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MG Midget and Sprite Technical - PCV retrofit

Following complaints from SWMBO about oil marks on the drive, I removed the timing cover breather/filter that had been fitted to my 68 Mk111 and back-fitted the PCV assembly that I'd kept from the ol' 66 MK11.
Now the tick-over is a bit lumpy, hunting between 1,000 and 1,300 and there's quite a bit of pop,pop,popping on the overrun. Otherwise its running/pulling ok.
I'm just wondering whether the diaphragm spring is a bit weak or is there a different rated spring for the 1275 engine.
I'd appreciate any thoughts on this.

Thanks,

Malc
M J Chapman

Sounds like it is drawing in air somewhere doesn't it? Is the threaded adapter sealed properly where it screws into the manifold?
Guy W

I assume so because I haven't touched it as it was sealed off with a short piece of hose fitted with a blanking plug.Mind you,I connected the PCV using the original pieces of hose, which admittedly, are not in the first flush of youth!( a bit like the owner actually!)
M J Chapman

Use thread tape on the adapter and ensure any other tie-ins on the inlet manifold are completely blanked off. Ensure all hose clamps/jubilee clips are tight and yes, no leaks in any hoses.
Mark O

IIRC there should be a fibre washer used with the threaded adaptor on the manifold.
You will know when it's working correctly - there will be clouds of blue smoke in the exhaust as the manifold suction draws the sump contents into the engine intake. :-)
G Williams (Graeme)

Guy, thanks for the lead on air in-leakage. I had a careful look at the diaphragm and eventually spotted a tiny pin-hole. I nipped out to Moss and fitted a new one and lo and behold - normal service resumed!
Tickover back to 900/1000 and overun popping reduced to a light burble.However, by comparing old and new diaphragms I could tell how much the old one had aged and gone stiff so I think it was this as much as the pin-hole causing the problems.
BTW Graeme, I have seen the blue clouds of success!
M J Chapman

This thread was discussed between 15/08/2013 and 16/08/2013

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