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Hector Munro

Hot Rear Brake Discs

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On advice from my garage I had the rear discs and pads replaced on my MR2 (2004 with 85,000 miles) at the end of January. I took care with the discs to wear them in. I have driven around 600/700 miles since the discs were changed. This has been on motorways, A road, country backroads and some town driving.

However, since the two discs were changed they have both been running constantly hot - over a distance of 12 miles and moderate braking you can burn the skin off your fingers, and hear the tink, tink, tink of cooling brake discs after the car has stopped. The discs heat up even if I don't use the brakes, or use them very gently.

The calipers have been stripped down twice and the handbrake cable adjusted as well. When the car is on the ramp the wheels turn freely and the handbrake cable works. - I have watched the mechanic turn the wheels.

However, all the post-change disc work has not solved the problem.

While I appreciate that heat is generated in braking, and that discs become hot through use, the heat generation seems a little excessive. Before the rear discs were changed I could drive for 180 miles and still have reasonably cool discs when I completed the journey.

Any ideas for a diagnosis?

I should add that the front brakes are running as normal. The changed rear discs are making a huge difference between the temperature between the front and the rear discs. Should this be the case? I've never had such a great temperature differential before in all the 85,000 miles I have driven the car.

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I've owned an Mr2 Roadster since 2003...and do my own service and repairs when possible. You say the calipers have been stripped down twice. Do you mean the caliper units has been refurbished or simply unbolted from the carrier - given a quick clean - then rebolted onto the carrier frame after replacing the discs? There's a BIG difference...as sometimes a garage will say they've 'stripped down' an item when all they mean is they've given it a quick clean with a wire brush!

From personal experience I can confirm that:

1) The caliper pistons do eventually seize slightly and combined with sticking slide pins it's enough to cause overheating discs.

If the garage has actually REFURBISHED the calipers and cleaned the slide pins and replaced any corroded pins/damaged boots then that only really leaves a sticking handbrake cable...

Dave C

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