My '77 F150 has a 302 in it that appears to not have much in the way of water circulation and seems to be overheating (my father-in-law said he could not see any signs of water movement in the radiator after the truck had been driven for about 15 minutes and the gauge is not currently working so I am going by the water splatter around the radiator cap as a clue). I drained the radiator and flushed the engine and found that whoever had the truck before me took the thermostat out. My question is threefold: 1) Could simply not having a thermostat cause overheating, 2) how can I check to know if my water pump is functional or not, and 3) where will I find the water temperature sensor?

KB

 

KB,
The 302 Temp sensor is on top of the intake manifold by the thermostat housing neck. Have you got a temp sensor or idiot light? Make sure you get the right sending unit. Is your fuel gauge working? If not, the problem is with the instrument panel voltage regulator and not the sending unit. Another way to check for wiring problems with gauges is to ground the sending unit wire to the block. Have a friend watch the gauge. Only ground the wire for 5 seconds. That should be long enough to watch the gage move. If it doesn't move, you've either got a voltage supply problem or a wiring continuity problem,"broken wire" or a burned up gauge. I get used gauges at the junkyard, be gentle, and snag the voltage regulator to, It just snaps off.
Secondly, You won't see that much flow at an idle. If you rev up the motor a little, you should see the flow pick up. If there is no thermostat then you should see major flow. If the water pump is bad you should be able to feel play in the pump bearing by pulling on the fan blade front/back. If it clicks, its bad. Usually when a pump goes bad, it will leak from bearing inlet or outlet holes in the pump casting after you shut the motor off.
Thirdly, A 302 can run hot without a thermostat. They can pump water through the radiator so fast that there is not enough time for the fluid temperature to drop. Getting the radiator boiled and brushed is a strong investment and great insurance for your truck.
Good Luck, Have Fun
Kingfisher

 

Disconnect upper radiator hose, you'll know for sure flush the radiator with the engine running, disconnect the upper radiator hose(after truck is warmed up and engine is off), then start the truck, hold a water hose in the radiator and watch the flow.
having no thermostat is a bad idea in my opinion, gives the radiator no time to hold the coolant. I live in south TX where cooling is a sort of a big deal (what with the 109 degree days we have)
GOOD LUCK!!!!!
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77'FORD F150 XLT 400

 

Not having a thermostat could make it over heat because the water doesnt stay in the radiator long enough to cool it just keeps going through.
Anthony DiPietro
79 F150 Ranger

 

I found an interesting site with regard to cooling issues. One of the things mentioned was this:

"A common misconception is that if coolant flows too quickly through the system, that it will not have time to cool properly. However the cooling system is a closed loop, so if you are keeping the coolant in the radiator longer to allow it to cool, you are also allowing it to stay in the engine longer, which increases coolant temperatures. Coolant in the engine will actually boil away from critical heat areas within the cooling system if not forced through the cooling system at a sufficiently high velocity. This situation is a common cause of so-called "hot spots", which can lead to failures."

Check the site out at http://www.stewartcomponents.com
Ed