VicL

After doing some research and looking up the slave cylinder in the PET I noticed the slave cylinder does not have a bleeder. Instead it has a return line attached to it. The PET catalog does list a Bleeder but it appears it's for maintenance only and is not permanently attached to the slave cylinder.

Does anyone know how to flush the clutch fliud on a 997.2?

Thanks in advance.

Edgy01

Do we know it to be different from the 997.1 cars? There is a bleed nipple for those back at the transaxle.

VicL

Hello Dan,
Yes, it is different. Attached is the PET part number for the 997.1 slave cylinder. Part number starts with a 996 for the 997.1, and 997 for the 997.2.

This is the rennlist link that started my research. https://rennlist.com/forums/showthre...ferrerid=37901

Edgy01

If there's a return line then the challenge is to sort out what the true fluid routing is so that you know that your purge is complete, and that you don't have a deadend of old fluid. Did the workshop manual address the change?

VicL

I do not have a workshop manual for the 997.2. This is a tricky one. I have never encountered a slave cylinder with a return line.

VicL

Notice the clutch fluid return line attach to where the bleeder is supposed to be. The return line goes all the way back to just below the brake fluid reservoir.
Has anyone bled a 997.2 clutch slave?

997_rich

What's the wire/hose coming out above the steel line? Can you crack that to bleed if you disconnect? Remember it's usually the highest point that you bleed so i'd look at that first.

I wouldn't recommend it for normal maint but if you've got air trapped and you're really just trying to get the car moving you can probably crack the highest-most fitting (even if it's not a bleeder) and pump the pedal a few times to push the air out. The fluid will pour down the side of the trans case (so make damn sure you clean it perfectly because that fluid loves to eat paint etc. ) but it will get you to the point where you can drive the car again.

cello

Sorry I am late on this..

Porsche makes a bleeder tool for the 997.2 clutch bleed for the upper fitting on Part 1, first drawing. The tool mates with the fitting and has a furled **** on one end that you can spin open to bleed the same once the system is pressurized. I don't know the part number, unfortunately.

VicL

Cello, never too late for a response.

I found the bleeder in the PET catalog but have come to the conclusion that you don’t have to use the bleeder to do a maintenance flush/bleed on this system unless the slave cylinder is replaced.

After lots of research, I believe the new slave cylinder has a built in fluid recirculation valve hence the return line. I say built in because all other parts are the same as 997.1 except for the return line and slave cylinder. If this is true, the slave cylinder is self bleeding and fluid circulates from the reservoir to the slave cylinder. I basically just filled the reservoir with fresh fluid, pump the clutch 20 times, drain and refill. The Porsche Bleeder most likely holds the valve open for bleeding.

The Brake Fluid Recirculation Valve links below is how I came to this conclusion. The Clutch slave cylinder functions basically the same as brake caliper pistons (extending and retracting) but because of the longer strokes would actually move more fluid.

Go to Brake Fluid Recirculator Sectionhttp://www.prosystembrakes.com/technical_info.htm

Brake Fluid Recirculating Valve http://www.dpiracingproducts.com/store/surestop.php

Go to Post #9 http://forums.viperclub.org/tire-whe...rake-fade.html

Not the definitive answer but until I hear otherwise...
Let me know what you think?

alexb76

Why did you need to flush the fluid? was there any issues with your shifting? how old/miles?

VicL

Regular 2 year brake fluid change maintenance. The 997.1 requires the 50ml to be flushed from the clutch slave cylinder but I don't know the requirements for the 997.2.

alexb76

Ha? you wanted to brake or clutch flush?!

VicL

Alex, Porsche uses the same fluid reservoir for BOTH brake and clutch fluid. When you flush the brake fluid, you should also flush the clutch slave cylinder too.

alexb76

Not sure if it's required as I didn't when I flushed my brakes. But maybe that's the ideal way of doing it.

cello

VicL - Nice post. I think you are probably right. It stands to reason that the fluid is circulated thru the system given the two lines and that there is a valve that permits its movement in one direction only, hence the 'return line'. I can see no reason why pumping the peddle would not push the old out, and the new in ...

Not a definitive answer either. I will check with my tech bud next time I see/talk to him and let you know what he thinks...

For a maintenance flush your procedure is probably all that is needed. If changing fluid to a higher boiling point type for track use for example it might be best to bleed with the tool under pressure to (1) completely remove the old fluid (2) be sure no air is introduced to/left in the system and (3) prevent mixing and the lowering of the effective boiling point of the new fluid.