Name of the engine side pressure cap seat

Hello dear Hi-jetters,

I've recently bought a Piaggio porter from 1998 with the daihatsu 1.0 engine. The car works great and I absolutely love it. Thanks to the infos on this board I was able to get my cooling system under control, there is just one little thing left: I noticed the water that I put in the radiator directly dribbles into the overflow tank. I replaced both pressure caps and the problem still pursues. I'm pretty certain it's the face where the lower part of the cap is supposed to seal, as it is a little deformed. How does that happen?
I tried putting in shims behind the seal to elevate it as I'm currently on vacation but it does not seem to help. It does close when I put in another rubber seal on top of the other, but I don't think it gives it enough room to open the overflow as pressure rises which could potentially lead to overpressure....

Does anybody know how that pipe which holds the engine side pressure cap is called so I can order it? Added an image to be clear.



Any other ideas as to how I could temporary fix this issue?

All the best and thanks for your time
Garbean

First question is are you sure it’s a 1.0? I know it seems a daft question but I have never seen that pipe on a 1.0 that is the shape that is. On a 1.0 it usually runs along the top endless of the rocker cover in a straight line (ok there is a very slight kink but not much).
Getting a new replacement is not going to be easy or cheap. The alternatives are yet a tap seat cutter from say B&Q and carefully reface the bottom face it seals to (I have done this, just don’t go mad). The second is to get a replacement radiator cap section and splice it into the existing pipe work to replace the old one. I used this one https://www.carbuilder.com/uk/in-line-radiator-filler-neck-25mm

https://hijet.forumotion.com/t1018-fitting-new-radiator-and-expanion-pipe-tube-pictures
That’s what a 1.0 usually looks like.

Thank you Raggy! I read many of your posts before and have learned a lot from you.

I wasn't questioning the engine size, the prior owner told me so and I just took it as that. How can I tell for sure? Here's some more images.







Thanks for your suggestions! I will insert the replacement radiator cap section once I'm back from vacation, very good idea. Maybe before that I'll try to even it out with a seat cutter as you suggested.

For anyone looking for the part number

1633287Z06000 for the 1.0 l engine




1650787Z07000 for the 1.3 l engine

The CB engine code is certainly a 993 or below designation. The shape of that pipe is a new one on me, but if it worked then great. Good luck getting it sorted.

Thank you. Will post updates!

From your experience if there is drops coming out from underneath the timing belt, does it usually come from the pump seals being gone?

It could come from the water pump or it could have dribbled down from the rad cap over that cover.