today on the way home, my 98 conv. started a pulsing in the steering wheel like a wheel threw a weight. Or, I thought, picked up a stone. The pulsing was worse on harder braking. Then I smelled something hot. stopped and looked. couldn't see anything. Then the vibration in the steering stopped but car pulled a bit to the left on harder braking. I stopped and checked the rotors to see if they were hot. Driver side front was noticeably hotter than the others. Maybe the caliper is grabbing. mileage is 56000, pads appear nearly new.

 

usually if the caliper is sticking that rotor even the rim will be hot to the touch compared to the other ones. So the steering wheel was shaking in your hand without hitting the brakes or when you hit the brakes?

 

Could be ABS but if it's pulling probably a caliper, This might be a stuck Guide pin or Piston, it's easy enough to remove and check them (often a brake pad replacement is just that and folks won't clean the caliper properly). Ah you did check the fluid correct?

 

fluid is good. the shimmy was independent of braking. the pulling to the left under braking occurred after the shimmy disappeared.

 

I finally got around to taking the wheel off.
the caliper pins are clean, pads look fairly new, rotors good, but the calipers drag. I removed, opened a bit, cleaned the pads. back on wheel turns fine. brief press on brakes, and wheel drags a lot. is this just internal caliper piston/bore corrosion, or a bad hose?

 

Could be both/either, The caliper piston could have some corrosion if the seals leaked (esp the dust seal) not allowing retraction. The JTIS recommends replacement of Brake Lines (from the wheel well point to caliper) for each brake change, which might be overkill but it is possible the internals of the hose has partially collapsed as well. You could pull the pistons (do a search there are a number of thread on caliper rebuild) and clean them and the seals up, you will then have to bleed them which will eliminate any already existing air if that were a issue. Otherwise try the hose (not sure if you can swap from side to side, I believe mine were identical)

 

I finally got caliper seals and tried to rebuild. the pistons barely moved. I can see I won't get them apart without damaging. So, off to shop for used or rebuilt. problem. I see used ones have jaguar cast in housing and use a banjo hose fitting. on mine, I see no id and the hose is a straight screw in end. the car only had 47000 miles at purchase, but it looks like the calipers have been replaced already with what? help!

 

correction. after closer examination, I see the jaguar casting and figured out the banjo fittings are for the rear calipers. there is a difference left to right. got that figured out and ordered a rebuilt. I will still try to redo the passenger side myself but won't be surprised if that one won't come apart either. the fluid look good but the only way the piston bore is this bad is if the fluid has a lot of moisture in it. I can tell i'll have to flush and put in all new fluid and probably rebuild the rears as well.

 

They will come out. Put a block of wood inside the caliper, and using compressed air in brake line hole give a quick pop of air the piece will pop out and I mean pop, do not get your fingers in between the wood and piston.
You can then evaluate how clean they were or if it needs replacing. You probably can polish them up but don't scratch them. It could be the seals have partially twisted locking the pistons from moving. I thought I had a pic but I didn't, You'll get the idea here:

 

this sucker is badly corroded. I don't know how the car moved. I've seen calipers with triple the mileage much better than this. I tried the compressed air. didn't budge. then 2 short screwdrivers in piston groove. only moved about 1/4 inch. compressed it back with c-clamp and block of wood. try again. no. ordered the rebuilt.

 

Too bad, I'd suggest you flush your brake lines and replace fluid. For it to corrode that bad there must be water getting into the back of the seals and hence into the fluid. You're already half way there anyway so might as well get it done.

 

got the rebuilt caliper in a few days. on and bled without incident. what a diff! today I took the pass. side one off and rebuilt it. boy! when its' not locked up the puck really does shoot out with air. cleaned up some minor corrosion on lip of puck back together and bled. tomorrow i'll bleed the back calipers to get as much as possible of the old fluid out. I noticed I got antilock fail warning. something else to do.