Radiator cap Volvo Penta 2040D

[landonshaw]

Just bought a new radiator cap for my Volvo Penta 2040D. The old cap looked like any radiator cap on a car. Set it on and turn to clip in and secure. The new one only presses on and there is an O ring that keeps it secure. Called where I got it, a NY marina, and verified that I got the correct part. Anyone else have a cap like this? Is it correct?

Very knowledgable part person at the store said there should not be pressure at this point, just the pressure from the circulating pump. If there is, you have some other problem. I mentioned about a car radiator, he Sid I don't own a car, I have a boat. Comments.


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[DougR]

Sounds like rubbish to me. Of course you have pressure in the expansion tank of the engine. Without pressure in a diesel engine cooling system you risk cavitation erosion on the cylinder walls/liners and also cavitation in the circ pump. Plus, without pressure the coolant will boil at a lower temperature than with pressure.

According to marinepartsexpress on line parts books, the expansion tank cap part number for a 2040C/D engine is 3581770. Is that what you received?

Can you post a photo of the cap you received?

DougR

[landonshaw]

Here is a picture of the new designed cap. The old looked like an ordinary car radiator cap.

[a64pilot]

OK, expansion tank is under atmospheric pressure only, however it is connected to the heat exchanger that is the same as a radiator on a car and will be under pressure, cap is what determines how much pressure.

Which cap are you speaking of? I assume you wanted a heat exchanger cap, but got an expansion tank cap, maybe?

No picture posted.

[landonshaw]

Te cap I ordered and received is the one on the left. When talking with the person I ordered it from, I called it a radiator cap. Explained that it is on the top of the heat exchanger.

[landonshaw]

The only caps on the Vovo 2040D is the cap on top of the heat exchanger and the oil cap. The rep looked up the 2040D, and then went to the drawing to identify the cap and the part number