OK, my turn.

Brakes lately have felt a little funny (56k) good pads. A little catch on the petal before they engage. Today, got a significant right pull before full braking.

Sounds like . . . sticking left front caliper. Then it did it on the left side.

Gonna bleed the brakes tomorrow.

Anyone experienced this? ABS? No codes.

 

I had a sticky right caliper on a different car, and it would actually cause the car to pull LEFT. The right caliper and everything it touched would get very hot, reducing the braking ability on that side. Then when I realized I had a problem and applied the brakes, the car would pull to the left because that side was cool. It happened to me several times, and each time it started acting normally again once I had allowed it to cool down.

So, a sticking caliper can cause the car to pull to the opposite side.

 

Oh yeah... after it happened two or three times I took the caliper off and greased those guide pin thingys (not sure what they are called). It happened again a month or two later, so I just replaced the right caliper. It was fine after that.

 

If you're going to open the bleeders anyway, compress the caliper piston to open up space between the pads and rotor. Then see that the caliper can still slide in and out on its slidey pin thingy (I don't know what its called either). If not, a lubage is in order.

 

Hmmm, I'm beginning to see a pattern developing.

 

Right ... I forgot the part about drinking heavily before attempting any work on your brakes.

There.

 

They're called slide pins, but I recommend lubing them before getting lubed.

 

Gesh, guys! All this talk of lubage and getting lubed and lubing the erect antenna so it will have a full erection is giving me naughty thoughts!! I guess I'll have to go and get me.................... a glass of wine!!

 

^ followed by a cold shower Lew!

 

NO! My doctor says no cold showers. Just take care of business!!
Oops! Too much wine!!

 

Bled the calipers, all front pads are about equally worn, 15-20k miles left. Lubed the slider thingys and the caliper pistons slid back without any obvious hangups. Still pulls. Pulls hard if pressed hard. Enough to change lanes unless you were expecting it.

Guess I will tear the brakes down and see what the matter is.

Discussion has been that you can get a second set of pads out of the original rotors. While evenly worn, and no groves, they have obviously been worn down by the pads.

Any thoughts beyond turning rotors and new pads? Heard you on the sticking caliper.

I do not come close to stressing this car. Advance AP has semi metallic OE pads for $33 and my son gave me a Advance Gift Card for Fathers Day.

Cannot imagine the the ABS is playing a part in this but the pull is so dramatic that it should show up in a simple inspection..

 

I'm stumped after that didn't work. Were the caliper pistons 'equally' difficult to move on each side?

Did you measure the thickness on the rotors...were they equal as well? How close to min thickness by spec?

If you're confident the brake bleed went well, I'd just put some new rotors and pads on it. My initial thought was about caliper piston travel, perhaps easy to move from closed position (in the caliper) but more difficult to move on its outer limits. ?? maybe

 

I'm thinking through this and typing as I think...

I may be wrong on this, but I think most cars are set up so that you never lose all four brakes at the same time. Typically the front left and right rear are one system, and the front right and left rear are another. That way if something goes out on one pair, the other pair should still stop you. If you have a problem with the master cylinder it could cause it to pull to one side.

A hard pull to one side or the other would obviously be a front brake, but you're saying that it's just enough to cause the car to change lanes. Have you looked at the back brakes? Perhaps one of them isn't working. That could cause a pull, too.

What is the condition of the brake pads? Maybe the caliper got stuck on one side and caused that brake pad to glaze over from the heat. Then when it got unstuck the pad wasn't as sticky. That causes the car to pull to the other side.

Those are my thoughts.

 

I had thought about the master cylinder. There are two circuits feeding the ABS unit but no sensors between it and ABS. If the front left/right rear had failed it would produce the listed symptoms. With all the sensors on this car you would think that something would identify an unequal master cylinder pressure.

My '82 Volvo does. It also has four pistons on each front caliper . . . inner and outer pairs each fed by separate master cylinder circuits.

 

After 56.4k miles the rotors were worn beyond resurfacing. Showed up on the lathe as significantly warped but I had not felt that in terms of brake shutter.

Got the car back together after several days of trading parts. NAPA, at least, has the 300 mm rotors listed as standard equipment for the '02 XK8. They finally found the 325 mm some where but it was substantually more than other sources.

Got the proper rotors, made in GB, OEM, and ceramic pads installed for a total of $174 including PITI and shipping. Installation was free. That fixed the pulling.

Searched for a re-manufactured master cylinder or rebuild kit during all this. No re-build kit, reman start at over $200 with new about $700. Glad the rotors/pads fixed the problem.

 

not too shabby, affordable also...good job!

 

Gotta take it back to that worthless mechanic. Wish I could find a qualified technician that was as inexpensive.

In gentle braking, no problem. Has the occasion to hit the brakes a little harder than normal from 60mph. Pulls to the left.

Came home and whipped out my handy dandy pocket infrared thermometer. Temp is pretty equal all the way around, within 10 degrees of so. Rotors are about 10 degrees below calipers. Made a couple more test runs, gentle and hard and temp was still about the same except a little higher, but consistent, on the hard braking test.

Guess I could pull the rear brakes down and see if there is anything obvious but it sure feels like the left front is 'grabbing' or the right front is not..

Both caliper pistons slid back in smoothly, guide pins greased but they were not binding when first removed.

Any other ideas?

 

Tom, i'd pull the rears also, if for nothing else but to clean them, re-lube the pins. Think about it, at light braking, its equal...and thats where the front take most of the work...at the beginning of the pedal. Only on harder braking do the rears assist, so there may lie the problem. Check pad thickness and rotor thickness, make sure all things go in/out smoothly, and the pads are correctly on there, I goofed once and almost installed them upside down.

 

Tom,
Have you thought about checking the ABS sensors and plug connections? It is hard to believe that your calipers would cause alternate pulling. My car had 2 calipers that were seized and they did not alternate. At this point after checking and changing I would be checking the sensors, connectors and the one at the ABS module.

 

Gus,

I have been wondering about the ABS but there is none of the shutter normally associated with the ABS activation. No codes, no nothing. I do feel a single 'almost' pulse on hard application but the pulling continues beyond that. Sorta like the MC or caliper is binding and then moves.

I am going to clean and inspect the rears tomorrow morning . . . . early. It's supposed to go to 98 tomorrow. Nap and a good book in the afternoon.

No more good guesses?