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[alisterdwatt]

Can anyone help diagnose my brake problem?

The brakes on my TR6 require a great deal of pressure to stop the car i.e. the barkaes do work but not very well. The master cylinder and reservoir appear to have no leaks.  There is however liquid pooled in the top of the pressure switch (PDWA). Is the need to apply a lot of pressure to the brakes consistent with a fault in the PDWA or is it symptomatic of another issue?

[herald948]

If that liquid on the PDWA is brake fluid, you do need to tend to that immediately. However, I rather doubt that is your problem. The PDWA serves ONLY to actuate the warning light in case of a drop in pressure on either the front or rear brake circuit.

From what you hint at, I wonder if your brake booster is shot?

[alisterdwatt]

Thanks Andy.  The wire is missing from the pressure switch so I suspect this problem has been around for a while.  Like you, I thought the booster was the culprit but I also wondered if the PDWA could be stuck and be directing all the braking fluid to the back brakes, possibly giving the symptoms I described. I will check the brakes on each wheel to test this theory.  Do you have any other suggestions before I tackle the booster?

[herald948]

Again, I doubt it's the PDWA, which doesn't redirect fluid or close off circuits. Fancy-looking as it is, it's only purpose is to trip the dash warning light.

You might try simply raising first one end of the car and then the other, each time having someone apply pressure on the brake pedal and seeing if the wheels lock up...just to see if you've got some braking on each end of the car.

[BobH]

Hmm.  Kinda sounds like a brake booster failure.  When the car is running (and not moving) you should be able to push down on the brake pedal...it should go down a bit and feel normal...right? Not rock hard?  Like on a newer car? If it just feels 'hard', then you prolly need a new booster. 

Second(ly), if you then turn the car off, you should get two or three pumps out of the brake pedal before it feels rock hard.  Failing either of these is indicative of a booster failure. 

Hmmm.

Thirdly-If you put your foot on the brake (car not running) and start the car--with your foot still on the brake--the pedal should sink down quite a bit.  If it doesn't...then it's your booster.  You could pull the vacuum line off of the carbs and connect a hand held vacuum pump (like they sell to bleed brakes) to the booster and pull a vacuum...and it should stay.

My booster failed a coupla years ago..I had some company rebuild it (through the mail)(and I can't find their name right now)--saved $$$.

Good luck--
BobH

Oh..and you should try to identify whatever fluid you have on top of your PDA.  I had mine apart, but I fail to remember what the sealing mechanism is...O-ring?  Brass washer? for the electrical portion of the switch...check a parts catalogue.

[alisterdwatt]

Thanks for all your input Andy and BobH.