Caravan: Both front calipers seized????

Two bad calipers are possible. Bad hoses that are frayed inside. Bad master cylinder, won't release pressure. Don't know if it has abs, but that is another possibility.

sounds like someone has adjusted the brake pedal free travel so the fluid pressure equalization circuit hole is blocked. probably happened while under the dash with the rack, they thought they'd "tighten things up". re-adjustment of the pedal travel back to standard spec should solve the problem.

how is that going to happen?

Programbo wrote in news:0a5ebb81-f345-43b4-a320- snipped-for-privacy@29g2000yqq.googlegroups.com:

Did the garage need to remove the master cylinder to replace the rack?

As a follow up..Is it possible the master cylinder is allowing fluid to freely pressure the pads into the rotors but not allowing it to flow back the other way and that eventually causes the problem I described?

It would have been more logical to check if the brakes were locking up or dragging. Have you checked for this? If you haven't, then you should.

kinda. but it's really the pressure equalizer valve being closed, so as the brake fluid warms up during use, it expands and starts to apply the brakes.

check out tegger's excellent write-up on master cylinder operation.

1. I was thinking that maybe they were almost freezing up already but not noticed.
2. Something the shop did to the calipers or bushings.
3. Shop stretching the hose and rupturing them internally during the r&p replacement.

Just thought of another thing: Vac Booster is not letting go due to: booster push rod out of adjustment bad atmospheric valve

Programbo wrote in news:a7e4be99-51ad-495d-9273- snipped-for-privacy@g25g2000yqn.googlegroups.com:

Yes. That's why I asked the question I asked.

It's not part of the procedure. Everything is done under the vehicle except disconnecting the outer tie rod ends.

After only 17 years?

Absolutely.

As far as anyone reading your account knows, the rack and pinion was changed because stuck brake calipers were causing the whole front end to shudder. Some of the symptoms may have been alleviated but not the root cause.

-jim

maybe, but if the symptoms are as bad as you say, you should have noticed before the rack was changed.

swap in crappy ones? that's not probable.

why do people so susceptible to this "ghost in the machine" argument? hoses are hollow rubber cylinders. any rupture goes external and you lose brake fluid. there's no internal componentry that can cause this effect. the only possibility is a twist in the hose causing a pinch. and that will be obvious if you take the wheels off and look.

before you do that though, press the brake pedal with your hand. if the free play has been adjusted out, you've found your problem.

not so. if a shop clamps off brake hoses with vice-grips etc. it's entirely possible that they may be damaged internally but that that damage isn't visible externally.

nate

have you ever seen this? have you ever tested for it? and what do you think is the mechanism for its occurrence?

yes. yes. a flap of material coming loose around the area that was clamped.

nate

There's a "whip" test for brake hoses. (SAE probably has it covered) Entirely possible for one of the braid layers to degrade and project into the internal passage at the completion of the test.

1. how does it form correctly oriented?
2. how does it form to be the correct length longer than the bore of the tube?
3. how does it manage to fold onto itself given that it has to be longer than the bore of the tube?

external clamping pressure can achieve none of these things - #3 particularly. there's no "flow" in the tube that can magically assist in this function either.