Cant make heat!
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From: Tennessee
Cant make heat!
1984 F-150 with 300-6. When I got the truck the engine never seemed to get fully warm. The temp gauge in the cluster would possibly get to the N or O in NORMAL but creep back down. I suspected the thermostat was removed entirely. I went and bought a 180* t-stat just to be safe and put that in. The original one was stuck open/failed open. Made sense to me-thermostat was sucking up cold coolant from the radiator. I put in the new one and checked for leaks. No issues there. Took it for a 25 min drive last night (it was about 28* out) and the temp gauge didnt even touch the N in NORMAL.
I did top up the radiator after I changed the t-stat. I remember seeing that it supposed to be a few inches below the pressure cap opening when cold. The heat in the cab is really weak at best. I dont know if the flap is moved over fully or not but even if it wasn't, the temp gauge should at least still rise.
I will buy a 195* t-stat next and try again. Any other ideas why it would run cooler than a stuck open t-stat?
I did top up the radiator after I changed the t-stat. I remember seeing that it supposed to be a few inches below the pressure cap opening when cold. The heat in the cab is really weak at best. I dont know if the flap is moved over fully or not but even if it wasn't, the temp gauge should at least still rise.
I will buy a 195* t-stat next and try again. Any other ideas why it would run cooler than a stuck open t-stat?
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From: Boise, Idaho
The stock thermostat temp is 195°, which is what the gauge is calibrated for.
I have a Holley Sniper EFI setup on mine and it has a coolant temp sensor. I can see the actual temperature on the digital handheld.
For what it's worth, the needle on the stock gauge doesn't even start moving until around 150° - 160°. Below 150° or so, it's dead cold on the temp gauge. At 195° it sits around the O in NORMAL.
So at 180-ish, it's not going to get much above the N, since as far as it's concerned, it's not fully warmed up.
As for your heater, you also might be having issues with a clogged heater core. Once you get your 195° t-stat in there, make sure the hoses going into and out of the heater box are both so hot they hurt to touch. If one is and the other isn't, you need a new heater core.
I have a Holley Sniper EFI setup on mine and it has a coolant temp sensor. I can see the actual temperature on the digital handheld.
For what it's worth, the needle on the stock gauge doesn't even start moving until around 150° - 160°. Below 150° or so, it's dead cold on the temp gauge. At 195° it sits around the O in NORMAL.
So at 180-ish, it's not going to get much above the N, since as far as it's concerned, it's not fully warmed up.
As for your heater, you also might be having issues with a clogged heater core. Once you get your 195° t-stat in there, make sure the hoses going into and out of the heater box are both so hot they hurt to touch. If one is and the other isn't, you need a new heater core.
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I saw on Gary's garagemahal page that the thermostat requires two gaskets? I suspected since the thermostat sits somewhat loosely in the water neck it's possible that it shifted and is allowing coolant to bypass it since the hole in the head is so much larger. But I'm glad to know that the O is about where it should be. I was considering an aftermarket temp gauge in a coolant passage somewhere.
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From: Boise, Idaho
I've never heard of, or used, two gaskets.
However, yes, it is important to get it to sit correctly in the groove. If it slides, it can cause a passageway for coolant to get around. Or worse, cause the housing to crack when tightened down.
When installing them, it's easy for them to slip. I usually will install the thermostat into the thermostat housing and put a tiny dab of RTV silicone around the outside ring, so that it sticks better in place, and let it dry for a few minutes. Then install the gasket and bolt it to the head.
However, yes, it is important to get it to sit correctly in the groove. If it slides, it can cause a passageway for coolant to get around. Or worse, cause the housing to crack when tightened down.
When installing them, it's easy for them to slip. I usually will install the thermostat into the thermostat housing and put a tiny dab of RTV silicone around the outside ring, so that it sticks better in place, and let it dry for a few minutes. Then install the gasket and bolt it to the head.
Fleet Mechanic
Joined: Nov 2002
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Install one.
And a suitable double seal 195*cap that allows the displaced coolant to be sucked back into the engine upon cooling.
Locate the bottle as high and close to the top of the rad as possible to make it easy to suck the fluid back in.
I do not think you need two gaskets. But do check the thermostat housing for flatness and true it up on a flat surface with sandpaper or equivalent.
Fleet Mechanic
Joined: Nov 2002
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