L6 - 250 Overheating
 

Stuck with the 250 till the 383 is done.

Have lots of trouble with overheating. Put in a bigger rad, tightened all the clamps, bigger fan, new cap, new thermostat, and rad is full.

Have to keep the truck at 90 km/h (55 mph) ot it will overheat. In summer, of course.

The L6 is a long engine and the temp sensor is at the back - far from the water pump. Is this part of the problem, or is it really prone to overheating?

Re: L6 - 250 Overheating
 

Is it really overheating or is the rad seeking the right level.
You don’t fill the rad full. Usually about 1 1/2 inches from the top.

Re: L6 - 250 Overheating
 

Check the water flow rate in the radiator....

sounds like a clogged core or water pump vanes have rusted away....

:chevy::chevy::chevy:

Re: L6 - 250 Overheating
 

New water pump.

Re: L6 - 250 Overheating
 

Here is a link to a previous post about overheating 6's....

https://67-72chevytrucks.com/vboard/...d.php?t=706872

Most suggest moving the sensor to the thermostat housing....also, did you burp the heater core?

:chevy::chevy::chevy:

Re: L6 - 250 Overheating
 

I just redid my whole inline six 250 cooling system like you. New 3 row radiator, 13lb radiator cap, fan shroud, heater core, water pump, fan clutch w/7 blade fan, 190deg thermostat, upper/lower hoses and heater core hoses. My temp sender is in the head about #2 cylinder up top. I thought it was running hot at first as the gauge reads about 2/3 to the hot. No where on the block with laser temp gauge have i ever been able to crack 190deg. Every time i shut truck down it has dribbled a tad bit of coolant to the point were it now sits 1 1/2” below the radiator cap. I just got a coolant tank reservoir to remedy that. But all has been well so far.

Re: L6 - 250 Overheating
 

That's funny, you're having L6 cooling problems in Canada, while my 292 L6 runs better in Tucson summers.
They are almost aircooled.

Things I'd look for:
-Thermostat
-Coolant mix
-Hoses and hose clamps
-Water pump
-Oil level