Is this normal? - Weird coolant temp gauge behavior

[philosopher84]

So I have a 2019 GT PP1, about 1800 miles so far. A few days ago I noticed the needle on the coolant temperature gauge drop pretty dramatically while accelerating at a moderate pace, maybe 30-40% throttle (engine had already reached normal operating temperature where needle was close to the middle of the gauge). It seems when I increase rpms, whether from accelerating, downshifting, or just revving in neutral, the coolant temp gauge, along with the readout for the cylinder head temperatures, drops pretty quickly and more than I'd expect is normal. Cylinder head temps go from just over 200 degrees F, down as far as 150-160 F pretty much in step with the coolant temp gauge. Just today I was driving along about 45 mph in 5th gear, temp gauge in the middle, and when I downshifted to 2nd, the needle on the coolant temp gauge dropped pretty far towards the cold mark. Correspondingly, the cylinder head temp readout went from around 200 F to around 150-160 F, mirroring the needle on the coolant gauge.

In every car I've ever driven, the coolant temp gauge starts from a cold level when the engine has been off for some time, and slowly moves until about the middle of the gauge, which represents normal operating temperature. Barring hard track driving or a cooling system issue, it usually stays there under normal or even aggressive driving. In any car I've driven, I've never seen the needle on the gauge move almost all the way to the cold area of the gauge when you raise the engine rpms. And it only seems to have started a few days ago. I've driven the car for about a month and never saw this behavior before, and I pay attention to things like that. The tech at the dealer couldn't find any error codes and thinks this is probably normal behavior based on the larger radiator that comes with the performance package.

My question to any here with PP1 or PP2 on their GT, is this normal behavior? Does your coolant temp gauge drop a lot when you raise the rpms? It just seems wrong to me for the gauge to fluctuate that much and still be "normal" behavior.


TL DR-
COOLANT TEMP GAUGE (ALONG WITH CYLINDER HEAD TEMP READOUT) DROPS A LOT WHILE ACCELERATING MODERATELY OR JUST RAISING THE ENGINE RPMS. IS THIS NORMAL?

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[TGGT]

I had this problem with my 19. I replaced the cylinder head temperature sensor and the problem was gone. It’s like $10 from the dealer

 

[brucelinc]

That does not sound normal at all. Once up to temp, mine doesn't fluctuate much at all.....never drops as low as you are saying.

 

[Silver Bullitt]

Yup, mine reacts just like bruce explained. Doesn't sound normal.

 

[m0.s550]

Just confirming what the others have said: doesnt sound normal. Mine goes to normal operating temp (middle of gauge), cylinder head temp runs ~200 +/- 4 degrees. When I step on it and run spirited for a few mins, cylinder head temp goes up as high as 215 degrees, not lower than the 200. This is on the street, not a track.

Good luck getting dealer to fix it, maybe ask them to check it against another car in the lot and also tell then about the sensors the above posters mentioned.

 

[Cobra Jet]

Pssssst, here ya go:
https://www.mustang6g.com/forums/threads/tsb-19-2049-cht-mil-dtc’s-p1289-or-p017d.120216/

TSB 19-2049 - seems to be a common issue with the early 2019’s.

 

[philosopher84]

Pssssst, here ya go:
https://www.mustang6g.com/forums/threads/tsb-19-2049-cht-mil-dtc’s-p1289-or-p017d.120216/

TSB 19-2049 - seems to be a common issue with the early 2019’s.

Thanks. Unfortunately, no DTCs are stored, which is why the dealer thought there was nothing wrong. I'll definitely look into that sensor though.

 

[Ghost50]

Count me as another 19GT PP1 who has no fluctuation in the coolant gauge levels.

I was eyeballing it closely the past week too because I put on the Mishimoto coolant tank and when I did that I had to add coolant. I was half a bottle low from the factory. That or my car is slurping up coolant somehow.

 

[TGGT]

Cylinder head temp sensor guaranteed. It won’t set a mil, but there may be a stored code for cylinder head temperature sensor range/performance

 

[philosopher84]

Do any of you know if there are 2 separate sensors for coolant and cylinder head temps, or is there a single sensor that is used for both values? I don't have a service manual for this car yet, but I came across something that made it sound like the coolant temp is inferred from the cylinder head temp sensor. That would narrow things down if that was the case.

 

[HiTekExec]

So I have a 2019 GT PP1, about 1800 miles so far. A few days ago I noticed the needle on the coolant temperature gauge drop pretty dramatically while accelerating at a moderate pace, maybe 30-40% throttle (engine had already reached normal operating temperature where needle was close to the middle of the gauge). It seems when I increase rpms, whether from accelerating, downshifting, or just revving in neutral, the coolant temp gauge, along with the readout for the cylinder head temperatures, drops pretty quickly and more than I'd expect is normal. Cylinder head temps go from just over 200 degrees F, down as far as 150-160 F pretty much in step with the coolant temp gauge. Just today I was driving along about 45 mph in 5th gear, temp gauge in the middle, and when I downshifted to 2nd, the needle on the coolant temp gauge dropped pretty far towards the cold mark. Correspondingly, the cylinder head temp readout went from around 200 F to around 150-160 F, mirroring the needle on the coolant gauge. Makes me think the thermostat is stuck open, so when rpms increase, the water pump spins faster and moves more coolant through the radiator and the system than is necessary, which drops the coolant temp that the gauge is reading.

In every car I've ever driven, the coolant temp gauge starts from a cold level when the engine has been off for some time, and slowly moves until about the middle of the gauge, which represents normal operating temperature. Barring hard track driving or a cooling system issue, it usually stays there under normal or even aggressive driving. In any car I've driven, I've never seen the needle on the gauge move almost all the way to the cold area of the gauge when you raise the engine rpms. And it only seems to have started a few days ago. I've driven the car for about a month and never saw this behavior before, and I pay attention to things like that. The tech at the dealer couldn't find any error codes and claims this is "normal behavior" based on the larger radiator that comes with the performance package.

My question to any here with PP1 or PP2 on their GT, is this normal behavior? Does your coolant temp gauge drop a lot when you raise the rpms? It just seems wrong to me for the gauge to fluctuate that much and still be "normal" behavior.


TL DR-
COOLANT TEMP GAUGE (ALONG WITH CYLINDER HEAD TEMP READOUT) DROPS A LOT WHILE ACCELERATING MODERATELY OR JUST RAISING THE ENGINE RPMS. IS THIS NORMAL?

Not normal. Temp should climb and settle quickly and hold stable.

 

[TGGT]

Do any of you know if there are 2 separate sensors for coolant and cylinder head temps, or is there a single sensor that is used for both values? I don't have a service manual for this car yet, but I came across something that made it sound like the coolant temp is inferred from the cylinder head temp sensor. That would narrow things down if that was the case.

Only cylinder head temp. There is no coolant temp sensor

 

[philosopher84]

Only cylinder head temp. There is no coolant temp sensor

Thank you very much for your response.

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