Electrovalve diodes - Myth or real?

Unread post by **CitroJim** » 01 Sep 2009, 21:51

That all makes perfect sense Kev

When the electrovalve switched to hard mode, the pressure would have leaked past the O ring, into the hole at the side just below the threaded part of the valve and reverse flowed up inside the valve and straight out of the leakage return. If you'd have looked in the LHM reservoir I'll expect you would have seen a high return flow until the security valve shut off.

In soft mode, with the shuttle lifted from the valve seat, system pressure can flow from the bottom of the valve to the hole in the side, which is above the seat but there can (or should) be no flow through the leakage return because the other end of the shuttle is holding it closed.

This is good. between us all, we've now worked out exactly how these valves work

I did once consider if the valve would still work if the leakage return was permanantly blocked off but the valve would then fail to operate as the body would be filled with LHM at full system pressure and the shuttle would be unable to move in any direction. That spurt of leakage on a change of mode is essential to the working of the valve.

KevMayer · Unread post by **KevMayer** » 02 Sep 2009, 20:14

Can't get a new O ring from Citroen. Only comes as part of a new electrovalve for £143.

Tried Pleiades too but they don't stock them. Although the guy at Pleiades agreed that a superglued O ring may last for quite some time.

The good news is that my suspension is switching to soft as soon as I start up. Repairing that O ring has cured a big problem. I just would like to fit a new one. I'll have to search ebay for O ring suppliers.

Now, even when I go back to the Activa after a couple of hours from shutting down and then open a door (without starting the engine), the front and rear switch to soft and can be bounced quite easily. This means the pressure is being maintained. Before working on the front valve I think I must have been suffering from a rapid depressurization each time I turned the engine off because it just wouldn't go to soft mode when I opened a door even 2 minutes after switch off. I must have been losing the pressure through the faulty O ring on the front electrovalve. So, it is indeed crucial.

My old blue Activa used to switch to soft mode every time I opened a door and I guess most of yours do too. It looks like I've eventually got my silver Activa to do the same and work properly.

Another thing I've found is that the STOP light goes out really quickly when I start the engine from cold, and, If I restart the engine after a short stop, the STOP light doesn't stay on at all.

It's looking good folks. I'm smiling from ear to ear. It's just a pitty that no one at home has a clue what I'm up to. You're the only people I can share this moment with.

Unread post by **CitroJim** » 02 Sep 2009, 21:02

KevMayer wrote:Can't get a new O ring from Citroen. Only comes as part of a new electrovalve for £143.

They've gone up some

I was going to treat mine to some new ones but not at that price... Well, not until I've had a good go at mine.

Good work there Kev

I just wish the rain would go off so i can get at mine and do same.

Keep us posted on potential sources of O rings. Surprrised Pleiades could not help...

Unread post by **Peter.N.** » 02 Sep 2009, 21:41

Unless there is something special about the 'O' ring you can get a box with pretty well every size in it from Tool Station or Screwfix or the like for about a fiver.

DickieG · Unread post by **DickieG** » 02 Sep 2009, 21:53

What size is the relevant 'O' ring? There are several sizes available for the main pump which may do the job.

KevMayer · Unread post by **KevMayer** » 02 Sep 2009, 22:19

I got a multi O ring kit from Halfords. The original O ring fell between 2 sizes.

When I tried the O ring larger than original (roughly 7 mm I/D and 1.5 mm dia) I assembled the valve and then removed it to see if all was ok, but, as the electrovalve body was screwed in, the top surface of this O ring had been shaved off. When it was out there was a complete thin shaved off ring which came off with it.

I tried the O ring smaller than original (roughly 6 mm I/D and 1.5 mm dia). This O ring needed to be stretched and was a much tighter fit which, to me, didn't feel right. Again, I opened up after assembly to see if all was well and it looked ok. But when pressurised I'm sure this O ring was either too small or, more likely, too soft. The original O ring seems to be a much harder rubber.

I've had a look around and James Walker (manufacturer) has some great info on their site.

It looks like the O ring should be from Viton (fluoroelastomer) with a shore 'A' (hardness) of around 80 and needs to be roughly 6.5 mm I/D and 1.5 dia.

I've seen some listed at 6.07 mm I/D x 1.78 mm dia and some at 6.35 mm I/D x 1.78 mm dia and then again 6.75 mm I/D x 1.78 mm dia.

It would be good to know what size Citroen specify for this O ring.

You can probably get them from James Walker as long as you order 6 million ..... lol.