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Is my Vacuum booster going bad?

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Leyland75 Avatar
Leyland75 Daniel Richardson
Deltona, FL, USA   USA
1975 MG MGB
Within the last month I've noticed I have to exert more pressure on the brake pedal when braking. The car will come to a stop but I don't recall having to push the pedal so hard. The pads and shoes are all fine and adjusted correctly, no evident leaks or loss of fluid coming from any of the lines. I've noticed that when the pedal is depressed I hear hissing like vacuum escaping from around the pedal area. If the engine is cold and I hit the brake pedal hard, the engine will stall. Once the engine is warm and the pedal is pressed, the car won't stall but you can hear a change in the idle speed. I'm thinking the booster has spring a leak but wanted to run by you guys before I order another.

Thanks in advance!

Daniel

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Leyland75 Avatar
Leyland75 Daniel Richardson
Deltona, FL, USA   USA
1975 MG MGB
I searched older posts and found the answer I needed.

pjkenny Avatar
pjkenny Gold Member Paul Kenny
Hammonds Plains, Nova Scotia, Canada   CAN
1979 MG MGB MkIII "Lydia"
Hey Daniel,

I have similar issue. Brakes are "spongy" they'll slow/stop the car but seems to take an awful lot of effort with the pedal.
I've searched through forum posts ( long winter nights in Nova Scotia waiting for Spring and haunting this site ) and found many suggestions and plans of attack, but would like to know which post you found.
Could you point me in the right direction of the post you unearthed?

Thanks



I saw this beautiful girl today
And yes she took my heart away
My old Lydia Oh Lydia
Oh Oh Oh

~Jonathan Richman

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ohlord Avatar
ohlord Gold Member Rob C
North of Seattle, N.W., USA   USA
1957 Land Rover Series I "EYEYIYI"
1971 MG MGB
1971 MG MGB "Bedouin 2"
Vacuum leak

Test servo
Inspect vacuum lines



"I'm a long way gone down this wild road I'm on
It's gonna take me where I'm bound
It's a long way around"



"These are the days that must happen to you"

RD2 Radar/ Electronic Warfare Technician
Vietnam 1969-1972

BumbleB74 Avatar
BumbleB74 William Milholen
Tidewater, Tidewater VA, USA   USA
hose can be bad too. You can get the right size locally and not have to order.

Let us know how it turns out!



1974-1/2 Roadster, "Bumble Bee", Corvette Yellow - in shambles, wire wheels
1976 Roadster, "Virus", Sandglow - "driver" condition (stock + 32/36 Weber DGEV, cast iron header, 25D distributor), bolt on wheels, ON the road!

Leyland75 Avatar
Leyland75 Daniel Richardson
Deltona, FL, USA   USA
1975 MG MGB
Thanks for the input guys. I did a quick test by pressing the pedal 3 times in quick succession and then turned off the engine whilst keeping my foot on the pedal. The vacuum depleted very quickly so i'm still leaning toward the booster. I also couldn't figure out why I would be hearing the aforementioned vacuum noise coming from the pedal area under the dash but then it dawned on me that the noise is probably being amplified through the enclosed pedal box making it appear that it's somewhere under the dash. The vacuum lines look old so i'll replace as a matter of precaution.

Thanks again.

Daniel

ohlord Avatar
ohlord Gold Member Rob C
North of Seattle, N.W., USA   USA
1957 Land Rover Series I "EYEYIYI"
1971 MG MGB
1971 MG MGB "Bedouin 2"
Also examine or replace the check valve
Gordon at the B hive 800-652-4483 often has good deals on servos



"I'm a long way gone down this wild road I'm on
It's gonna take me where I'm bound
It's a long way around"



"These are the days that must happen to you"

RD2 Radar/ Electronic Warfare Technician
Vietnam 1969-1972

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Leyland75 Avatar
Leyland75 Daniel Richardson
Deltona, FL, USA   USA
1975 MG MGB
Hi Paul. I cannot pinpoint all the posts I read earlier but it does sound like you are having similar problems to me, only you described having a mushy pedal, I do not have that issue. Air in the lines could explain part of your problem. When I got my B I also had a mushy pedal and it turned out to be a blockage in one of the rear lines where the T-piece branches at the axle. I Replaced the rubber flex hose and bled the brakes and the pedal firmed up again. Like others have mentioned, check all the vacuum lines, check the adjustment of the rear shoes, make sure one of the rear break cylinders isn't leaking. You could possibly have a bad booster but i'd start with the simple stuff first.


In reply to # 3472821 by pjkenny Hey Daniel,

I have similar issue. Brakes are "spongy" they'll slow/stop the car but seems to take an awful lot of effort with the pedal.
I've searched through forum posts ( long winter nights in Nova Scotia waiting for Spring and haunting this site ) and found many suggestions and plans of attack, but would like to know which post you found.
Could you point me in the right direction of the post you unearthed?

Thanks

Leyland75 Avatar
Leyland75 Daniel Richardson
Deltona, FL, USA   USA
1975 MG MGB
Thanks Rob I'll check that too.


In reply to # 3473086 by ohlord Also examine or replace the check valve
Gordon at the B hive 800-652-4483 often has good deals on servos

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pjkenny Avatar
pjkenny Gold Member Paul Kenny
Hammonds Plains, Nova Scotia, Canada   CAN
1979 MG MGB MkIII "Lydia"
Thanks Daniel, As soon as the weather warms up and I can get my handy Brother in Law to give me a hand I'll go over the suggestions.



I saw this beautiful girl today
And yes she took my heart away
My old Lydia Oh Lydia
Oh Oh Oh

~Jonathan Richman

. Hide banner ads & support this website by becoming a > Gold Supporting Member <

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