No heat at idle, slight smell of coolant

[JGood]

My 87 325is has good working heat while driving, but blows cold when the RPM's drop below 1500. Well, not cold, as the car doesn't have A/C, but it's no longer hot or even warm.

There is also a smell of coolant, most noticeable when I first turn the heat on.

The engine doesn't go past 1/2 on the temp gauge, and has a newer thermostat. The coolant system is bled, and stays at the full mark in the reservoir, and I've put a couple thousand miles on the car recently.

I'm having trouble thinking of a failure mode that would cause both of these symptoms: No heat at idle, and the smell of coolant. Ideas? I'm thinking I should replace the heater core and valve, as one of them has to be leaking to get that smell, and then just go from there.

[jlevie]

The smell of coolant when the heat is switched on strongly suggests a leaking heater core or valve connection. But that doesn't explain the lack of heat at idle, which could be from an obstruction in the heater circuit or an air bubble in the cooling system.

[JGood]

Thanks.

Maybe the heater core is partially clogged, and leaking. I'll pull it out tomorrow and see if I can see any leaks, and check flow.

My radiator just started leaking the other week, and I figured that was the problem, getting air in the system and causing coolant to blow around the engine bay and smell up the car. I put a new Behr radiator in, but it made no change.