water pump and clutch fan function

[78SilvAnniv]

Does the engine turn the water pump or does the clutch fan turn the water pump?

I ask this question because I had a summer run hot problem for many years and replaced the clutch fan yearly, t-stats, hoses, water pump, radiator flush and finally installed a GM crate engine with a new radiator and STILL had the summer run hot problem.

My run hot problem did not get resolved until I removed the clutch fan and installed a flex fan.

I had this thought, which led to my above question:
If the fan turns the water pump, instead of the engine turning the water pump, then my success with the flex fan shows (me) that the clutch fan does not move enough water through the system to cool it.
I understand that the clutch fan can 'spin' freely without engaging and I am supposing that when it spins it isn't being effective, however with the directly driven flex fan, water is constantly moving through the system and allowing the radiator and t-stat to operate at optimum effectiveness.

How sound is my theory?
Heidi

 

[cruzer99]

The engine turns the water pump through the "fan belt".
It sounds like the cluch fan was not working correctly. The idea is that as the air temp coming through the rad gets hotter the fluid inside the cluch fan housing gets thicker and turns the fan. The hotter the ais the thicker the fluid the more the fan is engaged and pushes more air.

 

[dmrodco]

Heidi, I friend of mine ( he's a master Gm certified mech ) said that the aftermarket clutch fans you buy at AZ and such are just pure junk ! they just don't last. He recommeded buying a OEM one and yes they are available from the dealers. they are just pricey. the engine turns the pump to which the clutch is attached. as the engine gets hot the bi metal spring on the end of the clutch moves and engages the clutch to turn the fan. It does turn when disengaged ( cool ) because of clutch friction. The key is when the clutch is engaged and it is not turning full speed the clutch is shot. The clutch will not fully engage even on a OEM until about 230 deg F. the flex fan change fixed your problem a OEM clutch would have as well . I would live with the flex fan as vetts need all the help they can get in the cooling department. make sure your radiator and fan shroud seals and the seal on top of the rad support are all in good working order . or you will loose cooling air around the radiator. these are VERY important

 

[JohnZ]

Also, avoid revving the engine up with the hood open and working over the fender if you have a flex-fan; they are notorious for shedding their blades due to fatigue failure, especially with age (which is why you don't see them as OEM). The GM fan clutches are far superior to the ones you find in auto parts stores - there's a reason they're more expensive.

 

[78SilvAnniv]

I don't know where we bought the previous clutch fans, I just know we replaced them yearly for11 years and had NO results, even after immediate replacement. Perhaps CarQuest, NAPA and Kragen, maybe Western Auto. (CA and WA)
I do keep an eye on my fan blades and I do have all of the seals and shrouds in place. I am so disgusted with dealing with the clutch fans that I will keep my flex fan.
Thank you everyone, for educating me on how the engine accessory parts actually work.
Heidi

 

[rsmlap]

Heidi, a question concerning your "Run Hot" problem. Was it runnning hot at all times, freeway speeds, or just around town driving. Mine seems to only heat up after about 30 - 45 min. on the freeway. All the air rams under the front end are in place. I had the radiator checked and was told it looked fine. It does have a new fan clutch, but not sure where it came from. I believe the fan is mostly for low speed cooling, but will try the flex fan.

 

[arrio]

I was told once that when you buy a new fan clutch you have to index the bimetalic spring in the correct notch. There 2 notches that secure the end of the coiled bimetalic spring. One position for a cooler clutch apply and the other for a hotter temp engagement. Not sure sure of the actual temp ranges. Perhaps someone else can add to this or correct me if I'm in error.

 

[78SilvAnniv]

Was it runnning hot at all times, freeway speeds, or just around town driving.

Freeway speeds.
In summer temperatures I could not drive faster than 55 or 60 without it heating up to about 210-220. If I used the AC it shot up to 240.
If I was in stop & go traffic it would also heat up but I lived rurally and rarely encountered any traffic congestion.

As soon as the summer temps cooled, fall-winter-spring driving was a blast and I could drive 65-70 with no problems.
Heidi

 

[rsmlap]

My symptoms exactly. Looks like I will be trying a flex fan.
Thanks for the reply