DP Surge Tank

[Chonburiman]

I've just moved into the Diesel world and I'm trying to understand my unit. This maybe a dumb question but what's the purpose of the surge tank on top ofthe radiator.

[smlranger]

It's bascially the reservoir for your coolant. When the engine is at operating temp and coolant expands, it surges into the tank. When the engine cools down the coolant level in the tank will drop a bit. You add coolant, when needed, to the tank.

It is always helpful to include the year and model of your coach in your signature or otherwise include that info in your posts.

[Triker56]

I thought the lower mounted overflow tank took care of the coolant expanding.
And where you added more coolant when it got low.
At least mine is made that way.

The tank on top of the radiator is filled to the top of the fill pressure cap.
So there is not much expanding done in that part. That top tank does have the low coolant sensor in it.

Some of them are metal and a lot of newer one are plastic. And a lot of the plastic ones of certin years are now starting to crack & crumble from age. And that part can be replaced for around $100 for the part.

But I have no idea why they make the radiator tank that way. Other then maybe to hold more coolant.