Issue w/1999 Minivan Front Brakes

Assuming an OEM part was installed I would lean towards a contaminated system. Look at the seals on the master cylinder top and see if they are swelled up to the point they protrude out. This would make the cap hard to put on. If this is the case, it is contaminated.

Glenn Beasley Chrysler Tech

As always, thanks for your advice Glenn. You are great about providing advice and sharing your knowledge. I have never had an issue like this ever before so appreciate the input all the more.

I removed the cap and the rubber seal in the cap appears to be fine. The cap was easy to unscrew/remove and then reinstall. Fluid was still full and looked clean through the translucent plastic reservoir. The master cylinder appears to be slightly different in size and shape from what I recall. Not sure whose part they used ... receipt does not indicate a name or part number. The cylinder is stamped "7C E6K" on the front. A Google search on E6K (7C possibly a date code?) and 7CE6K yielded nothing.

Just double checked the receipt and the vehicle has 1,200 miles since the second MC replacement. So assuming they used the correct master cylinder and the system is contaminated, what is the recommended remedy? An if not the correct MC, what would cause it to build this pressure in the lines over time?

Bob

I'd be curious, since there's no mention of the back brakes or wheels getting hot, only fronts. did anyone check to see if the front calipers are dragging or binding? is one brake pad in front wearing more than the other? that might be a sign. like i say, i was just curious if that had been looked into. I've had calipers drag due to a broken piston that would on occasion tilt sideways a little bit and drag like hell.

I've seen this more than a few times on the LH platform, master cylinder leaks fluid out the back, power booster is ruined by the brake fluid, specifically the pushrod where it passes thru the booster diaphragm, it gets corroded and won't allow full release of the master cylinder.

Do you hear a wooosh noise from under the dash when you press the brake pedal?

If the problem was not there until they installed the master cyl, get your money back or tell them to install a MOPAR part before going any further.

Glenn

Rob,

The calipers are functioning normally and do not bind. Both front brakes do get very hot so both are dragging equally it would appear. The rears, which are drum brakes are indeed cool.

Bob

Aarcuda,

Thanks for the additional thought. I'll report this to the mechanic and will also report Glenn's instructions to only use the Mopar part too and see what he says. That all said, the mechanic told me previously that the leaking master cylinder was a pretty frequent occurrence on that vintage minivan and said that they had replaced many of these over the years, but never seen the problems they are having with my van now.

Bob

Glenn,

Thanks again for the thoughts. There were no other braking issues prior to the preventive replacement of the leaking master cylinder.

As I just noted in my response to Aarcuda, the mechanic at this garage (who I trust) told me they replace these fairly frequently and have never had any previous issues like I am experiencing now. I'll ask them to look at the brake booster for the damage/issue Aarcuda noted and if that does not pan out, then ask that they replace the cylinder again with the Mopar part. I am willing to pay the difference in the cost of the part, but will ask them to eat the cost of the labor and re-bleeding the system since this is a safety liability concern. I also have issues with my wasted fuel, wear and tear on the transmission, and the worn out front pads and heated/warped rotors, but this will also likely be at my expense.

They have been pretty good about this thus far, so I am hoping we can come to terms on getting this fixed permanently.

BTW, Can you share any additional insight on why you feel that the Master Cylinder for this particular vehicle (1999 T&C Limited) must be Mopar to work properly?

Bob

The other suggestions are good but I wonder if the push rod is just adjusted too tight. The lines are supposed to be open to the reservoir when the pedal is released so that no pressure can build but if the push rod slack is adjusted too tight the pistons in the master cylinder might not fully retract and uncover the reservoir ports when the pedal is released. What this does is since the brakes are dragging slightly they start to heat up and the heat causes the brake fluid to expand but since the ports are closed the expanding fluid has nowhere to go and the pressure starts increasing which applies the brakes harder so they get even hotter and the pressure goes up more in a positive feedback cycle until the pressure either forces the master cylinder piston back far enough to uncover the port and bleed off or until the brakes lock completely.

Because the first 2 aftermarket ones caused a problem!

Daniel,

Another good idea to pass on to the mechanic doing the work. Based on Glenn's replies, it also could be that the newer (and after market) cylinder requires adjustment when installed. Thanks for taking the time to reply.

Bob

"Daniel Who Wants to Know" wrote in message news:l%Dek.197717$TT4.29107@attbi_s22...

I'll put my $1.50 on Daniel being right or the corrosion on the plunger mentioned earlier being right. It sounds like the master cylinder isn't being allowed to fully retract for some reason.

Steve B.

Thanks for the thoughts, but hits is NOT the issue. All calipers function properly and the proper shims are in place and the guides and pins are lubed and move freely. As I noted previously, BOTH front brakes seem to drag slightly causing the heating ... but this only happens after extensive miles are put on the vehicle. Driving around town for 5 miles and displayed fuel mileage seems normal, the brake pedal is normal and the front wheels are normal warm to touch. Drive 50 miles on stop and go highway (not Interstate) and pedal gets high/tight, fuel mileage decreases noticeably, and BOTH wheels are too hot to touch. Definitely some type of residual pressure issue in the front brake lines ... probably related to heating. I need to follow up ...others prior suggestions are the likely cause. Thanks for the time to reply.

Bob

I wanted to post this message to close out my own post from several weeks back regarding brake issues I had after the master cylinder was replaced on my 1999 T&C Limited minivan.

I took the vehicle back to the garage where the previous work had been done and gave them another chance to fix the issue. They told me that both of the previous master cylinders had come from the local Chrysler parts counter and that my VIN had been used to assure that they were indeed the correct part.

Based on what Aarcuda and Daniel had suggested in this thread and with some additional research from the Internet to support the diagnosis, I had them go ahead and replace the brake booster too. We've now had the van back for a week and a half and have noticed that the brake pedal feels better and we have not noticed the back pressure that was occurring previously. We are optimistic that this will fix the problem.

I speculate that the slightly leaking older master cylinder compensated enough for the bad brake booster that this was not an issue prior to having the master cylinder replaced. In any event, I just anted to close out this post so that anyone experiencing this brake pedal back pressure and dragging/locking front brakes in the future knows to look also at the brake booster.

Thanks again to all for the valuable comments and ideas that helped steer to this component.

Bob