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Alloy Header Tank Cap - pic inside
Kriss - 22/6/10 at 12:07 PM

All,

My crappy motor factors cap keeps failing every copuple of months. I think the metal on plastic combo along with the rough edge of the tank is not doing the cap any favours.

I am after a Alloy one which can take the pressure and stop failing.

To suit the below application

Bluemoon - 22/6/10 at 01:22 PM

I think you need to say what you mean by failing, it is a pressure cap so will leak when need..

Kriss - 22/6/10 at 01:33 PM

failing under pressure at the seal or the actual screw thread.

Just want a decent alloy or billet one.

blakep82 - 22/6/10 at 02:01 PM

the thread shouldn't be failing, its got all sorts of springs and stuff inside to allow the seal to push up at pressure. so the seal could be failing, but a alloy one woudn't stop that

Bluemoon - 22/6/10 at 02:38 PM

quote:
Originally posted by Kriss
failing under pressure at the seal or the actual screw thread.

Just want a decent alloy or billet one.


If it's a pressure cap (you can probably get blanks) then it will leak around the thread area as this is the vent path, when over pressure..

I had a problem with an old cap turned out that the thing was leaking when under pressure. Checked operation by adding a valve into the water system to allow pressure test (foot pump and old inner-tube value), found that the cap opened at the correct pressure but would not re-seal.. New one fixed this, now opens at correct pressure..

All of this was compounded by a lack of space (i.e. air, in the header-tank) to allow for water expansion, i.e. system would push water out of cap to reduce system pressure, once system had found it's level it's been fine..

Dan

[Edited on 22/6/10 by Bluemoon]

Kriss - 22/6/10 at 03:34 PM

should I maybe drop the water level half an inch?

blakep82 - 22/6/10 at 03:48 PM

have alook at what Dan said on my thread, which was prompted by yours

http://www.locostbuilders.co.uk/viewthread.php?tid=138434