So-why wont it stop?

[nigel bickle]

Bought the eminent 'Mrs B' a Saab c900 softop recently. Full heated leather & near new roof cover the £300 cost- if I needto break it!Needing a spot of welding (-now underway) and unresolved braking probs- but came with everything to replace the existing consumables. However- Saab franchise service history indicatesongoing long term brake probs...So-stripped the front end to find vented discs-never seen them on an early on before..Look near new,no ridges,no wear lines etc.Reckon they've done about 3000 miles.Pads looked OK too. Decided to fit the new ones-(had to cut the pad back a bit-vented discs took up too much space- but they are still 75% there).New fitting kits-pins etc-marvellousFreed the sliders up -lovely job. Nnew Goodrich flexis went on-that'll sort it.'Xcept it didnt.Took the rears apart-couldnt see anything wrong. Nevertheless, fitted new discs,pads,fitting kit etc -since I'd got them.Flushed ALL the fluid too -mucky job but best be safe- she's an ''expert'' at last minute braking....Braking is rubbish. Pedal is solid,near the top -feels right. Handrake feels OK-difficult to tell as its on the front wheels..It just doesnt want to stop- like its got gummy Minor drums on instead of whacking great vented discs that should stand it on its nose.No loss of fluid-no indication of servo issues (doesnt feellike that).Running out of ideas so thoughtI might ask '' learned'' for pointers.....please?Secondly- has anyone ever seen a rollbar for one of these? Think it might be prudent to add one-before I let her loose..

[Richard]

Does it have ABS? Could it be a problem in the pedal linkage?I have a friend who specialises in old SAABs, I'll ask him about it if you don't get sorted soon. I'll ask him about the roll bar too, though I suspect the windscreen pillars are supposed to do the job.

[Richard]

Ah, how many clicks does it take to apply the handbrake? The front ones need about ten clicks worth of travel for the self adjusters to work properly. Often you have to tighten them to please the MOT tester then slacken them when the test is over.

[mouseflakes]

I bought a Renault 12 on which someone had used a master cylinder rebuild kit but had put the bits inside in the wrong order - brakes were next to useless, though I rebuilt the bront and rear brakes a couple of times before realising this.

[dollywobbler]

If it's a hard pedal with no braking, I'd suspect the servo personally.

[Andrew353w]

Don't know if this helps by I know an excellent firm of SAAB specialists-very human and you can talk to them! They're in Hertfordshire but ARE good. Get in contact if you think they could help you.All the best!Andrew353w

[STUNO]

Bit suspicious about the front discs showing no wear. Are they doing much braking?Does Saab have a pressure device to give the correct amount of front -rear brake bias, that can give trouble by doing such things as applying all the braking to rear only. And as dollywobbler says a look at the servo would help. You might like to check the history re servo etc too.Or you could ask someone who has a clue what they are talking about

[mirafioriman]

I assume you have checked the caliper pistons are free and not seized? Take one pad out and g clamp the piston, then apply the brakes and see if you get braking on that wheel. Then repeat on the other wheels. Does it have single piston calipers with slides or a piston on each side of the disc? When you said you had to remove part of the back of the pad, what exactly did you mean? I have never had to 'modify' brake pads to fit them. If you had to do this perhaps there is an issue somewhere with the parts being incorrect?

[Richard]

Do you know that the direct piston has to be screwed back in when you change the pads?

[Richard]

Does it have single piston calipers with slides or a piston on each side of the disc?

It has a combination, the pistons are back to back with one operating directly and one operating via a slide.

[Mr_Bo11ox]

I wonder if your fat vented front discs might be the problem, those calipers on the front of 900's have a hellish handbrake mechanism which, as said above, needs to have a load of slack in the cable for it to work properly. Maybe the combination of fat discs and new pads are stopping the self-adjusting mech in the calipers from engaging and doing their stuff properly. Have you got any ordinary discs you could try lobbing on?

[nigel bickle]

Ok.

 

Yesterday I reverted to normal discs-no real change .

 

I locked off the rear brakes (clamped the flexi) no material change. So its not therears- and cos its dualcircuit, cant be one failed. Pulls up straight-eventually....

 

I've slackened the handbrake- no change (other than a slack handbrake!)

 

I' going to try softpads next -if I can get some tomorrow.

 

Pedal feels ''right'' -not hard-blown servo etc.

Master cylinder looks undisturbed -in a very long time- but guess I have to go there next.

 

No ABs to confuse issues-its too early a car.

 

 

 

 

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[nigel bickle]

Should add-that I have Saab's own toll for winding pistons in -free & uncorroded. Used new seals too -as I was 'passing'

[Mr_Bo11ox]

Looks like a great car for £275 NB even if you have to use the gears to slow it down!Does it have a servo, or some sort of hydraulic asistance? Is the servo doing its stuff? With the engine off, pump the brake pedal 10 times then, with your foot firmly on the pedal, start the engine - the pedal should sink by another inch or so as the servo 'assists' your foot.

[Richard]

I think the problem lies with your front callipers, they need to be very free to work properly.As you know you can't push the pistons back in the normal way but with the pads out the pair of pistons should move back and forward fairly freely.With the pads in you should be able to operate the handbrake lever on the calliper and the handbrake operation should be pretty decisive with very little effort required.If you haven't done so already, pop the pistons out and make sure the seals, and their grooves, are clean. The seals appear to be symmetrical, but they're not quite so pay attention. Needless to say the piston surfaces should be flawless.Other than that it may be that somebody has fitted an incorrect master cylinder or servo and there just isn't enough effort going into braking. Apologies if all the above is stating the bleeding obvious.

[nigel bickle]

Ta.Unfortunately-done allthat.Servo's fine- done the engine off & pump it bit.Slidersare freer than a free thing,pistons have beenout,cleaned,replaced with new seals.I'll try to get it on an MOT test rig I think-see if I can isolate.

[Barry Cade]

Richard, do you mean the Saab specialist in Cupar? If so, how's he doing? He is THE man for Saabs!There seems to be 2 different master cylinders fitted to 900's -up to 86ish. 20.6 mm and 22.2mm,after 87 they were all 22.2mm. Sloped nose 900's had a rear handbrake about 87 on. Has someone maybe been mixing and matching parts? Turbos' should have vented front discs 20mm thick, all others had solid discs 13mm thick?

[Richard]

That's the chap, he's doing fine. Still the man for SAABs around here. If I finish on time tomorrow I'll drop by and pick his brains.

[Barry Cade]

say hi to Ian if he's there too!

[nigel bickle]

Weather stops further checks.Its a'E' plate slope,T16s,withfront handbrake. With vented discs the pads need cutting down around40%- to fit.Cheers guys.

[Barry Cade]

Could you have turbo discs with standard calipers then? Turbo pads should be identical, but thinner,so may just be standard pads,turbo discs and calipers?

[Richard]

Dave thinks the one way valve in the servo pipe may be faulty and some of the boost pressure is finding its way into the servo. That wouldn't show up when doing the servo test because there is no boost pressure at idle to cause the problem.Ian was there so I said hello to him for you, Tiff.

[Barry Cade]

Has he still got that 155 for sale?