Caliper not releasing properly - wheel occasionally hot


While my car was in for a small repair recently, the mechanics noticed that one or both of the front brake calipers were not releasing properly - they cleaned up the calipers, found no corrosion or obvious damage, but warned me to keep an eye on it.

Which I’m doing, and have noticed that the front passenger-side wheel is occasionally noticeably hotter than the other wheels - though not always… so I guess I do have an intermittent problem with this caliper. 

Just wondering if this is something that I should get seen to immediately - i.e. could it ultimately prove dangerous, or might it just sort itself out in time? I’m inclined to leave it until it comes time to change discs/pads, as I’m not noticing anything when driving, but presumably this could affect the handling/steering accuracy if it gets worse? 

Any advice appreciated, not had any brake problems before so not sure how drastic a problem this is!



Very difficult to acertain what could be wrong but definately you have an imbalanced braking on the fronts if one is hotter than the other. The rears will be noticeably cooler to the touch as most of the braking forces will be loaded to the fronts.

One of two problems or both. One caliper piston is sticking/seized and/or the caliper slide pins are seized. If they have been recently stripped and cleaned I would be guessing the caliper piston is starting to give trouble and seizing. This happens with age and of course maybe past lack of maintenance, I can say it’s a reoccuring subject we get on the forum. Recon OEM calipers are available, advice don’t buy cheapo immitations unless members can verify their worth.

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Best get it sorted sooner rather than later. They can lock on, and this one is giving you the warning now. Count yourself lucky, but don’t push it. It won’t resolve itself. Also the problems with removing a locked caliper can be challenging.

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It’s an hours work to give the caliper a quick going over.

Check free movement of the slider pins, clean the sliding faces of the carrier and pads (and maybe lubricate with copper grease)

Being honest, the hardest part is probably jacking the car up and taking the wheel off.


I do not think the OP is a spanner thrower.

If that is the case it is not economic to pay to have the caliper rebuilt at the local garage.

Just get a refurbished caliper from one the known caliper remanufacturers.

Caliper say £70 plus brake fluid and labour total cost around £150 to £200 fitted.

Swapping over to an new caliper is one of the easiest fixes going if the OP has a socket set and a trolley jack - it is just two bolts and the slider pin. There are excellent videos on you tube.

I would get if fixed quickly as heating up the hub with a stuck caliper can finish off a wheel bearing which is definitely not a simple fix.

Well I’m a “spanner thrower” when I figure I can do no harm… I’m happy to strip down parts of the engine bay, change external belts/hoses/coolant/service parts, fiddle around with electricals etc, but I wouldn’t trust my DIY skills with something like brakes. Plus, the garage who spotted the problem did give them a good clean down and inspect already. 

Sounds like good advice not to mess around with this and just have reconditioned calipers swapped in - have found these sold from a few places for around £80.

Thing is though, have been checking wheel/disc temp several times per journey, and since I last posted have noticed no problems whatsoever. Front wheels always a bit hotter than rear, but that’s normal I think (isn’t brake bias about 80/20 in favour of front on mx5s?) but no noticeable difference between left and right. Also, I did a longish motorway journey yesterday - so high speeds and not much braking, which is surely circumstance in which a sticking caliper would reveal a problem - and stopped a few times to check wheels, found no undue heat.

First sign I see of any further problem, I will definitely get caliper changed, but for now I do think the pads may have just bedded in to a point where it’s fine - I should mention car was sitting in a barn for six years before I bought it, and there was some surface corrosion on discs - nothing MOT had any problem with, but I do wonder if it maybe was enough that the pads needed to bed in to the discs again properly? Rub a bit of the surface corrosion off that may have been causing friction? But like I said, my knowledge in this area is limited, so let me know if this sounds like a bad theory!

I was wondering, is there any point jacking the car up under the suspect wheel and seeing if it turns freely? Presumably if caliper wasn’t releasing fully, I’d notice the resistance? I don’t have a trolley jack, but couldn’t I just use the jack in the boot?




Buy a cheap Infra Red thermometer off ebay less than £10 and for the next few weeks check the temperature of both front discs 180 degrees from the caliper.

From experiance it will misbehave again and when you are away from home!

Agreed this is not a job to be done without supervision the first time as you are working on brakes.

Easy after the first attempt.

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Good idea - didn’t realise they were that cheap! Do you know what sort of temp range I’d need? Cheap ones seem to go up to about 380 degrees C. 




If there’s an issue with your braking not only is it an MOT failure - it’s down right dangerous to you & other road users - get it fixed ASAP.

I had a small leak in my rear callipers which I never knew about till I was getting a pre-MOT inspection, I got them replaced the next weekend i.e. yesterday £80 labour plus the cost of parts also got new rear pads done at the same time - MOT in a fortnight and unless there’s an emission issue she shold pass with no advisories - or maybe one for the exhaust being not done but on it’s way.

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This sounds like all good advice, I do appreciate it, but I have already absorbed this point, and have no intention of taking any risks with brakes. However, calipers were cleaned up by a trusted garage, and pronounced perfectly fine, but they recommended I keep an eye on them. If I took it in now, I’m not even sure which caliper would need replacing! Hence, what I need tips on diagnosing whether a problem might remain with either caliper or not. And there may be no problem. I think a lot of people would leave it at this, but I’m a bit more cautious, and do want to double/triple check that all is OK. 

Infared thermometer sounds like best idea, but can anyone confirm temp ranges needed? The ones I’m seeing go to around 380 C, but I’m sure I’ve read brake temps up to 700C mentioned? Although I guess this is after very heavy braking, and a 380C one should be enough to register any significant difference after a “normal” drive?


IMHO the infrared thermometer is a waste of time and money. When your caliper seizes on you’ll smell it and touching the wheel will burn you. You don’t have to know what the temperature is, just know that if it’s too hot to touch there’s something wrong. If this has had a good looking at by someone who’s know what they’re looking at, and looks fine. Then the problem will probably be the piston sticking. They can have problems with rust, this happens when the fluid isn’t changed regularly and absorbs lots of water. If you’re not convinced there’s a problem. Then monitor it. Just touch the wheels every time you get out the car. If it seizes on you’ll feel the heat from a foot away and smell the burning.

If the car hasn’t had an overhaul of the breaking system this may be a good time to do it and learn a little. It’s really very simple to strip them down, grease them up and reassemble them. There’s a really good ‘how to’ in the download section here on the owners club site. There’s another good guide on the Mazda Menders site. If the car sat doing nothing for 6 years, then it’s well overdue.

PS. I’ve owned my 5 for almost 4 years now. I’ve had 2 of the calipers seize. First the warning, with a hot wheel occasionally. Then the full on lock with the burning smell. I overhauled the brakes in the summer of 2015 with the help of the above mentioned guides, and everything’s been fine since. I don’t consider myself much of a mechanic. But I know my brakes are 100% solid.

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The temperature range of the thermometer is not all that significant for what we need.  After a normal domestic run the brakes in good nick might be somewhere between 25C and 35C, typically five to ten degrees above ambient.  The peak temperature might get very high, maybe even dark cherry red (>500C) from a heavy duty emergency stop on the Motorway, but by the time you stop the car at home and get out to measure them I would be very surprised if they were ever as much as 100C.

On my old Vectra it showed one wheel a couple of degrees warmer than the rest, and this turned out to be a tight rear wheel bearing (not brakes), not yet noisy but enough to be beginning to affect tyre wear pattern and occasionally throwing up the ABS light at motorway speeds because the apparent rolling resistance was different.

On the MX5 the front left brake was sometimes slow to release, but was always OK when tested with the wheel jacked up.  So I carried the thermometer in the car for a few months and did a quick read of the four wheels after every trip, less than a thirty seconds in all.  The only apparent symptom was it often but not always ran just a couple of degrees hotter, however eventually the one pad wore twice as quickly as the other three on the front.  So at the last service I asked them to clean the sliders etc on both fronts and and give them new pads.  Now it is always the same temperatures left to right and no hint of pull on the steering at any time.

However the thermometer is useful for many other things than cars, and I bough mine before thinking about using it on the car.  I first used it to identify hot spots on the house where it was losing too much heat in winter, and also the corresponding cold spots inside.  This allowed an economical cure, much cheaper than throwing lots of money at a builder.  I also used it to check on a couple of freezers, and confirmed that one of them (brand new from Zanussi) was not fit for purpose because of inadequate insulation.

I bought this thermometer, not the best (I only gave it a four star review), but good enough.



You will find the MPG much improved as well after the replacement 

I bought an infra red thermometer from Aldi. With free brakes I find the disc temperature after a run and then gently braking into my dive is around 30 C. When one of my front calipers was sticking that disc was about 90C. A seized caliper would be much higher. If you check your disc temperatures regularly it will give you advance warning of problems before they become more serious. It is also useful in measuring radiator temperature at the top and bottom.

In my days of manufacturing one of the mantras was 

Measure   Monitor  Maintain

It is just as valid for car maintenance.




Lifting the car and spinning the wheel by hand is as good as an indicator than anything else to be honest.

You’ll feel the resistance.


Going back to being a spanner thrower, if you can change a aux belt, spark plugs, etc, then your’e certainly capable of cleaning the brakes.

2 bolts is all that holds them on.

You could even get away with removing only one and pivotting the caliper on the other.


I’d want to invest in a set of axle stands or a block of bricks for support though.

The brakes are way easy than the aux belt. If you can tell a bolt is nipped up you can do the brakes. You will need to bleed the caliper if you change it. That though is also dead simple. ignore the postings where people seem to struggle with it but I avoid ezibleed like the plague - I’ve had two and all they have done is spray brake fluid over me and the engine bay. A bleed tube for £1, brake fluid, a jam jar and an assistant (I use my 8 year old daughter) works fine.

Many thanks for all this info, much appreciated, especially all the temp ranges I should be looking for. I have now ordered an infared thermometer (am sure it will be a useful addition to the toolbox in any event)

After a more vigorous run yesterday I did think the left wheel was slightly hotter again than the right, but obviously it’s hard to tell accurately just feeling wheel - but certainly nothing alarming, no smell either. Car also rolls fine on gentle slope - plus have been making a point of reducing speed a bit early at junctions, letting it roll the last few meters - again, no obvious resistance felt. 

It’s going to bother me until I’m sure though, so I think the thermometer is the surest way of finding out if I’m imagining it. If temps don’t seem right, will get caliper(s) replaced with no further hesitation.

As for doing the work myself, I do agree it doesn’t sound like a hard job technically (can’t be as damaging to the knuckles as replacing a mk1 alternator!), but I’m inclined to let the experts deal with this one for now - just in case there’s anything else going on there. However, once I’m sure all the basics are working fine, this is a task I may come back to, as it would definitely be useful to become more familiar with the braking system. 

Anyway, thanks again, and will be back with some temp readings in a few days!


When my first caliper seized, I let a reputable well thought of MX5 specialist do the work. When the 2nd one went I had time to do it myself, and overhaul the complete braking system. I found the caliper done by the MX5 specialist had no grease at all on the slider pins. They also failed to notice the brake pad on that caliper had worn at an angle and needed replacing. I don’t think it would have lasted long before I had problems with that one again. Sometimes it’s worth doing it yourself, then you know it’s done right.

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