1988 C3500 getting hot when towing

[Robudda]

Hi all new to the forums. Recently picked up a 5th wheel and according to all the info that the trailer place and I found I should be able to to a 12,000 pound 5th wheel. Empty the trailer is 9,200 pounds (Just had some food and clothes when I towed it last, got fresh water at camp site). Went on an outing with all our friends and there trailers. and found it is getting just under the check gauges light when towing flat, but when hit even a slight grade it jumps up there in temp. Never reaches the red but gets close. I installed a Trans temp gauge and it stays between 180-215 or so.

Below is what we have done recently and what is has. Any other ideas would be great otherwise I will be getting another truck for towing (Keeping this one of course)

63,000 original Miles
Flushed Coolent system
Replaced Fan clutch
Replaced thermostat
Cleaned external of radiator

It has trans cooler and external oil cooler.

When not towing it sits around 215-220 and occasionally drops to 210.

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[99'Subourbon]

Have you tried checking the temps with a scanner? My temp gauge tells me my truck is 160, all the time - scanner shows 210, opens, drops to 195, closes. OEM gauges, grain of salt...

 

[Robudda]

Thanks, However do the obd-1 vehicles display temps on the scanner? I did not think they did, but could be wrong. If not I may have to place an aftermarket gauge in to test.

Also does the temp gauge and idiot light trigger from the same sensor, or is there a second sensor on the engine for the idiot light?

 

[Supercharged111]

They do. I had problems with my 88 C1500 running a bit warm when towing. Luckily I only did it once and it was winter, so I made it. Since mine was a light duty, it had the 28" radiator. Moreso than that though, it wasn't a newer aluminum one and I suspect it must have had some scale buildup on the inside of the tubes in the radiator itself, because my 98 with 34" single row aluminum radiator is impossible to overheat and I pull much heavier so my foot's in it a lot. I've never so much as turned off the AC in the dead of summer with a trailer hooked up out back, it usually runs 180 but worse I've ever seen is 210.

 

[brutpwr]

"Supercharged 111" What temperature thermostat are you running. I'm pretty sure my trucks run at 190 but then I have stock 190 degrees thermostats so I'm guessing thats about right.

 

[kennythewelder]

When a radiator gets some age on it, it can build up some Contaminants in the cooling tubes inside the rad. A flush may not wash away all of these contaminants. You may need to pull the rad, and bring it to a rad. shop. They will pull the side tanks, rod out the cooling tubes and and boil out the rad. Replace the gaskets, and basically rebuild the rad. This will restore the cooling capacity of the rad. You could also replace the OE rad with an aftermarket unit with more cooling capacity.

 

[Supercharged111]

"Supercharged 111" What temperature thermostat are you running. I'm pretty sure my trucks run at 190 but then I have stock 190 degrees thermostats so I'm guessing thats about right.

I have a 180 stat, truck usually runs right there.

 

[Ckeene]

What gears do you have and what rpm are you running, and are you doing 55mph or trying to do 80 mph? Also I would put in a new radiator being low miles stuff probably had time to build up. 350 or 454?