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Tips
Tips

brake servo

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I

ichthos

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Hello,
I currently trying to get the braking system working in my TR6, which has been sitting for a number of years. I have inspected/repaired all components to the system, but I am not familiar with servo units. Can anyone tell me how to tell if the servo is working correctly?
Thanks, Kevin
 
Re: brake servo *DELETED*

Kevin, I don't know how up and running you are but you could compare pedal action with the unit hooked up then unhook the vacuum hose to the booster, plug the hose, compare the braking effort again...
Achtung
 
As mentioned above, this is all you have to do. The servo works by having atmospheric pressure on the rear side of a diaphragm and vacuum on the front. If the diaphragm is intact, you'll have light pedal pressure; if not, it will feel just like an old car without power brakes. The brakes will still function normally, but you'll simply not have the boost. There is a one way valve that plugs into the servo and attaches to the vacuum line from the intake manifold. You can do a suck/blow test to see if it is ok.
One note though. When you remove the master cylinder, you'll see a rod from the front of the booster to the rear of the master. That is adjustable, and if set too wrong, you'll have difficulty. Too short means you'll have too long pedal stroke before engagement. Too long, and you'll never completely release the master cylinder. So be sure to check the manual for rod length if it might have been messed with. (Just checked the shop manual, and there is no specification of rod length or adjustment procedure, so perhaps it is fixed; I cannot remember. But if it is threaded, pay attention to the length it prodrudes into the master cylinder, so that it just touches, but does not push the plunger.)
 
Hello Kevin,
a simple check, if you have your engine working, is to press your foot on the brake pedal, then start the engine and you should feel a small downward movement of the brake pedal.

Alec
 
Hey Kevin,
Mine had a small tear in the diaphram that showed itself as a small hiss when the brake pedal was part way down. I confirmed it with a vaccuum guage attached to the intake manifold. At idle with servo connected the vaccuum was 16", disconnected and plugged it rose to 18".
Steve
 
Thanks everyone for the tips! As soon as I am able to get my car started, I will be able to check it out.
Kevin
 
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