fan clutch

[ztim]

Could a faulty fan clutch cause overheating sometimes?

edit: I see mine has a spring on it so it should engage the fan when it gets hot. What I don't understand is it can be tested with a rolled up newspaper.

[Oldsfan]

Yes, it can. The clutch is designed to engage at a certain temperature, which then allows the fan to pull more air through the radiator. Below the determined temperature, the fan just sort of free wheels, and the only air you get is what is pushed through from driving. That's probably ok when driving, but not while stopped.

The spring is just part of it. There is a valve inside the clutch. And there is a fluid in there. At the determined temperature, the valve opens (or closes - don't know which) and the fluid flows (or stops flowing), locking the clutch and engaging the fan. Usually these fans will roar when you first start them, because all the fluid has settled. After running for a little bit, centrifugal force moves the fluid, the clutch disengages and the roaring stops. Actually, newer fan clutches are electric.

Never heard about the newspaper test. The only test I've heard of is spinning them cold by hand. They shouldn't spin freely.

Paul

[ztim]

I checked again and it seems to be a better option than using a finger when the engine is running. There seems to be a million things that can make an engine run hot. No wonder people get teed off at a mechanic who has to try everything until the problem is found. It can get expensive.

[Oldsfan]

Well, I certainly wouldn't recommend using the fingers on a running engine.

But I certainly hope you're not going to go sticking a rolled-up newspaper in there while it's running, either! That's just asking for trouble.

You need to spin the fan when the car is cold - and not running.

I don't know the exact threshold, but I don't think it should make a full revolution on it's own. It should only make a 1/2 or 3/4s of a revolution.

Paul

[ztim]

I just checked it and it would make just under a quarter of a turn so I guess it's alright. Thanks

[ztim]

I am not sure about different types, but as far as remove and replace, it pretty easy. There is just allot of things to move just to get at it to make it easier. Like the fan shroud.

[bonesbmx]

i just checked and the car was cold i couldnt move the fan it was fairly firm moved mabey an inch
i did not see a clutch. off of my water pump there is a pully for 2 belts then a spacer to the fan how is the fan being controlled is it on full when car is running all the time?
again thanks for the help im new to these engines

[ztim]

Mine is bolted to the fan itself. It is between the fan and radiator. I use Yahoo, and if you search on "Image," just type in fan clutch and you will get all kinds of pictures of different clutches. Who knows, maybe you don't have one.

edit: I just looked it up by typing in the year (72 Delta 88?) and it took me to several sites. If that is your car then, yes you have one. I guessed at your type of car so you might do your own search.

[bonesbmx]

i have a 72 cutlass supreme 350
i have a manual that says some no a/c models are equiped with a solid-hub type fans. what does that mean? can i just add a clutch to the front?if not whats controlling the fan speed or is it just full when on?
does the clutch just bolt
does anyone esle have no clutch?
im puzzled i cant find a picuture of the whole assembly



edit- heres another quote on models without a fan clutch, the fan and spacer are retained to the water pump hub by 4 long bolts
so this must mean the fan runs at full speed when car is on....right?

[88 coupe]

Originally Posted by ztim

........ There seems to be a million things that can make an engine run hot .........

There are not many and, in person, cooling system problems are easy to diagnose.

Does your engine run hot?

........ It can get expensive.

Not if one does not pay for the unnecessary parts and labor.

But that would be another topic.

Norm

[ztim]

The non-air conditioned that have a solid hub is just another way of saying it does not have a clutch. I'm learning more about this thing as time goes on. More than I planned for.

Heat is the controlling factor as to when your engine is hot enough to need the fan on. Some use a spring and others depend on oil inside. I guess it's like an old thermostat switch. Here is what my Haynes Repair Manual for Buick, Oldsmobile and Pontiac full-size models says. 1970-1990

Most vehicles in this manual have thermostatically controlled fan clutches. Some non-air conditioned models are equipped with solid-hub type fans. Here is how it says to check it.
Start with a lukewarm engine. Run it for two minutes only. Turn the fan and note the resistance. Drive the car to heat it up and check the resistance again. You should note an increase. If the fan clutch fails the check or is locked up you need to replace it. If it has a fluid leak or there is lateral play over a 1/4 inch then replace.

To replace it just says to remove upper fan shroud. Remove fasteners holding the fan assembly and unbolt the fan from the clutch. To put on a new one reverse the process. Do not try any short cuts. I learned the hard way. Good luck with it.

[bonesbmx]

from what ive read a solid hub is just the term for not having a cluch.
how can i find out if im suppose to have one?
or if the previous owner removed it?
is it absolutly neccesary?

how does the clutch tell the motor to increase rpms?
i no about the fluid or spring but how does it communicate and make it increase

[ztim]

I did a search on Yahoo and typed in the kind of car you have. I found a site:

Rockauto.com

that has a fan clutch for your car. It is an AC Delco part #154208 and is priced at $74.79. The fan clutch does not increase your RPM. It kicks in the fan only when it is needed. If you don't have one on now, it won't hurt you but will just make your engine work harder by keeping the fan on all the time. When the clutch expands due to heat, it kicks in the fan to cool the engine.

[bonesbmx]

well i going to leave it off for now im putting on new thermostat and water pump should i use thread lock on water pump bolts?
how many liters of antifreeze will it take to fill my 350?
thanks

[ztim]

I used a loc-tite on the bolts when I put a new water pump on. Be careful to map where each bolt came from which hole. I don't know how much coolant you would need. Go down to the cutlass section. I am sure you could get more help down there.

[PetChemMan]

Ah yes....thermostatic fans clutches. It reminds me of one of the more stupid automotive repairs I did in my youth. The fan clutch on my 1962 Olds Starfire went bad, so I made some brackets from angle iron and had them welded in place so that the pulley, clutch, and fan were locked together. It solved my over heating problem for a few weeks. Then one day , out on the Florida turnpike at 70 miles per hour, one of the bracket welds broke , and the bracket flew off. That created an imbalance in the fan, and in a few seconds it tore the water pump right out of the engine . It was a minor miracle that no other damage was done in the engine compartment. I called a friend , and he towed me home with a towbar. I haven't made any more "custom" fan components since !

[Oldsguy]

Originally Posted by PetChemMan

....and in a few seconds it tore the water pump right out of the engine......

EGADS! that makes me cringe thinking about it!

[Barneyo]

Long ago I worked on a clutch fan on a 340 Formula S cuda. That 'spring', the coiled
thing in the center, is a bi-metal material that coils tighter as it gets hot and uncoils
when it gets cooler. The 'coiling' turns the little shaft in the center which opens and
closes the valve inside. Inside is a heavy viscous silicone fluid and a mechanism that
kinda works like an auto transmission torque converter when its hot the valve causes
the fluid to drive the fan at waterpump shaft speed down to freewheeling as the
engine cools.

In my case the valve failed and allowed freewheeling most of the time ;-) I had to
replace the clutch itself. They can be bought separate from the fan blades so just
buy that if you find it is bad....

As another option look into an electric fan. Besides solving your cooling problem, it
will free up a batch of horsepower ;-) Get one of the ones with the curved blades
that look like a submarine propeller - they run much quieter and take less electric.

The electric kind is what I have recently been looking at on ebay for my new 62 F85
which Ive been told is likely to run hot in the summer time.

Also check your radiator cap. Use the recommended presure - if it leaks then the
fluid boils and that will cause overheating bigtime.

Hope this helps....

[ztim]

I still am losing water from somewhere and overheating. I can't find a leak so it must be doing it when the engine is running and while the car is moving. It also loses water over a long period of time, not all at once. I have to check it every few days which sucks because to replace the coolant is getting expensive. Maybe I should save for an electric fan.

[88 coupe]

Originally Posted by ztim

........ overheating ........

At highway speeds, stop and go, at idle? Or all three?

........ Maybe I should save for an electric fan.

Or you could look for the actual cause of your problem.

Have you followed up, on any of the above suggestions?

Norm

[xplicit666]

if you dont see coolant on the ground hook a coolant pressure guage and look for the leak then.. if still no signs of external leaking the intake manifold or head gasket might be leaking internaly

[ztim]

It hasn't overheated in the past two weeks. It seems it only does that when I tow my 12' aluminum boat and its skinny trailer.