SC front brake rebuild issues continue

Huh · 09-04-2007, 08:07 PM

Okay I have rebuilt my front calipers twice now. I followed instructions from the 101 project book and even switched out the original pistons with nice ones from another set I have. It appears that my drivers side caliper still drags a bit once they get hot. At first I didn't have the angle set correctly in the piston so I readjusted them to the 20deg offset needed. After readjustment I took the car out and I still get the drag (noise and the awful vibration in the steering wheel). I have not completely inspected the brake lines but my rubber hoses were replaced with steel braided lines. Having the steel braided brake line would lead me to believe I don't have a failure there. It appears unmolested. Is there a way I can run brake cleaning fluid through the caliper to see if there is gunk in the caliper? I don't want to split them but I may have to. I do have another caliper I can put seals in and try that. Rebuild kits are about $15 so not too much. There is no need to hone out the piston carrier from some of the rebuild sites I got from my last rebuild question. The only other option is to find a professional who can rebuild them completely and inexpensively (what is considered inexpensively?).

rallyracer · 09-04-2007, 09:43 PM

Quote:

Originally Posted by Huh

...I have not completely inspected the brake lines but my rubber hoses were replaced with steel braided lines. Having the steel braided brake line would lead me to believe I don't have a failure there.

I don't ever replace/rebuild calipers without replacing flexible brake lines, especially if I have a sticking caliper problem. If your SS lines are more than 2 years old, I would highly suggest replacement. That being said, the teflon hose in your SS lines probably won't give the valve effect like a failing rubber line, so I may agree the lines aren't your problem.
David

barney911rs · barney911rs's Garage

You could try swapping the braided lines from side to side and see if the problem moves? I would highly advise against splitting the caliper. When you rebuilt them, did you flush them out with brake clean and compressed air? That should of removed any gunk in them.

Driver8 · 09-05-2007, 03:05 AM

How old are your rotors?

dlagerstrom · 09-05-2007, 06:42 AM

Did you replace the spring and other hardware holding the pads in place?

The hardware kit isn't cheap, but it may be part of the issue if all you did was replace the seals on the piston.

Good luck.

John Brandt · 09-06-2007, 07:29 AM

YOur saying the problem is no different after rebuilding - and - you're certain there is no air in the system? if thats the case, you should look carefully at the rest of the system

Could be bad hoses... how old are they?
wheel bearings too tight / bad
uneven rotor wear / warped (mythically)
tire pressure unenven tire wear
bad suspension component , ie ball joints or tirerods

Huh · 09-07-2007, 06:02 AM

I am pretty sure that there is no air in the system. I have the same brake feel. Flushing the calipers out with brake cleaner then I will try polishing the hardware. The spring and slides are a bit weathered. The rotors are fine. It is completely annoying though

gtihop · gtihop's Garage

Are you getting a noise/vibration or is a caliper sticking on?
Noise/vibration is usually caused by a bad rotor-excess run out.
Caliper sticking is easy to check- get brakes hot by driving, jack up wheel and try spin it. If it's binding it could be the caliper or hose. If it's binding then open the bleeder screw, it it frees up then the hose is at fault. If not, then the caliper is bad.

Huh · 09-07-2007, 10:07 AM

Excellent. I will try that. Thank you.

Superman · 09-07-2007, 10:27 AM

Don't split the calipers. Compressed air will tell you whether there is a restriction inside the caliper. Use silicon grease on the rubber parts.

I once had a problem on a Nissan Pathfinder. Actually, it was on a hydraulic clutch system. The clutch pedal had been adjusted to remove most of the free play. It was just a tiny bit off from the factory spec. Unfortunately, this caused the master cylinder piston to not retract far enough. You see, the piston is supposed to retract far enough to allow fluid to flow between the MC and the reservoir. Without this free flow, the hydraulic system becomes "closed." When the closed system would heat up at all, it would cause pressure to build up. It acted like a worn clutch disk. Changing clutch disks on a Nissan Pathfinder is not a small project. Especially when the problem was a simple pedal adjustment.

Huh · 09-07-2007, 11:59 AM

I don't plan to split them right now but I may in the future. I have a great link for refurbishing the calipers. Compressed air pushes them out without any problems but I am going to investigate the hardware and also flush the calipers with brake fluid cleaner.

rusnak · 09-07-2007, 02:11 PM

+1 don't split the calipers unless you like throwing money away.

Did you try shaking the top of the tire by hand? If there is excessive wheel movement, such as from a loose wheel bearing or worn shock, then your rotor may move enough laterally to cause the dragging that you describe. Also check that the caliper is centered on the rotor. Maybe somehow you got them off-center.

dtw · 09-07-2007, 02:25 PM

1st thing I'd do is measure out the rotor and see if it is warped. It sounds more like a rotor issue than a stuck caliper.

2nd would be to replace the braided hoses w/new DOT rubber hoses. Many people that are much smarter than me recommend against braided lines for street use. If the rubber wall of the line failed, you'd never be able to see it per a visual inspection. Race cars that run these lines have them renewed frequently.