Coolant Flow?
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5th Wheeling
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Coolant Flow?
My ‘81 F100 with 302...I just replaced the thermostat with a Failsafe. However, I’ve noticed that if I crack the radiator cap off with the engine cold started, I can see coolant flowing through. Is this a normal occurrence or should it not be able to visibly flow until reaching the correct temperature?
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From: Virginia
Normally you should not see flow. If the upper radiator hose starts getting lukewarm right away that is another sign it's not working correctly. You have driven it and then let it cool off and then checked the coolant level correct? Air will get trapped in the engine after changing the thermostat and then refilling the system. That has to be burped out before it will work right.
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From: Virginia
The best way is right after you button the engine back up, take one of the heater hoses loose on the engine, and then start filling the radiator with coolant till it just starts running out of the fitting where the heater hose went. Then quickly put that back on, tighten it up and then continue filling. There will still be a little air in the system but not as much if you did not pull the hose off at all.
If you do not burp it at all, what usually happens is the engine starts getting very hot, almost overheating, and then it will start puking out the coolant you just put in (you should be running it with the radiator cap off during the first start up after the work is done). Then when the thermostat finally opens, it sucks what coolant you have left into the engine and all that cold coolant shuts the thermostat. It's usually not quite there after that first go round, so it might puke out again and do it all over till finally all the air is out of the engine and the thermostat stays open. Once the thermostat stays open and the engine is good a warm, you can top off the radiator, put the cap on, and put a little bit in the overflow bottle.
If you do not burp it at all, what usually happens is the engine starts getting very hot, almost overheating, and then it will start puking out the coolant you just put in (you should be running it with the radiator cap off during the first start up after the work is done). Then when the thermostat finally opens, it sucks what coolant you have left into the engine and all that cold coolant shuts the thermostat. It's usually not quite there after that first go round, so it might puke out again and do it all over till finally all the air is out of the engine and the thermostat stays open. Once the thermostat stays open and the engine is good a warm, you can top off the radiator, put the cap on, and put a little bit in the overflow bottle.
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