I have a 1966 F250 that I recently purchased and noticed that it seems to run hot? I replaced the water pump since the thermostat and radiator are new, thinking that had to be the problem. It still runs right up to the hot side of the normal op temp zone on the gauge. The oil pressure when running around town is between 10 and 30. Anyone have any suggestions? Could it be a faulty temp sensor? It's weird. It seems to cool down more at idle and gets hotter when driving...

 

One thing to check is whether you are running too lean fuel mixture - I'd take a quick look at the plugs.

Have you looked under the hood, does the engine seem to be running excessively hot? By that I mean, subjectively do you think the gage indication is correct?
Another possibility is a stuck thermostat, even if new I'd replace it just to try and eliminate that as a possibility.

 

The plugs do look a little on the lean side...whitish colored. It has a Holley 4 barrel on the 352.

 

Gonna pull the thermostat tomorrow and see what happens...

 

Trying to remember why, but it sticks in my mind that running without a thermostat is a bad deal. If you're running lean - whitish plugs - then maybe the carb has the wrong size jets. Maybe the idle circuit is why temps go down at idle.

 

I heard running without the thermostat temporarily helps with diagnosing the problem? I probably heard wrong...

 

The very first thing you need to do is to determine how hot it is. An infrared or laser thermometer is a great way to do this. It also allows you to check different areas of the engine which can be useful for trouble shooting.
Getting hot at high speed and cooling at low speed may indicate a restriction in coolant flow. Possibly a bad thermostat, bad radiator, or bad hose.
The oil pressure seems low but good enough to get you around.

 

I decided today to replace my thermostat on my '63 292 engine because it was time for a new hose, and the heater's never quite been hot. Figured a new thermostat was a good idea since I've never replaced it in the three years I've had the truck. Other than lack of heat, never had any problems running. Usually the gauge hovered around the low end.


When I pulled the neck off, to my surprise, there was NO thermostat. I suspect that's part of the heating problem; probably explains why it was such a cold beast in the winter time.


After putting in a 180 degree thermostat, driving around town (<45 mph) the temp gauge climbed steadily to about 225 and hung there. That's just above the normal line, but not to the HI mark. It made me very nervous. Is that an ok running temp for an old 292 Y block? When I turned on the heat, it was working like a champ (plenty of heat as opposed to previous lack of any real heat).


So, where should I expect the temp to be driving around town on a warm summer day? Am I worrying about nothing? Winter here in the Seattle area is just weeks away

 

225 is too hot if you have a 180 thermostat; you need to check temp with another instrument besides the aftermarket gauge you are reading the temp from. I suspect the gauge is incorrect.

 

Something is wrong. The sender location on a Y Block results in a temperature reading that is actually about 10 - 15 degrees lower than the temperature at the thermostat. So that 225 is actually 235 - 240 if it is indicating correctly.

If you have a 180 degree thermostat and the cooling system is functioning correctly, then the temperature should be in the neighborhood of 180 while driving.

 

I think the old gauges can be inaccurate. The infrared thermometer is a good idea, I'll try that on mine. I thought mine was running cool, gauge never goes any higher than 160*. I put in a new 180 thermostat, water pump (noticed a broken piece on it when doing the other stuff), and coolant, and the gauge will still go no higher than 160* no matter how hot it is outside.

 

On my 64 with a 292 my temperature gauge would climb to 230 then back down a little. This was enough to scare me.
First thing first, temp would climb in rush hour traffic, (not going anywhere) so I built a custom shroud for it, no help. Next had the radiator rodded out, no help. Put in a new thermostat, temp still climbed to 230. Damn.
Replaced sending unit and a NOS gauge, still climbed to 230, Damn damn.
Anytime my truck would get to 230 I pulled over let it idle then shut it off. Once it cooled down I'd head home, usually traffic was lighter so it got air and stayed cool.
Two years go by of doing the same thing I decided to go with electric fans.
The sensor that would kick the fans on was set to 195 same as my thermostat.
when we finally had it all installed time to test. Started the truck and watched the temp gauge climb, 180, 200, 210, 220, 230, I shut it down. Scared me again. We replaced the sensor with one that we knew was good. This time we were going to let it run until the fans came on or the engine blew up.
180, 190, 200, 210, 220, 230 (panicking) approximately 235 or (Hot damn hot on the gauge) the fans kicked on.
With the infrared temp gun we shot the entire cooling system all was normal.
The thermostat was doing it's job at 195 (which on my NOS gauge said 235) The fans came on when the thermostat opened all was working properly.
Now I was told there is an electronic device that I could put in between the temp sending unit and my gauge that would make it read correctly. I haven't looked into this yet.
To this day my temp runs hot, but when I here the fans kick on, I'm cool.
I spent a lot of money trying to keep my engine cool, when it was already doing what it was suppose to do. There is no moral to this story other than "Get an infrared temp gun" this will save you a lot of money down the road.

 

Thanks for all the insights. I'm going to look into a temp gun and find out what is really going on with the temp. Any particular place I should be reading off of, or just generally all over the engine surface (valve covers, block, manifolds, etc).

And to the earlier comments, in my case, this is the stock original temp. gauge that is reading high post new thermostat. I found it had no thermostat when I took it apart, and it took forever to warm up on cold days, and there was no real heat from the heater ever. I assume that was all due to the missing thermostat.

 

The method my dad used to check if a thermostat was opening at the correct temperature was to wait until mom was out of the house, and then drop the thermostat in a pot of water on the stove and use her candy thermometer to monitor the water temp. Slowly bring up the heat and see if it opens when it's supposed to.

Then he would wash everything off and tell me to not tell mom he used her candy thermometer like that, heheh.

 

I live in Georgia, hot summers, mild winters.


My 66 352 always ran cold and got horrible mileage. I decided to change the thermostat when the upper hose went out. When I pulled the housing off I saw that when the PO had installed the thermostat, it had slipped and was not centered in the housing, it allowed coolant flow all the time.


I installed a 190 degree thermostat (what the parts store had in stock), retuned the carb and all was well, I thought.


The truck idled better, ran better, and got better mileage.


The 190 was way to hot IMO, I should have waited and ordered a 170. With the old non-functioning thermostat the gauge was at the lower end of the normal mark, with the 190 it was at the far right of the normal mark. The radiator cap never vented, but I didn't like running so hot on an old engine. There is no safety margin, if the coolant gets low or I don't get clean air through the radiator, Im sure it would have either overheated or the cap would start venting.