1995 P32 Rotors Overheating

[1969SSCamaro]

I have a 1995 Georgie Boy Pursuit, 27', 454 TBI with front disc and rear drum brakes. Purchased the rig about 1 year ago and did a complete front end brake job: turned rotors, new ceramic pads, repack bearings, new rubber brake lines, new master cylinder, fluid flush, etc. I also meticulously cleaned all of the moving caliper parts with wire brush (using drill attachment) and applied grease (although I should have purchased extra as they don't give you much with the new pads). Since that time I have taken it out on several short trips and one longer trip (~500 miles round trip), but for the past 4-5 months it has been sitting in the driveaway. I try to drive it to work every 4-6 weeks when not using it. Last week I drove it to work and noticed a burning smell, which turned out to be the brakes. I measured the rotor temps at ~440 deg F -both sides; happend in the morning drive to work and the evening drive home. I drove it again to/from work about 3 days later and it was fine; rotor temps were ~ 240 degrees - both sides.

I have studied forums and two main causes appear to be bad rubber brake lines (swelling/pinched) or sticking calipers, but I supposedly took care of that with new hoses and brake job. The problem is evidently intermittent and the one time it did happen, both sides exhibited the same problem. Is it common for both sides to stick like that and/or could that help with diagnosing the problem?

Thanks for any/all suggestions.

[jyrostng]

Just to add to the thread, 1989 southwind 454 p-30 with hydroboost, leaking master cylinder was replaced with new Orielly unit. Bled fine front and rear disk brakes. first drive, high pedal but good brakes. 5 days later started on a trip, got about a mile, no free play in pedal and brakes dragging front and rear, bled pressure off on front and rear, worked fine for 500 miles. let sit for 7 hours at rest stop, again no freeplay in pedal and dragging brakes, bled pressure front and rear, fine for another 300 miles. I had determined the pushrod distance had to be off on the new master cylinder. I fixed it on the road by cutting a couple of 3/8's flat washers into U's and loosening the 2 master cylinder bolts, had the wife push on the brake pedal while I inserted the washers between the hydoboost unit and the master cylinder giving the piston more spacing to open the return ports to relieve the pressure when the pedal is released. No more dragging brakes the rest of the 3000 mile trip. I now have a full inch of free travel in the brake pedal.

[rgatijnet1]

turbojimmy wrote:
Glad you got it sorted out. I popped into this thread to ask you if you fixed it because mine was behaving oddly yesterday ('84 P30, rear discs). I replaced the rotors, calipers, pads and MC last year. It's been working fine. I took it out to get it inspected yesterday and about half way to the inspection station (about 5 miles in) the pedal got really stiff. The brakes still worked well - too well actually. The pedal was very "touchy". When I stopped at a red light I smelled that hot brakes smell. I pulled off into a parking lot and it was both front brakes that were hot and smelling. They were definitely dragging - I could feel it when I accelerated. I let it cool for about 15 minutes and it was fine again for the rest of the journey. But now I'm afraid it will do it again unless I can figure out why it did it in the first place.

That is almost a classic indication of contaminated brake fluid. The fluid gets hot, the water boils, which causes the brakes to drag. They will release as soon as the fluid cools and the water goes back to water instead of the pressure created by the steam. Try flushing your brake fluid COMPLETELY. Do not do just a bleed. It may take three quarts of fluid to properly flush all of the old brake fluid out of your master cylinder and all wheel cylinders.

[Gjac]

double post

[Gjac]

I am glad you got your brakes fixed. I spent a small fortune on my front end getting that right. Henderson makes some good replacement parts.Bell crank helped along with idler arm and ball joints. I would add the steer safe if you don't have it already. The other thing I would check is the ride height between the stops on the A arm. They are different for each P-30 chassis but you should have about an 1 3/4 inches. Good luck.

[turbojimmy]

Glad you got it sorted out. I popped into this thread to ask you if you fixed it because mine was behaving oddly yesterday ('84 P30, rear discs). I replaced the rotors, calipers, pads and MC last year. It's been working fine. I took it out to get it inspected yesterday and about half way to the inspection station (about 5 miles in) the pedal got really stiff. The brakes still worked well - too well actually. The pedal was very "touchy". When I stopped at a red light I smelled that hot brakes smell. I pulled off into a parking lot and it was both front brakes that were hot and smelling. They were definitely dragging - I could feel it when I accelerated. I let it cool for about 15 minutes and it was fine again for the rest of the journey. But now I'm afraid it will do it again unless I can figure out why it did it in the first place.

[1969SSCamaro]

The rotors were dark blue and trashed from overheating so many times; especially the last. He replaced rotors, calipers, brake pads and master cylinder. $1500 bucks (ouch), but we did not have any brake problems on vacation, so it was worth it. I guess it really might have been both pistons sticking, just strange that it was happening on both sides.

Just got home this evening after a 6 hour white-knuckle drive in 40mph cross winds from Lake Mead to home. The front end is still too lose and needs more work. I replaced the drivers's side bell crank and idler, which made a dramatic improvement, but it may be time to replace the passenger side bell crank as well. I will start a new post on this one as I am interested in installing a track bar, but worried the rear air bags might make that difficult or impossible.

[1969SSCamaro]

Mike,
Thanks, I will bring this up with the mechanic. I am going on business travel this weekend and need the MH working well as the day I return we are heading to Grand Canyon (BRRRR) for vacation. Tonight on the trip home fron rotors were 300 deg with ambient temp of ~55 deg. Let y'all know what I find out in the end. Thanks for all the great ideas/help - it is greatly appreciated.

[Mike_Hohnstein]

Push rod that seats against master cylinder piston clearance is critical. You might want to check into that, if the m/c piston isn't retracting quite far enough for venting of pressure on calipers, drag would be the result. Older medium duty truck applications typically had a adjustable brake pedal apply rod. Too much clearance you'd lose pedal, too tight brakes would drag. I went through about a gallon of brake fluid trying to get pedal on a old C-60 dump truck before I figured out the problem. Same deal on a old Ford bus chassis some time later, adjustable rod to master cylinder piston, brakes were dragging a little after rebuilding system, adjustment was very touchy..
I'm not suggesting OPs coach has adjustment but the way quality control can be, it's something to check into.

[1969SSCamaro]

enblethen wrote:
Looks like something is sticking.
Where did you find the cross reference on the O'Reilly website?
Doubt whether it is the hydro boost.
Does your rig have a proportioning valve on the rear brakes? It is normally located on right side. Linkage is attached to the differential housing then to the frame. It has an adjustment at the elbow in the linkage.

On Oreilley's website I just entered the GM PN and came back with multiple options, one of them being the Cardon MC I purchased. I don't believe there is a proportioning valve on the Diff as I recall trying to remove the input hose to the T-adapter where the lines split between LR/RR; The adapter was quite small and did not appear to have any adjsutments, but I will check a few other locations.

ON the drive in today the Front roters were at a smoking 525 deg and rear at 300 deg. I did brake a little harder on this trip and it showed. I normally baby the brakes and downshift at most stops.

[2bzy2c]

Here is my 2 cents - Since both front brakes are heating at the same rate, then the problem is common to both of them. That would pretty much eliminates sticking pads or pistons, since the temps seem to be so consistent with both front rotors.
Proportioning valve may be the culprit, but I sort of doubt it. Those rarely go bad.

I would continue to look at the Master Cylinder as the suspect device. Frankly, since you are dealing with a 7 ton beast, driving with possibly faulty brakes, I would probably defer to an expert in the field. Everyone here is trying to give you good advice, but none of us, including me are really qualified to offer reliable guidance to your solution.

It "could" be that your RV simply uses more front brake pressure due to the
fact it might be front heavy. That is often the case. A few stops could generate enough friction to heat up the brakes to over 400 degrees very easily. On my truck, my front pads get replaced about every 50K. My rear brakes at 180K are still at 50%.

You might not have a problem at all, but that could only be answered by a "qualified" brake expert.

Best of luck.

[enblethen]

Looks like something is sticking.
Where did you find the cross reference on the O'Reilly website?
Doubt whether it is the hydro boost.
Does your rig have a proportioning valve on the rear brakes? It is normally located on right side. Linkage is attached to the differential housing then to the frame. It has an adjustment at the elbow in the linkage.

[1969SSCamaro]

Oreilly's was only website I've found that could take the GM PN and spit out cross refrenced PNs and Cardone 131982 came up as replacement. So I think the MC is the right PN? Last night I drilled a hole in linkage and sprayed lithium grease - got some to come out the end of the linkage, so there was some penetration. I will drive it to work again today. Below is summary of temps for 13 mile drive to work;

Trip 1: Front 450 deg (did not measure rear)
Trip 2: Front 450 deg (did not measure rear)
Trip 3: Front 250 deg (did not measure rear)
Trip 4: Front 250 deg (did not measure rear)
Trip 5: Front 420 deg; rear 220 deg
Trip 6: Front 350 deg; rear 200 deg (this was last night)

Two other potential issues??
1) When I bled the brake system and replace the hoses, I was unable to replace the rear hose; could not get the bolt loose on the T-junction. I don't know enough about the hydraulic system to understand if that could be related in any way. The rear brakes appear to be working fine.

2) Could the hydrobooster be in early stages of failure (leaking seals?) and cause this to happen?

I am driving MH to work again today to see what happens. Strange that trip 3 & 4 everything appeared normal?

[1969SSCamaro]

Found the original GM PN below. Cardone does not have a PN cross reference capability on their website, but I will search a few auto store websites and eventually find it.


GM Part Number: 14066425
CYLINDER, Brake Master Cylinder
This genuine part is manufactured and warranty covered by GM.Your Price:$166.22

[1969SSCamaro]

For clarity the VIN is 1GBJP37N0S3318998.

I believe I verified that Cardone Select 13-1982 was compatible using the VIN, but can't recall which website I used that allowed me to enter the VIN.