Engine Temp Advice Sought

[KellerMAC]

My 72 temp gauge will run toward Hot over half way when I going down the highway and then it runs hotter sitting at a light. It never gets close to the max heat, but I worry about it. My truck has a new radiator and new water pump, with a new 195 thermostat. Here is my question - should I replace the fan clutch, do they go bad? How do I know that it is bad?

Also, I have a pretty good chunk missing out of the side of my shroud, would that cause me to run hotter?

Last, if I chose to replace the conventional fan, clutch, belt, and shroud with a electric fan, do you think that it will stabilize my temp and also will I pick up some pep from my 350?

Thanks

KellerMac

[Wrenchbender Ret]

Get a 180 degree therm. Half the new therms. we get are not good & 195 is too hot for these old trucks. Make sure the pressure cap is good. If the fan spins freely with the engine off or you can see oil around the thermal part it is good ind. it is bad. It should throw some wind back when you race the engine.

[buckskins4ever]

1. As Wrencher said....replace T-stat with a 185 maxx.
2. Fan clutches all go bad eventually. If you can spinit more than a few inches......its bad. Need to replace
3. What you will get with a electric fan will be the ease of using an Adjustable Temp Relay Switch, that you can adjust to engage the new electric fan. If you go this route, I would recommend going to a salvage yard and pulling the electric fan and wiring from a 1994-1998 Lincoln Mark 8....should run about $40, the switch another $40 at most. That fan moves more than 3800cfm of air.
4. While you will remove a little drag off your motor by removing the mechanical fan, you will not see any noticeable "pep". But what you will gain is room between the engine and the electric fan, and since the electric fan comes in its own built in shroud, you wont be having to worry about that chipped shroud, or making sure the should is covering the fan enough to properly draw optimal air.

[MikeyMan]

Make sure your gauge is accurate before you replace a bunch of parts.
Did the gauge read normal in the past? Have you changed the sending unit?
Certain new auto parts store temperature sending units can make a gauge read hotter.
I had that issue many years ago when I put a crate motor with a new sending unit in my 71. The gauge always read near the hot side, and fluctuated normally between highway and stop 'n go. The temp was fine, the gauge just a little off.
Something to do with the ohms and resistance between the sending unit and our stock factory temp gauge.

[rsavage]

I run 160 degree stats. You can get them at NAPA. I would start there. Get a thermometer that will read high enough and run the truck idling cap off (start out cold) and see what it runs temp wise once it is all warmed up. A meat thermometer usually reads high enough and you can stick it in the radiator fill neck (don't tell my wife about the meat thermometer thing). I have had a gauge that read hot in the past and had to replace it. It may be something as simple as that but you have to know what temp the cooling system is actually running at to eliminate it being the gauge reading bad. These old trucks have a tendency to push some coolant out the overflow after you shut it off when they run as hot as you say your gauge is running. You don't indicate that. Cooling system needs a clean radiator that flows as it should, good pressure cap, fan that is half in/half out of shroud, good stat, hoses that aren't collapsing impeding flow, and a good clutch on the fan if so equipped. But start simple and get an actual temp reading after replacing a stat which is cheap. When you do so, make sure that you get all the air out of the system.

[MARKDTN]

Don't worry about 195, there is no problem with 195. Just use a GM one or a Robertshaw. No cheapies. The hotter it gets, the more efficient it is. I used to worry about going over 180 but no more. If you stay under 200 you will be fine. You really do want the temperature to come up some. If it never gets hot, you will not get the condensation out of the oil. Too cold is actually worse than too hot. These old engines will handle a lot more temperature than we give credit for as long as the hoses are good.

Make sure your fan clutch is working. If not replace it with a GM one or a Hayden. Again, no cheapies.

Fix the fan shroud. You can epoxy or fiberglass a piece in.

Make sure your radiator cap is good. Replace with GM or high quality aftermarket.

Make sure if you have an overflow tank that the hose is good and clamps are good.

If you do all that, I think you will fix your problem. If you choose to go to electric fans, that is fine too. But you will almost certainly need a bigger alternator, especially if you go to dual fans.

[Rufton]

I prefer 195F T-stat to minimize engine wear.
195F T-Stat will not cause over heating unless it's stuck.
Stuck 160F is just as bad as stuck 195F t-stat.
IR temp gun great way to check engine temp.

Thermal clutch fans are more reliable w/ more CFM than many electric fans.
Takes very little HP to turn fan on moving car.
Clutch fans are available in std duty, heavy duty and severe duty; ranging from about 60% to 90% fan speed vs shaft speed.

Some thermal clutch fan tests:
Check fan tip play.
Check for leaked clutch fluid.
Check for loose spring.
When clutch kicks in you should hear more noise and it should blow paper harder.

Every 60's vehicle I've had cooled fine w/o shroud.
One time I went to trouble of installing shrouds on 2 cars.
Next time I did maintenance I took those shrouds off and put them in the attic; haven't missed them because they are a pain.

4, 5, and 6 blade fans are available.
Mild to steep pitch blades are available.
I prefer aggressive fan blades to help minimize under hood temps.

[KellerMAC]

Great responses everyone - a lot to think about - I really would like stay with the fan and not go to electric fans - I guess I am more of a traditionalist than I thought.

Rufton, when I have the engine off and I try to spin the fan, there is some resistance, it is not free spinning - is that the sign of a good clutch or a bad one? When you mention aggressive fan blades - do you have an example from a certain vendor?

Markdtn - You mention several times to be sure and use GM products, is there really that much difference in GM and other brands? I usually get my parts from the local auto parts house, i.e. O'Reilly's, Napa, etc. Should I be requesting GM parts from now on? Also, I don't have an overflow tank and don't think that it came with one from the factory - does anyone have a picture of where they mount?

Once again, thanks for the advice

KellerMac

[Rufton]

Originally Posted by KellerMAC

Rufton, when I have the engine off and I try to spin the fan, there is some resistance, it is not free spinning - is that the sign of a good clutch or a bad one? When you mention aggressive fan blades - do you have an example from a certain vendor?
KellerMac

Clutch fan doesn't free spin unless defective.

I don't like junk yards but that's where I've found quality fan blades.
Clutches are easy to find at local parts store.

[68gmsee]

A lower degree thermostat won't lower the heat of the engine if the one you have is working properly. Once you check the thermostat to make sure it's opening up by dropping it in hot water (I use a candy thermometer to check the water temp) then you will have to address the heating problem.

A few other things to check. These are not necessarily in the order of checking them but I always do the easy ones first:
-Pump for good water flow. Pump vanes can get rusted out and become inefficient.
-Install an overflow container.
-Fan clutch should stiffen up with warmer temperatures and loose when cool.
-Radiator and radiator cap. Buy a new cap rated for the engine you have and have radiator checked or cleaned by a radiator shop.
-Lower radiator hose. This is just to insure it's not collapsing when reving the engine or higher rpms.
-Head gasket for leaks. Bubbles in the radiator, losing coolant, white smoke in exhaust, do a leak down test.
-Timing to make sure it's not too advanced.

[MARKDTN]

Originally Posted by KellerMAC

...Markdtn - You mention several times to be sure and use GM products, is there really that much difference in GM and other brands? I usually get my parts from the local auto parts house, i.e. O'Reilly's, Napa, etc. Should I be requesting GM parts from now on? Also, I don't have an overflow tank and don't think that it came with one from the factory - does anyone have a picture of where they mount? ....

I used to do auto repair as a sideline business. The following is my experience. Take it for what you paid for it.

I have had bad luck with cheap thermostats. I have found that the Robertshaw is a good quality unit or it is hard to go wrong with genuine GM.

Cheap fan clutches are also a mixed bag. Some freewheel too much, some don't freewheel enough. If it is imbalanced it can reduce water pump life. I have not had a failure with a new GM clutch. The Hayden ones are also good quality.

Overflow tanks are often added even when not stock. If you drag race they are required. If you do have one, be sure the hose seals well. If you don't have one, the fluid level will "settle" but you won't have as much cooling capacity as you could. They are not required, but do allow slightly better cooling as the radiator is always full.

[cdowns]

a 160 degree thermo can cause you to freeze yer butt in the winter in a little to no heat cab