Fan clutch resistance question

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

codfish

Drive a hybrid. I NEED your gas!!
Joined
Jun 9, 2022
Posts
195
Reaction score
580
Location
Newfoundland
First Name
gary
Truck Year
84
Truck Model
K10
Engine Size
350
How much resistance should a cold fan clutch have when spinning it by hand? I can move it. But it certainly won’t keep spinning when I stop moving it. It’s stiff but it moves.

I’m trying to figure out why it never gets above 130-140°.

Gonna get another thermostat today and throw it in. I’ll test it in water before I install it. New coolant sensor already installed. In the head.

Aluminum rad last year due to busted stock one.

Fan clutch next suspect.

Codfish
 

PrairieDrifter

Full Access Member
Joined
Dec 28, 2014
Posts
3,858
Reaction score
5,656
Location
North Dakota
First Name
Mason
Truck Year
84,79,77,76,70,48
Truck Model
Suburban k10, bonanza k10, k30, k20, c10, gmc 1/2ton
Engine Size
350, 350, 350, 350, 350, 350
It should spin like 1/4-1/2 revolution with a good flick maybe a little more.
 

75gmck25

Full Access Member
Joined
Oct 13, 2016
Posts
2,279
Reaction score
2,223
Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
it’s full of fluid, which might have settled/gelled when it got completely cold. You might try starting up the truck, let it run for about 5 minutes, and then recheck the clutch to see if it loosens up a little.

Howeve, it sounds like it is probably working correctly.
 

codfish

Drive a hybrid. I NEED your gas!!
Joined
Jun 9, 2022
Posts
195
Reaction score
580
Location
Newfoundland
First Name
gary
Truck Year
84
Truck Model
K10
Engine Size
350
Good point

I’ll try that
 

codfish

Drive a hybrid. I NEED your gas!!
Joined
Jun 9, 2022
Posts
195
Reaction score
580
Location
Newfoundland
First Name
gary
Truck Year
84
Truck Model
K10
Engine Size
350
Still “stiffish” after 5 mins of running.

Well after going to town twice for a thermostat (wrong one in the first package-160 instead of 195), I have more questions. Maybe I’ll start a new thread.

After installing a new 195° thermostat and cleaning up the stock sending unit’s wire connection, I can watch the factory gauge creep up to 195-200, and watch it go back down when the thermostat opens. Great! I used my temp gun to confirm..

However, the temp readings on my Holley Sniper screen shows 150° or so. This was just idling in the driveway. Taking it on the highway in a few minutes so I’ll see what happens in driving conditions.

Why would there be such a difference in temps from the head to the thermostat housing? This is with a SMP sensor, as I assumed the supplied Holley sending unit was out of whack like others have suggested.

I was told the head is a better spot for the sensor. Might have to put the sniper sensor on the thermostat housing so I can get the required temperature for the sniper system to “learn”.

Thoughts?

Codfish
 

nvrenuf

Full Access Member
Joined
Jul 30, 2010
Posts
1,963
Reaction score
2,475
Location
Mobile, Al.
First Name
John
Truck Year
1991
Truck Model
K5
Engine Size
454
Seems like I remember reading about issues with the Sniper temp sender. Maybe check the EFI sub forum on CK5.com
 

codfish

Drive a hybrid. I NEED your gas!!
Joined
Jun 9, 2022
Posts
195
Reaction score
580
Location
Newfoundland
First Name
gary
Truck Year
84
Truck Model
K10
Engine Size
350
Yeah I’ve already ditched the Holley temp sender for an aftermarket sender.
 

Latest posts

Forum statistics

Threads
44,205
Posts
951,607
Members
36,341
Latest member
tmssldn
Top