View Single Post
Old 12-30-2021, 12:02 PM
RocketyMan's Avatar
RocketyMan RocketyMan is offline
Join Date: Jan 2020
Location: PNW
Posts: 502
RocketyMan is on a distinguished road
Originally Posted by o2bad455 View Post
Thanks! To be honest, I'm not sure if my suspicion was right or just wishful thinking. There's no abnormal feel or noise from the old pump, so I was actually worried that I guessed wrong until I buttoned it up and was pleasantly surprised that it was fixed. I really didn't want to have to R&R the rack!

Actually, I think the fluid I'd used for top-up a while back actually was CHF-11S, just in a smaller bottle (355 ml instead of 1 L). It was green too. Anyway, I'm sold on the full-synthetic CHF-11S. I don't like the idea of swollen seals from modern ATF. I've seen too much of that on other cars already.

Agreed. It seemed electronic to me, but apparently only because I'd never had a PS loss with no other symptoms before. The SVT control seemed a likely suspect, especially after discovering the servotronic valve, but it turned out to be a red herring! Go figure...

I'll measure temps again to see if it's much different. Come to think of it, I'd only measured temps just before, in and just after the reservoir this morning becuase those were easily accesible, but probably should have measured just before at and after the pump, possibly from underneath. I believe the PS fluid goes through a cooling loop before it reaches the points where I'd previously measured.

Honestly, the more I think about it, I probably just lucked out today... But I'll take that!

Well it makes sense if the pump goes. The TIS has quite a big warning about holding the steering wheel in the "locked" position for too long. This is VERY hard on the pump as there is no relief when the steering gear is trying to press all it's pressure on the locks. Once that happens, this causes a no-flow scenario and will then "burn up" the pump. Or in this case, the veins scar the housing, thus, no pressure being able to be produced.

You checked for SVT codes and didn't find anything. There is no "pressure sensor" in the steering--so it makes sense that if the module isn't complaining that the only other probable cause would be the pump since there is no feedback for pressure loss, other than no assist.

Here is a very limited PDS of the 11S:

Then something comparable like this for Valvoline MaxLife ATF:

Other than both being synthetic, the two have very similar viscosities at temperature. I would expect them to behave the same. Until a VOA of 11S proves otherwise, I'm not convinced it is much different. But ohwell...a topic for a different thread.
2003 BMW X5 3.0i -- MT5, 3.64s final gears, H&R lowering springs, K-Mac bushing kit
2007 BMW X3 3.0Si -- MT6
Reply With Quote

Sponsored Links