This is going to be the 3rd bmw forum I signed up for some help.
So I have a 1998 BMW 328i and since the summer came it began to overheat.
My main mechanic has been trying to fix this problem for 2 months now and no luck... He has a 1998 BMW 328is that's not overheating and he tried to replace part by part, but still no luck and he even saw that my parts were good. (previous owner had changed the waterpump to metal)
I changed thermostat, radiator cap, and fanclutch(replaced with spal puller 16" fan). And also bled it A LOT of times. He even took the tstat out to check it it flows freely and it does so the tstat wasn't closing. I even took it to 2 other BMW mechanics and they didn't know what the hell was going on, they even checked all the parts and did tests on the engine. They told me " we have some good news and some bad news.. the good news is that its not your head gasket and we found nothing wrong with the parts and the bad news is we don't know how its overheating "..
The mechanics are scratching their heads at the moment trying to find the solution to this.
Now lets get into how it overheats..
When I'm driving with the heater on, it doesn't overheat so I can drive as much as I want, then when the heater is off, it SLOWLY starts overheating maybe 10-15 mins driving normally until the overheating kicks in, then it starts making its way to the 3/4 line although I never let it get past the 3rd line before shutting it off.
Right now the cars at my mechanics and tomorrow hes gonna bleed it upwards so hopefully 100% there is no air bubbles stuck inside.
Also I notice when the car is in normal temp 2/4, the hoses are squeezable but when it starts to overheat they are really stiff(rock hard).
Thanks for reading and if you have any input, please tell me, thank you.
EDIT: Also BOTH of my hoses are equally hot the top and the bottom.