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Hot brake discs all the time

15K views 26 replies 14 participants last post by  RF Overlord 
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#1 ·
I have noticed that the brake discs on my 2007 4cyl 4wd RAV4, 1100 miles, are always hot to the touch when I pull in to my driveway. Typically, the last 5 miles of most drives are on highway at 50-55 mph, no hills, no braking, with only one significant slowdown with moderate braking from 55 to 15 mph, in 30-40 degree F weather (no snow). When I pull in to my driveway a couple hundred yards later, all 4 brake discs are too hot to touch. The first couple of times I noted an odor like hot brakes but I have not noticed this recently. Is doesn't seem normal for the disc brakes to be so hot after minimal normal braking. Also, I have noted worse than average gas mileage. The hand brake is not engaged, and this has persisted too long to just be poorly adjusted tight brake calipers. Any ideas about what is going on?
 
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#4 ·
So you both think this is normal? It just seems to me that the brake usage is not enough to heat the discs that much, and it is not obvious to me what other normal source of friction might be producing the heat.

It was the smell of hot brakes that I noticed at first that led me to investigate. Since then, I sometimes just check the brake discs even though there is no burning odor.
 
#6 ·
It's always hot. That's normal... excessively hot that's a different story.

The reason why brakes are hot even if you don't feel you used it enough is because they are constantly touching the rotor.... barely but they still touch.
 
#7 ·
Your rotors are moving parts. They will always be hot to the touch even under short distances. The smell is probably coming from the new components (pads and rotors) breaking in. Unless there is some noise or you see some cracks or truly uneven rotors (not smooth) I wouldn't worry about it.

Everytime you step on the brakes, the pads and rotors create a lot of heat. I would be more worried if you were having issues with stopping.
 
#8 ·
The rotors will be warm, but I wouldn't consider it normal to be "too hot to touch" after what you described.

If they are so hot that you have to yank your fingers away instantly, there is definitely a problem. One thing you can do is buy or borrow an infrared heat gun that reads temp remotely by pointing at the target. Then you might be able to walk into the dealer and tell him "My left front brake is running 27 degrees hotter than the others." That is always good for a laugh.

To those who ask why you feel the brakes: it's a habit mechanics pick up. It clues you in to emerging brake problems before they get bad enough to strand you or damage parts. I check my hubs and brakes at least once daily on a long vacation trip, esp the trailer. If one brake is hotter than the others, or a hub is too warm, something is going on. I use a Raytek temp gun so I won't leave skin behind....
 
#11 ·
flyingn said:
like I said already.. one stop will make the discs too hot to touch.. :roll:
Flyingn, it reminds me of the wheel well cameras that they use to view disc brakes in races at NASCAR short tracks where brakes are used to the point of boiling brake fluid. Those rotors can turn (burn) bright red in just a few laps. It is neat to watch those rotors turn from a cast grey steel color to Barcelona Red in an instant. :egad:
 
#12 ·
Unless the original poster lives at the bottom of a freeway offramp, his brakes should NOT be very hot when he gets to his driveway. Sure they will get toasty after slowing hard from highway speeds, but they will cool rapidly in city driving, and certainly when tooling through typical residential streets.

When doing a brake check, you should try to stay off the brakes and drive conservatively as much as possible to minimize heat buildup so they will stay reasonably cool - then any abnormalities like a sticking caliper will be obvious. Slamming to a halt and then checking is pointless, and will probably result in a burned finger.
 
#14 ·
John E Davies said:
abnormalities like a sticking caliper .
From my experience the most common cause of calipers dragging on the rotor is the lack of adequate lube on the caliper guide pins. The calipers/pads 'float' laterally in the open and clamped positions. Without adequate lube the calipers can lock-up or at least not fully retract. Then pad wear accelerates in inverse proportion to MPG reduction. :shock: Sometimes it is so insidious that the driver is unaware of the problem.

Be advised the next time you have a brake job/pad replacement be certain that the mechanic specifically relubes the guide pins. It only takes a few minutes to do this. I believe many are in a rush and skip this critical step.

BTW, I always do my own brake work. 8)
 
#17 ·
RAV4Don said:
John E Davies said:
abnormalities like a sticking caliper .
From my experience the most common cause of calipers dragging on the rotor is the lack of adequate lube on the caliper guide pins. The calipers/pads 'float' laterally in the open and clamped positions. Without adequate lube the calipers can lock-up or at least not fully retract. Then pad wear accelerates in inverse proportion to MPG reduction. :shock: Sometimes it is so insidious that the driver is unaware of the problem.

Be advised the next time you have a brake job/pad replacement be certain that the mechanic specifically relubes the guide pins. It only takes a few minutes to do this. I believe many are in a rush and skip this critical step.

BTW, I always do my own brake work. 8)
What kind of grease/lubrication do you use on the caliper guide pins? Thanks!
 
#18 ·
RAV4 Toy said:
What kind of grease/lubrication do you use on the caliper guide pins? Thanks!
Any auto parts store carries a tube of this high temp, silicone (I believe) based thick grease. I can't think of a brand name off hand, but it will be label specifically for "disc brakes". It is also used for drum brakes on the star wheel and other contact points of the linings. If you buy remanufactured calipers (from CarQuest , AutoZone, etc), the kit generally include a small tube. DO NOT use any other type oil or petroleum grease or you could experience brake failure. :shock:
 
#19 ·
RAV4Don said:
RAV4 Toy said:
What kind of grease/lubrication do you use on the caliper guide pins? Thanks!
Any auto parts store carries a tube of this high temp, silicone (I believe) based thick grease. I can't think of a brand name off hand, but it will be label specifically for "disc brakes". It is also used for drum brakes on the star wheel and other contact points of the linings. If you buy remanufactured calipers (from CarQuest , AutoZone, etc), the kit generally include a small tube. DO NOT use any other type oil or petroleum grease or you could experience brake failure. :shock:
lithium grease
 
#20 ·
I doubt that the brakes are truly dragging but....

There are ways to check. If all the brakes are equally hot then that means all of them are dragging. My first question in this case would be are you driving with both feet, one on the brake and one on the gas. If so then maybe you are lightly dragging the brakes without knowing it. If that's not the case then I would on an empty road while going about 5-10mph put the car into neutral and see how far it coasts. It should coast quite a long distance. If it stops within just a few feet then you have a problem. Another way to test would be at a stop on a level road put it into gear and let the brake off without applying the gas. If the car doesn't role away without you applying the gas then the brakes are dragging.
 
#21 ·
Hot brakes on front, then back too.

I have a 2007 RAV4 V6 4WD with 86K. No problem with brakes until a week or so ago. Started smelling odor in cabin on a highway and stopped in a parking lot 13 miles from home to check rotors. HOT! in front only, back ones warm. Drove on to destination another 45 miles at 60-65mph and last few miles thru town traffic to another parking lot and checked again. COOL! Since then, have continuously had symptom of hot brake smell during any trip over a few miles. I've checked front mostly to find they are always hot. Back rotors have been hot sometimes. Dealer can't determine a fault at this time. Said 150-250 degrees is normal. I won't dispute that, but when I checked the one time where the rotors were luke warm /cool to the touch, that certainly isn't 150 degrees. I left the dealer once, drove maybe 5 miles in town traffic, with stop and go driving, checked them at next destination and they were just as hot as if I'd traveled 50 miles. The pads are down to 4mm in front and 6mm in rear. Just on the edge of replacement I'm told. Average mpg is not unusual so far. Have a long trip coming up and am uncertain I want to drive this vehicle. Advice?
 
#23 ·
And most brake pads are built a little too big. I always end up shaving to shave off a few mm on the "wings" so that they can actually float. Basically you should be able to remove the pads with just one finger. Other, your properly lubricated caliper pins will not function properly.
 
#26 ·
rotors will get hot during normal braking, but if you smell burned brake pads they are overheating. This could be due to the caliper piston not releasing and or corroded. In addition to the guide pins. The method I prefer is to jack one of the tires off the ground and block the other tires from moving and put the car in neutral. Spin the tire that is off the ground it should turn freely...if not its most likely the caliper piston not releasing thats causing the drag. Check all other wheels if they are moving freely or dragging its easy to tell this way...Other wise its possibly your brake booster.
 
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