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Brakes lock up

Charlie H. Krop
Delaware Valley Jaguar Club *

forum user since 2012-03-14

 

Hi sll,
Rally need some help. I have been working on my restoration of a 66 OTS. I am closing in on the mechanics. My problem is that when the engine is running and I step on the brake the pedal gets hard as a rock and the brakes lock up. I can only release them by removing vacuum to the braking system. Welsh Jaguar told me it was the reaction valve on the master cylinder. The MC is new but I bought and installed one which did not work. I suspect the brake booster since it is the only thing that I did not replace with a new part. Any help would be greatly appreciated.




Brakes lock up

Charlie H. Krop
Delaware Valley Jaguar Club *

forum user since 2012-03-14

 

No Ideas??


Brakes lock up

Jay Weber
Jaguar Club of Austin *

forum user since 2008-10-21

 

Hi Charlie,

The reaction valve is indeed a likely culprit, and thankfully one of the cheaper components to replace. You can try disassembling yours, but probably better just to replace it.

When the brake booster goes out, it typically leaks vacuum to the extent that your engine will idle fast or rough, and the booster then provides little to no assist when you apply the brakes.

Hope this helps, and good luck!
Jay

1972 Series Three V-12 E-Type FHC
1967 Series One 4.2L E-Type 2+2 FHC
1961 RHD Mark IX saloon


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