[5erFan]

Hey all, new to this forum but a long-time BMW owner and DIY'er/weekend warrior. My wife's 528xi recently got out of CPO warranty so it's now in my capable hands. We recently got a CEL and read a P0597 code which is for a thermostat heating element that is integral to the thermostat itself. The part is less than 60 bucks at FCP or Amazon or myriad other places.

Pouring over multiple Google searches I found odds and ends of this DIY job as well as a couple videos of it. I thought I'd add a few tips and tricks to help the next person do this job.

First of all, this is a one or two banana job, max. Really a piece of cake. The difference between this particular DIY and most posted online I did NOT want to undo the splash pan under the car if I didn't have to, nor did I want to drain the entire cooling system if I didn't have to. I had JUST had the cooling system flushed at the dealer a couple weeks ago so the coolant was effectively brand new. So, I went uncharted into the job with a nice piece of Tupperware and a small funnel hoping that I could catch most of the coolant from the t-stat connections with a combination of those two items. It generally worked and I ended up only losing about 1/3 gal of coolant, max.

There's an obvious air intake pipe and a crankcase ventilation pipe that have to come off, easy peasy. Just be careful with the plastic tabs on the CCV pipe as they can be brittle particularly on the lower portion. A little oil on the o-ring for the CCV pipe goes a long way as far as making reassembly easier. It fought me a bit coming out.

Eyeballing the location of the thermostat on the front of the N20 I could see that it was maybe 1/2 way up relative to the height of the radiator. There are 3 hoses that connect to the t-stat, all with different connection methods which I found kinda funny/ridiculous. The "lower" rad hose ties into the thermostat (the t-stat is integral to its housing, it's a one-piece deal BTW) via a standard BMW plastic cooling system fitting like many other BMW coolant hoses. There is another hose which tees into the reservoir and connects to the T-stat via a standard screw clamp. So you know the entire reservoir is going to be emptied. Doing this again I'd have just siphoned that out. A third hose connects to the t-stat via a spring-style hose clamp and goes up into the head. Again just eyeballing the physics of it I knew this job could be done with most of the coolant being captured rather than splashing all over the place.

I decided to undo the screw clamp coolant hose (the lowest one on the T-stat) and slip my hose removal hook (greatest tool ever, by the way) in between the hose and the t-stat barbed nipple. Just enough to get the coolant flowing. Below that I had a small funnel feeding right into a small tupperware bowl sitting right on the steering rack. I filled that bowl up probably 3x, carefully maneuvering it up and out of the engine bay and pouring it back into a bigger container. A bit of a dicey maneuver but nothing crazy.

The rest of the job is fairly straightforward. The two torx T-30 screws mounting the T-stat to the block are nearly impossible to see. You will need a socket version of the T-30 to break them loose and I used an inspection mirror to locate them. This really was the only annoying part of the job. A screwdriver version of the T-30 was the right tool for putting those screws back in, and again it's a nearly blind job.

The self-bleeding procedure for the N20 is well documented and I was totally impressed with how that worked. So neat.