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Bluest

Member Since: 23 Apr 2016
Location: Lancashire
Posts: 4227

2007 Defender 110 Puma 2.4 XS CSW Java Black

Puma VCV Post Mortem

I replaced my Volume Control Valve or Suction Control Valve (SCV) today after the cold weather brought my lumpy idle back. New valve has fixed the idle so thought I'd dismantle the old one. I think this has been done previously by another member but I couldn't find the thread.

Inside the the valve the valve is a piston under spring pressure. The piston has a few orifices and looks to be ground very accurately and maybe heat treated too. On my old one the surface finish on about a quarter of the sliding surface was worn to the point you could feel the roughness with a finger nail. O suspect this is what causes the problem as it will probably be causing the piston to stick in the bore and not move smoothly.

Picture of the valve assembly:

Click image to enlarge

Piston from two angles showing the smooth side the the worn rough side. Camera phone is rubbish so it might not be clear enough

Click image to enlarge

Click image to enlarge 2007 110 TDCi Station Wagon XS

11th Nov 2017 4:05pm

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 17527

2007 Defender 110 Puma 2.4 DCPU Stornoway Grey

I have no doubt you'e right, and more often than not it will be moisture from the fuel which starts the surface deterioration.

11th Nov 2017 6:33pm

ickle

Member Since: 22 Jul 2010
Location: South Vendee
Posts: 1802

2008 Defender 110 Puma 2.4 CSW Alpine White

opening up the old can of worms (no not brexit

) do you suppose adding 2 stroke will help prevent this?

Keith

11th Nov 2017 6:37pm

agentmulder

Member Since: 16 Apr 2016
Location: Outer Space
Posts: 1324

Interesting. I think I kept my old one too, when I stumble across it next I'll do the same. Solved the bowel problem, working on the consonants...

12th Nov 2017 12:07am

smb

Member Since: 15 Jan 2013
Location: Cheshire
Posts: 1232

2011 Defender 110 Puma 2.4 XS CSW Santorini Black

Hi Bluest,

Having just changed a vcv(last weekend) following a month of lots of white smoke(smell of unburnt diesel) on cold start up and other running issues and having read this thread I decided to do the same. And low and behold mine looks identical. Polished finish on about 270-300' of the circumference on both the long and the short cylinders with the remainder looking very slightly rough. Looking down the length all the marks/edges of roughness were in line so it looks like it wasn't rotating inside.poss due to lack of lubrication.

It has lasted 145,000miles though of which the majority had 2-stroke added so maybe that's a positive for 2-stroke. Who knows? I wonder what lifespan a vcv should have? It's amazing how such insignificant looking wear can have such an effect.

Will post photos when I have access to broadband, but they look almost identical to yours.

Click image to enlarge

12th Nov 2017 4:51pm

agentmulder

Member Since: 16 Apr 2016
Location: Outer Space
Posts: 1324

Would be good to open a new one for comparison huh? Solved the bowel problem, working on the consonants...

12th Nov 2017 8:08pm

Bluest

Member Since: 23 Apr 2016
Location: Lancashire
Posts: 4227

I think it’s safe to say a new one wouldn’t have those marks. Whether the marks are what actually cause the poor running or there’s is another fault is hard to say. The Piston seemed to still slide smoothly and freely enough. I’m not actually how the valve works. I assume there is a coil in the body that moves the piston like a solenoid or something. 2007 110 TDCi Station Wagon XS

12th Nov 2017 8:26pm

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