Hi,
I just had my car in at the dealer for some warranty work, which included the oil filter housing gasket and valve cover gasket. After the repairs were done I got in my car to leave I noticed the check engine light was on and read the code as p0597. I went back in and they suggested replacing the thermostat, which costed me $960

Is there any chance that the oil filter housing gasket would have set off this code but not actually been an error? I know that coolant will leak out when the oil filter housing is taken off, so I'm wondering if that's what set off the light.
I've already had all the work done, I'm just a little concerned because of how coincidental it is that the check engine light was on when I picked up the car and nobody had said anything about it to me. I checked my dashcam footage and saw that the techs were revving my car right after a cold start and driving it pretty hard during the test drives, but there's no way to tell exactly when the light came on.

Any thoughts/suggestions would be greatly appreciated

 

The only connection I can put together goes like this:

-They drained the coolant to do the OFHG
-They added coolant back but didn't bleed the system properly and created air pockets
-They test drove the car hard and created an overheat situation that caused the t-stat to fail in the open position (your code)
-They tell you the t-stat is broken

I would hope a dealer would not be this dishonest. I suggest you have a conversation with the service manager.

 

Yeah, I'll give them a call and see what they say about it. I know the thermostat is also a common problem on the R56. I probably won't be returning to this dealer though, for a variety of reasons.

 

Damn -- I thought paying $704 last week for the thermo housing was exorbitant!

On the plus side you're warrantied for two years and it shouldn't fail on you now at a more inconvenient time...

 

As you likely discovered, the t-stat housing is a common problem for leaking coolant onto the top of the trans from the gasket deteriorating and because of the poor design of the housing with only 3 bolts, not necessarily for a failing t-stat. Most modern t-stats are designed to blow in the open position in the event of an overheat so the coolant can keep circulating.

I just replaced my OFHG and when you do this procedure, just about all of the coolant is drained, much more than just replacing the t-stat housing. Even after filling the coolant back and pressure bleeding, my radiator smoked on start up and I shut down the car. It took a few more bleed procedures to get coolant fully circulating. Most dealers use a better procedure than mine, pressure, vacuum, etc, but they could have created a situation where the t-stat blew.