The Stovebolt Site Forums The Shop Area Engine Shop Overheating problems

Hi gang,
Got a problem with overheating. I have been round and round on this issue and its driving me nuts. I have a 57 chevy p.u. stepside with a 350 and 3 spd tranny. It has a fluidyne alum. radiator. The motor is fairly new with only idle and approx 100 mi on it. It will heat up very quickly for short drives. I have put additives in the coolant as well as removing the t-stat, changing to all water and it seems that I can't keep it cool. The motor has a mild street cam and the waterpump is working fine. It is using a 180 t-stat right now. The timing is dead on too. I am at my wits end. The motor seems to be running ok, just pegging the gauge to the hot mark. Any suggestions? Thanks!

lack of a fan shroud is most likely, if the fan isn't within about 1/2" of the rad, which it won't be unless you've moved the rad back

Bill

Plus removing the thermostat can be counter productive. I seems counter intuitive but speeding the coolant flow up that way can reduce the heat transfer to the coolant that needs to take place.

How hot is it running,in degrees. The 350s are noted for running a little on the hot side,210 to 215 with no problems. Ya might wanna check your heat gauge as it could not be giving you a true reading.I have a 350 in my 55 2nd and it always runs at 200 plus.If I take the thermosta out it drops to about 170.First of all,check out that heat gauge, then install a 160 degree thermostat.Should take care of your problem,if you even have one.

Thanks for all the feedback. I do have a fan shroud around the fan that indents the fan about half the blade depth. I am wondering about the guage though. As dale937 stated 350's being on the hot side that may be it. I'll try the 160 t-stat and buy an aftermarket guage to see what I am running at. Hopefully this will be a quick fix. Thanks again for all your input.

I had a similar problem. Chased wiring, thermostats, all the standard stuff. Ended up being a crappy connection at the sending unit. The one I had on it was tight, but it didn't read right until I put the proper blade on it. Just a thought.

I respectfully disagree with Dale though. If you have all the proper stuff in place, there's no reason for a 350 to run hot...

a lower stat isn't going to help overheating, they just set the minimum, once they're open they're open, and a small block likes to run 180+, I think most 350 specs call for 185 or 190

Bill

I agree with Dale. 215 is not hot for a 350 engine. With the proper coolant mixture and the proper pressure cap the coolant won't boil out even at 225.

What kind of water pump and belt/pulley system do you have? Did you go to a serpentine with reverse running water pump? Did you get the right direction water pump?

And if I read this right, the temp goes to 215-225 after short drives. I even read about a "pegged meter". That's not comforting if I want to go for an all day drive. To try and let him think this is normal isn't helping. The cooling system should be able to fairly stabilize the temp within reason. 30 to 50 degrees in either direction is not stabilized to me. The water temp will go up after shutting the engine off because you have stopped circulating the water. Is that when your gauge pegs?

When ever I encounter this sort of thing where the engine runs cooler with the stat out, I suspect that the stat is not opening properly. I test the stat by placing it in a pan of water and turn on the stove then measure the temp of the water to see at which temperature the stat actually opens. Just because they say 180 degrees, it doesn't mean that is is really opening at that temp. It costs nothing to test.
John Hill

I'm suggesting checking to see if the coolant is flowing through engine and returning to radiator. It may have an air pocket. Another thing is to have a pressure test performed.

Good Luck and keep us posted.

The guage pegs to the H after running for about ten minutes or so. I have run with and without a t-stat. System has been burped of air also. I am beginning to wonder if it might be the temp sender? It is an aftermarket sender and I have heard that they can be inconsistent with the guage. I am using the original guage on the dash. Regular V-belt pulleys and water pump is fairly new. Water is circulating.

You need to check it with an infrared thermometer. If you don't know a mechanic with one who'll check it, buy a cheapie.

What part number is on your water pump?

I don't have access to the truck right now, but if you may be referring to a pump with reverse rotation, I am pretty sure that it is turning in the right direction. It is a short pump that I bought when I rebuilt the motor.

The problem, and maybe mine too, could be the pump is a high volume unit that pushes the water too fast not giving it ample time to be cooled in the radiator. Mine seems to be fine as long as the ambient air temp is not much over 90 degrees or cruising on the highway. When it's hot outside my temp gauge has gone as high as 235 stopped in the bank drive-thru. I couldn't believe it didn't pop something.

The problem has been located! Thanks to Cletis! I bought a thermal gun and lo and behold the temp sender is the culprit! I ran the engine to operatiing temp on the gauge and it registered on the therm as 140. The gauge started pegging and the temp had not even gotten to 180 yet. All this chasing things around an it was the simplest thing! I put that sender in the motor when I first built it relying on the parts man's expertise on sending units for older trucks. I should have know better. Thanks again Cletis!

Good diagnosis! Next time, use a little common sense- - - - -if you're not losing coolant out of the overflow, the coolant isn't boiling- - - -PERIOD, end of discussion! A pressure cap raises the boiling point 3 degrees F. for every pound of pressure on the system, so a 15# cap raises the boiling point 45 degrees, to 247 degrees F. at sea level. If you're losing coolant, something, somewhere in the system is either getting WAY too hot, or there's a compression/combustion gas leak that's overcoming the pressure spring in the cap. A system that will go 10 miles or more, regardless of speed or outside temperature, without puking coolant is not boiling, or getting a major pressure leak, regardless of what the temp gauge is reading.

The most common cause for high coolant temperature that's not gauge-related is a dirty radiator, or one that doesn't have enough cooling ability to handle the size of the engine. Fan shrouds and other airflow enhancers just make a marginal radiator work at the upper limits of its capacity without a boil-over. The solution is more cooling capacity,with a clean, correct-size radiator.
Jerry