Coolant temperatures while towing

[wb292]

Thanks for asking. I had posted in my build thread, but forgot to update this thread.

Since starting this thread we’ve taken two trips; one with the stock system, and the second with the new 7 blade fan and a new fan clutch installed.

The first trip, in June, was to Grayson Highlands in SW Virginia. It was a brute of a trip, particularly the last 10 or so miles. Without the new fan, temps got pretty high - 230º or 240º for the coolant, and the trans briefly reached 256º.

In July, once the new fan and clutch were installed, we went to Douthat State Park, near the West Virginia border. Not as steep as Grayson Highlands, but still a pretty good workout for this Suburban. Coolant temps were in the 190º - 205º F range; once or twice getting to 220º, but no higher. Transmission fluid temps were mostly around 180º - 200º, with a high of 210º. The old fan clutch was apparently shot, as the fan was much more noticeable when it came on. Both temperatures were significantly lower than on the previous trip.

I’m now confident that this beast will handle any sort of towing we ask of it.

Good to hear it worked out.

 

[whataTRUUUCK]

You guys won't believe this but the owner manual actually states that its normal for the temperature to fluctuate between 210 and 260 while towing heavy loads....I don't know how much to believe that infor but am now wondering has anyone blown a head gasket from running it between those temps?

 

[Cadillacmak]

I believe (but could be wrong) that the OBS does not have enough air flow to cool a 454 under load due to its aerodynamics and grill size. I had a 1989 and a 1994 and both had issues. The 94 454 is now in a lift 74 square body (my daughters) and cools fine.

 

[Supercharged111]

My 454 dually with a Whipple generally doesn't exceed 210* at 20,000# GCW and a massive aero signature. That's 100* in the middle of Kansas with a ridiculous cross wind not overheating. When it gets hotter than that the fan clutch kicks on and the needle stops climbing. How dirty is your radiator and AC condenser?

 

[L31MaxExpress]

My 454 dually with a Whipple generally doesn't exceed 210* at 20,000# GCW and a massive aero signature. That's 100* in the middle of Kansas with a ridiculous cross wind not overheating. When it gets hotter than that the fan clutch kicks on and the needle stops climbing. How dirty is your radiator and AC condenser?

That is where the clutch fan in the Express van picked up with the thermal clutch too and where I have it set to really come on strong with the EV clutch as well. I also have it set to ramp up strongly at 350 psi of ac pressure and 190F transmission temps. When the clutch comes in it will drop from 210-215F down to 198F in about 20-30 seconds.

 

[whataTRUUUCK]

My 454 dually with a Whipple generally doesn't exceed 210* at 20,000# GCW and a massive aero signature. That's 100* in the middle of Kansas with a ridiculous cross wind not overheating. When it gets hotter than that the fan clutch kicks on and the needle stops climbing. How dirty is your radiator and AC condenser?

I recently bought this 95 suburban 2500 7.4L and Ive done everything possible to try and get it running cooler such as flushing and backflushing all the cooling system inlet/outlet tubes, installing a lower temp 180 degree thermostat (and testing it before installation), making sure none of the coolant hoses are kinked, properly bleeding air out of the system, testing the temp sending sensor for accuracy.....but still on a hot day driving uphill just for 2 miles the temp will reach 230ish even while blasting the heater. The only thing left I can think of is a bad coolant temperature sensor or remove the dual electric fan conversion installed by the previous owner and get a heavy duty clutch fan. What do you guys think?

 

[South VA]

I recently bought this 95 suburban 2500 7.4L and Ive done everything possible to try and get it running cooler such as flushing and backflushing all the cooling system inlet/outlet tubes, installing a lower temp 180 degree thermostat (and testing it before installation), making sure none of the coolant hoses are kinked, properly bleeding air out of the system, testing the temp sending sensor for accuracy.....but still on a hot day driving uphill just for 2 miles the temp will reach 230ish even while blasting the heater. The only thing left I can think of is a bad coolant temperature sensor or remove the dual electric fan conversion installed by the previous owner and get a heavy duty clutch fan. What do you guys think?

In my case, the two variables that made the difference were the fan clutch, which apparently was shot, and a seven blade fan.

 

[Supercharged111]

I recently bought this 95 suburban 2500 7.4L and Ive done everything possible to try and get it running cooler such as flushing and backflushing all the cooling system inlet/outlet tubes, installing a lower temp 180 degree thermostat (and testing it before installation), making sure none of the coolant hoses are kinked, properly bleeding air out of the system, testing the temp sending sensor for accuracy.....but still on a hot day driving uphill just for 2 miles the temp will reach 230ish even while blasting the heater. The only thing left I can think of is a bad coolant temperature sensor or remove the dual electric fan conversion installed by the previous owner and get a heavy duty clutch fan. What do you guys think?

You didn't answer my last question.

 

[Schurkey]

95 suburban 2500 7.4L

installing a lower temp 180 degree thermostat (and testing it before installation)

Mistake. Put a tested functional 195 degree 'stat back in.

properly bleeding air out of the system,

There's no special procedure for that. Air naturally rises to the top, gets blown past the thermostat, and is seen as "low coolant level" in the radiator. Fill the radiator and overflow tank, good-to-go.

testing the temp sending sensor for accuracy

The sending unit for the gauge? Is the gauge itself accurate?

The only thing left I can think of is a bad coolant temperature sensor or remove the dual electric fan conversion installed by the previous owner and get a heavy duty clutch fan. What do you guys think?

Aftermarket electric fans and their shrouds are often a disaster. I'd drop those electric fans like a broken rubber. Does the shroud have openings that allow airflow when the fans are not running, but close when the fans come on?

OTOH, whether you need or want a "heavy duty" fan clutch is still debatable. What is stock on your engine? Regular-duty? Heavy duty? Probably not "Severe duty".

And there are fan upgrades to go with the fan clutch. Lotsa info on them in the Engine section of this web-site. You'll also need a fan shroud that fits whatever fan/clutch combo you select.

However, are you sure the radiator is OK? Coolant tubes not scaled/restricted? Air fins not corroded?

 

[Supercharged111]

Mistake. Put a tested functional 195 degree 'stat back in.


There's no special procedure for that. Air naturally rises to the top, gets blown past the thermostat, and is seen as "low coolant level" in the radiator. Fill the radiator and overflow tank, good-to-go.


The sending unit for the gauge? Is the gauge itself accurate?


Aftermarket electric fans and their shrouds are often a disaster. I'd drop those electric fans like a broken rubber. Does the shroud have openings that allow airflow when the fans are not running, but close when the fans come on?

OTOH, whether you need or want a "heavy duty" fan clutch is still debatable. What is stock on your engine? Regular-duty? Heavy duty? Probably not "Severe duty".

And there are fan upgrades to go with the fan clutch. Lotsa info on them in the Engine section of this web-site. You'll also need a fan shroud that fits whatever fan/clutch combo you select.

However, are you sure the radiator is OK? Coolant tubes not scaled/restricted? Air fins not corroded?

AC core and radiator fins not plugged full of God knows what from the last few decades? AC fins not all smashed over thus restricting airflow?