my car is over heating. please help

[E30 touge]

I have a 1990 325i and it all of a sudden started over heating. no matter how i drive, if im driveing down the freeway it starts to overheat and when i turn on the hot air to cool it down, it will suddenly start blowing cold air... i think its the heater core. any help would be greatly appriciated

[redhatpat]

If your heater blows cold air when the engine is hot, you've either got a bad heater valve (won't open) and/or the coolant isn't bled fully. A bad heater core leaks coolant, it won't make your car overheat unless it loses too much coolant for the cooling system to maintain temp.

Overheating while driving could be a bad water pump, bad (plugged up) radiator, leaking head gasket, or the coolant isn't bled fully.

You need to do some testing and troubleshooting.

[turboeta]

Ever get this figured out? I'm having the exact same problem...

[Kilomph]

Me too. I've noticed coolant leaking from my driver side wheel well (1988 325iS) when I stop driving. My car doesn't over heat on the highway (I always top it off) but won't blow hot air when at idle, only while moving. Pretty sure my heater core is leaking, I don't have any time to work on it though!

Let me know what you guys figure out.

[dashboardmonkey]

Sounds like a water pump to me.

Ninja edit: change your timing belt too.