Advice on Overheating Rear Discs

either the hand brake adjustment wasnt slackend off when they replaced the pads, which would mean with new pads in the brakes will be on all the time, or the pistons have stuck or the pads have stuck int the holders.

either way there is a serious fault.

if the brakes are hot to start with when you come to use the brakes they will have lost some effiency because of the heat.

also there is a danger of the brake fluid boiling thus causeing rear break failure.

try jacking a rear wheel up secure the front wheels ( do not jack up on a slope) release the hand brake and see if you can easily turn the wheel.

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There's also another possibility that can cause brakes to stick and overheat that is often overlooked by everybody. Somewhere in the hydraulic run from your master cylinder to each brake there is a short flexible hose. The inner tubing can collapse and act like a check valve that keeps a small amount of pressure on that brake. Most brake repairs and inspections just look at these hoses to verify that they are not externally cracked and/or leaking. But this hidden internal failure can give exactly the symptoms the OP described.

My daughter had a little ford and that had a problem with brakes not releasing, high fuel use and new brakes. After sticking it up mechanic they discovered a small spring had broken in the master cylinder and was not allowing brakes to come all the way off. The comment, nothing was wrong was one I got from the mechanic at the time, it seems that no one these days questions why something occurs just grab new bits.

It may not be your problem but worth following up if brakes are staying on, your fuel useage must also be high as you are dragging the brakes.

I'm with Peter. I would check the hand brake adjustment first.

Maybe the pistons are sticking in the calipers? When was the last time the brake fluid was flushed?

Most manufacturers suggest flushing out old brake fluid every two years. It picks up moisture that migrates down to the calipers. Can cause corrosion and sticky pistons. Good brake fluid is almost clear to slightly yellow in color. If it's brown, it's contanimated with water and should be flushed.

Not hard to do, with a helper, bleeder hose tool for less than $6 and a couple of bottles fresh of brake fluid, you can do it in less than an hour. Avoid sucking air into the master cylinder by bleeding down the old fluid until it's just above the inlet on the master cylinder and then add fresh fluid. Bleed the wheel farthest from the master cylinder first, then work your way to the closest wheel. Bleed each wheel caliper until you see fresh fluid in the bleeder hose.

Good luck with your quest.

Be aware that if you have one set of brakes hot, front or rear, then the front ones are the ones that should be warmest as in most vehicles they do from 60 to 80 percent of the braking. This is why they are usually larger in front than they are in the rear. The dealer is not going to be real quick to say that there could be a problem as he might have to make a repair for free and most mechanics today are parts replacers not true mechanics. I doubt that you could find very many left that have ever done a true total tune up or used the old Sun Distributor machine and most would not know that the handiest thing to set the points on the old Ford distributors was a book of matches. But then I can remember when you started your car, turned on the radio, and heard nothing but static for the first few min until the tubes warmed up. Have them check the brake fluid lines and make sure that they differential valve is properly working and then have the dealer check temp of the brakes themselves. If they can't fix it then call Mazda and keep complaining. Do not adccept that it is the "floorboard carpet" causing the problem or some other oddball answer. If they can't find it an fix it then aske them who can. They should know better.

Rich Hurd

My thanks to you and to all other responders for advice. My position is that although I have in the past maintained a variety of aged cars myself, and therefore already have a fair working understanding of car mechanics, I have with this vehicle left all the servicing to the main dealer I bought it from; I most certainly was not expecting to undertake any diagnostics or therapeutics. I agree with you that the main work is done with the front brakes. The service manager claims that the front brakes don't get warm because they are ventilated. My view is that this does not explain an enormous difference after trivial braking at speeds appropriate to country roads and villages.