giulia Sprint GT Veloce- Twin Spark Converted
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