Questions about Cooling System

[304065]

Gentlemen,

A friend of mine has a 1989 944 Turbo that is having some cooling issues. I have the following questions:

1) How many cooling fans are there?

2) Are they all electric, or is there an engine-driven fan? (I'm a 911 guy so only know from engine-driven fans)

3) How are the fans turned on and off?

4) What major components (wires, resistors) are present in the fan control circuits?

5) Are there common failure points? Do the fan relays fail, for example with the same frequency as a DME relay?

Also, my friend is having difficulty with a high NOX level. I believe this is due to high combustion temperatures. Could this also be caused by a defect with the cooling system?

Thanks in advance for helping an aircooled brother help another watercooled guy.

[944 Ecology]

1) Two fans, both electric.

3) Fans turned on and off by inputs to relay from air conditioning and thermoswitch on radiator.

4) Black box... but expect to find transistors, resistors, capacitors, wire.

5) Fan relays fail. Thermoswitches fail.

6) I doubt that high NOX is due to hot radiator. Of course, here in Upstate NY, we don't have emissions testing for cars, so we don't care about NOX or CO, for that matter.

[legion]

John, I had a slight overheating problem (engine was running hot...but not dangerously hot).

The following two simple steps helped fix it:

1) I had been running 10W-30 oil. I switched to 20W-50.
2) While in the process of removing my A/C, I found that the A/C condensor (which sits directly in front of the radiator) was dented and clogged with debris...this prevented adequate airflow through the radiator. For me, I removed the condensor completely, but maybe a new condensor is in order.

I hope these suggestions help out.