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73 v12 brake problem

Posted by eric cole 
Jaguar E-Type Masthead

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73 v12 brake problem
December 07, 2005 11:35PM
I have a type E V12 1973 with brake problems. After replacing the rear brake pads, when applying the brakes, the brakes are working fine but won't release immediatly. It takes like a second or two to freed the wheel. The P.D.W.A. light is on and I can't find the problem.
LRG
Re: 73 v12 brake problem
January 04, 2006 02:38AM
It sounds like your calipers are sticking slightly. It may go away by itself but if not then try removing the pads and spraying brake cleaner around the pistons. It's generally not a great idea to do that but if you're potentially going to have to rebuild them then it's worth a try. I had the same problem on my fronts not long ago but I took the car out for an "Italian tune-up" one day and the brakes were fine when I came back. It may just take some use and/or wear on the new pads for it to free up.

Your problem with the warning light may be an off center brake failure switch. I had this problem once on my TR-8 and it was caused by pushing too hard on the brake pedal after I had put in new pads and was repressurizing the system (those first couple of strokes on the brake pedal before it gets stiff again). The failure switch is a metal "tube" about 4" long with brake lines on either end and an electrical connection in the middle. It's designed so that if either of the two brake hydraulic systems fail (the Feds require that there be two hydraulic circuits) the higher relative pressure on one side of the switch will displace a small ball bearing and trip the switch. When you replaced your pads you probably pushed one piston in a caliper further in than the other so when you pumped the system back up at the end of your job one piston hardened up before the other and tripped the switch. The good news is it can be reset but it's tricky and will probably take a few tries. You'll need to open the bleed nipple part way on one of the calipers and push lightly on the brake pedal. The nipple should be only part way open, enough so you'll get a pressure differential but not so much that the fluid just squirts out like crazy. Leave your ignition on and watch to see if the warning light goes out. If it goes out and stays out you're lucky, you're done. If it goes out very briefly then back on again you pushed too hard and off center the other way and will need to push it back. To push it back you'll need to switch to the other caliper. If nothing happens on your first try then you're probably doing it from the wrong caliper and should try the other side (or aren't pushing hard enough.) It took me a half dozen tries to do this on my TR so be patient and if get a helper as it's much easier. You might be able to do this from the front calipers but since the problem started with your work on the rears it may be better to try to do it there. That should fix your light. Next time you replace the pads push the pedal very lightly until the pressure returns to the whole system and the switch will stay centered. Good luck.



LRG
1973 E-type
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