What is the coolant tank and cap difference

Coolant expansion tank
1J0 121 407 D ($57.24 genuine VW)
vs
1J0 121 407 F ($19.95 genuine VW)

Coolant tank cap. These are two types of caps. Essentially the same price. Both genuine VW. Is there a difference in pressure or something? My original on my 2000 beetle is the top one, but many vendors don't sell that kind anymore.


Also, is there a reason a non oem tank and cap would not work?

They started using the bottom on in 2005 on most models. They work the same. Although the older type is easier to grip to twist.

That's a great answer. I wonder why there is such a price difference in the tank

The D suffix is for Golfs and Jettas. The F suffix is for New Beetles. The difference is the NB's has the cap at an angle, so you can get at it due to the tight confines of the body.

They are not interchangeable although I suppose you could use the NB's in a Golf or Jetta if you had to, but using the G/J one in a NB would make it difficult to access. Maybe impossible.

And that is why I came here for the answer. Thank you!

I've been losing coolant for a while, and I notice that this cap doesn't seem to seal as well as it should. Could this be the source of my leak? I don't see signs at the expansion tank, but I haven't removed it yet.

Because of the leak, I've been using straight water for coolant(since the warmer weather arrived). I don't see water under the car, but it would evaporate. The water in the tank looks very good.

Could the non-sealing cap allow enough vapor to escape that I'm losing water this way?

I replaced the original expansion tank a couple years ago due to a crack, but the cap wasn't replaced.