Apparently not mate! All the ones I have, the large rubber bit is slightly too big and doesnt squash down enough to allow the cap to go on. Also the Altezza one has an extra smaller diameter rubber bit that seals down inside that all other caps I have dont have!
I found the source of my water leak though - and it was so silly and a massive school boy error!
I got home last night and it wasnt leaking but thought Id keep the engine running, monitor the coolant temperature on Torque and get it hot in the hope it would leak. Meanwhile, jacking the front of the car up so I could look at ball joint but also get under to find the leak.
Well about 5 mins later it started and luckily was leaking quite a bit so I could tell it was coming from under a heat sheild which protects the water pipe round (to the thermostat/oil cooler) from the exhaust manifold.
So I cracked on with the ball joint to then let everything cool and then removed the exhaust manifold.
This is the heatshield:
(you can see where the water has been running and stained the top of the engine mount to bottom left of photo)
And here is what I found underneath:
Spot the difference with how it should look! LOL:
No it shouldnt be more blurred but it should have the clips on the hose in the right places!! LOL I took photos of every single bolt and clip I took off the car/engine when I lifted the engine out but thinking back, this must have been when I already had the engine out and was cleaning things up. I intended to take the hose off to clean it out but Dad said not to worry and crack on with getting the engine sorted to go back in so I must have walked away and then put the cover back over it at later date and completely forgot to put the hose clamps on!!! Doh! So it has been heating up and causing the water to leak out of sight under that cover and under the exhaust manifold and get slowiy worse! Luckily it didnt completely blow the hose off and give me a massive overheating issue!!!
While I've got things in bits and heading to get a new balljoint tonight, i have decided to get a new and slightly longer bit of heater hose to replace it and then also put the clips and a couple of jubilee clips on for good measure! LOL
I doubt this is your issue mate but thought I would post it up just in case you did a similar thing when replacing the thermostat O ring etc (though I doubt you would be as stupid as I was! LOL)