Wrong fan size

[franks]

I just bought a 1990 525i. The engines overheats in stop and go traffic. The gauge goes to the 3/4 mark and almost to the red. The gauge is usally a little past the 1/2 mark when driving. I checked the fan and it has 9 fins and it should have 11 fins. Could this be making it over heat?

[John in CT]

Does the fan come on when its hot? How's the coolant level? Is it fairly fresh?

Let us know,

John in Ct
1995 525i

[franks]

When the AC is working both fans are running. The coolant is new and full. How difficult should the fan be to turn when the engine is hot?

[632 Regal]

make SURE your auxillary electric fans are working, turn the AC on and you should hear them running from the front of the car. It shouldnt matter to the extent of heat as to the number of fan blades, its more important that the fan clutch is good.

[shogun]

I assume it is your fan clutch. Usually when driving on the highway or not in traffic jam, there is enough oncoming air forced thru the radiator that one basically would not need a fan.

[franks]

I assume it is your fan clutch. Usually when driving on the highway or not in traffic jam, there is enough oncoming air forced thru the radiator that one basically would not need a fan.

When the engine is hot and ideling should the fan be running faster than we the engine is cool and ideling?

[632 Regal]

frank, if the engine is hot like with the AC on in a hot climate if you rev the engine a bit it will sound like a schoolbus. if it does the clutch is fine, if you dont hear any fan sound the clutch is toast and might as well get the correct blade with the new clutch. someone might have just grabbed one from a junk yard at a previous point to get by.

[franks]

I just ran a test on the car. The gauge was slightly past the 3/4 mark and the aux. fan was not running, however if i turn on the AC on the aux fan comes on. At what temp should the aux fan turn on? Also, there is no difference in the resistance of the fan when the engine is hot or cold. Do I have two problems?

[632 Regal]

well I never did believe in the "spin the fan cluth test" and thats why I mention the fan sound. With the hood open and everything HOT you should hear and feel a lit of wind blowing. if not bad clutch.

as to the aux fans coming on with the AC you eliminated the chance that the relay or fans are bad, next step is to check the thermo switch that send a signal to the relay for the fans. Others have a LOT more expertise in this electrical function than I do, Im the mechanical man.

the clutch fan without the AC on should never allow the temp to get high. You might even want to look at the variable of a bad thermostat, unusual for the engine to build more heat than the fan can dissapate.

[franks]

Thanks for your help. The clutch must be bad because the fan air voulme never increases. I just orderd a new fan blade, clutch and thermo switch.