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MG MGB Technical - Dropping oil pressure

Hi people,
I got a 1967 MGB GT, MK 1. It running great at the moment, starts on the button & goes like the clappers. However, (you knew it was coming) if I leave it ticking over or get stuck in traffic the oil pressure starts to drop. It's normally at 20psi on tick over & 60psi while driving. Then, when in traffic, the oil pressure will start to drop of, eventually it will drop to below 5psi and cut out. I have to keep on hitting the trottle to keep therevs up & the engine running.
Just did an oil change using Millers Classic 20w50w oil in the vague hope that it was the oil. Not sure what else to try. Any help would be great. Thanks in advance.

Donal
Donal Higgins

Any idea how many miles on the engine?
My '67 was exactly the same. I was to the point of adding STP to my 20W50 (talk about cranking oatmeal in the winter!).
My big scare was in mountain roads as I noticed a little "dip" in the pressure on sharp turns (right-handers, I think). Having read the McComb on MG and remembering that this little transient is what killed many racing MG's, I got worried.
When I got the opportunity I tore the engine down and, indeed, the bearings were worn down to the shells. Fortunately, I did this before any of them spun and destoyed the crank.

Having said that, it could be something simple like a broken or tired oil bypass spring... but I doubt it.

Try pushing in (engine off) the crank pulley and pulling it back out. If you get any noticeable play then it is most definitely time for a rebuild! If you are lucky, you may be able to re-ring and install new bearings.

Mike!
mike!

Do you have an oil cooler? Many people say that the B doesn't need one, but I found there to be a big difference in the health of the oil pressure with/without the cooler, especially on a tired engine.

ttfn,
--
Olly
Oliver Stephenson

Ditto Olly, word is that the factory started fitting them as standard to because of owner concerns of dropping pressure in hard usage, but they only work when you are moving! My roadster normally idles at around 35psi under most conditions but if left for a long time in warm ambients it can drop to 20. The book quotes 10 to 25 for a hot idle, and the 10 must really be considered an absolute minimum IMHO. First step is to verify the gauge with another, then check the relief valve. But if you are getting running pressures of 60 when driving it looks like bearings or pump.
Paul Hunt

This thread was discussed between 08/07/2004 and 09/07/2004

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