Fan Clutch going bad?

joe mama

Original poster
Member
Mar 26, 2012
27
I've noticed more and more lately that my '03 with 105,000 miles has the fan engaged when I start it up. After a few minutes of driving it usually turns off, or I can get the engine to 2500 rpm to disengage it and quiet down. I don't recall in the past that the fan was engaged, unless it was really cold outside (freezing) when I started it up. It's been 60-80 degrees here lately. Sometimes when I stop at a red light, the fan is engaged again, but not always.

I recently had the PO128 code, and got following work done (no more codes since all the work was complete):
- new plugs & coil pack
- new temp sensor
- new thermostat
- flush and fill w/ DexCool
- cleaned throttle body

When the fan clutch goes bad is there anything that noticeably degrades gradually as it dies? Are the symtoms I described anything that indicates it is going bad?
 

Mooseman

Moderator
Dec 4, 2011
25,192
Ottawa, ON
There are different symptoms.

- fan locks up and you have the sounds of a jet engine under the hood
- fan has a ticking noise caused by a defect from early models
- fan clutch bearing is failing and fan can be moved back and forth, may eventually lead to lock up

I'm sure someone will chime in with some other symptoms. Another thing you should check is your water pump.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Engagement at start-up is a symptom of the 2005+ redesigned fan clutch as well. If it goes away with a few minutes of driving it's OK. It's a condition that may get worse with age on an old fan. It actually helps out by giving extra cooling to the AC condenser if it's a hot summer day and you have a roasting cabin temp.

Sooner or later you may want better AC cool-off performance right after start-up, so a new fan clutch plus the dealer-only PCM update might be attractive.
 

scalawag

Member
Mar 28, 2012
17
The fan clutch in your 03' is a thermal type fan clutch, thus it will be engaged momentarily during cold start up since a thermal clutch that isn't spinning is designed to drain fluid into an engaged state, however, it can't do this long since the valve in a spinning thermal clutch at cold state will force the fluid back to the reservoir. The fact the clutch is disengaging at 2500 RPM is a good sign so long as the engine temp is normal. The clutch fan should engage when the air passing through the radiator is at around 170° or 185° engine temp I believe. Also at high engine speeds a defective fan clutch will usually roar like hell—which generally means it is locked up.
Signs are what I just mentioned, and also excessive lateral play in the shaft (1/4 inch or more) some play is normal. Leaking fluid. Turn the fan and feel/ liston for grinding or if it is hard to turn. Try and spin the fan by hand, if it spins more than three revolutions somewhat freely this is also a bad sign. It should spin easily but with enough resistance to slow it down in about 3/4 of a revolution to 1 1/2 depending on age (they gradually get worse over time). Also, check to see if the fan speeds up when your engine is getting hot or if the clutch is waiting to long to engage after the engine is already too hot. And if the AC does not work very good at idle.
Anyways, the clutch will engage and disengage depending on engine bay temperature and nothing more. If your engine bay is hot enough to activate the thermal spring inside the clutch when you pull up to a stop light then the clutch will be engaged and if it isn't hot enough then it won't be engaged. The theory behind the thermal clutch is to have the clutch disengage more precisely when it isn't needed so as to help with mpg and wear and tear. It sounds to me as though it is working correctly, unless the noise of it engaging is extremely loud (it shouldn't be that noticable really).
Sorry so long
 

Sparky

Member
Dec 4, 2011
12,927
No the 03 doesn't use a thermal clutch. 02-07 used the electronically controlled clutch. In 08 GM went back to the tried and true thermal clutch, though personally I think they should have just done efans to start with :tongue:
 

scalawag

Member
Mar 28, 2012
17
That's correct sparky, thanks, forgot about the EV fan clutch, but I thought they only used it through '06? Anyways, Joe Mama, the EV fan clutch is still essentially a thermal clutch, just controlled electronically by temperature readouts. I know some normal operating conditions are improperly diagnosed as faulty, however. The fan will usualy be engaged 1:1 with engine speed at start up for around a minute, often times higher if parked front end up on a grade of some 15% or greater and also the EV clutch an be quite loud if the vehicle was shut down with the EV fully on. Other than that, as far as I know, it fails with the same symptoms as any other thermal clutch.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
scalawag said:
... just controlled electronically by temperature readouts. ..
With the additional algorithm input (added around 2005 by a PCM update) that spins the fan at higher speed right after start-up on a hot day when you have a really hot cabin and need extra airflow over the AC condenser. The original PCM algorithm only looked at ECT and at start-up, the engine didn't need much cooling so airflow was low. If you started up, and went right into bumper to bumper traffic or idled, waiting for the AC to cool the cabin off, AC performance was suffering and owners griped. So there was a PCM update around the same time as GM updated the fan clutch design for better reliability.
 

scalawag

Member
Mar 28, 2012
17
I meant electo controlled by temp reads as a generality. So I was under the impression the clutch received a pulse at startup before the update, and that the update merely increased fan speed from the original design to help with AC. So am I wrong in this, or did it originally engage dependent on valve orientation much like a mechanical thermal clutch. Also, aside from the issues that brought about the update, what was the big problem with EV clutch besides overkill?
 

Sparky

Member
Dec 4, 2011
12,927
If the valve was on its side or whatever at shutdown it can cause it to roar for a short time at startup. Mine does that on occasion.

The biggest problem compared to a standard clutch was it would fail too darn often. Mine still works normally *knock on wood* but I'm ripping it out next month for some efans anyway.
 

scalawag

Member
Mar 28, 2012
17
So I think it's safe to say that the original poster's fan clutch may be aged and slipping some, but otherwise in correct working order—might be time to start preparing for the eventual replacement sooner than later.

I guess I have gotten lucky with mine as well, I didn't realize they were having a premature failure issue. I thought about efans also when it's time, what are you planning to go with? The only thing I'd be towing is a little pop up camper.
 

Sparky

Member
Dec 4, 2011
12,927
I have some 99 Montana fans that I'm planning to rig up with a Derale controller. Then I'll get a PCM4L tune and have them delete the fan codes while they are at it.

The tricky part will be having the AC fan override but I'll figure something out for that.
 

scalawag

Member
Mar 28, 2012
17
Awesome, make sure you post something about the install and how it turns out if you don't mind. I'd be interested in seeing how it works out for you.
 

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