Overheating. Again.
 

96 m44 318ti. Replaced the expansion tank with a Behr unit. It immediately leaked at the seal, so embarking on a 500 mile trip, I had to add a quart of water every 100 miles. Also discovered a crack in the radiator. I work at an Auto Value so I ordered a Parts Master (Spectra) radiator since I could get it next day. That immediately leaked at the expansion tank seal as well. So I've only been driving the car around town which usually doesn't exceed 10 miles one way.

Saturday my family came to visit and my sister wanted to learn to drive stick. Halfway through the lesson I saw the temp needle in the middle of the red zone and immediately shut the car off. The water (not coolant since I haven't re-replaced the radiator) level was fine but the coolant was boiling. Both hoses to the radiator were hot. No sign of coolant in the oil, no white smoke that I'm aware of, no sign of oil in coolant. Could I have a stuck thermostat? Water pump? I'm beginning to fear a head gasket anyway.

The way the ti's expansion tank is designed with the o-ring at the base is a huge pita. I eventually went to a Nissens radiator because my behr kept leaking. That being said, once I swapped I went to a behr Z3M radiator and that has been perfectly fine since 2016.

It seems like aftermarket radiators are a crap shoot these days, tried to put a CSF in my Jeep and it leaked immediately. Replaced the CSF with OE Mopar and it's been perfect.

Thermostats usually stick open, it's possible that it would stick closed but you'd never see the temp stay in the middle it would keep climbing straight into the red zone. Same with the water pump, if it's not pumping the engine will get hot fast. Have you changed the two cooling pipes?

You know there is a leak at the radiator. You could rent the cooling system pressure test kit and see if there are other leaks.

Well, after replacing the radiator I test drove it again. Leaking at the lower rad hose. Repositioned the clamp, stopped that leak, test drove again. Now it's leaking like crazy from the back of the motor from I think the infamous heater hose fitting. Which is stupid because the guy I bought it from told me he'd replaced that one in particular. Now I'm facing the question: what's next? I know, I know, it's a $15 part, it can be done, but where is it going to leak next? This car was not maintained very well at all. The only things really going for it as a Ti in particular is being under 200k and having those sweet glass headlights with the low beams converted to HID. I have rust issues on the rockers and wheel arches, possibly an ongoing oil leak, something throwing a CEL, the fact that it's sitting on garbage Ebay coilovers that rattle with every bump in the road, etc, etc. I owned an e46 330i for 3 years and it never gave me this constant level of trouble. And I bought it for $900! And my current e28 of two years ($1200) only forced me to call a wrecker when my shoddy o2 sensor job came apart. Bottom line: how much more should I fix before deciding to throw in the towel and get something else? E30 perhaps?