fan clutch testing

[cdr63corv]

Last summer my car started to run a little hot around town, wich it never had before. pulled the radiator wich looks in good shape and was wondering if there is a easy way to test the fan clutch to see if it is engaging, it cant be two years old thanks for any help guys...

 

[WayneC]

The only test I've heard is to have someone shut down the engine when it is idling at operating temperature, while you watch the fan (it may be helpul to have a white mark on the end of one blade)... the fan should not spin more than 3 or 4 turns after the engine stops. Tests that involve spinning the fan by hand are said not to be reliable.

 

[Ron Miller]

Try the method suggested by this site.

http://www.racingking.net/Parts/PartDetails.asp?ProductID=98

There is a definite difference in the sound, amount of air moved, and resistance to turning (with the engine off, of course, to check resistance to turning) between a thermostatic fan clutch when the engine is cold v.s. when the engine has warmed up. I assume you know that you do have a thermostatically controlled fan clutch. (Not all viscous fan clutches are thermostatically controlled.) Thermostatic controlled fan clutch will normally have either a coil spring or a metal plate on the front of the clutch where air temperature can cause the fan to engage & disengage.

Hope this is of some help.

rlm :cool

 

[Subfixer]

This probably isn't the most popular answer, but based on my own experience this year, here's my opinion:

I had the same problem as you. "Worked fine last year and ran hot this year." Turned out to be the radiator.

There is no way, other than taking the radiator apart (destroying it), to determine if the radiator is good inside. Don't believe anyone who tells you otherwise. you can't recore the original aluminum ones, nor can they be "boiled" out. Flow testing does not prove anything other than it can pass water from the inlet to the outlet.

I replaced every single part in the cooling system before biting the bullet and going for a radiator. Nothing worked until the radiator was replaced.

There are some other things to look for.... Lower hose collapsing, usually at high RPMs only, marginal thermostat, clutch fan, as you have questioned, coolant replacement, bad impeller in the water pump.

But, the real question is, how old is your radiator. If you suspect that its the original, believe me, it's toast. BTDT

There are many overheating posts in the archives with additional information as well.

 

[cdr63corv]

Thanks guys, did put in a couple differrent thermostats, wich really didnt seem to help the fins look to be in pretty good shape on the radiator and the inlet and outlet to the radiator look in good shape as far as I can see into it no corrosion to speak of. Took the radiator to a friend who owns a speed shop said he wanted to try doing somthing to it guess Ill wait to see what he says after hes done. He actually suggested checking the fan clutch. Dont believe the radiator is the original it has the correct part number on the top but no date code. If I have to replace the radiator any suggestions?

 

[allcoupedup]

Other factors to consider before replacement:

Timing Map - not enough advance can cause additional heat.
Temp Sender accuracy - many vette owners have gone nuts trying solve overheating only to find that everyting is just fine
Shroud to radiator fit - air gaps make the fan less efficient and less air is pulled through the radiator.


brian

 

[Subfixer]

If radiator replacement is required, there is only one place to go. Tom Dewitt. He makes correct replacement aluminum radiators. The radiator is a bit spendy, but it works correctly, looks correct, and fits correctly. If you average the cost over the number of years it's expected to stay in the car, it's a good deal.

Here's the web site:
http://www.dewitts.com/

 

[JohnZ]

What kind of radiator do you have now? Is it the original Harrison aluminum (no end tanks) or a copper/brass replacement? If it's original or a GM Harrison service replacement, it'll be dated just to the right of the inlet, and if it's more than 10-15 years old, it's toast; there's no way to tell by "looking at it" whether it can still transfer heat to the air.

 

[cdr63corv]

Got the radiator back today it flow tested allright so guess Ill just replace the fan clutch try that anyway thanks guys

 

[JohnZ]

Hope the new fan clutch takes care of it - if not, it's probably the radiator. A "flow test" really doesn't tell you anything about a radiator except that it isn't clogged; it doesn't take much buildup of internal scale in the tubes to become an insulator which prevents effective heat transfer from the coolant to the tubes to the air going past the outside of the tubes.