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Q: Coolent pushing up into reservoir, on 2008 Isuzu i370 Pickup

I drive a diesel truck and recently had lots done on the truck,
the radiator was replaced
the thermostat was replaced
the turbo was serviced
the boost pipes where replaced

On a hot day like today or when the vehicle is working uphill then the coolant pushes up into the reservoir not all the way to the top but a decent amount from the (max line)

The vehicle has been pressure tested and no problem on the system.

What is the acceptable amount for a diesel truck to push coolant into the reservoir on a hot day on long climbs....?
What seems to make the problem better or worse? when the engine is hot
How long have you had this problem? 2 days after servicing...
coolant rising in expans, isuzu, i370 pickup
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If the coolant returns to the normal range, I would expect this is just thermal expansion from the high heat generated by high ambient temperatures and high engine temperatures.
However, if the temperature of the engine is not climbing with the coolant level in the reservoir, I would be concerned that combustion gasses are being passed into the cooling system.
Since the coolant is new, I recommend using a combustion gas test kit for the engine coolant. This will show if combustion gases are making it from the combustion chamber to the cooling system.
When I drive. Ormally around town. No problems. When I drive long distance and continuous climbing. Then it would push up. If the vehicle is left overnight then It would return. Not all the time though.

Should the coolent be filled in the expansion tank to the max line?

I think I must burp the syatem as well...

Could also be a faulty one?
Since the coolant moves back down when it cools, I would say this is normal expansion of coolant, and maybe overfull.
It should be up to the max line when the engine is at full operating temperature, and should not dip below the cold line.

If there is some air in the cooling system, it will expand much more than coolant, so that would explain a greater than normal rise and fall of coolant level.

Thermostat would make your engine overheat or overcool, so I'm not worried about it unless one of those are happening.

I really would do the combustion gas test kit for the coolant. If you have a leaky head gasket, that's a sure fire way to tell.
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