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95 Impreza One Rotor gets hot


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15 replies to this topic

#1 Ravenwoods

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Posted 16 May 2018 - 12:10 AM

My daughter’s 95 Impreza with 182,000 miles, has a slight shake in the steering wheel. The breaks don’t pulse like one gets warped rotors. So I assumed a bad wheel bearing. One could feel the right wheel was hot after driving. I took it apart tonight but the bearing appeared fine so I put it back together.

The only problem I had was getting the brake assembly stuff to fit over the break pads. I couldn’t depress the cup thing that actuates the brakes so I left off those two anti vibration shims. Seems like it is too tight. She’s had the car for 10,000 miles and we didn’t replace the pads at all.

So I got it all back together and test drove it. It seems like the slight shaking in the steering only starts after a few miles. This time I felt the right rotor with my fingers and it was too hot too touch after driving six miles with minimal breaking. Left rotor was only warm.

So should we assume that right one is warped even though there is no pulsing when applying breaks? Any recommendations one what to do?

#2 el_freddo

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Posted 16 May 2018 - 02:45 AM

The caliper slides will not be smooth in operation, as in one side or both are stuck/have excessive friction.

These can be removed, cleaned up then have some high temp grease applied to them. I'm not sure the exact grease to use, hopefully someone will be able to share that info.

You may see your brake pads wearing oddly in a different angle other than parallel to the metal brake the pad is mounted to.

I need to check this same issue out on my brumby :/ but it's not getting THAT hot.

Cheers

Bennie

#3 lmdew

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Posted 16 May 2018 - 05:05 AM

You can easily push the piston back in before you remove the caliper by putting a large straight slot screwdriver into the open window on the top middle of the caliper and using it as a lever against the rotor.  Pull the handle out and it will push the caliper piston back into the caliper.

 

Make sure you apply the brakes slowly and only partial stroke to get the piston back out before you drive off.



#4 1 Lucky Texan

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Posted 16 May 2018 - 07:50 AM

not common but, that caliper may have a stuck piston or bad hose - w'ever the actual reason, the caliper is not free to slide and center itself. As said, most often it is rusted or bent caliper pins or bad rubber pieces on them.



#5 Numbchux

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Posted 16 May 2018 - 08:39 AM

I couldn’t depress the cup thing that actuates the brakes so I left off those two anti vibration shims. Seems like it is too tight. She’s had the car for 10,000 miles and we didn’t replace the pads at all.

 
This is the problem. Caliper piston should compress into the caliper fairly easily, otherwise the pads are dragging all the time. Rebuild or replace the caliper. Lube the slides with a good high-temp caliper lube (not just grease/anti-seize).



#6 Ravenwoods

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Posted 16 May 2018 - 08:49 AM

Actually the caliper piston was already fully pressed in. It is as if the brake pads are too thick. It looks like the previous owner replaced them at the same time he put in new cv joints. I had my daughter push on the brake pedal to see if the caliper piston would move and it did and I was able to press the piston back in fully.

I find it interesting I don’t notice any of that hot brake smell one normally notices after you come down a long steep hill. Does that not happen with ceramic brake pads?

#7 1 Lucky Texan

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Posted 16 May 2018 - 09:07 AM

you may have 2-3 problems, not impossible with an older car.

 

the brake issue needs to be addressed. The caliper should be able to slide on the pins, rust should not interfere with pad or caliper movement, etc. It's also possible to receive aftermarket parts that are built wrong, or are intended for a different model.  "warped' rotors are often due to a panic stop putting a deposit of pad material in one position. If the pads/calipers on one side have been overheating the rotor, a 'bedding in' procedure might help, if it doesn't, you may need a new rotor.

 

the car may have worn inner tie rods or other steering parts/bushings.

 

try swapping rear tires for the front. Good time to inspect, calipers, pads, lug nuts and studs, and wire-brush any flaky rust from rotor surfaces.

 

check the alignment.

 

while a fairly simple system, brakes have a lot of important details and can be a challenge to get into top condition on older or neglected cars.

 

bearings; Subaru bearings can fail with several different symptoms.  with the corner or end of the car in the air, rotate the wheel while feeling the spring for roughness - or get a mechanic's stethoscope and listen to the hubs. Also, a bad bearing will sometimes allow the wheel to be lifted/rocked up-and-down in the 12 to 6 o'clock direction. any movement is bad - compare side to side.


Edited by 1 Lucky Texan, 16 May 2018 - 09:14 AM.


#8 Ravenwoods

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Posted 16 May 2018 - 10:11 AM

The caliper pins appear to be well greased and slide easily. The steering feels tight while driving. Tires are almost new. The bearing does not appear to allow any place and is quiet. The alignment seems fine as the car does not pull to the left or right.

I did notice that one of the brake pads appears thinner than the other. I believe it was the outside pad. I swapped them.

#9 1 Lucky Texan

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Posted 16 May 2018 - 10:37 AM

there shouldn't be any differential pad wear in theory. My limited experience is that the inner pads wear slightly faster than the outer pads. 

 

The caliper on that wheel may have been sticking slightly and unable to slide outwards easily, leading to more wear on the outer pad.



#10 Numbchux

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Posted 16 May 2018 - 12:49 PM

Yep, if everything is working correctly, the pads should wear evenly. So if the outer one was worn more, that tells me the pins are sticking or bottoming out, and not releasing the pressure on that pad. If you swapped the thicker one to the outside, and then had trouble getting the caliper to clear it, that confirms that the pins are not traveling as they should.

 

Overheating brake components can absolutely cause a vibration, so I wouldn't look seriously at steering/tire/bearing problems until you get the brake issue sorted.

 

Take the pads out, bolt the caliper back on, and then move it back and forth on the slides. Sometimes they can move freely individually, but bind when they have to move as a unit.

 

Too much grease can also prevent the pins from compressing all the way.

 

 

 

Or, save yourself the time, and buy a remanufactured semi-loaded caliper. The NAPA Eclipse brand ones are a premium BBB reman, and (here anyway) are competitively priced to the unpainted competition from BBB or Cardone. 



#11 Ravenwoods

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Posted 16 May 2018 - 01:44 PM

"Or, save yourself the time, and buy a remanufactured semi-loaded caliper. The NAPA Eclipse brand ones are a premium BBB reman, and (here anyway) are competitively priced to the unpainted competition from BBB or Cardone. "

 

I think I'll recommend this to my daughter. The Eclipse semi-loaded caliper you mention is $54.69 at our local Napa. A new rotor is about $36 (saw one for $26 too).



#12 el_freddo

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Posted 16 May 2018 - 09:42 PM

Also be looking at the other side of the car for these issues.

This side that's run in hot could be doing more work than the otherside - but that's usually noticeable from pulling one way or the other under braking loads.

Cheers

Bennie

#13 idosubaru

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Posted 17 May 2018 - 06:13 AM

check all the slide pins again - they need to move perfectly freely and be greased properly.

 

i would diagnose the issue first before swapping a caliper. 

 

you already said the piston moves fine, so swapping the caliper could easily be pointless waste of time and money. 



#14 Numbchux

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Posted 17 May 2018 - 10:31 AM

check all the slide pins again - they need to move perfectly freely and be greased properly.

 

i would diagnose the issue first before swapping a caliper. 

 

you already said the piston moves fine, so swapping the caliper could easily be pointless waste of time and money. 

 

Semi-loaded comes with bracket, pins, etc. That'll fix the problem.

 

 

The only time I replace a caliper, is if the bleeder is broken off. But I have an electrolytic rust removal rig set up, brake cylinder hone, thread taps, other cars to drive, etc.  It's his daughter's car, so he may not have the time to keep cleaning and lubing and test driving. A $60 caliper is an option, and for many people, it's a reasonable option to just slap a caliper on it and be done with it.



#15 idosubaru

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Posted 17 May 2018 - 11:04 AM

Semi-loaded comes with bracket, pins, etc. That'll fix the problem.

 

 

The only time I replace a caliper, is if the bleeder is broken off. But I have an electrolytic rust removal rig set up, brake cylinder hone, thread taps, other cars to drive, etc.  It's his daughter's car, so he may not have the time to keep cleaning and lubing and test driving. A $60 caliper is an option, and for many people, it's a reasonable option to just slap a caliper on it and be done with it.

 

totally agree - cleaning dirty bores and rusty pins isn't easy or effective half the time anyway. 

 

what I actually meant is i still think he should diagnose this. a pin check is at least free and easy, though still not diagnosis.  seems odd to remove shims and take it all apart and not notice any physical symptoms anywhere, so seems a little foggy. 

 

a collapsed brake hose or wheel bearing could still be the culprit, although there should be some noise and Subaru hoses rarely do that. 

 

doubtful this is an issue now, but the "replaced CV" is a general red flag if it's aftermarket.



#16 Ravenwoods

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Posted 19 May 2018 - 05:20 PM

I put on the new rotor and caliper yesterday evening and lubed up the caliper on the other side. My daughter drove it this morning and when she got home I checked the rotor temperature and it was cold. She says the shaking in the steering wheel is gone.

So it seems the old caliper wasn’t opening up enough and while driving the pads were rubbing on the rotor getting it hot. The rotor expanded from the heat causing the brake pads to grab even more and that caused the shaking in the steering wheel.

Thanks everyone for suggestions and help.




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