Left rear brake disc (yes, rear disc) overheated last trip out to the point the brake fluid boiled and disc was smoking. Whether it was a sticking piston or internal kink in the final section of brake hose is moot now. Need to replace hose and caliper seals at a minimum. Left rear was the only one with an issue as I limped home (only 20 miles) by stopping every few miles and checking the temperature of each disc. Only left rear was overheating. Even with frequent stops, it got over 400 degrees by time I reached the house.Talked to resident automotive expert at work and he said the disc was probably softened due to annealing, the seals in the caliper ruined due to overheating and grease cooked away in the bearing. Been researching and I read the pads get glazed and ruined when overheated.So now what was going to be new hoses and maybe a caliper has turned into, at minimum; new caliper piston seals, new pads, new hoses and repacking the bearing.At worst it could be all that and new bearings and new caliper instead of rebuilding.I will replace all the brake hoses. I think 25 years is more than long enough.Anyone ever had a dragging rear caliper like I described? What was your experience with the work required to set things right again?

Doubtful that the bearings got overheated as they are probably oil bath. As for the caliper and rotor? Replace everything. Rotor is probably warped, the pads are shot and the caliper is probably already got serious issues. Would not hurt to replace the hose too. Then your entire brake system needs to be flushed and refilled with clean proper grade fluid.

Replace brakecaliper. Check both rears for cracking of the rotor.Check the rubber lines. There is three, one on each wheel plus in the center. Overheating could have been caused by fluyid not releasing back to the master cylinder.

Common problem, happens all the time. It can be a couple of different things. People always point at the sliding pins on the calipers but I have never had them be the culprit. More often the pads seize in their slots and very often a piston will seize due to swollen seals. I've had bad seals in the caliper piston bores only stick when the caliper is hot - when it cools off the piston freed up.Always replace brakes in axle sets - if you do one side, do the other side too. If you replace the discs you should replace the pads as well, and vice versa. Discs are not heat treated, are cast iron not steel, and can't be annealed. Heat won't hurt them, only abnormal wear. What can be damaged by heat are pads, caliper seals and brake fluid.Edit: bad on me for being unclear. Cast iron brake discs are indeed heat treated, but not to harden them. In the manufacturing process the discs are brought up to around 900 degrees Celsius (1650 F.) for around 4 hours. This is cherry red, and would probably cause the tire to catch fire. This anneals them, although I call it normalizing. Brake discs are also sometimes cryogenic treated, which involves taking them to a very cold temperature, which makes them a lot more wear resistant.Brian

The replies have given me hope this will be easier than my worst fears. I know I need to determine make of rear axle. I think it is a Dana 70 but it could be a Dana 80. If it is the oil bath variety I won't worry about the bearings.JD had several variants of chassis, some with the 70 and some with the 80. The parts and shop manuals I have list both axles.So new brake hoses everywhere is definitely in the plan. New calipers and pads across the rear sounds like a wise move. More money but mechanically easy to do. Maybe I can find new seals and rebuild the calipers cheap.

I would have a professional look at the rotors. If they have heat stress cracks they should be replaced. Easier to do when it is torn apart then to do it later.

Rotor and pads and bearings. Oh my! | Good Sam Community

23 Replies

VintageRacer
Explorer
Oct 28, 2013
Common problem, happens all the time. It can be a couple of different things. People always point at the sliding pins on the calipers but I have never had them be the culprit. More often the pads seize in their slots and very often a piston will seize due to swollen seals. I've had bad seals in the caliper piston bores only stick when the caliper is hot - when it cools off the piston freed up.

Always replace brakes in axle sets - if you do one side, do the other side too. If you replace the discs you should replace the pads as well, and vice versa. Discs are not heat treated, are cast iron not steel, and can't be annealed. Heat won't hurt them, only abnormal wear. What can be damaged by heat are pads, caliper seals and brake fluid.

Edit: bad on me for being unclear. Cast iron brake discs are indeed heat treated, but not to harden them. In the manufacturing process the discs are brought up to around 900 degrees Celsius (1650 F.) for around 4 hours. This is cherry red, and would probably cause the tire to catch fire. This anneals them, although I call it normalizing. Brake discs are also sometimes cryogenic treated, which involves taking them to a very cold temperature, which makes them a lot more wear resistant.

Brian
enblethen
Nomad
Oct 28, 2013
Replace brakecaliper. Check both rears for cracking of the rotor.
Check the rubber lines. There is three, one on each wheel plus in the center.
Overheating could have been caused by fluyid not releasing back to the master cylinder.
donn0128
Explorer II
Oct 28, 2013
Doubtful that the bearings got overheated as they are probably oil bath. As for the caliper and rotor? Replace everything. Rotor is probably warped, the pads are shot and the caliper is probably already got serious issues. Would not hurt to replace the hose too. Then your entire brake system needs to be flushed and refilled with clean proper grade fluid.

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Rotor and pads and bearings. Oh my!

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