Header cap wont come off - 2014 Grand Picasso C4 2.0 L

[binraider]

For some reason my header cap wont come off. It sorts of unscrews then "clicks" at what seems like a critical point, and never raises up. Trying to tighten it up - it goes quite tight, then if you go further it clicks and is a little bit loose. It has been fine since i bought it - now this!

The cap is a Febi Bilstein one - only 2000 miles old, as I had some overheating issues and i bought a new one then. The car has only done 57k. Short of buying a new header tank and cap does anyone have any ideas what i should do?

This is the one i bought: https://www.amazon.co.uk/dp/B006DHWLII? ... asin_title

[mickthemaverick]

That sounds like the thread may be damaged on the tank. I'd go for a replacement tank from a scrapyard and give that a try first.

[Paul-R]

Try pushing the cap down at the same time you're unscrewing it.

[binraider]

I have ordered a clean one from ebay with what looks like an original PSA cap - so fingers crossed. Thanks for your suggestions

[PaulC5]

You could even buy a new one from a Citroen dealer, the expansion tank caps are common across many Citroen and Peugeot cars.

When fitting it does not need to be done very tight, just until it starts to feel tight, otherwise the plastic threads on the cap or tank could be damaged. I find they take a bit more effort to undo than to do up.