Cooling System Confusion

ForeverDriven

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Hello again everybody, I want opinions.

I have a 1997 Mustang with a SC coyote swap, but recently tore the motor down a little and put it all back together. Here's my issue.

Once it gets up to temp and I'm driving around, the computer monitored coolant temp stays perfect. Right where you want it around 190-200.

However, my mechanical coolant sensor starts reading up into the 220-230 range, fluctuates a bit. It is located on the bottom driver side of the block, where the block heater normally is.

I immediately thought headgasket like anyone, as I did not have the block decked while the heads were off, only scrapped old gasket off (the heads were cleaned by a shop). But, there are no bubbles in the coolant on startup and it passed a CO2 tester.

The gauge is a glowshift setup, I'm imagining the sensor might've just ate it while the car was apart and it was exposed to air, but I can't tell. I've heard mixed things about GS and my gauges worked well until this little issue.

Its funny, I bought the mechanical gauge because I didn't trust the head sensor and now I don't trust the mechanical sensor! Lol.

Any help is appreciated,
Blake Hammond
 

lwarrior1016

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Hello again everybody, I want opinions.

I have a 1997 Mustang with a SC coyote swap, but recently tore the motor down a little and put it all back together. Here's my issue.

Once it gets up to temp and I'm driving around, the computer monitored coolant temp stays perfect. Right where you want it around 190-200.

However, my mechanical coolant sensor starts reading up into the 220-230 range, fluctuates a bit. It is located on the bottom driver side of the block, where the block heater normally is.

I immediately thought headgasket like anyone, as I did not have the block decked while the heads were off, only scrapped old gasket off (the heads were cleaned by a shop). But, there are no bubbles in the coolant on startup and it passed a CO2 tester.

The gauge is a glowshift setup, I'm imagining the sensor might've just ate it while the car was apart and it was exposed to air, but I can't tell. I've heard mixed things about GS and my gauges worked well until this little issue.

Its funny, I bought the mechanical gauge because I didn't trust the head sensor and now I don't trust the mechanical sensor! Lol.

Any help is appreciated,
Blake Hammond
I’ve installed some glow shift gauges at our shop and I’m not impressed, to say the least. Sometimes they are accurate, sometimes they are not. I would maybe try a different gauge, like one of the autometer gauges with a stepper motor. That’s the same spot I use for my gauges and it typically reads a little lower than head temp.
 
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ForeverDriven

ForeverDriven

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I’ve installed some glow shift gauges at our shop and I’m not impressed, to say the least. Sometimes they are accurate, sometimes they are not. I would maybe try a different gauge, like one of the autometer gauges with a stepper motor. That’s the same spot I use for my gauges and it typically reads a little lower than head temp.
I thought about Autometer, until I saw their prices! I know you get what you pay for, but at this point I have 3 GS gauges and if I had to shift the other two to Autometer as well, I'm hitting a $200+ bill.

Moreso, the confidence in your non-confidence helps me not worry that I'm overheating lol. I think I'll try a replacement sender from GS, then if no good, I'll shoot for autometers.
 

lwarrior1016

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And, you can take this into consideration, Ford has MANY vehicles running around that rely solely on the head temp sensor. You can pretty well bet that it’s trustworthy.
 
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ForeverDriven

ForeverDriven

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And, you can take this into consideration, Ford has MANY vehicles running around that rely solely on the head temp sensor. You can pretty well bet that it’s trustworthy.
I fully trust it for everyday driving, the car gets tracked sometimes tho so I like having a mechanical sensor in the block for a second reference.

Also when the heads were redone, I don't know what the shop did with the CHT sensor when they cleaned em. If they took it out, Ford says its a one time use sensor so ‍♂️. Dunno what the effects of a used sensor would be, but maybe it reads low now.

Who knows, the gauges matched temps pretty well originally. Now I'm between a sensor I know is cheap and a sensor I don't know how the shop handled! Lol
 

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