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Hi All, on my 74, I just completed a radiator flush, replaced the thermostat, and the temp. sensor with all OEM parts. The car still heats up to about 210 after driving it for about an hour without AC running. I have been looking at comments on the forum and its seems that every year between 70 and 75 with overheating issues there is reference to the fan clutch along with other items. With that said, on mine there is no fan clutch with the fan when I got the car. My question is, should there have been a fan clutch with it or where there models without it?
My 73 small block manual transmission with ac had a fan clutch. I believe every C3 that comes to our car show has a fan clutch, the only exception would be cars with electric fans. If the fan clutch is working correctly, once the internal oil gets warm, the fan will spin freely and not be dependent on the belt, I think I got it right?
The stock setup has a different fan and a viscous fan clutch. You should be able to find the correct parts from any corvette vender. I would also suggest you make sure that the radiator seals are all in place and air is making it thru the radiator and not around it. If you changed the sending unit for the temperature gauge, what specific one did you get? Most replacement gauges are not correctly reading. I would verify yours is reading correctly using a IR temp gun. I think Lectric Limited is the only sender that is properly calibrated. What thermostat did you put in the car? I would consider 210 normal operating temperature and not overheating.
you have a non OEM flex fan with no clutch.. it is spinning 100% of the time.. a clutch will not help your situation.
no clue how effective that flex fan is, but it may be your issue.
- what is the temp of thermostat yo used?
- what does the inside of radiator look like?
- all seals in place? take lots pics.. is the spoiler there under car? not sure if 75 had one though.. more pics..
VERY clean looking engine there!!!
Flex fans make me nervous..
i would consider factory fan and clutch
If that was my car the first thing I would of is put the correct OEM fan and fan clutch back on the car. I'm with interpon on this, that flex fan is spinning razor blades and gives me the heebie jeebies.
I'd be installing electric fans so fast, it would make your head spin.
But anyway. Are you driiving on the highway for an hour when this happens? In other words, not in stop and go traffic? If so, a few other things come to mind:
Do you have a front air dam to direct air towards your radiator?
Intact seals around the radiator?
Do you have a spring in your lower radiator hose to keep it from collapsing?
Do you know that your rad cap is good?
you have a non OEM flex fan with no clutch.. it is spinning 100% of the time.. a clutch will not help your situation.
no clue how effective that flex fan is, but it may be your issue.
- what is the temp of thermostat yo used?
- what does the inside of radiator look like?
- all seals in place? take lots pics.. is the spoiler there under car? not sure if 75 had one though.. more pics..
VERY clean looking engine there!!!
Flex fans make me nervous..
i would consider factory fan and clutch
Hi and thank you everyone for the feedback...
These are the parts I replaced:
ACDelco Professional G1852 Engine Coolant Temperature Sensor
Edelbrock 8604 High Flow Thermostat 053 mm / 2 3/32 in. 180 Deg. High Flow Thermostat
Additional PICs:
My experience with this has always been when refilling the system with water, not getting all of the air out of the system.
If the air is not removed, you create an air bubble. The air pocket or bubble can affect the way the water circulates in the system.
The way I eliminate air when refilling with water is to drill a hole in your thermostat to allow the air to escape (I personally drill 3 holes).
This has been discussed here before in this forum.
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by Chaz74
Hi and thank you everyone for the feedback...
These are the parts I replaced:
ACDelco Professional G1852 Engine Coolant Temperature Sensor
Edelbrock 8604 High Flow Thermostat 053 mm / 2 3/32 in. 180 Deg. High Flow Thermostat
None of what you did has any effect on your overheating problem.
.
The thermostat has no control over maximum temperature. The thermostat only controls minimum temperature
Get rid of that horrible, ineffective JCWhitney/Checker Auto Parts mail-order suicide flex fan. Install the correct, factory, heavy duty 7-bladed declutching fan that was stock on your air conditioned engine. Your fan setup is a total POS - those things are simply horrible.
Set up your timing correctly. Badly set (retarded) timing is the #1 cause of overheating. Make sure your vacuum advance control unit is functional and that it's hooked up to manifold vacuum. Set up your timing as outlined in my timing papers - available from me via e-mail request. With vacuum advance hooked up correctly and initial timing properly set, your actual timing at idle should be close to 30 degrees. I'm going to bet that you have about 6 degrees initial with no vacuum advance at idle, making your timing roughly 20 degrees retarded, causing a severe heat problem.
Get an IR temp gun and "shoot" your actual engine temperature at the intake manifold water crossover near the thermostat housing. Verify you actually have a problem. But get rid of the nasty-*** flex fan whether you have a problem or not.
Lol... Thanks again all, its a unanimous decision amongst all, get RID OF THE FLEX FAN... I have been shopping Corvette Central, Top Flight, etc. it seems every place has the clutch fan but no fans. I was able to find the following Fan and Clutch Fan from Summit below, any comments on these would be greatly appreciated...
Is that shiny chrome alternator rated at 100 Amps or more? If so, I wouldn't waste any time with a clutch fan. Just get an electric setup. Single brushless, dual (brushed) Spal, or the setup from a C5. There are lots of examples on this Forum, including wiring instructions.
And don't forget to order an IR temp gun, to ground truth your coolant sensor.
Group 1.050
Clutch, Engine Air Cooling Fan
74-75 W/AC GM PN 343721
Mounting bolts are 5/16-18 x 5/8"
I'm not seeing a lot of options out there for used, there is a NOS Fan and Clutch on eBay but they are pretty proud of those parts. NOS Fan NOS Clutch
I did run across a NOS 342715 Fan on Seattle Craigslist that was listed 16 days ago, if I was looking for a correct Fan this would be the one I go after. NOS Fan
Lol... Thanks again all, its a unanimous decision amongst all, get RID OF THE FLEX FAN... I have been shopping Corvette Central, Top Flight, etc. it seems every place has the clutch fan but no fans. I was able to find the following Fan and Clutch Fan from Summit below, any comments on these would be greatly appreciated...
First.....I second everything Lars said....especially about the timing and the salad cutter......
Second......have you removed the rad to see if you have any debris between the condenser and rad? 50 years is a long time for a car to collect ****......
Third...that Allstar fan will not work....I urge you to find the right 7 blade fan new or used........and the "HD" fan clutch.......I use both on my 500hp 406 small block with a bone stock cooling system and run 190-195 degrees......
If I was you I would stop changing **** around and perform this step:
-Get an IR temp gun and "shoot" your actual engine temperature at the intake manifold water crossover near the thermostat housing. Verify you actually have a problem.
Hi all, thanks again for all the feedback… With that said, it has been a great struggle trying to find a 7-blade/17.5 width w/AC fan. It seems all corvette supplies have stopped supplying and salvage yards just don’t have one. So, unless I can find a fan, which I really want to, to keep the originality of the car I am starting to look at electric fans to add to existing radiator or replacing with an aluminum radiator with fans combo. Any suggestions on adding an electric fan to existing setup vs combo and manufactures would be much appreciated.
1974 Corvette Overheating
