False high temps....HELP
Thread Starter
Drifting
Joined: Jul 2003
Posts: 1,613
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From: Orlando FL
False high temps....HELP
i am having a really odd problem....i haven't driven her for a week and today when i went in the garage, there was a puddle of anti-freeze under the purge tank....i opened it up and it was FULL...but it hadn't over heated, etc...so i started it and the temp ran up really fast....to about 215* (then i shut it down) and the t-stat didn't open (its a 180*)...this HAD to be a false reading because the upper hose was still cool to the touch and so was the entire engine...i ran across this problem once before....the reason was an air pocket had formed behind the gauge sensor in the front of the intake base and the air naturally heats up much faster than the water, hence the false reading....my question is WHY is this air pocket forming and WHY did all that antifreeze go into the purge tank when the car has been sitting for a week? and most importantly...WHAT can be done to fix this?
Le Mans Master
Joined: Feb 1999
Posts: 5,381
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From: Pineville, Louisiana
The temperature sensor is on the engine block in the front so how is it reading the air temp? If the thermostat isn't opening then the hose would be cool because it is not letting the coolant flow thru the hose and the coolant would be hot because of the engine temp. Not sure why the purge tank is overflowing but if the thermostat isn't opening then it could be pumping coolant back to the purge tank 
I know the coolant expands when it gets hot so that would make the purge tank rise. Hope this helps some but surely someone else will chime in with a better answer. 
I know the coolant expands when it gets hot so that would make the purge tank rise. Hope this helps some but surely someone else will chime in with a better answer.
Drifting
Joined: Nov 2000
Posts: 1,428
Likes: 1
From: Jacksonville FL
These cars use a 15# pressure cap. If the cap is old or the rubber seal is damaged the pressure can cause the coolant to leak from the system into the overflow tank.
I once had an old Ford P/U truck that had 2 cracked cylinders and blew the back of the radiator top tank out.
I once had an old Ford P/U truck that had 2 cracked cylinders and blew the back of the radiator top tank out.
Thread Starter
Drifting
Joined: Jul 2003
Posts: 1,613
Likes: 0
From: Orlando FL
coolant was just changed recently because i had to change the water pump. radiator cap was changed to one of those pressure release style ones that that you can open the cap even if the car is hot. t-stat is new. drove it today and went to a car show no problem.
I'll pressurize the system again, but with the tester that i use, ya gotta remove the cap. so is it just a process of elimination thing?
i know the t-stat works because under normal conditions, at 183* it opens and the temp drops, then stabilizes at 183*. i have learned that when the temp rises as fast as it did (to over 200* in less than 3 minutes) that there is an air bubble in the system in the block behind the water temp sensor that runs the dash gauge. The air in that bubble heats up much faster than the antifreeze that should be running by it, therefore it creates the false reading on the dash. in reality, its not that hot because the t-stat is still closed.
so would a bad cap create this problem? i also noticed that the cork seal on the purge tank cap is shot. could that be causing any problems?
I'll pressurize the system again, but with the tester that i use, ya gotta remove the cap. so is it just a process of elimination thing?
i know the t-stat works because under normal conditions, at 183* it opens and the temp drops, then stabilizes at 183*. i have learned that when the temp rises as fast as it did (to over 200* in less than 3 minutes) that there is an air bubble in the system in the block behind the water temp sensor that runs the dash gauge. The air in that bubble heats up much faster than the antifreeze that should be running by it, therefore it creates the false reading on the dash. in reality, its not that hot because the t-stat is still closed.
so would a bad cap create this problem? i also noticed that the cork seal on the purge tank cap is shot. could that be causing any problems?
