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How to test booster and/or MC?


Grover

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I have the standard big brake upgrade with Volvo calipers and the 320 drums in the rear. My pads are quite new and adjusted properly so far as I can tell. However, my brakes just don't have the initial bite I want. I've driven another FAQ'ers car with an identical brake set-up, all the way down to the types of pads, and his is SO much more powerful up-front. I'm curious what I'm missing in achieving this and wondering if either my booster or MC is working less than optimally. Are there ways to test these items? I'm not leaking any brake fluid whatsoever, if that's any starting point. Thanks in advance, as always.

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I have the standard big brake upgrade with Volvo calipers and the 320 drums in the rear. My pads are quite new and adjusted properly so far as I can tell. However, my brakes just don't have the initial bite I want. I've driven another FAQ'ers car with an identical brake set-up, all the way down to the types of pads, and his is SO much more powerful up-front. I'm curious what I'm missing in achieving this and wondering if either my booster or MC is working less than optimally. Are there ways to test these items? I'm not leaking any brake fluid whatsoever, if that's any starting point. Thanks in advance, as always.

There really isn't any way to quantitatively test the booster or M/C, but you can do some simple go/no-go testing. The primary method is to stop the car on a low hill and perform a couple of low speed stops. Then, stop the motor and perform a few more low speed stops. If your booster is OK, you should feel a progressively firmer pedal with commensurately increased pedal effort (as compared to the effort with motor running) to stop the car in the first few stops. If not, then your booster is fubar.

The test for the M/C is to turn off the motor and bleed off the booster as per above. Then, hold your foot to the pedal with continuous pressure for 30 secs. or so. If the pedal holds firm, the M/C is likely OK. If it sinks at all, then the M/C is leaking past the seals and is bad.

Chris B.

'73 ex-Malaga

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rotors NEW ? or were they 'turned' machined at any time?

rotor thickness and pad material

mean everything in friction and stoping power

assume you installed used parts ?

what size tires ?

brake fluid hoses ?

type / brand of brake fluid ?

method of bleeding used ?

M/C = hold light pressure on brake pedal at

standstill - with easy on - off pressure keeping

light pressure and if the pedal fades to the floor-

your master cyl. is toast.

BOOSTER = with motor off - pump brake pedal 20 -

30 times to delete all vacuum reserved in booster.Then apply pressure to brake pedal - then start motor - and the pedal should

have some upward build-up as vacuum builds.

You could have a poor vacuum supply from poor hose, check valve,

or lousy running motor, or lastly, poor booster caused by prior

brake fluid contamination - replace the booster.

'86 R65 650cc #6128390 22,000m
'64 R27 250cc #383851 18,000m
'11 FORD Transit #T058971 28,000m "Truckette"
'13 500 ABARTH #DT600282 6,666m "TAZIO"

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