Overheating

[Sam_Fear]

A good read about cooling systems:
http://www.arrowheadradiator.com/14_rules_for_improving_engine_cooling_system_capability_in_high-performance_automobiles.htm

 

[zzrodder]

How about a couple pics of the engine compartment, and one from the front, maybe we can spot something that could help.??

 

[NitroJohnny]

 

[sgtpontiac]

Is the motor stock or was the block bored?

Seems to me if the block was clogged up that bad it would heat up at idle...read some of the article that Sam posted.....nice info....but seems you've been down most of those roads...guess if you knocked out a freeze plug or two you've have your answer on the block but if you had the pump off i'd think you would have noted a ton of crude / rust in the front of the block..or attached to the pump.....
Only thing I might ask about the front is that the radiator is totally dependant on the front grill area...is it possible that it doesn't allow enough flow at speed? Those big holes in the hood and the slots on the side of the hood....do you think it might pull a ton of the air away from the radiator? Or maybe with the front down low and kind of raked in at the bottom, maybe it's pushing the air around the front and not thru the radiator....kind of a stretch but I'm no aerodynamics engineer....truck looks cool as heck though!![cl

 

[NitroJohnny]

Yea, the block looked clean when the pump was off. There was rust water in it when I drained it the first couple of times, but thats kind of normal with these older engines. I'll still check the block anyway.

I also considered the front grill area. It cant be changed and I have ducted it all to the radiator. Theres not much of a gap anywhere for the air to escape around it. But the bent grill and being low to the ground might be an issue. Good thing is that when it does start to heat up, all I have to do is slow down and it drops back to 180 and at worst just stop for about a minute and let it idle and it drops fast.

And I do know that 190-200 isnt horrible. I just think it should run cooler than it does at speed. So it really isnt an overheating issue any longer. Just trying to get it a touch cooler.

 

[sgtpontiac]

Suggestion from my number 2 son....

Roughly stated: Josh Says try ducting all the air that comes thru those big a$$ holes in the hood into that shrouded area so it dumps it directly in front of the radiator.... like blacked out deflectors that force air into that shrouded area at the core support....ram air for the radiator so to speak.... me, I'd try removing the grill and drive it at highway speeds might be able to determine if it's air flow problem.....but kid seems to think making those holes in the hood a ram air system ducted in front of the rad....[S

 

[BigIrish]

Seems hard to believe that airflow would be a problem on a truck designed to cool an old flathead V8, one of the hardest engines to cool properly.

You might try driving it in 2nd gear to get the revs up, but still moving at a slow speed. If it still heats up, then you know it's RPM related, not high-speed aerodynamics related. Then it's got to be something with the coolant flow.

 

[Sam_Fear]

What are you checking temp with? The gauge only? Where is the sender? Try using a IR thermometer in different spots - both rad tanks, the hoses, different parts of the block and heads. Should give you a better idea of what is going on.

 

[NitroJohnny]

I can try the slower speed deal in 2nd gear. I also dont think it is wind or air related. Ive cooled plenty of race motors that had heat issues the same as this is set up.

On the temp it is being read on a new temp guage when driving. At the house I use a IR guage. But at idle its at 180 all day. I havent checked the tanks to see what kind of temp drop I am getting but I already planned on checking that. Just havent had time to mess with it.

 

[zzrodder]

I think Sam Fear was referring to the location of the temp sender on the engine - is it in a location that might give an erratic reading? Try it in a different location if there is one available. Also I see you've run the heater hose outlet from the pump to a spot below the thermostat - could that be bypassing some of the pump output from going thru the engine? Just grasping at straws here - you could try just plugging those two outlets off to test that......

 

[NitroJohnny]

It is located on the bottom side, inlet side of the Tstat. Yes the pump out for the heater is bypassed. This could be blocked I suppose.

 

[scottw.auto]

have you tried running it without the tstat to see what happens?

 

[offroadrolls]

my .02

In the past 2 years I've seen a 1/2 dozen Car Quest thermostats that are complete crap. I quit buying them there and go to the dealer for imports and Napa for old domestic iron.

Air flow is king and a mechanical fan kicks the heck out of any after market electric fan I've had.

A long time ago I used to see GM inline 6's with warped heads that would leak compression between cyls. 3 and 4. But I don't remember if they over heated when they ran like crap.

 

[Dhamblin]

Another thought!

Is it possible that the engine is running lean at mid rpm's? I had the exact same issue on a stock mopar 318. It was 2 bbl, with aftermarket dual exhaust. On the highway, it would run about 220 degrees. After doing all the cooling stuff to no help, I put on a edelbrock 600 cfm carb and it never went over 205 degrees.

 

[NitroJohnny]

Drove it Saturday am and it never got above 185. I'm going to flush the block and block off the heater ports at the pump to get more flow through the block. That should do it.

 

[Dirtyrat]

Is it possible that the engine is running lean at mid rpm's? I had the exact same issue on a stock mopar 318. It was 2 bbl, with aftermarket dual exhaust. On the highway, it would run about 220 degrees. After doing all the cooling stuff to no help, I put on a edelbrock 600 cfm carb and it never went over 205 degrees.

Might be able to take a look at the plugs and see a lean condition as well...

 

[NitroJohnny]

Plugs look fine. Checked those when I pulled the head.

 

[Old Iron]

Bare with me here,
1. Are you using a 50-50 mix of antifreeze/coolant or straight water ?
Straight water will do exactly what you're experiencing.
2. When you installed the new radiator did you check the air flow direction of the new fan ?
3. One last thing, you can add water wetter to help.
These 250 inline 6 engines are not hard to cool so it's got to be something simple.

Ockham's razor;
"All other things being equal, the simplest solution is the best."

 

[NitroJohnny]

50/50
fan is correct.
I could use wetter but I dont think it needs it.