964 power steering fluid

iamtheari · 08-03-2011, 08:17 AM

Yes, I have searched the forum and Googled a lot, and yes there are answers out there. But none of them felt quite definitive enough to make me feel confident without at least asking for confirmation. So, here we go (maybe I'll retitle the thread "definitive power steering fluid for 964" if some solid answers come in, to make the next person searching for this information a little less likely to post yet another thread on the topic like I'm doing).

My understanding is that my 1990 Type 964 Carrera 4 requires a Dexron II-compliant or Dexron III-compliant automatic transmission fluid to be used for the power steering. However, the conflicting information that keeps me from just buying two quarts of O'Reilly Dexron III-H/Mercon and doing the job this evening is that the Pelican catalog lists Pentosin CHF 202 for the 1990-1998 cars.

So, which is it? Do I pick up the Dexron III stuff tonight or order the Pentosin and wait? Thanks!

milutintin · 08-03-2011, 08:33 AM

I think Porsche recommends Pentosin.

Look at this: http://www.pcarworkshop.com/images/f/fe/PowerSteering_OIL_1996_640696.pdf

lucittm · lucittm's Garage

I used Pentosin in my car after a rebuild and so far zero problems.

Think - Porsche recommended Pentosin, they probably don't make any money on that recommendation, so there had to be a good reason they would stake their reputation on something as simple as PS fluid.

Mark

iamtheari · 08-03-2011, 03:31 PM

My understanding is that the various fluid choices don't mix and that the year of the car decides what to use. Here is a thread showing what I mean: Power steering fluid in 993?

Here is a Rennlist thread that reaches the same conclusions, as far as I can tell: Power Steering Fluid Recommendation - Rennlist Discussion Forums

I wish I had the time and resources this summer to rebuild the steering rack, as it is one of three known leaks in my car.

But here is finally something authoritative (linked in the Rennlist thread): http://www.pcarworkshop.com/images/3/30/4800_1996_640696geolab.pdf

I wish I had found that first! Conclusion: Pentosin CHF 11S is recommended. Cars before March 25, 1996 were shipped with ATF. ATF and Pentosin CHF 11S can safely be mixed. I'm ordering the 11S now. Good thing I checked, or I'd have a couple liters of CHF 202 with nothing to use it in (just like my redundant distributor vent kit - I ordered it before I picked up the car and realized that it already had one installed).

Thanks for the reply. I hope the next guy in my shoes spots this thread.

porterdog · 08-08-2011, 06:17 PM

Redline D4.

iamtheari · 08-08-2011, 06:18 PM

porterdog: I already ordered the Pentosin CHF 11S. Can you explain your recommendation for Redline D4?

porterdog · 08-09-2011, 07:35 AM

I'm sure the Pentosin is fine. The Redline product I've been using in various cars since '99 or so and have had nothing but great luck with it. It stopped my turbo Miata puking ATF at the track, and is known to sometimes reduce/cure leaks by swelling the seals slightly. It also has a rep for cleaning out the system, something to do with their PAO chemistry I guess. I did a couple Subarus that way- empty the res with a turkey baster, add Redline, drive, repeat until your quart is gone. The first couple drains were gross but after that the fluid stayed clean,

iamtheari · 08-09-2011, 07:37 AM

Do you know if Redline D4 can be mixed with Pentosin the way Pentosin and ATF can safely be mixed without having to completely flush the system before adding any? If so, it will be good to know since Redline products are a lot easier to come by when out on the road than Pentosin.

RSTarga · 04:51 PM

I top mine up with mobil synthetic power steering fluid, that should mix with anything.

dfink · 08-25-2011, 07:24 PM

Im pretty sure the owners manual for my 92 C4 listed Dexron ATF.

iamtheari · 08-26-2011, 07:23 AM

I unfortunately do not have an owner's manual for my '90 C4. I am relying on the Porsche service bulletin linked above. It appears that Dexron ATF should be just fine but the latest recommendation from Porsche is to switch to Pentosin. My thought is that, as long as you have one or the other in the tank and it's not starving the pump, the steering system is safe.

SAM DACOSTA · SAM DACOSTA's Garage

Quote:

Originally Posted by dfink

Im pretty sure the owners manual for my 92 C4 listed Dexron ATF.

You are correct for the C2/C4 models. I'm reading my manual as I type and it clearly states ATF Dexron as the choice for our 964 vehicles.