C900 front rotor screw size?

A friend of mine just bought an '86 900, and it needs front rotors. Those are on order, but I remember there's a torx-head screw holding the rotor to the hub. Does anyone know what size torx bit he needs for that?

Dave Hinz

Reply to
Dave Hinz
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Dave,

Does it really matter? I mean, what your friend should probably be sizing is the drill bit he will need to drill off the head of the torx screw. It seems that every one I have come across, the screw material is so soft that the torx head strip out before the screw breaks loose, even after liberal application of PB Blaster. ...and NO! Do not heat that sucker with a torch.

-Fred W

Reply to
Fred W

Hey brother Fred.

While I forget the size too, the trick to that particular bolt is a first aid kit, patience and an old fashioned manual impact screw driver with a fresh torx head.

My wrench at the time had spent some real time with English stuff here in salty Nova Scotia and what he showed me was that you first soak old SAAB bolts at all points with thinned (3/1) release oil - wire/bottle brush them off/out really carefully - then give it one (and only one) quick, solid, whack with the impact driver counter clockwise (loosen). You know you have that hit right if a little wisp of rust comes up because it will not appear to move at all. His trick was to then douse a gauze pad in regular release oil, wire it tightly over the bolt head and leave overnight in a warm place.

The next morning, bottle brush out the torx head - oil and give it another single whack with the impact screw driver clockwise (tightening) - then reverse (loosen) using the same driver. He tried to make sure that the torx bit was always in the same slots for the hits and marked both at the outset. To no one's greater surprise than our own - it worked almost every time.

Clean the hole with a tap, remount with *lots* of anti-seize and check every so often (twice a year when we swapped tires) for loosening. If the bolt hole was open to the elements on the other side, he would add a second gauze pad there before removing and put a little dab of hi-temp gasket sealer in the back of the hole after remounting the rotor.

He was of the unofficial opinion that the factory may have been worried about loosening and had allowed for a little corrosion in the threads just to make sure it never fell off on their watch.

You know - I miss Mike still. We used to get together Friday's and mess around.

Reply to
Dexter J

Why not with a torch, Fred? Isn't that standard operating procedure for seized bolts?

Serious question... Dave

Reply to
Dave Hinz

Yup spot on ... on my 900 I then replaced with cheap soft straight slot screws (bolts) ... more surface area to grip next time. And on the present 9000 I have replaced the damn thing with a shawn off locating pin so it can come out with a 10mm spanner.

Charles

Reply to
Charles Christacopoulos

For J Dexter,

Appending to my previous ... the bolt with the locating pin for the wheel is showing here in the first two pictures:

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It appears to be the same P/N for NG 900 and 9000 ie. 89 68 588.

On my 9000 as with the same wheels as the first car shown at the above url I can fit an extra bolt with the locating pin cut off flush with the nut. There is enough clearance so it does not foul the wheel.

If it helps at all. Charles

Reply to
Charles Christacopoulos

Well that is novel, thank you very much for the pix on it. I think I will do the same next time I have to do the rotors. Very sensible solution to the problem.

Cheers.

Reply to
Dexter J

For the record, I got all 4 torx bolts out of the front rotors on the '86 today, with _zero_ grunting, swearing, penetrating oil, or anything. Wrench in, twist, click, "that was easy". All 4 brake bleeder nipples loosened fine too. Brakes are still crap; the pedal is soft and goes all the way to the floor slowly, although I'm not losing any fluid. I assume this is master cylinder rebuild time. Anyone have a goood online DIY guide for a vacuum-assisted Saab c900 brake master cylinder? I already know I can't just take it off the front of the booster with the two bolts which look like the obvious method.

Dave Hinz

Reply to
Dave Hinz

When I did that on a 1983 900... you could get an overhaul kit ... with the rubber seals etc. Next time I looked the kit included the pistons. One issue with overhauliing the old one is if the culinder is in good condition if not you need a complete replacement.

I have an old haynes manual it has half a page of text on the issue and

1 page of diagram. Do you have it?

Make sure no fluid gets on the paintwork as it will strip it off.

Nothing hidden in removing the master cylinder from the car. Undo the two bolts you talk about, *all* the pipes + wires connecting to it ... and it comes off.

There is a rubber O ring between the cylinder and the servo unit. That and maybe a bit of rust have stuck the two together. If everything is diconnected try maybe a tap with a soft hammer.

Your car does not have ABS, does it? (not on 1986 model) Then it is different to what i have been saying above.

If it helps at all.

Charles

Reply to
Charles Christacopoulos

I've got the local Beck Arnley guy getting a kit in for me, will probably be just seals. If I get it open and find big problems, then I can always get a new cyl, but I've had pretty good luck rebuilding in the past.

Need to dig it out, I've got the Saab manuals for the 900 series also, but I was surprised when the MC didn't come off the booster as expected.

Probably just stuck then, I'll get more aggressive with it. Thanks.

Nope, pre-ABS by 3 years or so I think. My '88 900T didn't have ABS, although it did have the light for it in the instrument panel.

Yup, thanks!

Dave Hinz

Reply to
Dave Hinz

Yes, it is for me too, but not on the brakes. It's just something I have heard or read and have never challenged. I think that they are worried about warping the disk or something...

-Fred W

Reply to
Fred W

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