MatraSport Forum

My original 11.6psi Murena radiator cap seems to be working fine, despite its age. But because of it’s age I’ve been concerned for a while that it might fail one day.

I’ve now found an exact equivalent – 11.6psi/0.8 bar and exactly the same size, including short reach. It’s made in the UK by Vapormatic, the parts division of John Deere (the tractor people), and can be ordered from a local agent or online. The reference number is VPE3262.

Here’s the part on Vapormatic’s website:

• https://www.vapormatic.com/search/vpe3262/541vugamomg

I bought mine from this company locally for £12 (no postage):

• https://huntforest.com/parts/

Here’s one online company that will send one (plus postage):

• https://www.carpentergoodwin.co.uk/Products/Claas-Ares-836Q-Cooling-System/VPE3262

In both cases they were a special order. Mine came in the next day.

See the photo below of the cap on my 1.6 (later) expansion tank, plus others.

Well found Alan, and thanks for the information.  I will add it to my website on my return from France.  I had recently added the information for the two caps either side of correct, at 10 psi and 13 psi, which could have been used if necessary, but this is even better.

Roy

Well done, looks good! I might as well replace my 40 year old one.

Awesome, these are sold across Europe it seems. I found some of the renault ones on polish tractor parts sites as well by the way. Will get me a spare one along with a new tank somewhere this year I think.

Looks good, but Murena cap has  valves to let air in and out at different pressures as far as I know.
Works this cap the same?

That's the first I've heard of different pressures, this cap does exactly match the spec of the original and the only alternatives would be 10psi or 13psi which are very different.

This page of the manual tells about opening pressures.
2 pressures are written .
1 blow of and the other untherpressure

Strictly this means that the cap must release at 0.8 bar to allow air (or coolant) out, and at an under pressure (or vacuum) of 0.055 bar it must allow air back in.  Actually the note is slightly incorrect as the overpressure release pressure should be 0.85 kPa or 0.85 bar according to the manual.

Now 0.055 bar is just 0.8 psi, so what it is telling you is that the cap second sprung seal (just under the cap) must not be so tight that it prevents air being drawn back in when the coolant temp. drops and you get a slight vaccum in the system.  This really defines the design of the cap to the neck fitting.  If the design is not correct then the seal could be too tight, owing to the greater compression of the spring, and there will be too much pressure on the seal to release as the pressure drops below atmospheric.  As long as the design of the cap is the same as the original, then the cap should be fine.

Roy

Yes, Alan, the vacuum release is a function of all caps to allow air back in as the system cools, and this is one reason why the design of the cap sprung seals must match the neck of the radiator or expansion tank deisign.

Roy