There’s a metallic squeal coming from my front end, sounds like it may be brake related. I changed the pads and rotors (left one was a tiny bit warped, but not so much that I got a vibration), but the noise is still there. The pads showed no sign of eneven wear, but they also looked pretty new. I’m sure I had several thousand more miles left on them. I saved both sets of pads and rotors for emergency use in the future. The wheel bearings also looked good.
One thing we did notice was a potential problem with the left caliper. There are two cylinders that push the pad against the rotor. With the pads off, the rear cylinder comes all the way out, but the front one stops after one pump.
Is it possible that the pads are getting pushed out unevenly, causing the squeal? It is most noticible on left turns or even a left drift (changing lanes, left curve, that sort of thing). There is no noise or pull on straightaways with no brake, and there is only noise on a straightaway brake.
I just want to confirm that this may be the problem before I spend more money on it. I probably didn’t need to buy the new pads and rotors since the change did nothing to lessen the noise. I’d just as soon not waste more money if the caliper may not be the source of the noise.
It’s a '98, 2WD. Wondering if it might be something we’re not considering. Other than the noise, there seems to be nothing at all wrong with the brake system or front end.
Is there a way to fix the caliper other than replacing it?
You can buy rebuild kits for calipers (or at least you could), and they’re not too difficult to use, provided that there’s nothing seriously wrong with the caliper, in which case you’re better off buying a rebuilt one.
From your description, I’d say that you’d pretty much covered everything else. I would, however, check your brake lines to make sure that they’re not kinked, since you mentioned a problem when the car turns left.
I believe that a loaded caliper is one that has a spring on it, generally used for the parking brake, but I don’t know for certain.
You only need to mess with the caliper that’s having problems. If the other one’s fine, you don’t have to fuss with it (providing, of course, you put new pads on both of them).
You did not say if the squeal is constant, varies with road speed, engine speed, or is only around when you step on the brakes. It makes a difference.
If the noise is there when you are NOT using the brakes, it very likely is not caused by the brakes.
how about a few more details.
Not constant. Road speed or RPMs don’t seem to matter. Really only manifests itself when breaking, drifting from the right lane to left lane, or taking a left hand curve. In almost all cases, I have my foot on the brakes (stopping or exit ramp bearing left). My gyess is that the rear part of the brake pad is making contact with the rotor, while the front isn’t. Instead of the pad contacting flush, it contacts at an angle, with the pad more scraping and making the noise than slowing, know what I’m trying to say? What other info would be helpful?
It didn’t do it on my way home from work though. It’s been raining all day, so maybe the front cylinder, being wet, was able to lubricate itself into working properly? Just brainstorming.
One question: Dual or single pistons on the caliper? If it’s a single piston, then you might have gunk behind part of the pad, causing it to stick out farther and thus rub against the caliper. If it’s dual piston, then it might be that one piston’s not retracting like it should. Not a high probablility that either of these possibilities are the cause of your problem, but they can’t be totally ruled out.
If it only makes noise when the brake is applied, it’s almost certainly typical disc brake squeal. The things to do to minimize the chance of having such noise are use premium grade pads, properly lubricate all points where the pad’s metal backing touches anything metal (caliper, clips, springs, etc.), in certain cases apply quieting compound (a kind of rubbery glue) between the pad backings and the caliper and caliper piston, and replace or resurface the rotors. Any one of these things not tended to can result in noise. However, in many cases, the simplest and usually most effective way to get rid of this type of noise is to use premium pads specifically designed for quiet operation.
The difference in caliper piston motion is not necessarily a problem, although it could be. Apparently one piston develops more resistance than the other after it moves a bit, at which point the piston with the least resistance does all the moving. If you blocked that piston, then the other sticky one would probably move instead. If it does, then they would both move under normal operating conditions. If it doesn’t, or if there’s a significant amount of stickiness, then it’s a potentially significant problem. Depending upon how far it moves, however, it may or may not have reached the sticky point yet with new (full thickness) pads and rotors in place.
Loaded calipers have pads with them.
It is generally recommended to replace calipers in pairs to ensure even operation on both sides. It is not always necessary. If you replace one and the braking is even – no pull – it should be OK.
Often to properly rebuild a caliper you need to replace the piston(s) as well as the seals. This reduces the price difference between rebuilding and replacing. In a repair shop situation, with additional labor charge for rebuilding, replacement is usually the more attractive option.
Damp weather may affect the noise. If that’s the case, it will return when it’s dry.
The noise may go away after the new pads and rotors are fully broken in. Try a few vigorous stops to help burnish them.
It’s been raining all day, so maybe the front cylinder, being wet, was able to lubricate itself into working properly? Just brainstorming.