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I have a UK 93 CDE 2 litre LPT with mark IV abs and have worried about the brakes ever since I got it nearly 2 years ago but in the end have accepted they are different compared to other cars. With the engine running, pedal is initially soft with poor feel, has a lot of travel and requires some effort to stop quickly. Without the engine running the pedal travel is a lot less since the servo (booster) is not helping which is normal. The brakes pass the annual MOT test at the garage and the tester says they are up to standard. There are lots of comments on the brakes on this site.
Things to check (probably already done) are that the rear brakes are adjusted and I find running the abs pump occasionally clears out any tiny amounts of air that builds up in it. On the mark IV the pump only runs for less than a second on start up when the car reaches about 20 mph - you can just hear it. There is no accumulator. The abs pump is the black cylinder to the left of the master cylinder.
Saab do a manual on the mark IV abs and is useful if you bleed the brakes since the black pump has to be run and the valves opened if the system has been drained. Running the pump is needed when bleeding the back brakes to get a good flow of fluid. This can be done by replacing its relay with a wire and switch so it can be switched on but should not run for more than a couple of minutes. Look on the side of the relay to see which pins need connecting.
To improve brakes have done the following but no big changes so bear this in mind if about to embark on a lot of work:
- fit all PTFE braided hoses - front ones had ballooned at the struts.
- checked for leaks.
- replaced discs and fit Saab pads. Rear pads are Textar which are a bit hard. For some reason the front pads are chamfered so they take a while to properly bed in but the Saab ones work better than previous Textar.
- removed and cleaned all caliper pistons - front left had seized partly.
- replaced abs pump/master cylinder/valve block with lower mileage second hand.
- replaced rear calipers since old were not maintaining adjustment and were clicking.
- replaced section of corroded brake line.
- bled brakes many times.
- checked brake pedal area for corrosion.
- replaced engine hoses which had perished and maybe giving air leak affecting brake servo (booster).
- checked resistance from brake pedal travel sensor fastened to servo. This gives position of pedal to the abs so it knows if there is a problem.
- every now and again adjust the rear calipers.
posted by 53.122.20...
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