P6 V8 brake pedal conundrum...!!!

G

grifterkid

Member
I own a 1974 S2 P6B auto' and apart from a few niggles it's a real gem... One of these niggles (characteristics...?!) is that when stationary, at traffic lights for example, when I have my foot on the brake (when the car is in 'Drive') I feel the brake pedal get firmer and actually rise back into its upper position! Of course all I do is apply a touch more foot pressure (or put the car in 'Park') to keep the car stationary and all is fine but I just wonder what is causing this? Any help or suggestions would be hugely appreciated as this is quite peculiar to say the least...
 
Is the servo losing vaccum so the same foot pressure has less braking effect and you have to push harder on the pedal ?
 
DaveHerns said:
Is the servo losing vaccum so the same foot pressure has less braking effect and you have to push harder on the pedal ?
Click to expand...
This may well be the case... How do I check for this...?
 
Turn off the engine and pump the brake pedal till it goes hard .You should get 4 or 5 pumps .Any less and the servo is not holding vacuum.Any hissing noises from it while the engine is running ?
 
grifterkid wrote,..
when stationary, at traffic lights for example, when I have my foot on the brake (when the car is in 'Drive') I feel the brake pedal get firmer and actually rise back into its upper position!
Click to expand...

Hello grifterkid,

I have experienced exactly the same in the past. The booster was replaced with a reconditioned unit at the time and the problem was no more. The problem normally stems from the air control control side of the booster, and usually when problems occur here the booster as a whole will need an overhaul.

Ron.
 
DaveHerns said:
Turn off the engine and pump the brake pedal till it goes hard .You should get 4 or 5 pumps .Any less and the servo is not holding vacuum.Any hissing noises from it while the engine is running ?
Click to expand...

Did the above and guess what...?! I'm getting about 1 nearly 2 pumps before the pedal goes solid... So, what now? Is it time for a new servo or (as Sydney' suggests) a new booster? If so to either where do I source them and are they easy to replace...?!
 
I think booster is Australian for servo .You should get more than 2 pumps out of yours
Replacement is the best option .You can rebuild them but it's often not 100% succesful
You need to check if the bores are corroded /scored
 
Hello grifterkid,

As Dave said, booster and servo are one and the same. The complete assembly is removed from the car and a reconditioned unit is then fitted in its place, or you can have your existing servo reconditioned. This typically involves resleeving the slave cylinder if it has not already been done along with fitting all new seals and any other parts which may require replacement.

Brand new servos originally manufactured during the 1970s are next to impossible to find, and even if one could be found it is a certainty that it would require an overhaul prior to being used due to bore corrosion within the slave cylinder, so in essence you would still have a reconditioned unit.

Ian Wilson at Rover Classics should be able to advise where to source reconditoned servos from, and then usually it is a matter of buying on exchange. You give them yours and you receive a reconditioned one, or have them overhaul yours specifically.

Ron.
 
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