Overheating..help!
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Overheating..help!
I have a 69 f100 that is overheating... I have rebuilt the top end, including water pump, less tha 8 months ago. still overheating. Yesterday I changed the waterpump again, but still overheats. New radiator, thermostat, what else???? Could there be air in system that isnt allowing it to open? If so, how do I bleed??? Any help?
Hotshot
Joined: Oct 2002
Posts: 18,488
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From: The Big, Oregon
Welcome to FTE!
One thing that comes to mind is the heater valve. If this is closed, then chances are it'll have a big pocket of air in the heater core. Frequently, the cable breaks, so even if you have the control in the hot position, the valve may be closed.
Also, if the stock warm-up valve is still in place, make sure it is opening. If not, it will be routing all the exhaust through the right side manifold, through the heater passage in the intake.
One thing that comes to mind is the heater valve. If this is closed, then chances are it'll have a big pocket of air in the heater core. Frequently, the cable breaks, so even if you have the control in the hot position, the valve may be closed.
Also, if the stock warm-up valve is still in place, make sure it is opening. If not, it will be routing all the exhaust through the right side manifold, through the heater passage in the intake.
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ok, im under the hood now, where is the warm up valve, and do you mean that the heater has to be running in the cab, or is there something under tha hood i should be looking at? Sounds like you might be on the right track. thanks!
Hotshot
Joined: Oct 2002
Posts: 18,488
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From: The Big, Oregon
At the base of the left side exhaust manifold, where the pipe attaches, there is what looks like a spacer. Inside that is a butterfly valve that is actuated by a bimetal spring, depending on it's temperature. These rust up over time, and stick in the closed position.
Also, does the truck actually boil over, or is the temp gauge just reading hot?
Also, does the truck actually boil over, or is the temp gauge just reading hot?
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Fleet Owner
Joined: Jun 1999
Posts: 24,552
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From: Creedmoor, North Carolina
UB, You can not us human touch as a guideline for how hot the coolant gets. I think some of the firing banks reach temps of around 1000º and the thermostat should open after the water temp reaches 180º if you are using a 180º tstat.
If you are running a 360 engine, fill the radiator to about 2" to the top. Do not fill to the opening. Drive the truck for a few miles and after it has cooled check to see if the level is where you left it.
You can have the Tstat in backwards and cause issues with the temps.
good luck
John
If you are running a 360 engine, fill the radiator to about 2" to the top. Do not fill to the opening. Drive the truck for a few miles and after it has cooled check to see if the level is where you left it.
You can have the Tstat in backwards and cause issues with the temps.
good luck
John
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Before switching out the water pump, the top hose was rock hard, and the bottom part of the radiator seemed cooler than the upper part, and when I released the pressure with the cap lever, it poured out of the overflow tube. Now, I don't seem to have quite the same amount of pressure, (meaning there is some flexability now), and when I released the cap pressure, I didnt have anything coming out of the overflow tube. However, the temp gage on the dash is still reading at 3/4, and that is after driving it down the road. The thermostat is a 190 degree, if I remember right. Should I go to one that opens at a lower temp??? Will try to find valve on the manifold...update soonest. Thanks for the help !
Fleet Owner
Joined: Jun 1999
Posts: 24,552
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From: Creedmoor, North Carolina
ub, A 190º Tstat is fine, and you haven't raised any flags that would cause me to be concerned.
Before you cold start the truck on your next 3-5 or greater mile trip, look in the radiator at the fluid level. After you have driven the truck 5 or more miles, and it has rested and returned to a cold state recheck the level.
As long as the fluid level is remaining constant, you don't have anything to worry about, regardless of what the temp gauge is reading. IMHO
If after the fluid level reaches about 2" in down from the top and stays, and is not puking the coolant, you have no problem. The system needs the 2" down for expantion.
John
Before you cold start the truck on your next 3-5 or greater mile trip, look in the radiator at the fluid level. After you have driven the truck 5 or more miles, and it has rested and returned to a cold state recheck the level.
As long as the fluid level is remaining constant, you don't have anything to worry about, regardless of what the temp gauge is reading. IMHO
If after the fluid level reaches about 2" in down from the top and stays, and is not puking the coolant, you have no problem. The system needs the 2" down for expantion.
John
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ok i just ran it in the driveway, it heated up to 3/4 plus, shut it down and released the pressure from the radiator cap, and its boiling out the overflow tube. i will wait until it cools completely and then check fluid level. then drive as directed, ill let you know what happens
Fleet Owner
Joined: Jun 1999
Posts: 24,552
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From: Creedmoor, North Carolina
ub, Any time you open the system while it is hot you are allowing expanded coolant to excape. That is the reason for letting the system finds it's comfort level (about 2" down) and monitering it at cold condition only. That is where it will settle back to.
At 2" down you should have aprox 2 1/2 gallons of coolant in the system and a pretty large radiator.
John
At 2" down you should have aprox 2 1/2 gallons of coolant in the system and a pretty large radiator.
John