Before my major, I could lock up my brakes at will... Now, car stops well but can't lock the brakes... Brakes led with the Motive bleeder. Pedal is rock hard. When I was bleeding the brakes, I tested the pedal travel when done. It was pretty good. I then pumped the brake really fast 10 times which made the pedal really stiff...but cut pedal travel quite a bit. It seems to me that I have less pedal travel than before, then the pedal hits a hard resistance. Did I somehow over pressurize the system? The vacuum assist seemed to be fine, should I somehow test that? Oddly enough, my Porsche 914 has the same issue. Rock hard pedal, but less than optimal clamping force. I changed the master cylinder, with no change... No vacuum assist on that one... Does this have anything to do with using the Motive?
I just used the Motive on my C63 AMG which has a Brembo factory brake system. I didn't see what are you are describing. Did you start with the caliper furthest from the master cyclinder first? Perhaps try redoing it. How much pressure was the Motive set to? It should not be at more than 10-15 psi.
Sounds like seized calipers. Common problem with brakes of this age. Overhauling is pretty straight forward and there are many threads on this subject. 302Tim has also written up a concise procedure.
you may go on a "roller brake tester" ( right word?? ) to see what will happen when you push the pedal. you changed the pads also?
Certainly make sure that the check valve in the line coming off the 7-12 intake plenum and going to the vacuum booster is working correctly (and is oriented correctly -- arrow points to the intake plenum -- should be able to "blow" thru in same direction as arrow). The step beyond that would be to "T" in a vacuum gauge at the vacuum brake booster vacuum inlet to confirm vacuum is reaching the vacuum booster.
Thanks guys... Oddly, took car for a drive today, and the issue is gone... Brakes work fine again... Last week right after a brake bleed, was when I had the issue. Weird. Rubber brake lines look fine, but age unknown. At least 10 years old... If it happens again will check brake vacuum, thanks Steve. Would old brake line cause something like this by blocking internally? System sat for a year with no fluid as the major took that long... Just waiting for tires to be available from tire rack again, and will rebleed the system. Calipers weren't frozen before the major, seemed fine. Pads are 90% didn't touch them... Perhaps the Pistons did slightly seize from lack of use and now broke free?
The moving component inside the check valve can get stuck on its seat (either by corrosion or contamination). The vacuum level at idle on a TR is not very high so one thing to watch is if you have no vacuum boost immediately after engine start-up, but do have vacuum boost after a hard engine deceleration (which creates much more intake vacuum and can crack a sticking check valve open) = that can be a sign the check valve internals are sticking. Of course, if the trouble never recurs = that's OK too
Or when removing the valve cover on the left bank, they snapped the vacuum pump shaft while removing the pump.
Thanks for the info... Very educational. I really appreciate you pros sharing your wisdom. We all appreciate it... Will pay attention and see if it recurs...
Thanks. Did the major myself, shaft looked fine... Though if I have low vacuum will recheck... As a cool factoid, googled this issue and an old post of yours showed up that predates ferrarichat, from 2003 . Ain't the Internet grand? Forever immortalizing our ramblings for the next generation... Thanks guys
It's advised to exchange old brakelines (metal and rubber) after so many years .... but how many of us really did ?
