I have a 93 300d 2.5l. Pertaining to the coolant system, how does the overflow tank for coolant function? It seems that the coolant level in it never changes and it appears never to circulate into the radiator. It keeps me guessing as to its function.

Many Thanks

Ice

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1993 300D 2.5L 240,000+ miles

Do you mean the coolant reservoir in the engine bay or the overflow bottle tucked in the fender? The reservoir is part of the pressurized system. The level won't change if you check it under the same conditions. It might be a little lower when cool and a little higher when hot. The hose by the pressure cap goes to a bottle that collects overflow. I don't know why MB never meant for you to see it.

Sixto
87 300D

THe reservoir is what I see in the engine bay. And it just always seems to be there never doing anything. Does fluid actually flow through the cooling system from the reservoir. Because I have look at it when the car is warm and it just seems to be at the same level as when it is cool. No fluctuations seem noticeable. I thought maybe the coolant leaves reservoir only if the main radiator fails

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1993 300D 2.5L 240,000+ miles

Coolant doesn't flow through the reservoir per se. There is a hose that leads to the lower radiator hose or that area, and a small hose that goes to the top of the radiator or the upper hose fitting on the block, depending on specific car model. Obviously there will be some movement of coolant but it's not part of the main loop as, say, the heater core is when ACC is set to heat.

If you don't have engine temp problems, don't worry about it. If you have engine temp problems, it's probably not the reservoir.

The reservoir provides a useful view of the cooling system. When you see oil floating on coolant in the reservoir, the head gasket has leaked.

Sixto
87 300D

Thanks Sixto

That answers my question. Now I won't be scratching my head.

Marty

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1993 300D 2.5L 240,000+ miles