Brake fluid, go cheap or expensive?
07-17-2002, 01:41 AM
#16
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David,
I think you may have a point there regarding the vacuum assist version versus the electrically assisted vehicles. The ABD may not have existed on vacuum-assisted versions. I'm not sure if ABD was even available on any non-AWD car. Other owners out there may have to comment on this one since I only have a version with the ABD. It may not be something to worry about for you in that case.
On a slightly off-topic subject, the ABD feature is a confusing item since the ABD is linked to the limited slip capability of the vehicle (as I understand it). My sticker indicated that I had the limited slip differential and also ABD, but the rear wheels didn't spin in the same direction when the mechanic was checking for limited slip. I suppose that the ABD is a virtual (active) limited slip where the brakes are applied to achieve identical speeds instead of a mechanical lockup.
*****
I think you may have a point there regarding the vacuum assist version versus the electrically assisted vehicles. The ABD may not have existed on vacuum-assisted versions. I'm not sure if ABD was even available on any non-AWD car. Other owners out there may have to comment on this one since I only have a version with the ABD. It may not be something to worry about for you in that case.
On a slightly off-topic subject, the ABD feature is a confusing item since the ABD is linked to the limited slip capability of the vehicle (as I understand it). My sticker indicated that I had the limited slip differential and also ABD, but the rear wheels didn't spin in the same direction when the mechanic was checking for limited slip. I suppose that the ABD is a virtual (active) limited slip where the brakes are applied to achieve identical speeds instead of a mechanical lockup.
*****
07-18-2002, 01:35 AM
#17
*****,
My c2 has abd w/ limited slip as well, so it can't be limited to the 4wd cars. I don't know which cars get the electric assist brakes. My only guess is that it applies to the 4wd cars.
Check the archives for a way to test the function of the abd. From previous discussions, there is a way to test its condition w/ the car off. It seemed at the time that there a lot of people with abd not working.
Kim,
Go ahead and bleed your brakes; you certainly won't harm the abd circuit. I have never had any problems after bleeding mine.
David
My c2 has abd w/ limited slip as well, so it can't be limited to the 4wd cars. I don't know which cars get the electric assist brakes. My only guess is that it applies to the 4wd cars.
Check the archives for a way to test the function of the abd. From previous discussions, there is a way to test its condition w/ the car off. It seemed at the time that there a lot of people with abd not working.
Kim,
Go ahead and bleed your brakes; you certainly won't harm the abd circuit. I have never had any problems after bleeding mine.
David
07-19-2002, 04:19 AM
#18
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Kim, David,
The ABS/ABD-limited slip option is a confusing one. My mechanic couldn't explain it enough for my satisfaction and ended up pulling out the Porsche manual, which didn't do a good job of providing any useful info either. The nearest conclusion that we came up with is that the ABD-limited slip option was a factory delete option for the mechanical limited slip (verified via the rear wheels not spinning in the same direction when the vehicle is up on a lift) and replaced by the auto-braking functionality of ABD. There's got to be a pump of some sort to activate the brakes independently to control wheel-spin; don't know if this auto-braking is for rear-only or for all 4-wheels, in the case of the AWD's.
I don't think that regular bleeding the brakes will harm the ABD circuit, as David had already mentioned. However, I do believe that the flush is not complete if you don't exercise this portion of the circuit. I believe this is also true of the ABS circuit; I've heard of some folks intentionally activating the ABS by braking hard so that the system pumps the brakes to clear this circuit, not sure how to get the ABD to activate though (maybe some ice driving).
On the brake flushes, I'm planning on doing most of the brake flushes myself as you are planning to do. However, on the first flush, I'm seriously thinking of going to a garage that has the $10K "Hammer" to clear out all brake fluid passages. This will set a baseline for me and subsequent changes I'll do myself and perhaps go back again to get the Hammer after 2-3 flushes.
My thinking is that if you don't flush ALL the system out, leaving untouched the "hidden" circuits that are only accessible via the "Hammer", then when you initiate an emergency stop (where the ABS circuit is activated, but still unflushed) you're calling upon essentially the old fluid to save you during a rather critical time period. I know, I know, this is worst case analysis, but better safe than sorry ... in real life this may not matter that much since the stock Porsche fluid is rumored to be ATE #200 (amber) which doesn't absorb much water anyways.
*****
The ABS/ABD-limited slip option is a confusing one. My mechanic couldn't explain it enough for my satisfaction and ended up pulling out the Porsche manual, which didn't do a good job of providing any useful info either. The nearest conclusion that we came up with is that the ABD-limited slip option was a factory delete option for the mechanical limited slip (verified via the rear wheels not spinning in the same direction when the vehicle is up on a lift) and replaced by the auto-braking functionality of ABD. There's got to be a pump of some sort to activate the brakes independently to control wheel-spin; don't know if this auto-braking is for rear-only or for all 4-wheels, in the case of the AWD's.
I don't think that regular bleeding the brakes will harm the ABD circuit, as David had already mentioned. However, I do believe that the flush is not complete if you don't exercise this portion of the circuit. I believe this is also true of the ABS circuit; I've heard of some folks intentionally activating the ABS by braking hard so that the system pumps the brakes to clear this circuit, not sure how to get the ABD to activate though (maybe some ice driving).
On the brake flushes, I'm planning on doing most of the brake flushes myself as you are planning to do. However, on the first flush, I'm seriously thinking of going to a garage that has the $10K "Hammer" to clear out all brake fluid passages. This will set a baseline for me and subsequent changes I'll do myself and perhaps go back again to get the Hammer after 2-3 flushes.
My thinking is that if you don't flush ALL the system out, leaving untouched the "hidden" circuits that are only accessible via the "Hammer", then when you initiate an emergency stop (where the ABS circuit is activated, but still unflushed) you're calling upon essentially the old fluid to save you during a rather critical time period. I know, I know, this is worst case analysis, but better safe than sorry ... in real life this may not matter that much since the stock Porsche fluid is rumored to be ATE #200 (amber) which doesn't absorb much water anyways.
*****
