Okay so my car began overheating today, but before we get to that. I already replaced the thermostat with housing and gasket (preventative maintenance), an aluminum coolant tank (previous was leaking a tad). I check my fluids everytime I need gas. Today I was at half a tank of gas and overheated. Coolant was low.

What could it be on these cars given everything I’ve replaced already? Water pump?

Thanks for any insight.

Gotcha I’ll look into that.

Thanks.

Are you losing coolant at the cap?

Some of these expensive replacement aluminum tanks use the same plastic cap as the OE plastic tank. If so, that OE cap is a part with a moderate failure rate, possibly higher than the tank itself.

If it’s not holding pressure, you’ll spew coolant and overheat.

naah I don’t remember which one i got but here’s a pic of when I installed it.

I think this may be the issue with my car... Like the first post, I've replaced the thermostat and coolant expansion tank (albeit an OEM one) which came with a new cap so I doubted that was the issue.

I had overheated in the middle of a hot day in completely stopped traffic and I had checked and my reservoir was empty and the engine bay was all wet - from what I've heard though, it's not abnormal to boil over even with a good cap (right?).

After refilling and bleeding and finding no leaks or losing coolant, I tested the fan via this video ( ) and got the low speed to work but just a click when giving power to the high speed. After some investigation, I found out my 2002 S doesn't use a fuse box high speed fan relay so it's gotta be in the fan itself then, right? (that's why the fan clicks when giving it power...?)

What I don't get though is that everywhere I see mentions the resistor in the fan which commonly dies, killing the low speed fan, but my low speed fan does seem to be working. I also couldn't find any 2002/2003 wiring diagrams either to find more information on how they differ from 2004+ because I know minimally they don't share the same stage 2 relay.
Any thoughts on what I should be replacing to fix the high speed fan?

A replacement fan unit for the ‘02 R53 is about $85 on Amazon.

We replaced the one on ours about a year ago with the TYC branded one from Amazon and it’s been working just fine The old fan lost the low speed, but high speed was still working.

Now low speed comes on right away (along with the power steering fan) as soon as the A/C is switched on. I don’t hear high speed as much anymore after changing out the thermostat, but I know it’s working as well.

Check to make sure your power steering fan is also coming on when A/C is switched on. I believe the fans are somehow on the same circuit.