rear brakes getting hot

[jrtredo]

Hi,
I have a 2004 4runner. My rear brakes get very hot on longer trips especially. I have replaced the rotors and pads. I have replaced the caliper on one side and totally backed the e-brake off. Both brakes are still getting hot. Does anyone have any ideas here, i'm stumped. I read somewhere that maybe it is bad brake fluid. I think my next try will be to replace the brake fluid

Thanks!

 

[Bftfan]

Have you ever bled the brake fluid? It really should be changed every few years as it does asorb water and is hell on components.

 

[BlackWorksInc]

Brake fluid should be changed I believe every 2yrs/30k, I could be wrong on that though. But it does degrade and absorb water which will make it less effective and potentionally damaging to components.

What do you mean by "hot" as in the brakes are smoking? or just that there is radiant heat? What type of driving style do you have? Are your long trips up and down hills, winding roads, ect?

 

[jrtredo]

They are much hotter than the fronts. I mainly just do short trips but on longer trips the brakes get really hot and you can smell them. It's seems as though there is residual pressure being left at the rear brakes somehow

 

[E-Man]

Have you checked the adjustment of your parking brake?

 

[toyotatech84]

Do you have toyota oem brake pads? ive had some cases where the material of the brake pad and or rotor will affect the brakes.

 

[jrtredo]

yes, i backed the parking brake off and they are aftermarket pads, but they are not hanging up on the caliper

 

[settytb]

Mine are doing the same. it happened after i changed the rear pads...It seems to be getting better after about 700 miles...but still warmer than the front...

 

[DC runner]

Aftermarket pads, which work great, but have lower dissipation rates probably hold heat longer.


Drilled rotors are a good investment. They dissipate heat much better. Considering do a rotor swap on my truck at some point.

 

[4RunnerFan]

Check the wheel bearings? Just a thought...

 

[jrtredo]

ok thanks for the input. How would i check the wheel bearings?

 

[DC runner]

Pull them. Not a complicated job. If you are going to, you want to check your bearing grease and the bearings themselves. The sit in a ring. If the grease looks/smells burnt then you should replace it and repack your bearings. Easy. You can buy a little tool to help you do it at autozone for 5 bucks. All it is, is a cup with a plunger that helps you FORCE grease INTO the bearing holder to get it good and packed.

You can on some vehicles, check bearings by pulling the tire and taking hold of the wheel mount and trying to jiggle it. If it moves a lot in wierd ways, you know the bearings are going out, since the axle/wheel connection is made at the bearings, to much space or movement means that the bearings are wearing odd... obviously this isn't exact science and newer vehicles have much, much tighter clearances and you might not be able to tell.




An afternoon, with beer breaks, will do ya.

 

[jrtredo]

ok, the bearings look fine, i tried pulling the trac control fuse to see if that would make a difference and that didn't help. Anyone else have any more ideas?

I notice that sometimes when I hit the brakes there is a sound thats hard to explain, just like an electrical sound coming from power booster or something

 

[jrtredo]

ok, so i broke down and took the 4runner to the mechanic. He thought it was the cheap pads i was using so he put on ceramics, now it doesnt stop as well and they get just as hot, anyone!?

 

[jrtredo]

anyone have any ideas here? master cylinder???

 

[KB084RUNNER]

I believe 4 runners have a electric proportioning valve/pump in the braking system to allow the rear brakes to take up more of the braking than the traditional 30%. So I would try bleeding the brake fluid in all 4 wheels with the ignition key "on" and use the pedal pumping method only so the electric proportioning system is activated.

Do not use a power bleeder. This is just a thought but it is easy to do.

 

[DC runner]

Really? http://www.ncttora.com/fsm/2003/4runner/215/ncf/brake_brakecontrolsystem-abs.pdf

Taking a look at it and I don't see a proportional valve. I do see fluid electric controlled abs pumps connected to the vehicle stability/traction control.


I was under the impression that LSPV (Load Sensing Proportioning Valve) were used on vehicles with a drum/disc brake combo. While disc work better, they require more physical fluid force so they LSPV drops the fluid pressure down by a certain amount so you don't lock up your rear drums every time you need to stop.

The Nereid 4runners are 4 wheel disc brakes, negating the need to have the lowering of pressure. I could totally be wrong, but I am sitting here looking at the schematics looking for a always on/constant proportioning valve; the kind of thing that if stuck, could cause the brakes to stick.

 

[MikeInNH]

A stuck caliper could cause this problem also.

 

[jrtredo]

does anyone else have any experience with that valve in the master? they are 4 wheel discs.
The calipers are free and one of them is brand new and that one is still getting hot

 

[KB084RUNNER]

For brake drag in SM:

1. Brake pedal free play (Minimum)
2. Parking brake pedal travel (Out of adjustment)
3. Parking brake wire (Sticking)
4. Parking brake (Shoe clearance out of adjustment)
5. Pad (Cracked or distorted)
6. Piston (Stuck)
7. Piston (Frozen)
8. Tension or return spring (Faulty)
9. Brake master cylinder (Faulty)