This question is about my 83 K20 454. It has ,never ever, had any other overheating problems. I have an 8' Fisher plow on it winters, I live in so. NH. I had a severe duty fan clutch of unknown manufacturer purchased over 15 years ago, it was close to $100. It started leaking so I replaced it with a Hayden #2797 which they claim is severe duty fan clutch. It was physically smaller, the parts guy assured me it was a severe duty fan clutch. Now the truck heats up over 30mph, it will push heavy snow all day, idle in traffic in 90f heat, with no problems, it was fine with the other clutch. 3 fan clutches a couple thermostats, with no change. Nothing else has been changed. Yes, Stupid threw out the old one! I could add electric fans, air deflector, etc. The other thing that baffles me is, in the Hayden catalog, #2797 is listed for a 4.3 Astro all the way to a 454ci P Chassis, hows that work?? Where and who makes a high quality severe duty fan clutch?? :confused:
Thanks and Happy Holidays to all
Kirk

With a plow attached, the whole cooling system needs to be as close to 100% as possible. Not only because of the extra heat generated when pushing snow, but also to make up for the reduced airflow at road speed. You lose much of the ram-air effect because of the steel wall in front of the radiator. It also makes the engine work harder to move the truck at road speed so more heat is generated.
At road speed, the airflow around the plow actually creates a low pressure area in front of the radiator. The fan is losing efficiency by trying to overcome the low air volume, not something it was designed to do. It was also not designed to move enough air at speed to cool the engine.
When plowing, the air blockage is much less than when going down the road.

Any scale or blockage in the radiator reduces the heat transfer. Limiting the airflow when the engine is making a lot of heat means it will run hot(ter). Add in a little bit of scale compromising heat transfer and you can get an overheat condition. You mentioned a lot of parts, but not the radiator. That would be my #1 suspect, especially if it is original.

- How old is the radiator? If you look down the filler neck and see ANY scale on the tube ends, it's time to replace it.
-If the truck has AC, flush the dirt and debris from between the radiator and condenser. Do it from the middle outward.
-Is the shroud intact and attached properly?
-Are the seals between the radiator, condenser and core support all in place and intact.

I hope that made sense.

2797 is a severe duty clutch.

I live in NY and have done plowing for for over 40yrs and maybe there was fine snow & ice packed in the raidator and or ac condenser if truck has ac.

Also,when the motor was hot /overheated did you get out & pop the hood and rev the motor to see/hear/feel airflow to see if in fact the fan clutch was locked up ?

I have seen that fine snow and ice pack ice overheat trucks/pickups mult times over the yrs.
You wouldnot think this couldhapen with hot coolent in the radiator but it doe,thats for sure.

But if there was in fact snow & ice pack then there would not be much or any airflow thru rad to hlpe heat up the front of the thermostarting fan clutch to lock it up.

Scott

Thanks for the replies. The problem started immediately replacing the fan clutch, I've been working on this problem since the middle of the winter before last. I'm looking to purchase a quality Severe Duty Fan Clutch other a Hayden brand. I tried the non thermal clutch and fan from the Chevelle, same results. A makeshift air deflector cured the problem, but it look like a loosing invention on Junk Yard Wars!


Questions back to me;
My truck operates at normal temp at all under all other conditions.
I understand the plow is deflecting air flow from passing through the radiator.
I had a fan clutch that, would move enough air at speed to cool the engine.
The radiator is a few years old, it's pretty clean, I flushed out last winter when the tried a high flow thermostat.
No AC.
Has correct fan shroud for application, excellent condition.
I don't believe early 80's Chevy trucks have rad. to support seals.

#2797 cataloged as a severe duty by Hayden
I've been plowing for many years also.
Snow blocking air flow, could happen. Not the cause here, happens regardless on weather conditions.
The clutch is not engaging when needed, all 3 of these #2797's function the similar to a non-thermal. As soon as the temp reaches 220f I slow down or stop, it drops right back to 180f.

Please don't take I've said as wise-ass remarks.
Thanks for your thought and time.
Kirk

This isnt meant to be wise ass either but could you have accidentially installed the fan backworks on the new clutch or is it defective?

I say that because someone in t/chevelle had done that very thing one time casung same issue your having.

In winter plowing a Hayden seven duty thermostatic fan clutch is of decent enough quality to do the job,something strange must be wrong that your missing if its not the fan being accidentiaqlly installed backwords or the new clutch being defective .

Make sure the fan is pulling air thru the rad and blowing air over the motor.

Its just funny that you said "everything was ok untill you changed the fan clutch " and if thats truely the case then it has to be either a defective fan clutch and or the fan was installed backwords unless your missing some thats wrong like possibly a partially stuck open/closed defective t-stat that is open enour to allow enough coolent flow to cool the motor at idle /low speeds but at faste speeds there isnt enough coolent flow and the motor heats right up.

If you find the fan is installed right ,verify fan clutch is working ok,then i would change the t-stat for piece of mind,its cheap and easy to do and see if that helps.

If new stat doesnt help greturn current clutch as defective and get another svere duty clutch and try that ,if still NG maybe the radiator is clogged up and or olde enough the it isnt doing the job anymore?

But i am leaning towards bat t-stat and or defective fan clutch.

Scott

You may have the wrong fan clutch. The Factory fan clutch is large with Square corners and not tapered like a LS-5 fan clutch. I had a slight heating issue with my 468 with a factory 4 core in my wagon.
The fan clutch that is on it now ( It will fit in a 772 blade ) it is from a Chevy dealer. The clutch I bought is for a Mid 80s-3/4 ton, 454- Burb.with dual A/C. Chevy Pt. # 88961767
List for $228.92 I paid $125.91 plus tax or 133.46. Now on a very hot day with the A/C on it will go to 205-210. It has gone to 215 when sitting for a long while.
Yes it is expensive, And YES it gets the job done, And yes I played with all types of clutches because I didnt want to spend the money. This may not work for your application, I am NOW a cool and happy camper.
Bob:thumbsup:

I also live in NH, (Epsom) when I was working for GM dealers and putting plows on the trucks of those years, we used to take the thermal coil on the front of the clutch and turn it a half turn to tighten it. That made the clutch work sooner. Never had anyone come in with an overheating issues until they changed the body style in '88

Questions back to me;
My truck operates at normal temp at all under all other conditions.
Even at idle or in slow traffic on a hot day? If so, there's nothing wrong with the fan clutch.
The fact that it doesn't overheat when pushing snow (plow down, liw speed, load on the engine) also indicates that the fan clutch is doing it's job quite well.

I understand the plow is deflecting air flow from passing through the radiator.
Ok

I had a fan clutch that, would move enough air at speed to cool the engine.
And if it doesn't overheat at idle on a hot day or when pushing snow, you still do.

The radiator is a few years old, it's pretty clean, I flushed out last winter when the tried a high flow thermostat
How many is "a few". How do you know it's clean inside? If the bottom few rows are plugged.......
Did you clean the OUTSIDE of the radiator? That's something that many people overlook.

No AC.
Good.
I have to ask, though: Did it ever have AC? I've had people say their vehicle "doesn't have AC" when it was actually there but just didn't work.

Has correct fan shroud for application, excellent condition.
Good.

I don't believe early 80's Chevy trucks have rad. to support seals.
OK. I didn't know if they did or not. You could try adding some.

The clutch is not engaging when needed, all 3 of these #2797's function the similar to a non-thermal.
If there's not enough heat coming fron the radiator, a thermostatic clutch won't engage. The clutch not engaging is a Symptom, not the problem.

As soon as the temp reaches 220f I slow down or stop, it drops right back to 180f.
If the clutch was bad, it wouldn't drop back down when you stop.
(Just a thought;, are you sure the gauge is accurate?)

Please don't take I've said as wise-ass remarks.
Nothing even remotely smartass about any of them. :beers:

Kirk, I have $10 that says the culprit is the radiator. It's a "few" years old and probbly has a coating of "gook" on the inside of the tubes that's compromising heat transfer under severe conditions. Reduced airflow while shoving the plow through the air at ~50-60 mph is about as harsh as it gets.

Another random thought; You can rule out the fan clutch if you can attach a fixed fan temporarily. If the problem goes away, it was 3 bad fan clutches. If not, there is a different problem.

No AC condenser, trans cooler and a small PS cooler. I'll drain the radiator down and take good look, I'm pretty sure it was relatively clean before and after the Tstat change and flush. I'll blow all the cooling fins out next time I mess with it. I did try another gauge sender and check with my meter temp probe. The fixed fan sounds like a good idea to try as is tightening the temp coil "that's pretty clever" I'm sure the fan is on correctly, will double check to rule out my stupidity. As far as the fan being correct, I believe it's 7 blade has a steep pitch and square ends, may be from the donor C30 the engine and other dodads from. Not 100% sure on that one. I put the 454 in 20 years ago, originally 350 TH700 light 3/4 ton.
It's snowing now and they're saying 11"-15" Fortunately I don't have to run it over the road with the plow on right now!
Thanks again everyone for the time and thought, several inexpensive experiments to try! If or when it's fixed I post it.
Happy Holidays to you and yours
Kirk

Dont forget the $6 t-stat,that can bite you in butt when overlooking it,it can be permanantly stuck in a partially open/partially closed postition resulting in poor coolent flow esp with a stock type t-stat ,i have seen that happen before .

It may not be the t-stat at all but it could be and its cheap & easy to change so dont overlook it

Scott