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Okay, last time--brake flush with PSM


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If I do not have access to the PST and therefore cannot flush the lines to the traction control system, should I bother flushing the brakes. I'm trying to understand the relative volume of and importance of these lines. If their 1% of the system volume I'm not too concerned and would go ahead and flush the system. If they're 25% I'd take it to the dealer or and indy to take care of things. I'm about to do a DE and want to make sure my system is up to par.

Thanks, Shawn.

PS--I started looking that PSM connector pin assignments but I don't have the time to fool around with trying to trick the system into operating at the moment. I heard one suggestion of running the car while on jack stands so the PSM system see's slippage and operates. Thoughts on that?

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If I do not have access to the PST and therefore cannot flush the lines to the traction control system, should I bother flushing the brakes. I'm trying to understand the relative volume of and importance of these lines. If their 1% of the system volume I'm not too concerned and would go ahead and flush the system. If they're 25% I'd take it to the dealer or and indy to take care of things. I'm about to do a DE and want to make sure my system is up to par.

The factory service manual (for the 986) only seems to recommend using the PST2 when something major (like the master cylinder) has been replaced. Otherwise, they just describe a normal procedure using a pressure bleeder. I can't tell you how much volume you're missing, but I know I wouldn't worry about it. The fluid you really need to worry about is the stuff that's in the calipers which has been abused by heat.

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Okay, after reading the manual more closely it answered my question. The additional work of driving the booster pump while bleeding is only necessary when removing air from the system. Simply flushing the fluid does not require this step.

If I do not have access to the PST and therefore cannot flush the lines to the traction control system, should I bother flushing the brakes. I'm trying to understand the relative volume of and importance of these lines. If their 1% of the system volume I'm not too concerned and would go ahead and flush the system. If they're 25% I'd take it to the dealer or and indy to take care of things. I'm about to do a DE and want to make sure my system is up to par.

The factory service manual (for the 986) only seems to recommend using the PST2 when something major (like the master cylinder) has been replaced. Otherwise, they just describe a normal procedure using a pressure bleeder. I can't tell you how much volume you're missing, but I know I wouldn't worry about it. The fluid you really need to worry about is the stuff that's in the calipers which has been abused by heat.

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When you activate the ABS you move fluid throught the system. As such when you bleed the brakes after the ABS hs been ingaged you do a partial flush on the ABS unit. Stands to reason that after several flushes a good portion of the original fluid in the ABS system would be replaced.

Is it perfect, no. But it would help.

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Okay, after reading the manual more closely it answered my question. The additional work of driving the booster pump while bleeding is only necessary when removing air from the system. Simply flushing the fluid does not require this step.

...

That's absolutely correct. People don't seem to understand the difference between bleeding the brakes (if there is air in the system) and merely changing the brake fluid.

The manual states two different procedures and not even the workshop in the factory in Stuttgart runs the PSM booster pump when they just routinely change the brake fluid.

Cheers

Uwe

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