header tank 996 leaking reasons why?

[cbr786]

hello everyone i know this topic has been covered many times ... bu the reasons have not .

why are these header tanks prone to leaking ? bad design ? or is it because its old now ? sone people on here have bought new bottle and it has leaked again with in a few mths ? is it because the car is running abnormally hot also could be due to exra pressure build up in the expansion bottle and the bleed valve not working correctly thus causing rupture in tank weld seam ? or is it due to the old style cap on the bottle ending with 00 ?

would it be stupid to replace with a good used unit that I have lying around but has really old part number on it 996 106 147 54 ?

is it wise to change cap as well for a new one when I change header tank for a new cap ?

the one with the old part number is still white and the plastic has not yellowed, unlike the one on my car which ends with 55 part number and the lastest one now with OPC is ending with 56 part number they keep changing them ?

also I think it would be alot easier to refit this bottle with the engine lowered slightly even on a 1999 C4 car the bottle is too big to squeeze into that cavity causing pressure on surounding items like plenium camber etc especially the bit that juts out for the fuel filter to sit on ...

your comments are appreciated ...

[bmohr]

went through 2 tanks before realizing the cap was causing issues. If i make it through another year without a leak i'll assume the cap made a difference.

[mp911]

I changed mine to latest version. It cracked on a corner on the back side, probably too thin in that location due to molding. It has plenty of nooks, crannys, and corners for a crack to start.

IMHO because it is such a pain to replace I would go with latest tank and cap. I took the support bracket out and that gave me room, but I think lowering the engine slightly might have been better. I will see next time ;)