Mixing fluids in power steering causing leak?

gks · Post by **gks** » 21 Mar 2023, 11:20

Hi,
I have a 2003 v70 showing signs of a leak in the rack. The local Volvo specialist quoted $2700 for OEM replacement (citing issues with rebuilt racks that I have seen discussed in various threads here, but saying that it can be done with a rebuilt rack if selected carefully). I was told that if I keep the PS fluid topped up, the leak might get worse but the car will be fine. I know I'm polluting as I let this stuff leak, and I beg eco-forgiveness, but $20 a year for fluid I can afford, and replacing the rack (currently) I can't.

I asked the shop if ATF (as listed in the manual) was the correct fluid, but they said this was an error, and told me to use CHF-202. (Here are threads I have read on this topic if anyone else is wondering: www.matthewsvolvosite.com/forums/viewtopic.php?t=99135; www.matthewsvolvosite.com/forums/viewtopic.php?t=95837; the consensus seems to that either can work, but that they shouldn't be mixed)
I have committed to CHF at this point, and have gone through close to a liter in a little over a year, adding a few ounces at a time when the level is low, but the system was never flushed, and I know that it has been topped up in the past, most likely with a different fluid—generic PS fluid, or possibly ATF.

My question is what exactly the issue is with using incompatible fluids, and whether having some mix of them poured into the reservoir at different times might be at play in the leak itself. Could it damage the seals? the pump? Is it possible that adding the wrong fluid at one time could have worsened (or even caused?) the leak? Conversely, is it possible that draining and replacing the fluid might lessen the leak?

Post by **jonesg** » 21 Mar 2023, 16:38

mine has been leaking for the past 4 years, it can keep leaking.

Post by **scot850** » 21 Mar 2023, 17:06

You could try a stop leak?

I would expect your car to have been on Pentosin (CHF-202) steering fluid and not ATF. If I recall correctly these are NOT compatible. On later P80 models (99-00?) I recall you could use either but only one and it was advised to be Pentosin.

Neil.

Post by **June** » 21 Mar 2023, 19:38

According to my dealership mechanic the P2 platform came with two rack options. The ZF rack must have the greenish CHF-202. The ZF rack is the optional variable effort steering (standard on S80 T6). All other cars are equipped with a Nippo Japanese rack which uses Dextron ATF. I asked this years ago when my S80 needed a replacement rack.

You can add some STP to slow the leak until you're ready to do the job. A little STP goes a long way so be sparing. Also Lucas transmission additive I hear does the same. June

gks · Post by **gks** » 21 Mar 2023, 21:06

Thanks all for the wisdom. Was wondering specifically about *what* makes the fluids incompatible, i.e. what effect mixing them has on the system. It's probably a stretch, but I wondered if this might have any connection to leaks emerging in the first place.

In any case, I'll keep topping up, might try a stop leak additive if it gets worse, although I have heard that THAT can cause problems for pumps and such...

Post by **June** » 21 Mar 2023, 22:06

No stop leak. My understanding of stop leak additive is it works by swelling seals. You don't want that happening in say the pump or your new rack later on. I know in the 1980s and 1990s it was the equivalent of brake fluid. At least the data provided by GM at that time. A thinking agent like STP oil treatment works via viscosity rather then swelling seals. So be mindful when selecting a product. Scott Kilmer recommends a product I believe called AP 205. I bought some when my S80 was leaking oil. I noticed it smelled like brake fluid so I didn't use it for the leak. June

Post by **jonesg** » 22 Mar 2023, 04:24

gks wrote: ↑21 Mar 2023, 21:06 Thanks all for the wisdom. Was wondering specifically about *what* makes the fluids incompatible, i.e. what effect mixing them has on the system. It's probably a stretch, but I wondered if this might have any connection to leaks emerging in the first place.

In any case, I'll keep topping up, might try a stop leak additive if it gets worse, although I have heard that THAT can cause problems for pumps and such...

one has wax the other is wax free, if mixed one can curdle the other.