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-   -   964/993 owners test your ABS and do it regularly. (http://forums.pelicanparts.com/porsche-964-993-technical-forum/984904-964-993-owners-test-your-abs-do-regularly.html)

heliolps2 01-20-2018 06:13 PM

964/993 owners test your ABS and do it regularly.
 
Hello Friends

We just had some snow in DC and I have a 300 foot long driveway, Perfect place to test my ABS, I took my 965 out this morning did a few tests runs and my ABS seems to work, The pedal did what I expected just like my 2017 Jetta that I test just prior to compare , I even opened the door to see if the rear ABS was working , All good, back in the garage she went.

The exercise got me thinking. Firstly how many of us drive around not knowing if the ABS is working or not.. The only reason they would seize like this is because they haven't been operated on a regular basis?

Conclusion...test your ABS and do it regularly.

Bill Verburg 01-22-2018 05:58 AM

Quote:

Originally Posted by heliolps2 (Post 9894217)
Hello Friends

We just had some snow in DC and I have a 300 foot long driveway, Perfect place to test my ABS, I took my 965 out this morning did a few tests runs and my ABS seems to work, The pedal did what I expected just like my 2017 Jetta that I test just prior to compare , I even opened the door to see if the rear ABS was working , All good, back in the garage she went.

The exercise got me thinking. Firstly how many of us drive around not knowing if the ABS is working or not. Secondly, the pump and these pistons are 'dry'. They are not lubricated by brake fluid. The only reason they would seize like this is because they haven't been operated on a regular basis?

Conclusion...test your ABS and do it regularly.

The ABS pump is totally saturated w/ brake fluid, unless you get air into the system somehow. It couldn't work otherwise

Nine9six 01-26-2018 06:24 PM

For brake and clutch slave fluid flushes, if you don't have a Bosch hammer, PST2, PIWIS diagnostics tool; or physically exercise the ABD and/or ABS systems as mentioned above by the OP, you will eventually end up with a non-functioning, gummed up system.

I would recommend exercising the abs/abd systems AFTER brake fluid flush to purge those components of the old brake fluid, and in the process refilling the system with the fresh brake fluid.

I would then, re-bleed the brakes to purge the system of the old brake fluid that was just exhausted by the ABS ABD systems components.

Here is an old Rennlist thread on the subject...

https://rennlist.com/forums/993-forum/489683-solution-for-soft-brake-pedal-caused-by-abs-pump.html

Just my $.02

Bill Verburg 01-27-2018 06:43 AM

Quote:

Originally Posted by Nine9six (Post 9902226)
For brake and clutch slave fluid flushes, if you don't have a Bosch hammer, PST2, PIWIS diagnostics tool; or physically exercise the ABD and/or ABS systems as mentioned above by the OP, you will eventually end up with a non-functioning, gummed up system.

I would recommend exercising the abs/abd systems AFTER brake fluid flush to purge those components of the old brake fluid, and in the process refilling the system with the fresh brake fluid.

I would then, re-bleed the brakes to purge the system of the old brake fluid that was just exhausted by the ABS ABD systems components.

Here is an old Rennlist thread on the subject...

https://rennlist.com/forums/993-forum/489683-solution-for-soft-brake-pedal-caused-by-abs-pump.html

Just my $.02

That's is true, the ABS working part is either 3 or 4 main pistons whose function is to connect or disconnect the pedal and individual caliper pistons from each other There are also a proportional # of aux pressure control pistons. All of the pistons create numerous pockets of normally stagnant brake fluid. The default is pedal connected to calipers until the wheel sensors signal an excessive difference in wheel speeds, at which point the brain tells an offending piston to disconnect that caliper from the pedal. Over time when not flushed a waxy substance and moisture builds up in the various piston bores, this substance interferes w/ and degrades ABS performance.

Here is a schematic of a 3 channel abs
https://cimg9.ibsrv.net/gimg/rennlis...ed5c970b49.jpg

Paperboy 01-28-2018 07:34 AM

Interesting. Diagnostic tools are mentioned. Been meaning to get one to amongst otherwise things make bleeding of the C4 AWD solenoids easier. When it says they have ABS function does this mean the activation of solenoid valves mentioned above? Also, this from A Streathers book: 'Automatic ABS system self testing at 7 kph/4 mph can be felt by the driver, because the return pump in the ABS hydraulic united will run briefly.' This is apparantly testing the wheel sensors. Any light on this? How should it feel?

Nine9six 02-09-2018 05:07 PM

Yes.
I believe this will feel like when the ABS is actuated/working. (Quick pulsing/shuddering feel at the brake pedal).

hkspwrsche 02-15-2018 04:24 PM

Quote:

Originally Posted by Paperboy (Post 9903624)
Interesting. Diagnostic tools are mentioned. Been meaning to get one to amongst otherwise things make bleeding of the C4 AWD solenoids easier. When it says they have ABS function does this mean the activation of solenoid valves mentioned above? Also, this from A Streathers book: 'Automatic ABS system self testing at 7 kph/4 mph can be felt by the driver, because the return pump in the ABS hydraulic united will run briefly.' This is apparantly testing the wheel sensors. Any light on this? How should it feel?

Never noticed

Nine9six 02-16-2018 04:10 PM

Quote:

Originally Posted by hkspwrsche (Post 9927912)
Never noticed

Hmm, that's not a good sign...

I would take the car out onto some snow or wet surface and actuate the ABS by hard braking (hard enough to lock up the wheels).

I don't recommend doing this in the dry because if the ABS doesn't work, you'll end up flat spotting the tires.

If the tires need replacing, test to your heart's content.


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