Weird cooling issue
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Cross-Country
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Weird cooling issue
Hey y’all..hopefully you guys can help me out. I have an 84 f150 with a 302. I’ve had it for a little while now but have driven it semi seldom just because I’ve been working on it. When I do drive it, it seems to run fine. But yesterday I installed an electric temp gauge and it seems that I’m overheating a bit. Gauge pins at 245, I haven’t seen it go above that. I just put a new thermostat in it, less the 1000 miles ago. I’m getting no obvious signs of overheating and when I’m under the hood it doesn’t seem abnormally hot.
However, if the engine is cold and I start it up and get it to operating temp or higher, if I touch the upper rad hose it’s room temp. But almost as soon as I shut the motor down and touch it again, it’s hot.
Ive never experienced this before...any suggestions?
Im in the process of doing a flush now...
thanks!
However, if the engine is cold and I start it up and get it to operating temp or higher, if I touch the upper rad hose it’s room temp. But almost as soon as I shut the motor down and touch it again, it’s hot.
Ive never experienced this before...any suggestions?
Im in the process of doing a flush now...
thanks!
Lead Driver
Joined: Nov 2013
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I'd start by confirming the accuracy of this new gauge. Beg, borrow, or steal an infrared thermometer and point it at the thermostat housing. Your new gauge and the thermometer should be pretty close.
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Cross-Country
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So you previously had no symptoms of overheating? Installed a gauge of unknown accuracy and voila?
I'd start by confirming the accuracy of this new gauge. Beg, borrow, or steal an infrared thermometer and point it at the thermostat housing. Your new gauge and the thermometer should be pretty close.
I'd start by confirming the accuracy of this new gauge. Beg, borrow, or steal an infrared thermometer and point it at the thermostat housing. Your new gauge and the thermometer should be pretty close.
Also, what about the upper rad hose being cool to the touch until after I shut it off? No biggie?
Post Fiend
Joined: Feb 2008
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From: St Albert, Alberta
The upper rad hose getting hot after you shut it off after short run is normal. When you shut the engine off there is still the residual heat in the block and heads whose temps are higher than that of the coolant. Now that the engine is shut off and coolant is no longer circulating its temp will begin to rise as the heat from the block and heads is absorbed by the coolant. Eventually, it will rise to the point to of opening the thermostat and the cooling system will start to circulate just due to convection much like the old thermosiphon cooling systems of 100 years ago thus making the upper rad hose hot.
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Cross-Country
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The upper rad hose getting hot after you shut it off after short run is normal. When you shut the engine off there is still the residual heat in the block and heads whose temps are higher than that of the coolant. Now that the engine is shut off and coolant is no longer circulating its temp will begin to rise as the heat from the block and heads is absorbed by the coolant. Eventually, it will rise to the point to of opening the thermostat and the cooling system will start to circulate just due to convection much like the old thermosiphon cooling systems of 100 years ago thus making the upper rad hose hot.
Post Fiend
Joined: Feb 2008
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From: St Albert, Alberta
Ahh..ok..heat soak. That’s what I was kinda thinking too just not sure. So I’ll finish the flush since it doesn’t hurt anyways..and get a infrared thermometer. If it is a a faulty new gauge, could it the actual wire to the sending unit? Like picking up engine heat and causing extra resistance?
No it would not be enough to affect the gauge that much. Best guess is the gauge is faulty. as long as your connections are sound.
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Cross-Country
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oh ok..my connects are solid for sure. Guess I’ll double check the ground tomorrow morning. I’ll definitely pick up a thermometer to double check that as well. Hopefully a faulty gauge is all that it is.
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Cross-Country
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So I got a infrared thermometer..got the truck to operating temp. The gauge pins at 245. The thermometer at two separate points at the thermostat housing reads between 188 and 190ish. So should I assume that the gauge reading is what’s throwing it off?
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Post Fiend
Joined: Feb 2008
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From: St Albert, Alberta
If the wiring is sound the gauge is faulty. Those are normal operating temps.
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Cross-Country
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Thanks everyone for your help
Lead Driver
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A marginal ground at the sender can throw off the accuracy of the gauge. The quickest way to rule this out is run a test jumper from the sender body to the battery’s negative post. See if the gauge now behaves itself.
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Cross-Country
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Figured it out. It needed up being a not so good ground. Followed your guys’ advice and grounded it to the battery and now it’s pinning at 190ish. Check the thermostat housing with my thermometer and it’s spot on.
Thanks so much!
Thanks so much!
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