Cooling System Problem

[jwesner]

I have a 1995 325i. A few months ago the ACC pulley locked up and I had a friend replace it along with a few other things. Ever since then my Low Coolent warning comes on only when I shut the car off, but it does not appear to be low on coolant. However, now that it is cold outside, I have noticed that when I start my car the engine warms up as usual but no hot air blows out of the heater until I get on the highway. As soon as I exit the highway and return to a slower speed the air goes cold again. In addition to that, my wife told me tonight that she left the car running in the driveway for 20 minutes and when she went to pull out something blew up under the hood and steam was coming out. I haven't had a chance to look at it yet but my dad told me that the plastic part of the radiator where the return hose fits on had broken off. Any ideas on what the problems are and if they are related? Do I need to replace the radiator?

[93 325i]

You will definitely need to replace the radiator and thermostat. Sounds like you will need a fan clutch as well. I am in the process of re-doing my whole cooling system: water pump, radiator, thermostat w/ aluminum housing, hoses, belt..the whole works. For your work expect to shell out at least $500- more if you dont buy the parts online- less if you DIY. But it is more than the average DIYer can handle..

[Gkamysz]

Sounds to me like the system had air trapped in it. Air in the heater core means no heat. At high RPM the water pump would push enough water through to make heat. At idle there wasn't enough water running through the head, it boiled in the top of the engine and you have the result.

The car should probably be checked for effects of over heating. Cracked or warped head, failed head gasket, and so on.

I pays not to ingore problems like this. I let this happen once, and paid for it. Luckily it wasn't a BMW. A cracked head, $800 and a whole saturady later I was running again. I don't want to know what this costs for a BMW.

Good luck.

PS. It's possible the plastic water pump has failed and caused this problem. Fan clutch may be an issue, but also check the electric fan to make sure it works.

[Passatie]

Yeh i bet it is the head gasket on number 4 cylinder and its caused pressure in the coolant system and blew the radiator

It happened to me and i had to have the head skimmed, head gasket, new radiator and new thermostat adn cost the best part of £400 ($680)

Sorry about the bad news but a bm specialist told me over the phone what was wrong and sure enough it was, he said its a common problem with all 3 series