The 300e sometimes blow out hot air, someimtes cold. And it is drinking lots of coolant. I suspect a burnt head gasket but cant find trace of oil in the coolant.
Here is the list of symptoms:
1. AC someties hot, someimtes cold. Someitmes need to restart the car so that it keep blowing cold air.
2. Coolant consumption is very high, almost 3L for a few 10s KM run.
3. No obvious leak
4. Coolant temp rise up to >100 in a few seconds traffic stop
5. fuel gauge pointer flickles
6. lack of power in Low rpm <1500
7. no trace of coolant in oil
8. no trace of oil in coolant

Somemore description on the AC:
It always blow out air when i swtich it on with the big round black button, from ) to IIII. BUt mostly it gives hot air only, depending on the engine temp. Cooler air when the car is movin fast, hotter when it's stop.
I have to push the 3 small square buttons several times to make cold air coming out. But sometimes it doesnt work, i have to stop the car, off it, and restart to make it cold.
The ignition key may has problem too cas when i switch it fully to the right, the AC stop blowing air. when i release it blows again.



I heard that ther is a heat hose connecting the AC unit with the coolant. Maybe it be the culpit that cause the overheat and AC problem?

Sorry for my bad english, and thanks for your patience. Please advise.
I would like to look at the serivce manual on how to remove the engine head and the AC components too. I have the offical Benz service manual but it doesnt has dessemble instructins on those parts.

You need to pressure test the cooling system to determine where the coolant is being lost. It could be corrosion between water jacket and combustion chamber in the cylinder head. This can happen if coolant is not changed regularly.

Good luck,