Burning smell

[Blingenfelter]

2015 Bighorn Hemi 162K miles
Burning smell from front, but shop thinks it's the rear calipers...So I went ahead and changed the rear calipers. After I went for a drive about 30 minutes all of a sudden the front end of my truck started shaking I pulled into a parking lot and measured the temperature of the front rotors at almost 600°. So today I changed the front calipers. I went for another drive same thing happened. I noticed that about the time the shaking and smell came, the oil temperature started to rise above 220°, close to 225°. I'm pretty sure I'm not low on oil. Anyone have any ideas?

 

[HEMIMANN]

Leave a brake bleed screw open?

 

[crash68]

did you change the hoses to the calipers?

 

[Blingenfelter]

Nope. Plenty of brake fluid. It was doing it before I changed the calipers anyway. And the engine is dry as a bone. So confusing.

 

[Blingenfelter]

I did not change the hoses. Why? I didn't see any bulging or anything to make me suspect them. You think fluid is getting clogged?

 

[crackerjack1957]

Edit..........faulty ABS module

 

[crash68]

I did not change the hoses. Why? I didn't see any bulging or anything to make me suspect them. You think fluid is getting clogged?

Due to they're high pressure capabilities, brake hoses have a tendency to internally collapse without any visual bulging. This can cause your caliper to appear that they're sticking and drag the pads.

 

[Blingenfelter]

When I bled the brakes after doing the calipers, fluid squirted out of all 4 bleeders. Would that imply the hoses are okay or not?

 

[Knee Deep]

No, You have more pressure going towards the calipers then you do coming back though the lines to relieve the pressure on the pads.

like @crash68 said, the lines collapse internally acting like a one-way check valve.

 

[Blingenfelter]

All right. I'll check that after Christmas. I had to rent a car for holiday travel, so I'll get back to the truck in a week or so.
Repairs like this always hit at such convenient times.

 

[averageguy]

No, You have more pressure going towards the calipers then you do coming back though the lines to relieve the pressure on the pads.

like @crash68 said, the lines collapse internally acting like a one-way check valve.

Yep, had this problem on a Ford Tempo once. When you push the brake pedal, it forces the brake fluid through the internally collapsed line. When you release the pedal the fluid can not flow back the other way. Jack up the truck, put it in neutral and see if the wheel turns. If it does, press the brake and release it and see if it will still turn. If it won't, loosen the bleeder to relieve the pressure and try again. If it squirts out alot and the wheel is fee again after you loosen the bleeder, the line is collapsed internally.

 

[Blingenfelter]

Thanks. I'll do that.

 

[Blingenfelter]

Welp. I replaced the hoses AND the bearings on the front. I thought it was fixed for about 30m. ABS module the next culprit?
@crash68 @averageguy @crackerjack1957 ??

 

[Blingenfelter]

@crash68 @averageguy @crackerjack1957
So at this point, I've changed
1) all the calipers
2) front bearings (the wheels were off and they needed changing)
3) front brake hoses.

Rotors are still sporadically hitting 500+ degrees.
What is next? How do I assess ABS or Main Cylinder? No dummy lights on this whole time.

 

[crash68]

If the ABS was kicking in you would probably notice but you could try pulling the F26 fuse, that will disable the ABS electrically to rule that out.
If you have already try flushing/bleeding the brake fluid out completely with all new.

 

[Blingenfelter]

This is getting crazier and crazier. I took it back to the shop and they did an "automated ABS flush"... and for a day or two, the truck drove great. Temps on the rotors of <100 degrees. I was almost breathing easy when I felt those calipers seize a bit. Temps in the high 200s... which isn't terrible, but not cool. SO I decided to pull the ABS fuse just to see if I could rule out the ABS completely, maybe see what happened. Guess what? This is what I saw in the fuse box.
It's not there.
NVM. I was reading the diagram wrong. I'll test it and get back.