[hackzaw]

I recently had my 06 MDX in for an oil change. They warned me about a potential problem with my rear drivers side wheel. They said when they had it the air they could hardly turn the wheel.... I thought they were just fishing for extra work and would check it out myself before doing anything.

I drove home and grabbed my cheap infrared thermal sensor to measure the temperature of each rotor, and sure enough, my rear driver side rotor was about 100 C and the rear passenger side was about 50 C. As an aside, the next day I repeated the test but tried to mostly coast limiting as much as possible how much braking I did, and I got the same result but this time I also check the front rotors. On this occasion, all three read about 100 C with only the rear passenger being about 50 C.

I also jacked up the car on each rear side only to rotate the wheels by hand. There is a definitely a difference in resistance from drivers side to passenger side, but it didn't fell like a "huge" difference. I haven't jacked up the front yet. While the car was jacked up I test the E-brake and noted that with it depressed I can't rotate the wheel, but with it off, I can rotate the wheel.

I personally did the brakes about a year ago and would have lubed the slides etc, at that time.

As a side note which I think is totally unrelated, I periodically get the VTM-4 and Check Engine Light which might stick around for a day or two and then go away. I changed the VTM fluid about 4 years ago. Perhaps this deserves it's own thread but if you think it's related.

So my question would be... Do I have a problem at all (brake performance has been normal)? Do I have a problem with brake rotor temperatures? Do I have a problem with the 3 brakes that all read 100 C, or do I have a problem with the 1 that read 50 C?

What should I check? I was about to unbolt the calipers and make sure all the sliders were moving freely and make sure the piston moves okay.

Thanks

 

[forbin404]

I wonder if the parking brakes spring broke and locked open.

 

[Bluepill]

1. Front brakes do about 75% of the work, and it is normal for them to run hotter.

2. With an 11 year old car, it is certainly possible that you have a sticking piston on the caliper. Try re-lubing the slide pins first to see if that fixes the problem. If not, retract both rear pistons with the bleeder screws open and compare how hard it is. Use a 1/4" vinyl tube to catch the fluid and not introduce air into the system. If you retract pistons with the bleeder closed, you are pushing dirty fluid back into the master cylinder and ABS unit.

 

[skirmich]

You should not have all 3 rotors being the same temp..
(Fronts should always be hotter than the rears since most cars brake bias favor the front).

So your drivers rear brake is having some issues... I will blame the sliding pins being stuck causing the caliper to not float correctly when the brake is released.

Having the Fronts 100°C and the Rears 50°C is the normal thing.
Having 1 rear brake as hot as the fronts is not normal.

 

[DrCaldre]

I am not quite sure about some of the wheels not rotating as freely, I would have to look at the car to check it out. Maybe the pistons are not getting enough pressure, pads are worn or pistons aren't traveling far enough, so the rotor isn't fluctuating like it should under use. It can also depend upon what kind of brake pads you have how the rotors respond to the friction. Is that 50c read pad the same type as the others? Just a thought.

 

[habbyguy]

You're already on top of this - using the IR thermometer is really the best way to check for a dragging brake. And while I wouldn't get my panties in too tight a wad over a 50° C difference side-to-side, it does indicate a problem, and most likely won't get better by itself. FWIW, if it was mine, I'd pull the caliper and clean and re-lube those slide pins again. Then I'd check the cable to both sides to see if it feels proportionally equal (that is, make sure there's the same tension on both sides - I haven't played with my parking brake, but the specs say you should get 4-6 clicks with a 66 pound force push on the pedal, and 6-8 clicks with 100 pounds. If it seems like you're getting less movement than that, you could loosen the emergency brake cable (the adjuster is just to the inside of the pedal lever).

The manual says to tighten the parking brake until the wheels start to drag (sounds like they're there!) and then back off the adjuster nut until you get 7 clicks pushing on the pedal with 100 pounds of force. Sounds easy enough, and might well fix your problem.

 

[TooManyToys]

There's some old tales of information in this thread, but it's a common problem. This ain't your father's Oldsmobile.

The assumption that four wheel disc vehicles have the same braking bias as disc/drum is not true. I had a 30 year career in brake development for my old company, most of the time in vehicle testing. Rotor temp can vary front to rear depending on the braking conditions, speed, distance between stops, etc, which is really depending on the air flow cooling. And there are vehicles out there that actually wear out the rear brakes faster then the front due to the brake bias being more equal front to rear and the friction material volume of the rear pads is smaller then the front.

Having the same design of brake on all four wheel ends, and having ABS on-board to control skids (usually with dynamic proportioning at incipient skid) allows the brake engineer to utilize the four corners more effectively without concern of low deceleration skids from the less ladened rear tires.

So saying the temp is always going to be hotter at the front brakes compared to the rear is not true. You have to find your own set of driving results. But side to side by axle, temps should never vary more then 75F.

 

[skirmich]

^ Might apply to domestics or other cars...
Honda and Acuras FAVOR the front wheel brakes always. For example the 2G TL-S has a fixed 80/20 split proportion which was famous from warping the front rotors. I do track days on the TL-S so I know very well the temps of the brakes..

Even the 2G MDX and Up with Electronic Brake Distribution will not distribute any braking bias unless there is cargo in the rear (Owners Manual). On normal driving conditions the rear brakes will do very little, I have done touge sessions with the MDX as well, Never recorded the temps but just by the handling I can tell the brake distribution by feeling.. It drastically favors the fronts.

ABS/VSA will only engage the Rear Brakes harder under: Slippage, Skid or Heavy straight line braking.

So yeah Hondas and Acuras are somewhat Oldsmobiles in that regard today.
That is why they still keep solid rotors in the rear instead of ventilated.

 

[hackzaw]

Thanks for all the tips and advice.

I've now had a chance to take the rear brakes apart, so I'm just reporting back my findings.

1) Drivers Side Rear (the one that was ~100 C) - had a moderately seized caliper pin (the sliding guide pin with the boot). Also, the pads were extremely tight in the caliper bracket. The caliper itself was fine - the piston retracted easily.
2) Passenger (the one that was ~50C) - caliper pins good, caliper piston good...... pads very tight in the caliper bracket.

So I ended up replacing the rotors and pads on each side anyways. Putting the new pads in the caliper brackets was still a very tight fit (used the new pad retainers that came with the pads). I had filed off what rust was there. If the fit of the pads is still quite tight, is it acceptable to take a little material off the ears on the pads for a more comfortable fit in the caliper brackets?

 

[habbyguy]

If there's any question about the guide pin, it's time to swap it out (they're under $10 a set new). Doesn't make sense to leave any possibility of a binding brake over such a cheap part.

I'm not quite sure about the problem you're having with "tight" pads - they're certainly good and snug when they fit right, but you shouldn't have to file off any material to get them to fit in the calipers. I'm concerned that you might get unwanted movement of the pads if you remove material, which could result in odd noises or vibrations. Bottom line, everything should fit fine, though of course you'll have to press in the caliper pistons all the way to fit new pads and new rotors.

 

[TomcatSTL]

Fyi. I replaced both my rear calipers with AZ remans a couple years ago when one of the originals froze up. I saved a few dollars and got the caliper bodies minus the brackets.

Fast forward a year and both of the AZ calipers took turns freezing up, as well.

I suspect mismatched calipers and brackets. I upgraded to the remans which included the large mounting bracket along with the caliper body. I have been ok for some time, now.

Short story - buy the calipers with the brackets.