Coolant Temp - Just checking if normal

[DesertBob]

My 1985 K20 (8600 GVW) has the 350m, AC and a Manual Trans. The AC was just converted to r134a with all new parts. On Sunday it was about 95 degrees and very humid. Driving home on the highway at 65-70 mph the truck hit 210 degrees with the AC on MAX. It has never gotten that hot but then I have not driven it that far, at that speed, with the AC on MAX. When I got off the highway it cooled back down to its normal 195 degrees. I have a new 195 degree thermostat, new coolant, cap, hoses, no vacuum leaks and it is timed at 8* BTDC. The radiator appears to be the original HD. Stock Fan shroud and the fan clutch appears to be working. Gears are 3.4x and I roll on 32" tires. Does all this seem pretty normal behavior for this setup?

 

[f1shman]

If you were moving at the time and had good airflow going through the condenser and radiator your temperature should not be going that high. I'd check the condenser and radiator for blockage either by debris or bent fins. Be sure to check both sides and also between the two by unbolting the upper radiator brackets and tilting it toward the engine a tad. If everything checks there, make sure your lower hose still has the spring inside of it to keep it from collapsing.

What's your coolant mixture, 50/50?

 

[DesertBob]

Coolant Mixture is brand new premixed 50/50. New AC condensor. I will check the radiator for blockages. Will check lower hose. I don't remember if it has the spring or not.

 

[DesertBob]

BTW. The truck did not overheat or blow any coolant into the overflow. I also replaced the waterpump a little over a year ago. Forgot to mention that.

 

[89Suburban]

Do you actually hear the fan clutch kicking in and out?

 

[DesertBob]

Do you actually hear the fan clutch kicking in and out?

No I do not. But then again I have not been listening for it either. I did the friction test. When It was hot I tried to spin it and it only moved about 3 inches. As I understand if the fan clutch was bad it would spin freely when hot. Is this incorrect?

 

[89Suburban]

No I do not. But then again I have not been listening for it either. I did the friction test. When It was hot I tried to spin it and it only moved about 3 inches. As I understand if the fan clutch was bad it would spin freely when hot. Is this incorrect?

I have no idea and would like to hear how it is tested because I want to test mine. I know on the newer trucks and even the same year S-10's/15's you could hear that sucker kick in and it is loud. Only time I heard it on mine is once in a while pulling out on a cold motor it would roar for like 10 seconds then cut out and I never hear it come on when it's hot, and I had this sucker get real hot a few times with that cracked head problem and never heard the fan actually blowing air.

Makes me wonder if there is something wrong with mine too. I was under the assumption that the fan would be direct driven and not slip when at the proper temp to kick it in.

 

[89Suburban]

Also wondering if there is aftermarket fan clutches availiable that are a little more reliable and piece of mind.

 

[DesertBob]

For grins I went out and tested my fan clutch again. Haven't driven in 2 days and it spins the same as it did when it was hot. Thinking my Fan Clutch might be the next thing I replace. On the O'Reilly site they had Heavy Duty and Severe Duty clutch fans - both were from Hayden. I wonder what the difference is as there was only a $6 difference in price? was leaning toward the Severe Duty one but would hate to spend the extra money if it wasn't worth it.

 

[Irishman999]

I could be wrong but I am pretty sure the fan clutch lets the fan spin at low speeds and idle. At highway speeds the fan should not even be moving, you could take your fan completely off and cruise at 65 and the temp should be normal.

I drove a Dodge Dakota that had the electric fan fall completely off and never fixed it, if I sat at a stop light to long it was get warm but as soon as I was cruisin again the truck would cool off.

There is an aftermarket solution, I had one on my truck and threw it away last summer. It was a Flex-a-light fixed fan with dangerously sharp thin blades, I do not recommend using this fan. Biggest problem I had with it was the obnoxious noise it made, I went back to oem style.

 

[89Suburban]

I could be wrong but I am pretty sure the fan clutch lets the fan spin at low speeds and idle. At highway speeds the fan should not even be moving, you could take your fan completely off and cruise at 65 and the temp should be normal.

I drove a Dodge Dakota that had the electric fan fall completely off and never fixed it, if I sat at a stop light to long it was get warm but as soon as I was cruisin again the truck would cool off.

There is an aftermarket solution, I had one on my truck and threw it away last summer. It was a Flex-a-light fixed fan with dangerously sharp thin blades, I do not recommend using this fan. Biggest problem I had with it was the obnoxious noise it made, I went back to oem style.

Those flex fans are sharp as ****, lol. Another thing to watch out for with them is if you have a reverse rotation water pump it you need to make sure to get a reverse rotation fan. I put one on my Dad's GMT-400 when I inherited it not knowing that and wound up overheating it because the fan was blowing hot engine air forward into the radiator. I never saw a reverse rotation setup before I owned these trucks.

I do remember my granpaw's '78 Burb when he restored it he was running the motor at high speed parked in his driveway and the fan would kick on and off as needed like clockwork.

 

[Irishman999]

Those flex fans are sharp as ****, lol. Another thing to watch out for with them is if you have a reverse rotation water pump it you need to make sure to get a reverse rotation fan. I put one on my Dad's GMT-400 when I inherited it not knowing that and wound up overheating it because the fan was blowing hot engine air forward into the radiator. I never saw a reverse rotation setup before I owned these trucks.

I do remember my granpaw's '78 Burb when he restored it he was running the motor at high speed parked in his driveway and the fan would kick on and off as needed like clockwork.

HAHA yeah by the time I got that stupid fan off my truck my hands and arms were cut to hell, I cant believe that company is still in business.

I think the reverse rotation is needed for serpentine belts and standard for everything with v groove belts.

Im just talkin out my ass here, someone feel free to correct me.

I think the fan clutch has a thermal metal spring wound up inside that will engage or disengage the fan depending on the temperature, same metal that is in your thermostat.

It should only kick the fan on when the demand for the fan is there, so if you sit in your driveway and hold the engine at 4k rpms for a while it should be kicking the fan on and moving a **** load of air to the point its cool enough the fan kicks out until the heat comes back and kicks the fan back in.

 

[DesertBob]

So if my truck is running hot at Highway speeds it must be a flow issue. Either the Radiator is plugged, the lower hose is collapsing, or the Radiator needs a new core. Am I on the right track here?

 

[Irishman999]

Start small, what about the thermostat? also the radiator cap, both of those will cause issues. If all that is good I would look into a radiator. Ever truck I have ever had I always battled heat issues.

 

[Irishman999]

One huge problem is people running tap water in the cooling system, its a dormant problem and takes some years but it will leave calcium deposits inside water jackets and everything else and it acts like an insulator, it also breaks off in little flakes and plugs radiators and heater cores. I delt with that nightmare with one pickup for a while.

I would look into having your radiator hot tanked and rebuilt, or maybe one of those aluminum replacements they sell now. I found this one discontinued at Carquest for almost 400 bucks and it works GREAT.

Almost forgot to mention, a coolant flush needs to be done too. Let me know if you want to know the procedure I used last summer on mine and I can explain it in detail.

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