The keys to this project are correctly-assessing the problem to work out if the brake master cylinder is actually faulty, being careful when doing the changeover due to hazards presented by brake fluid and the requirement to prevent contaminents getting into the brake lines, and properly bleeding the brake lines afterwards to ensure there are no air bubbles or old (possibly decayed/contaminated) brake fluid trapped in the lines which would affect the operation of the braking system.
Origin of the Species 8-)
The origin of this project came about the first day near the middle of 2004
that I had my 1985
900i towed to my place from the previous owner's place elsewhere in
Sydney. He'd told me that there were problems with the brakes (amongst other
things), and I'd half-heartedly checked out a few things over the course of
the next 12 months not really getting the inspiration to solve it
properly.That was partly because I simply didn't know enough about the braking system. My 1983 900S is the first car I have ever owned (yep - I didn't own my first car until 2003 when I was 34 years old!), but I love things which are built tough to last the distance so it's just been Yet Another Challenge for me! 8-)
Through most of February and March 2005 I was on annual leave from my work, so I had far more time than usual to work on the cars and after doing plenty to the 900S early on in the annual leave I decided to try fixing some of the things wrong with the 900i. After all, it's not much good having a car which is running if it can't be driven on the road (even though it hadn't yet been re-registered!) because the brakes didn't work...
So one day in early March 2005 the 900i's brakes were on the agenda in a VERY big way so one of the goals for my annual leave - getting the 900i at least driveable SAFELY on the road - could be fulfilled. A noble goal.
My 'shadetree' analysis after driving the car fairly hard along the length of the firebreak and slamming on the brakes (taking ages to stop) was that since the brakes on one set of diagonally opposite wheels looked like it was working a little (slight wearing off of the rust on the brake discs), but the brakes on the other pair of diagonally-opposite wheels showed almost no pressure being applied to the brake discs via the pads, it was a high probability that the brake master cylinder had an internal leak around the piston which controlled one of the two hydraulic brake circuits.
The other clue was that the brake pedal fell to the floor when pressed and if the brakes were 'pumped' they started to work better. Since I had acquired a couple of new master cylinders specifically because the previous owner of my 900S had to get the master cylinder replaced early in 2003, I decided this was the path I'd take.
Getting Jiggy With It ...Second thing I did was loosen the large 17 mm nuts holding the brake master cylinder onto the vacuum booster. These nuts are not nylock nuts but standard nuts secured with spring-washers.
Next step was to push a cloth underneath the master cylinder to soak up the brake fluid that would spill out as the brake line nuts were undone from the ports on the side of the master cylinder.
Once I started to undo the brake line nuts (hollow nuts through which the flared-end metal brake line passes), I realised my first mistake! Make sure you unbolt the radiator expansion tank (see the pictures) and move it out of the way otherwise you can't move the metal brake line ends out from the ports in the master cylinder far enough to prevent damaging them when the large 17 mm nuts are finally removed. 8-)
Ok so that was solved and the radiator expansion tank moved out of the way a little. Because the brake line nuts were now loose, a fair bit of fluid (expelled because of the residual pressure in the lines?) was soaked up by the cloth so putting the cloth in place was a Very Good Move (tm)!
After fully removing the nuts and spring washers holding the master cylinder on the booster, a bit of careful jiggling freed the master cylinder and it's rubber washer which was then easily removed from the car. The rubber washer was in an awful state so at that point I saw nothing to be gained from putting the new master cylinder in with the old, decayed, rubber washer so that was the end of the first day of work.
Note the green staining on the spill cloth - that's the old brake fluid leaking out as the residual brake line pressure is released when the hollow brake line nuts are being undone.
Getting Jiggy With It - Phase
2
Be careful when filling the reservoir on the new master cylinder with fresh brake fluid due to the hazards involved with handling brake fluid, especially the glycol-based compounds used in DOT-4 specification brake fluids that are specified for use in Saab C900 brake systems.
The old master cylinder can be rebuilt using special kits of parts (such as these kits from Parts for Saabs) if you want to repair it to keep as a spare. The plastic brake line plugs removed from the new master cylinder (if it came with some) can be used to protect the brake line ports on the old master cylinder to ensure that dirt, etc. doesn't get in.
Bleeding for The Cause!The beauty of this product is that it enables brake-bleeding to be a one-person job, and it's energy source is simply a spare wheel inflated to about 20 psi.
The large plastic bottle is filled with brake fluid and air pressure from the tyre keeps the reservoir on the master cylinder filled as the energy stored in the compressed air pushes brake fluid, etc. through the lines to the calipers at each wheel!
The brake fluid which was expelled from the the right-rear caliper was highly contaminated (looked like someone has used engine oil in the past to top it up!), and contained a fair bit of suspended solids. The trick is to bleed fluid slowly until the flow out of the bleeder nipple is clean (which means fresh fluid has run all the way through) and has no air bubbles.
Also, if you haven't bled the brakes for a long time, the bleeder nipples might be blocked and instead of fluid coming out the hollow in the nipple, it'll dribble out around the outside (through the thread). The right-front one (in the picture above with the plastic tube attached) was blocked and I think the line might still have some bubbles, though the solid feeling of the brakes post-bleeding makes me think it's ok.
A few more pics are coming soon also.
The Phoenix has Risen! 8-)Later in the afternoon I took the car for it's first drive on the road in almost 2 years, and because the pads at the front were almost new at the time I bought the car, after about 10 km's of driving along a fairly undulating windy road in the adjacent national park, I had loads of smoke from the brake pads on the right-front wheel! That just meant that the brake fluid I'd spilt when doing the first bleed, and whatever oils, etc. had sat around the brake caliper for 12+ months, was burning off.
During the brake bleeding I took the opportunity to remove each wheel in turn and have a very good look at the other parts. I found that the bushes for the rear suspension links were very cracked, and one of the ball joints for the front wheel hubs was damaged (boot cracked, etc.). That's all stuff I need to learn how to fix though. The best way to save money is fix the car myself (if I can)! 8-)
September 2005 Update: Subsequent tinkering has revealed that the driver's side front brake caliper has a leak around it's piston seal so that will require replacing the caliper or rebuilding the existing one. That might become a seperate project page of it's own depending how things progress!
Well in the ensuing weeks it has turned into a seperate project as a lot more stuff needed to be dealt with...
If you'd like to contribute any additional or updated information for this page, please let me know. The email address is deliberately modified to defeat lame email harvesters. Remember to unpoison the email address to make it valid.
If you would like to discuss this page and it's contents with other Saab enthusiasts, please visit the Saab C900 Tehcnical Forum at Craig's Classic Saab Workshop.
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BRAKE FLUID IS
POISONOUS AND HARMFUL TO PAINTWORK! Always ensure a supply of water in a
clean bucket or garden watering can is on hand to dilute and wash away any
spills on your car or your skin!
