Possible overheating

[w6tractor]

Picking this up from several months ago. Looks like I still don't have this fixed. I have a 72 3/4 ton with 402 BB. All cooling system has been replaced. It has a trans cooler in front of radiator and an aux fan in front of the radiator blowing through the radiator-comes on when AC compressor is running. It has a 160 degree thermostat and HD fan clutch with original fan. It will hold temp until on the road. Temp climbs to over 210 while driving in moderate weather with AC on. Temp comes up to near 230 when slowing down, takes a while to recover back to 210 plus. What could the problem be? Thanks

[6772owner]

Do you know that the fan clutch is good/engaging? Do you have a fan shroud? Open or closed cooling system? Bad waterpump? Air in the cooling system? Possibly a collapsing (soft/sucking closed) radiator hose?

This is the main problems I can think of off the top of my head... Other things would be problems with the engine (i.e. headgasket, lean fuel condition, clogged/rusted water jackets)

Hope this helps, let us know what you find out on this.

[cdowns]

have you taken the temp of the coolant with a known good thermometer?

where is the temp sending unit located on the engine? most accurate place is in the head not in the intake manifold

if not blowin steam and or chugging the motor from overheating my first guess is always the gauge setup

[kevmic28]

I was dealing with something similiar for months and finally traced it to a bad temp gauge.

[geezer#99]

Do you have a wire coil in the bottom rad hose. Could be collapsing. Mine did the same thing until I put a coil in.

[Wrenchbender Ret]

What size radiator do you have? The big block should have the big thick core. Try a different therm. About 20 per cent of the new ones are not good. I agree with some of the other posts, make sure the lower hose is not sucking closed.

[w6tractor]

Thanks for all the feedback. As stated earlier, all cooling system is new: waterpump, radiator (4row new from NAPA), new hoses (bottom has wire), new HD fan clutch, closed system (aftermarket-not losing water) thermostat new, but I have a replacement name brand to try. Second aftermarket gauge-first was manual, this one electric, both seem inaccurate, but not sure. Both have been mounted in the driver side head. I've checked with a IR thermometer and it reads cooler by about 15-20 degrees, but I'm still concerned with the wide variation. Am I being paranoid? It never seems all that hot.

[chevytruckluver]

You may try a hotter thermostat 180 or even 195. If the stat opens at 160 and circulates through the radiator it wont stay there long enough to cool down.
good luck

[DANTIP]

This may sound stupid, but if your voltage regulator is bad, it can make your temp gauge read high due to excessive voltage. You need to compare the temp gauge to your IR thermometer and check the voltage across your battery when your truck is running (should be around 14 volts).

[6772owner]

I agree with all the above suggestions, I have also read/viewed on here that closing off the radiator support around the grille helps the temps by 10-15* There are panels available on E-Bay for the top "gap" and a lower could be fab'd pretty easy. I am going to try this on my 72' to try and pull more air through the trans/oil coolers. I may also "block off" the sides of the radiator support opening to the grille.

[NoNeck]

A mechanic friend of mine who eats and breathes big block chevy engines recommended adding "Water Wetter" to my sons 396 cooling system.

My son will be running an aluminum radiator and twin electric cooling fans, and I felt confident that there would be no overheating issues with his truck. But, my friend runs it in his big block Camaro and swears by it. He says it will lower the engine temp by a minimum of 10 to 15 degrees.

Not a commercial, and I don't own stock in the "Water Wetter" company... just sayin'.

I picked up some of the stuff at O'Reilly ($7.95 I think) for a bottle. We'll let you know!

NoNeck

[shrike]

I second the Water Wetter. I used to own a few C3 corvettes and they always had temp issues because the radiator had to sit at an angle.
It won't fix the problem, but it does bring the temp down a bit.

My truck is having similar issues, but the water pump is questionable as is the fan clutch. I have a feeling the prob will disappear after I replace those.

[fastwillie 696969]

i dont know why wouldyou want to have a electric fan and fan clutch with fan ,160 thermo ,is the aux fan a pusher or puller ? i would put in a 190 thermostat and remove the fan clutch and fan