2018 Buick Encore Overheating Randomly - for the puzzle solvers

[hjohnson0445]

My 2018 Encore w/ ~55K miles has been overheating when on the interstate traveling distances greater than 70 miles since late May. I accidentally left the reservoir cap off while on my way to FL from TN and that is when it initially overheated. After that, I had to replace my ignition coil and spark plugs because the engine was misfiring. After repairing the misfire, the engine still overheats randomly. I have done a pressure test, changed the thermostat, replaced the coolant, and bled the air out of the radiator. If I run the *heat* while on the interstate, the heat will stop working randomly and the car will immediately overheat. The car is also using a small amount of coolant. Since I do not see leaks and the pressure test was negative, I'm not sure what else it could be on a basically new car. Any help is greatly appreciated!! I have been to 2 different dealerships and they don't want to put the time into figuring it out.

 

[Again]

Is it still under warranty?

 

[MelsRegal]

Have you done a hydrocarbon test of the engine coolant which if positive would show you possibly blew a head gasket the first time it overheated.

 

[MelsRegal]

Delete

 

[hjohnson0445]

Is it still under warranty?

It is under powertrain warranty, but until the dealer can identify the problem to ensure the failure is part of that warranty, they aren't going to fix anything. I want them to replace the water pump, but they won't do that until they can pinpoint that its causing the problem. Which is valid, but unfortunelty they are unable to find the cause.

 

[Again]

Like MelsRegal said if you needed plugs after the first incident chances are you either blew a gasket or warped the head. You won't see a coolant leak if it's coming out the pipe. This would also explain your heater getting air locked. Compressed gasses are probably getting in the coolant and creating air locks. Changing the water pump will do nothing to help you. A good mechanic will see which cylinder is leaking just by looking at the plugs.

 

[MelsRegal]

It is under powertrain warranty, but until the dealer can identify the problem to ensure the failure is part of that warranty, they aren't going to fix anything. I want them to replace the water pump, but they won't do that until they can pinpoint that its causing the problem. Which is valid, but unfortunelty they are unable to find the cause.

Did they do a hydrocarbon test of the coolant?

 

[agaric]

Those are classic blown head gasket symptoms.

 

[MelsRegal]

Did you buy the vehicle from either of the dealers?
Did you tell the dealers you left the cap off?

 

[hjohnson0445]

Like MelsRegal said if you needed plugs after the first incident chances are you either blew a gasket or warped the head. You won't see a coolant leak if it's coming out the pipe. This would also explain your heater getting air locked. Compressed gasses are probably getting in the coolant and creating air locks. Changing the water pump will do nothing to help you. A good mechanic will see which cylinder is leaking just by looking at the plugs.

Since the car was at 55K miles (I bought it around 45K), I thought it wasn't necessarily unusual for spark plugs to need replacement at that mileage. Granted, I don't know if they were changed since the car was sold new. The Buick dealership said 2 of the plugs were bad and replaced all 4, and didn't note seeing anything out of the unusual. I asked if they thought it was odd a new car would need a new ignition coil/plugs (indicating it could be an underlying problem) and they didn't care to think further into it.

Now that the plugs have been replaced for 2 weeks, will a mechanic be able to see the cylinder leak? Hopefully a hydrocarbon test will work, but I worry it may give a false negative if the leak is small and only induced at high temperatures.

 

[Again]

A good mechanic will know just by looking at the plugs or the top of the piston. Hope you didn't tell them you left the cap off, that might void the warranty.

 

[MelsRegal]

Since the car was at 55K miles (I bought it around 45K), I thought it wasn't necessarily unusual for spark plugs to need replacement at that mileage. Granted, I don't know if they were changed since the car was sold new. The Buick dealership said 2 of the plugs were bad and replaced all 4, and didn't note seeing anything out of the unusual. I asked if they thought it was odd a new car would need a new ignition coil/plugs (indicating it could be an underlying problem) and they didn't care to think further into it.

Now that the plugs have been replaced for 2 weeks, will a mechanic be able to see the cylinder leak? Hopefully a hydrocarbon test will work, but I worry it may give a false negative if the leak is small and only induced at high temperatures.

There is no 'small' leak only at high temperature, you either have a blown gasket or you dont.

 

[agaric]

Look at the bottom of your oil filler cap and dipstick for any froth or foam.
If there is ANY then the head gasket is bad.

 

[G-276308]

Look at the bottom of your oil filler cap and dipstick for any froth or foam.
If there is ANY then the head gasket is bad.

No indication of coolant mixing with the oil.

 

[MelsRegal]

Look at the bottom of your oil filler cap and dipstick for any froth or foam.
If there is ANY then the head gasket is bad.

The color of the deposits will be a creamy brown in color.

 

[hjohnson0445]

Did they do a hydrocarbon test of the coolant?

Hydrocarbon test was negative

 

[MelsRegal]

You never see any amount of excessive white smoke from the exhaust and the oil filler cap is clean?

 

[G-752399]

Since the car was at 55K miles (I bought it around 45K), I thought it wasn't necessarily unusual for spark plugs to need replacement at that mileage. Granted, I don't know if they were changed since the car was sold new. The Buick dealership said 2 of the plugs were bad and replaced all 4, and didn't note seeing anything out of the unusual. I asked if they thought it was odd a new car would need a new ignition coil/plugs (indicating it could be an underlying problem) and they didn't care to think further into it.

Now that the plugs have been replaced for 2 weeks, will a mechanic be able to see the cylinder leak? Hopefully a hydrocarbon test will work, but I worry it may give a false negative if the leak is small and only induced at high temperatures.

Have you performed a cylinder leak down test with the coolant pressure tester installed on the tank ? If coolant gauge goes up when pressurize any of the cylinders you have engine issue. Such as head gasket, warped or cracked block or head.