"Urambo Tauro" (urambotauro)
02/05/2018 at 12:00 • Filed to: saab 900, project, wrenching
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"Urambo Tauro" (urambotauro)
02/05/2018 at 12:00 • Filed to: saab 900, project, wrenching | 3
| 3 |
Time to throw ’em on? Well, not so fast...
After opening up all the boxes to make sure everything was there and correct, my brother proceeded to remove the old rear calipers. There’s about $90 coming back his way once he sends those cores back, which will come in handy for the next order.
But before bolting the remanufactured ones on, he’s decided to paint them first (good choice!). In the meantime, the old rear hoses are clamped tightly to keep fluid from leaking out.
There were some complications with trying to unscrew the LR hose from its caliper, so we elected to simply cut the hose downstream of the clamp instead. All of these hoses are getting replaced anyway, so there’s no need to be gentle with them.
The front calipers and hoses are going to have to wait until we’ve put the rear ones on, which will free up the pliers so that we can use them to pinch the front hoses. Right now, the plan is to paint the rear calipers, pinch the rear inner/upper hose, install both rear calipers and outer/lower hoses, then quickly replace the rear inner/upper hose to minimize fluid loss. We will then perform a preliminary bleed on the rears before moving on to the front. The last thing I want is to allow air to get into the ABS pump.
What happens if air does get into the ABS parts? In some cases, you’re expected to use a fancy dealer tool to work it out. Sometimes you can get away with just driving it on a loose surface like gravel and stomping on the brakes to activate ABS and cycle the valves, in hopes that another bleed will be enough to purge the system of air. Curious to see what Saab had to say about it, I consulted the service manual.
Much to my surprise, it appears that we may have gotten ahead of ourselves again. Saab’s recommended brake bleed procedure calls for the front circuits to be bled first. I’d never heard of such a thing. Supposedly, you’re to bleed the fronts, then use the ABS pump to do the rears.
Well I’ll be a monkey’s uncle. I’d always done the rear lines first. Interesting.
As for the front calipers and hoses, well that’s going to take a little longer to do, because we’re actually going to rebuild those calipers instead of replacing them. Not only do we have to take them apart and put new seals in, but there’s also a bunch of surface rust to be cleaned up before any painting can be done. I’ve never rebuilt calipers before (my brother’s new to this too), so this will be a neat learning experience.
TheRealBicycleBuck
> Urambo Tauro
02/05/2018 at 12:33 |
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That makes me wonder if the car only has ABS on the rear.
I’m in the process of replacing pads and rotors on the WRX. I finished the fronts before the cold front rolled through and it started raining (garage is full, have to work outside). Next weekend will be the rears. Then it will be fresh fluid throughout the system. I had some issues with brakes at the track, so I’m upgrading the rotors, pads, and going with a higher-temp fluid. Should be fun!
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Urambo Tauro
> TheRealBicycleBuck
02/05/2018 at 13:01 |
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There are sensors located at each of the four wheels, but the rear calipers are both fed by the same rear fluid line coming from the ABS unit. So it’s not a true 4-wheel ABS system. The book shows some models to be equipped with individual rear hydraulic circuits, which would allow for differential braking at either wheel, but I guess that’s not the case here. At least the fronts have their own lines.
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TheRealBicycleBuck
> Urambo Tauro
02/05/2018 at 14:32 |
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Ah. I thought it might be like my old truck. It had ABS only on the rear wheels to keep the rear end from swinging around under hard braking on slick surfaces. Trucks tend to do that when unloaded.