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Re: [Mgs] [MG-MGB] oil pressure problem or perception thereof

To: <MG-MGB@yahoogroups.com>, "Mgs@autox.team.net " <mgs@autox.team.net>
Subject: Re: [Mgs] [MG-MGB] oil pressure problem or perception thereof
From: "Paul Hunt" <paul.hunt1@blueyonder.co.uk>
Date: Sun, 29 Jan 2012 10:05:49 -0000
Can't say I've ever noticed the pressure going *up* on either of mine as the 
oil warms, 10W/40 or 20W/50.  The V8 takes a while to get there, a slow and 
steady rise, but it does that regardless of temperature.  That used to be my 
daily driver, kept outside in all weathers, several periods of well below 
freezing.  Rarely take the roadster out in freezing weather, only it's not 
been out for a month because of the weather, and then only on the salt-free 
roads in the immediate locality.

The gauge is easy to check - simply try another one and tube on the engine. 
It's possible it's nothing more than a pinched or gunged oil gauge pipe 
severely restricting how quickly cold oil can move up the pipe to move the 
pointer.  With air in the pipe the oil has to move several inches.  I've 
seen recommendations to bleed the pipe, which does greatly reduce the 
distance the oil has to move, but then it has the friction of the whole pipe 
to contend with.  I've tried both ways on my V8 and it made no noticeable 
difference at all.

I can't see the pressure relief valve being the problem, if that were 
sticking when cold pressure would be high, not low.  I can imagine very 
thick oil being difficult for the pump to pull through a restriction and 
causing low pressure, but 10W/40 shouldn't be that thick, so it would have 
to be a significant restriction.  I could imagine that on one engine, less 
so on two.  If it is a restriction causing pressures to be that low it's 
flow through the bearings that would be the concern.  But the bottom line is 
that those pressures on the 64 are on the low side anyway.

PaulH.

----- Original Message ----- 
> So the problem is what happens in cold weather. I had to evict the 64B 
> from the garage while doing some work on the 72B and when I start the 64B 
> at temperatures below maybe 20-25 degrees, the pressure only comes up to 
> 10 psi and stays there for 2-3 minutes until the engine starts warming up 
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