Engine temp spikes on highway

[DavidCola]

I have a 2019 Platinum, with 89k. I was having interior heater issues. Heat would be intermittent. My local mechanic found a tiny leak in near my reservoir tank. He said that was allowing air into the coolant system. That was fixed. Drove it for a day, and another leak develops at another hose that feeds the heater core. That was fixed. No heater or leak issues.
So now at highway speeds, 70+, my temp gauge will spike to up to 238 degrees, then back to normal within 10 seconds. I took it back in and he bleed some air out but it is still happening. He said this is normal for this engine. As long as it below 240, it is ok? Is it? Has this been happening before and I just didn't notice? I asked if the thermostat should be replaced and he said no.
BTW,,,, I called my local dealer and said they were 2 weeks out to look at it!
Thoughts?

 

[5280tunage]

240 degress, not sure I buy that. mine I don't believe mine has ever gone over 220 while towing at highway speeds gaining several thousand feet of elevation. In fact, I had been debating on putting in the 180 degree thermostat I bought over a year ago.

 

[99WhiteC5Coupe]

I have a 2019 Platinum, with 89k. I was having interior heater issues. Heat would be intermittent. My local mechanic found a tiny leak in near my reservoir tank. He said that was allowing air into the coolant system. That was fixed. Drove it for a day, and another leak develops at another hose that feeds the heater core. That was fixed. No heater or leak issues.
So now at highway speeds, 70+, my temp gauge will spike to up to 238 degrees, then back to normal within 10 seconds. I took it back in and he bleed some air out but it is still happening. He said this is normal for this engine. As long as it below 240, it is ok? Is it? Has this been happening before and I just didn't notice? I asked if the thermostat should be replaced and he said no.
BTW,,,, I called my local dealer and said they were 2 weeks out to look at it!
Thoughts?

I’d bet you still have a small leak, which allows coolant to escape and air to be drawn into the system when the engine and coolant cools down.

The high engine temperature on the highway indicates air in the system. If the radiator cooling fans were not operating properly, there would still be enough air forced through the a/c condenser and radiator to cool the coolant.

After several engine heat-cool cycles, check your coolant reservoir. Is the level dropping? Perhaps mark the current cold coolant level with a piece of painter’s tape, and then check it each day after it cools down.

 

[wakeboarder]

Mine has never been over 220° either even while towing. I changed my thermostat proactively since I had the old style. It now averages 10°F cooler than before I replaced the thermostat. I replaced it with the stock part number.

 

[SyndicateZ]

I have a 2019 Platinum, with 89k. I was having interior heater issues. Heat would be intermittent. My local mechanic found a tiny leak in near my reservoir tank. He said that was allowing air into the coolant system. That was fixed. Drove it for a day, and another leak develops at another hose that feeds the heater core. That was fixed. No heater or leak issues.
So now at highway speeds, 70+, my temp gauge will spike to up to 238 degrees, then back to normal within 10 seconds. I took it back in and he bleed some air out but it is still happening. He said this is normal for this engine. As long as it below 240, it is ok? Is it? Has this been happening before and I just didn't notice? I asked if the thermostat should be replaced and he said no.
BTW,,,, I called my local dealer and said they were 2 weeks out to look at it!
Thoughts?

I also have a 19. This is a dumb question, how are you able to see the exact temp the engine is at? The temp on my cluster just shows the blue bar but no digits..

 

[DavidCola]

Mine is the same. When the temp hits 228+, it actually shows the number. This is why I am perplexed. The mechanic says this is normal but how have I not noticed in the prior 89k of miles??

 

[DavidCola]

I’d bet you still have a small leak, which allows coolant to escape and air to be drawn into the system when the engine and coolant cools down.

The high engine temperature on the highway indicates air in the system. If the radiator cooling fans were not operating properly, there would still be enough air forced through the a/c condenser and radiator to cool the coolant.

After several engine heat-cool cycles, check your coolant reservoir. Is the level dropping? Perhaps mark the current cold coolant level with a piece of painter’s tape, and then check it each day after it cools down.

Thanks. That makes sense. I was told that a pressure test was done. IDK.

 

[99WhiteC5Coupe]

Thanks. That makes sense. I was told that a pressure test was done. IDK.

On my 2015 Expedition, purchased new, the water pump was replaced at about 70,*** miles. It had a slow leak, which wasn’t apparent. The dealer declared it had no leaks after a pressure test (despite a dropping coolant level)

I returned and insisted it be inspected on a lift. The mechanic quickly saw signs of a coolant leak from the water pump. It apparently was only leaking while being driven, and did not drop any coolant on the ground while parked.

 

[scottdm]

I also have a 19. This is a dumb question, how are you able to see the exact temp the engine is at? The temp on my cluster just shows the blue bar but no digits..

Not a dumb question. Forscan allows you to change settings to allow the instrument cluster to display the values for the engine temp, transmission temp, etc. Check out the Forscan section on this forum if you're interested in trying it out. It's a free license and there is a spreadsheet that provides common modifications that users have validated.

 

[scottdm]

Mine has never been over 220° either even while towing. I changed my thermostat proactively since I had the old style. It now averages 10°F cooler than before I replaced the thermostat. I replaced it with the stock part number.

Mine has also never been over 220 F. I had wildly fluctuating temps displayed recently and had the thermostat replaced, and temp now consistently runs 185-190F in normal driving after engine is at operating temp.