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MG Midget and Sprite Technical - Low Oil Pressure when warm & idle - Midget 1500

Hi everyone, I just bought a 1977 midget 1500 in the UK, after 15 years of longing!

Took it for a first decent run today, and noticed the oil pressure got lower as it warmed up. It got down to about 8lb pressure at idle after 6 miles or so, and eventually stalled as I got it home, presumably due to the lack of pressure. It had an oil & filter change just before I bought it (20w50). Couldn't see any leaks underneath, and engine temp seemed fine. Pressure increased with revs, but really struggled when idling, so I'm a bit stumped. I'm pretty inexperienced when it comes to car mechanics, but planning to learn and service it myself up to a point.

If anyone has any ideas or can offer any advice, even if it's telling me I've picked up a dud, I'd be very grateful!
R George

Welcome R (Robert, Richard?)

That’s not good.
The 1500 is known to have durability problems with the big ends as they are very narrow- engine was stretched from a 800cc Standard engine over the years and with the rubber bumpers gets rather hot which can increase wear etc -hence an oil cooler is a good addition.

Does it make any knocking noise ?
Can you check pressure with another gauge ?
If it’s making noise do not run it as you could wreck the crank or worse break a con rod etc.

Did it suddenly loose pressure ? If so look and see if there’s an obvious leak - is the new filter screwed on tight - is the sump still full of oil ?
Did it have low oil pressure when you bought it ?

The other problem they can suffer with is the crank thrust washer wearing and falling out.
If you get someone to depress the clutch whilst you watch the front crank pulley - does it move forward as clutch depressed? If so likely thrusts have dropped out.

You could drop the sump and have a look at the big ends and thrust and possibly replace, for a short term fix.

Unfortunately for a long term fix it maybe an engine
out and overhaul.

I’m sure others will respond shortly.

With Midgets it’s easier to sort mechanical things - body rot is the real problem - hope you get it sorted and enjoy Spridgets !

Richard B.
richard b

If you do check thrust washers do this with the engine off !
Don’t want any accidents! Car leaping forward etc !

R.
richard b

Could be a poorly seated oil pressure relief valve?
Pressure on the 1500 when warm and idling shouldn't go much below 25 or maybe 20 psi.
GuyW

Just on an off chance--the 20/50 oil, was it a mineral oil or synthetic---if it's synthetic, there's the problem
willy
William Revit

Assuming this was a private sale* then I'd start by draining the oil and examining for metal (silver/copper/brass colours), and maybe even cut open the filter** and see what is in there. If you find any non-trivial quantity then that's bad and you are probably looking at an engine stripdown; if not then add new correct spec oil and filter from a reputable MG supplier and try again; ideally get someone who knows what the engine is supposed to sound like to listen as it starts from cold.

"and eventually stalled as I got it home" -> seems odd if no nasty noises; what was the actual engine temperature, has it still got coolant in it, could it just be running hot?

* If it was a dealer then just take it back as cars have to be free of faults when sold, if you have an insurance policy with legal cover they can probably give you some words to use.

** There are various horror stories heard of people installing new filters and leaving shrink wrap or labels on them which then block up the flow.

"I'm pretty inexperienced when it comes to car mechanics" -> read up on safely jacking and supporting a vehicle before going underneath, ask again if unsure.
AdrianR

Hello R, welcome to the family!

I have added some of my answers to your original text, highlighted by **s. More thoughts to follow... Out of interest, where in Bristol are you? North, middle or South? If you are Cheltenham side, I could be tempted to pop down and help out if you need it?

Took it for a first decent run today *great!*, and noticed the oil pressure got lower as it warmed up *normal, as the oil gets hot it thins*. It got down to about 8lb pressure at idle after 6 miles or so *not good, 8lb is low, and 6 miles isn't far enough to get it properly hot*, and eventually stalled as I got it home, presumably due to the lack of pressure *lack of oil pressure shouldn't cause stalling, different issue there, we can come back to that!*.

It had an oil & filter change just before I bought it (20w50) *it's a start, at least they used the correct grade oil*. Couldn't see any leaks underneath *must not have any oil in then! - joking!*, and engine temp seemed fine *good*. Pressure increased with revs *normal, pump is connected to crank, so more revs, more oil flow*, but really struggled when idling *concerning*, so I'm a bit stumped. I'm pretty inexperienced when it comes to car mechanics, but planning to learn and service it myself up to a point. *good stuff, wanting to learn is good attitude, there will be a lot to get your head round!*

If anyone has any ideas or can offer any advice, even if it's telling me I've picked up a dud *... no such thing, anything is fixable! :-)*, I'd be very grateful!

Malcolm

This thread was discussed between 11/02/2024 and 14/02/2024

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