Brake Problems

gwalls · 12-08-2008, 10:10 AM

Finally drove Jeep after 2 1/2 years of rebuilding. Put about 20 miles on it Saturday. Right front brake is dragging and overheating and causing it to lock up. I've got new stainless steel lines and proportion valve from inline tube. New rear wheel cyclinders and all brake hardware. New Power Booster. Rebuilt master cyclinder and front calipers. The Proportion valve is really close to my inframe Headman Headers. Would Proportion valve getting too hot cause the right front caliper to stick or is it just a bad caliper and it sticking? Thanks for any advice.

Saltydawg1 · 12-08-2008, 11:20 AM

Sticking caliper would be my first guess.

gwalls · 12-08-2008, 11:34 AM

Thanks. Just don't really know how proportion valve works. Was wondering if fluid could be getting too hot and causing expansion and pushing on caliper.

**jatepper** · 12-08-2008, 12:10 PM

I dont think the fluid would be getting too hot. Do you have a brake warning light in your cluster? Does it come on? If it comes on, it is likely a prop valve problem. IMO

gwalls · 12-08-2008, 02:32 PM

Brake warning light not hooked up. I put in a new Painless wiring harness and then when I had to replace the proportion valve the old harness was a 2 wire hookup and the new valve is a 1 wire hookup so not really sure how to hook this up.

**Mike Romain** · 12-08-2008, 03:11 PM

The rubber line from the steel one to the caliper can separate internally acting like a valve which can cause that. How old are they?

gwalls · 12-08-2008, 03:50 PM

Not sure about the rubber lines. Will have to look at that tonight. Thanks

gwalls · 12-09-2008, 10:37 AM

Pulled wheels last night. Seems as both sides are sticking but passenger side is worse. Would the fluid boiling next in lines next to the headers cause the fluid to expand and put pressure on calipers? Also if the fluid got to hot does it need to be changed out? If I pull the caliper off the wheel spins free. If I push the piston back in and remount it still spins free. But after driving for a while it sticks and causes the wheel to be hard to spin.

MikeMCJ · 12-09-2008, 10:48 AM

what year CJ? Did it once have drums? There may be a residual backpressure valve that is keeping too much pressure in the lines. I'm no expert at Jeep brakes, but I am pretty sure there are 2 different backpressures based on drum (10 psi) or disc (2 psi). Discs need less pressure as they don't have to deal with return-spring tension.

I'm currently collecting parts for a knuckle swap and power brake booster/mc/p.valve from a wide track (got the axle parts and picked up the booster/mc/p.valve last night), so I would like to hear from the people that have done the research so I don't end up PO'd because I didn't assemble the right parts the first time.

**esearscj7** · 12-09-2008, 10:52 AM

I second what Mike Romain suggested about the rubber brake lines. I had that happen to 2 cars. If they are old that is most likely the problem.

Saltydawg1 · 12-09-2008, 10:54 AM

Mike brought up a good point about the rubber lines. Those are the second thing I'd check after looking for a sticky caliper.

If it's only one wheel sticking the problem is usually a rubber hose or caliper.

If both wheels up front or in the back are acting up then you may have proportioning valve or master cylinder problems.

Brake fluid is designed to handle high temperatures very well. Its still possible to have heat soak problems but I would make sure your rubber hoses and calipers are in good shape first.
I had just assumed that since you replaced pretty much everything else you would have naturally done the rubber hoses. It is a pretty common problem to find among aging vehicles and ones that have sat for a long period of time.

**Mike Romain** · 12-09-2008, 11:01 AM

Quote:

Originally Posted by gwalls

Pulled wheels last night. Seems as both sides are sticking but passenger side is worse. Would the fluid boiling next in lines next to the headers cause the fluid to expand and put pressure on calipers? Also if the fluid got to hot does it need to be changed out? If I pull the caliper off the wheel spins free. If I push the piston back in and remount it still spins free. But after driving for a while it sticks and causes the wheel to be hard to spin.

The headers could be an issue, but the pressure would go away when they cooled down.

Did you put a new master cylinder in? They make two flavors, the one for drum brakes will cause the calipers to load up like that and drag. I have seen the wrong one in the box also...

gwalls · 12-09-2008, 11:08 AM

The rubber lines were replaced with new braided lines. Rear wheel cyclinder, inline tube stainless prebent lines and proportion valve, booster: all new. Calipers rebuilt from Advance auto parts. Master cyclinder rebuilt from Oreilly's. They seemed to match the old factory one when pulled out but no way to tell now as I've returned them for core. The right front sticks to the point I can almost not turn it by hand. The driver side wil turn but still dragging more than it should.

**Mike Romain** · 12-09-2008, 11:18 AM

The only thing in the system that is supposed to 'hold' a back pressure is the master as far as I know. If they have the wrong valve in there it will hold too much.

MikeMCJ · 12-09-2008, 11:28 AM

Quote:

Originally Posted by Mike Romain

The only thing in the system that is supposed to 'hold' a back pressure is the master as far as I know. If they have the wrong valve in there it will hold too much.

exactly, a residual pressure valve, most often incorporated into the MC.

I doubt the heat has anything to do with it. ever see how hot cup car's rotor gets at a short track? brake fluid boils, but it would act spongy

my guess would be the MC. I do not suspect the proportioning valve.

12-09-2008, 10:48 AM	#9
MikeMCJ Registered User Join Date: Oct 2008 Posts: 485 Profile Gallery Classifieds My Jeeps	what year CJ? Did it once have drums? There may be a residual backpressure valve that is keeping too much pressure in the lines. I'm no expert at Jeep brakes, but I am pretty sure there are 2 different backpressures based on drum (10 psi) or disc (2 psi). Discs need less pressure as they don't have to deal with return-spring tension. I'm currently collecting parts for a knuckle swap and power brake booster/mc/p.valve from a wide track (got the axle parts and picked up the booster/mc/p.valve last night), so I would like to hear from the people that have done the research so I don't end up PO'd because I didn't assemble the right parts the first time.