Running a little warm at idle

[KYdirte30]

Have an '88 325is. Intermittently at idle or in stop and go traffic it will start to get a little warmer than usual. Most it's gone is like 1/3rd past the half way line towards the 3/4 mark in the coolant temp gauge.

Should I be worried at all? I was thinking on putting in a new thermostat.

[e30davie]

if the cooling system is working as it should, for a given journey in the same environment, the engine should get up operating temperature and the thermostat should regulate and keep it at the temperature.

Gaining temperature when you are stopped implies that you aren't getting the required cooling when you have less air flow over the radiator. The last time i experienced this was when i was quite low on coolant due to a leaky hose. Other options may include your radiator fan isn't working like it should and isn't moving enough air when the car is stationary (dodgy fluid coupling on radiator).

I would investigate if i were you.

[c0rbin9]

Something is amiss, either airflow or coolant flow.

Make sure your clutch fan is moving lots of air at idle. If that's good, you may have a sticky thermostat. Clogged radiator/coolant passages are another possibility.

Just because your temperature goes down when you're moving doesn't mean lack of airflow is your problem. I had those symptoms on my 318is and it turned out to be a sticky thermostat. Gummed up coolant passages in the radiator and block are also possible considering how old the car is, especially if coolant changes were neglected.

[7pilot]

1, Test the clutch fan by gently introducing the end of a rolled up newspaper to the blades.
If it shreds, change the water pump.
If the fan stops easily, you may need a new fan, and if the temps don't stay normal with the new fan, replace the waterpump for sure.
An old headgasket, and a long section of aluminum, I would not waste too much time investigating.

m

[scabzzzz]

+1 fan clutch. unless you have leaks in the cooling system, its likely going to be that.

[CanadianDirty30]

had the exact same problem as you, idle i began to overheat but when driving it was fine. Changed the thermostat and the fan clutch. Do the rolled up newspaper test on the fan, if you can stop the blades then its the fan clutch, worked for me.

[KYdirte30]

Thank you for all the help guys. Ended up changing out the thermostat and fan clutch and everything is good now