New pads & rotors dragging on my Oldsmobile
 

I put front brakes on my wife's Olds yesterday. I bottomed out the pistons in the calipers, installed the new pads, and installed new rotors. Putting the calipers on, they were a bit tight (sliding the pads over the rotors). I had to tap them into place with a hammer. I recall that they're always a bit snug with new pads & rotors. I pumped the brakes to center the pads, then I test-drove it one mile down the freeway and one mile back. On the way down, it seemed like it was dragging. After the return run, at the top of the off-ramp, both front wheels were smokin'!
Any ideas?
I did everything the way I've always done it. I put on new rubber sleeves and lubed them well with silicone lube. I put hi-temp caliper grease on the caliper-to-steering knuckle contact points. I cleaned the new rotors with brake cleaner.
Maybe Murray's sold me the wrong pads and/or rotors, and they're too thick?
Whatever the problem is, I've probably warped the rotors and glazed the pads, right?
I called Murray's to see if maybe I got the wrong parts. Their "brake expert" said it's possible, but according to my receipt, the part #s are correct. So I have to check the cartons to see if maybe they pulled part numbers different from what's on the receipt.
What blew me away was what he said about "seating" new pads:
I told him about the smoke and heat, and said I wanted new stuff because I probably glazed the pads and warped the rotors.
He said that with new pads, you need to heat them up real good to "seat" them.
I've always heard that you should go easy on new pads for the first few hundred miles. In fact, the Textar pads I buy for my Mercedes come with instructions that say to make a few gradual stops from highway speeds, in increments as follows: from 50 mph down gradually to 25, then lift off and let them cool, then gradually from like 25 to a complete stop. They say you should then go very easy on them for the next 100-200 miles.
Is it possible that frying my new pads to the point where they smoke is actually good for them?
Also, should I insist on new parts or will the pads & rotors be OK?

I think I would drive it a few miles and see what happens. You may be pleasantly surprised.

Are these floating calipers? If so, are you sure the pins and everything were in good shape?

Good luck,

Thanks, Larry.
I guess they're floating; I'm not sure what that means. The bolts that mount them to the steering knuckle go through steel bushings, which in turn sit inside rubber sleeves lubed with silicone gel. I replaced the rubber, thoroughly cleaned up the bolts, and lubed everything.
I hope you're right and they'll be OK. I will first rule out wrong parts. Then I will trust your experience and instinct.
I'm still wondering if you're supposed to really heat up new pads, or go easy on them, or if tit depends on the mfr. The parts store guy said he's got 34 yrs. experience as a mechanic and you need to work them hard to "seat" them. He said he's never heard anything different.

Do you still have an operable 600k+ mile Merc Diesel?
I need to put some miles on mine or I will be leaving it to my heirs even if I live to 80. It only has 102k miles.

Warped rotors will translate into a vibrating brake pedal while braking, and new pads can smoke a bit. However, you should not feel any dragging. Does the car pull to one side while driving or braking?

'Smokin' is for sure not right. Having to hammer the pads into place is not also. The pads should NOT contact the disks when newly installed, until the brakes are applied. Otherwise indicates either you did not fully retract the pistons, or the pads are incorrect.

When the piston pushes the pad against the disk under hydraulic pressure, The piston seal is in an 'extended' position. On releasing pressure, the seal should retract the piston a few mils, and this should prevent the problem you are having. Note that a fully extended piston with old pads may have contamination hidden by the dust bellows. This can also prevent proper piston retraction if the assembly is not serviced properly.

Steve

RE the smoking - I assume you used silicone rated for brake service? Maybe you cooked some lube. (I don't mean to question your ability but I'm trying to cover all the bases, please don't be insulted) :)

I have had some new pads smoke during the break-in. I've put pads on my Alfa that said to do ten 30 to 0 stops in a row which really heated them up, the textars I put on the Benz had break-in instructions that I do not recall mentioning "going easy on them". I think most brake pads need to be "bedded in" by getting them good and hot.

I have changed many a GM brake pad and I have received the wrong pads once - they were TOO DARN THICK like you said. Many GM applications use the same backing plate with varying thickness pads, I ASSume, so the probability of getting a incorrect pad is high. If you really cooked the rotors (Evidenced by a shiny multicolor appearance and reduced braking action) get new pads and if necessary reface the rotors with a small disc grinder with a 400 grit disc, forming radial scratches; this can be done on the car although it takes some maneuvering (do it with the old pads on there if they allow the rotor to turn).

Are you SURE you got the pistons all the way in? Some vehicles need to have the piston turned as if being screwed in.

Sorry for the long answer....

P.S. I guess this means there is no GM forum like MercedesShop.com ;)

-Tom

My Olds brake job
 

Thanks, guys, for helping me cover all the bases.
The Textar pad instructions say to make several GENTLE stops, from 80 kph down to 40, then let them cool for a few seconds, then brake to zero kph. After that, they say to go easy on them for 100-200 miles, not letting them get too hot.
My friend noted that the parts store guy is working the parts counter after being a wrench, so consider the source!
I used the silicone lube that came with the new rubber sleeves. I know that's not what's cooking, because I know the smell of hot pad material all too well.
The brakes are definitely dragging.
The fact that the billowing smoke came from BOTH wheel wells tells me it's not that I failed to bottom out the pistons, or that I installed the pads incorrectly. I have to go home and get the part #s off the parts cartons. If that doesn't indicate that they gave me wrong parts, I'm still going to demand new rotors and pads, and compare thicknesses. If they're all just as thick, I'll buy them somewhere else.
Thanks again.

Throwing out a suggestion. Did you bleed the brakes and also are the shims in correctly? I had one shim that was somewhat crooked on a Honda and it made the brakes drag due, to a stripped caliper bolt from the previous person who did the brakes.

Regarding piston retraction -- two points
 

1. Did you open the bleed screw when you pushed the pistons back in? If you force fluid back toward the master cylinder sometimes crud from the calipers or hoses will block the fluid return holes in the master cylinder and cause dragging brakes. It is especially important on cars with ABS that fluid not be forced back upstream from the calipers, because there are lots of expensive parts with ruinable seals between the master cylinder and the calipers.

2. Sometimes, when a car ages, the inside of the flexible brake lines begins to deteriorate before the outside, and chunks of rubber can form blockages which cause drag, especially, again, if the caliper pistons were forced back without opening the bleed screws.

:eek:

Sounds exciting, at least!

Fimum,
Your input seems to cover the most ground from a technical standpoint. I thank you; it seems plausible. I am not well-versed in the idiosyncrasies of ABS; in fact I never did like the concept. I consider myself a very good driver and I abhor unnecessary expense & complexity. But we got (what seemed like) a good deal on this bloody Olds.
I still find it odd that both sides decided to act up at the same time (I've done two other front brake jobs on the car, with no problem). No, I didn't open the bleed screws; I didn't know it was a no-no. But I didn't do it the other times, either.
By the way, I went to another auto parts store and miked their rotors & pads for this car. The stackup was even thicker than the parts I put on. The counter guy (I love these guys) said "Oh, yeah, they will get hot and even smoke until they're worn in. I've had 'em burn the paint off the metal part of the pad." This seems so odd to me...
Anyway, I put my parts back on. They slid right over the rotor this time, so I think I may be in the clear. I will drive very cautiously for a bit and pay close attention to braking performance.
I look forward to ridding myself of this, our last piece of Detroit iron for the foreseeable future (except the ones that are a "can't lose" like the '79 T-Bird winter beater I just bought for $300; it runs! What fun!).
My wife's next car will be a previously-owned M-B, preferably a Diesel.
Say hello to Chewbacca and Pizza the Hut.
Thanks again.

Had this problem on one side with the family van. One of the calipers had similar difficulties with the piston but eventually the new pads went in ok. Upon initial drive I could smell the burning and I felt one wheel was overly hot to touch. I wound up replacing the bad caliper and brake line and problem was solved. I had heard that the brake line could be a factor with the release mechanism and it was cheap so I did that too...

I do recall in my Buick days that the rotors on some GM cars had to be turned when new! The Factory surface on new rotors was supposedly inadequate for proper ABS performance. We took just enough off to apply a non-directional surface. The non-directional finish removes the spiral effect of turning the rotor, which in turn keeps the pads from moving up and down in the caliper. Anyway, the point I'm making is they may have accounted for this by producing the rotors slightly oversized. If and when you replace your front rotors again tell the shop you want them turned with a non-directional surface. If they don't know what you’re talking about, it would be best to take them to a GM dealer and have them done.:)