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Discussion Starter #1
Hi good ladies and gentlemen! First post here.
So I have 1995 9000 Aero, which I love. A couple of months ago, I started to see problems going WOT, where the clutch would be slipping a lot unless I applied only gentle force on the throttle. Clutch hadn't been changed in 5 years or so, I thought I'd throw in a new one and forget about it. Only it kept happening with the new clutch, so I started my investigations on the trans side.
Parallel to that, I had a weird vibration issue that happened randomly, where the whole car would shake upon applying the brakes at highway speeds. Took the front calipers apart, re-greased everything and the problem lessened a lot: it would still occur at the same random rate, but the shaking was a lot less worrying. So started work on the rear brakes...
Original set turned out to have the handbrake adjustment screws all broken (they would turn and grind but nothing would happen on the piston side), so I replaced them with new calipers and while I was at it, threw in a new set of discs and pads.
That's when the rear brakes started to noticeably drag. I went for a quick test drive and the pads were smoking. I thought, installation mistake... redid everything, bled the system, went to work (kinda had to): discs were incandescent, and that was a short 10 minute drive.
Next on the list were bad brake hoses and/or bad calipers, so I ordered a new set of both and the brakes were still dragging. A lot less mind you, but enough that it would smell of burnt pads after a drive to or from work.
Rusty handbrake cable? Disconnected the lot, rear brakes still dragged.
So I went to my mechanic and we decided to unplug the ABS unit, why not? Worked well for a day, then the dragging started again.
So last night, I took off the main brake relay so there was only me, and the brakes, no ABS, no assist, no nothing. Went for a short, frightening drive: no drag, brakes are cold. Drained some of the fluid from the tank, just in case I had over filled it (I was running out of ideas). Went for another quick drive: no drag. Oh and also, the clutch won't slip anymore, implying that maybe it was mainly fighting the brakes for friction...
So I put the whole thing back together and now it's dragging just a tiny bit not enough to burn the pad material, but enough that rear wheels feel noticeably warmer than the front.
So there I am, I have no idea what is going on with those rear brakes. If that helps, my car has TCS, where the ABS pump seems to include the master cylinder so I have to swap the whole unit if it turns out it's faulty. Any ideas?
 

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There are no new rear brake calipers available. You must have bought remanufactured calipers. There are no emergency brake parts available so remanufactured calipers aren't remanufactured. They are disassembled and cleaned then reassembled with new rubber seals. That's it. My mechanic had to go through half a dozen remanufactured calipers for each side just to get enough good parts so that two could be rebuilt so that they worked.

If the internal adjuster mechanism doesn't work the rear besides seize. The symptom is they adjust just fine but do not back off that mm or two needed to keep the pads clear.
 

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Discussion Starter #3
Well, actually, there are new calipers being manufactured. I have both old and new models here. Virtually identical, except for the absence of the adjusting screw, and two holes on top of the piston so you can back it up using the GM piston tool on the new ones.
They turned out to be perfectly functional though, which is a good thing, but doesn't solve my problem. :D
 

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Well, actually, there are new calipers being manufactured. I have both old and new models here. Virtually identical, except for the absence of the adjusting screw, and two holes on top of the piston so you can back it up using the GM piston tool on the new ones.
They turned out to be perfectly functional though, which is a good thing, but doesn't solve my problem. :D
Not understanding your claim.

Who is manufacturing new "almost the same" calipers that work?

Why don't your new calipers work?

If you bought new ones just turn them in for exchange under warranty for ones that do work?
 

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I've given up on the handbrake for parking. I know it will work for emergency stops, but I'm tired of it sticking.
Handbrake isnt the problem. It's the self adjuster which has nothing to do with the handbrake.

Handbrake issues are cured by new actuation cables and a little cleaning of the actuating levers.
 

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Handbrake isnt the problem. It's the self adjuster which has nothing to do with the handbrake.
Right, the lever itself is fine, but pulling it ends with me crawling under the rear of the car, which is inconvenient.
 

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Discussion Starter #8
Yeah, I don't use the handbrake either, unless I'm parked in a really steep hill. But handbrake isn't the problem here. My rear brakes will drag whether I use it or not.
Or would, should I say, since the problem looks like it *sorta* fixed itself since I played with the relay the other night. I've done several 'spirited' runs since, and only the rear passenger side wheel gets slightly warm-ish now, the other one was completely cold.
I still have no clue as to why it happened or seems to not happen any more. Another clue might be that, since the brakes decided to not drag any more, I now have the ABS dashboard light constantly on. Which I don't mind. I'd just really like to get to the bottom of this so I can prevent it from happening again, and maybe help other people in the future. :)
 

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Discussion Starter #9
Not understanding your claim.

Who is manufacturing new "almost the same" calipers that work?

Why don't your new calipers work?

If you bought new ones just turn them in for exchange under warranty forbines that do work?
Maybe I didn't word my first post properly: The calipers are fine. They are a different design, not the same as the original set, as in they don't have the hole where the adjusting screw would be, or the nut that plugs it, just a flat surface and they're supposed to be self-adjusting. Which they are and they function perfectly, we've sort of established that the dragging problem was not the calipers' fault.
I'll post pictures of both sets when I'm home, so you can see for yourself.
 

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Maybe I didn't word my first post properly: The calipers are fine. They are a different design, not the same as the original set, as in they don't have the hole where the adjusting screw would be, or the nut that plugs it, just a flat surface and they're supposed to be self-adjusting. Which they are and they function perfectly, we've sort of established that the dragging problem was not the calipers' fault.
I'll post pictures of both sets when I'm home, so you can see for yourself.
Your description is of failed internal clearance adjusters. The ABS has nothing to do with your problem. But you go ahead and look for other causes. Looking forward to the post when you discover I'm correct.
 

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Discussion Starter #12
Thank you for your very helpful reply.
The calipers have been tested, taken apart, changed for a new set, taken apart again. They do work as intended. I've been on that issue for 2 months or so, calipers were my first theory, it turned out to be something else. Now I'm sure there are other people you could enlighten in other threads, and since I didn't ask for your help specifically, feel free to go help someone more deserving than I.
 

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So the pads are not dragging any longer?

I did wonder if you set the pads at the 2mm minimum clearance when you installed the calipers. If you don't do this it is possible the pads will drag until they wear that 2 mm specified gap.

I note you have TCS. Malfunction of the TCS might cause pad drag but you'd expect isdue on the front brakes since TCS operates on the drive wheels.
 

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Discussion Starter #14
So the pads are not dragging any longer?
No, they don't drag any longer. Or at least a lot less. :S

I did wonder if you set the pads at the 2mm minimum clearance when you installed the calipers. If you don't do this it is possible the pads will drag until they wear that 2 mm specified gap.
Yes, I had left some clearance. But it didn't help. When I removed the first set of pads I installed, they had been ground to the point where there was only 2 or 3 mm of pad material left anyway, so I'm not sure it would have changed a thing.

I note you have TCS. Malfunction of the TCS might cause pad drag but you'd expect isdue on the front brakes since TCS operates on the drive wheels.
Yes, that's what's been puzzling me. Everything does point to either faulty rear calipers or faulty brake hoses, but both have been changed for new parts, to no avail.
I thought maybe a restriction at the master cylinder level, where pressure would build up in the brake line and could not be evacuated properly, but then again, that should also affect the front wheels. Same thing.
 

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SAAB uses dual diagonal brake lines so any fault with the MC leading to brake dragging shows up at opposite corners: eg front left right rear.

The specified pad clearance on installation is 2 mm. Anything less and your brakes will drag until the clearance reaches 2 mm.

Reason is the internal self adjuster is countered by the caliper piston seals which withdraw the piston slightly when brake line pressure is released. The self adjuster only turns internally as the piston moves that 2 mm distance.
 

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SAAB uses dual diagonal brake lines so any fault with the MC leading to brake dragging shows up at opposite corners: eg front left right rear.

The specified pad clearance on installation is 2 mm. Anything less and your brakes will drag until the clearance reaches 2 mm.

Reason is the internal self adjuster is countered by the caliper piston seals which withdraw the piston slightly when brake line pressure is released. The self adjuster only turns internally as the piston moves that 2 mm distance.

There are no new rear brake calipers available as far as I can tell, only remanufactured or used.
 

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Discussion Starter #18
SAAB uses dual diagonal brake lines so any fault with the MC leading to brake dragging shows up at opposite corners: eg front left right rear.

The specified pad clearance on installation is 2 mm. Anything less and your brakes will drag until the clearance reaches 2 mm.

Reason is the internal self adjuster is countered by the caliper piston seals which withdraw the piston slightly when brake line pressure is released. The self adjuster only turns internally as the piston moves that 2 mm distance.
Thanks for the heads up. I didn't know the exact distance. Unfortunately, as you can see, there is no way to set any kind of clearance with the new calipers. They'll just do whatever the hell they want. :)
 

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There is an internal adjuster that can be manually screwed in or out to set the correct clearance. Without that internal adjuster the rear brakes will not work.
 

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Discussion Starter #20 (Edited)
There is an internal adjuster that can be manually screwed in or out to set the correct clearance. Without that internal adjuster the rear brakes will not work.
Oh, yes, I missed that part. Yes, I did that. I backed both pistons all the way, the wheel turned freely and everything looked set to work as it should. Look, I really appreciate you taking the time to examine the problem with me, really. But I don't think it's the calipers, or me not knowing how to put calipers on a car. There's a reason I titled the thread 'seemingly unsolvable brake issue', it's I've been pulling my hair out trying to get to the bottom of this one. I've examined the caliper angle for long, it is indeed the most obvious suspect, but nothing conclusive came out of it.
Now when I started tinkering with the ABS assembly is when things began to change, counter-intuitively so, which is why I'm quite puzzled and asked about it here hoping someone had encountered the problem before, or there was something obvious I was missing. :)
 
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