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MG Midget and Sprite Technical - Oil Pressure 1500

Just had a great time in Malham and surrounding area for a few days. Car pulled well and drove lovely in them thar hills. (some more than 1:5) :-)

On the way back yesterday on the A1M the traffic built up and we crawled for a while. Temp went up as expected but all OK on the coolant front. The main problem was oil light came on slightly from time to time in the crawl. Its never done this before. A quick rev and all OK. Got off motorway, stopped and checked oil. A bit low but not down to lower mark on dip stick. Put some oil in and came back through Doncaster until South of A1M then back on A1 and all OK.

Went to Ilfracombe a few weeks ago (Nearly 600 miles round trip) and no problems with some steep hills but no real crawls in traffic like this.

Anyone had anything similar? Is this a known phenomena?

Cheers, Dave
Dave Squire

Dave,
I take it you don't have a gauge?
Fit one to really see what the oil pressure is doing.
Do you get any bottom end rattle when starting from cold? If not, consider changing the pressure switch. If it does rattle then you could be looking at a crank refresh but to be honest they will run like that for years...

Best of....
MGmike
M McAndrew

Hi Mike,

Checked oil this morning and all OK after steady troll down 40 miles of A1 last night. Cursory glance at pressure switch connections and its oily and dirty. Will start with a clean up after a short run this morning.

Cheers, Dave
Dave Squire

Do you have an oil cooler Dave?

Malc.
M Le Chevalier

Dave - to address your original post "Yes and Yes".

I have seen oil pressure dropping to alarming levels at hot idle on my 1500, which is fitted with an aftermarket OP gauge.

And yes - 1500s are notoriously hard on their oil. I speculate that BL discontinued the OP gauge for this reason, so that customers wouldn't know their pressure was low when hot (or am I being cynical)?

What I don't know is if the same engine in the Spitfire suffers the same syndrome; it would be interesting to find out.

However, as Malcolm suggests, a thermostatically controlled oil cooler kit is deemed pretty much essential by the people who know the engine way better than I do, which is why I bought one.

It's not helping much because I haven't got round to fitting it yet, but I will soon!

An electric OP gauge is an easy addition, but it's one more thing to worry about. I can't take my eye off the bloody thing!
Greybeard

No oil cooler just standard car apart from ignition. Long journey to Ilfracombe made it hot but not much standing apart from Taunton where we were in traffic at Lunch time. Went down the hill at Glastonbury and across town. Some road works at the time so must have took half an hour of stop starting.

Agreed fellers it seamed to be when very hot.

However have now used car OK today on shorter journey's. (4 lots of 7 miles with some in town traffic lights and islands). Up to temp OK. However tick over down below 1000 rpm if standing a while like at lights, and then of course the green light, so I am wondering if my last fill up was contaminated with something or at a tank with water in it. It was a main roadside services on the A1.

Dave Squire

How low does the pressure have to be for the light to come on ,my 1500 at tick over when hot shows around 20psi but has an oil cooler on
mark 1500 on the road Preston Lancs

Dave,

When we had a 1500 we fitted a cooler to help pressure in the very hot/traffic situations - it seems underbonnet temperature/air flow was much worse in the 1500 Midget than a Spitfire and hence raised oil temps.

I replaced the big ends as a precautionary measure and was surprised that copper was just starting to show on one shell - but I seem to remember you have already had the sump down a little while ago ?

An extra oil filter change is also a good investment.



R.
richard boobier

Gday Dave
What oil are you running? 20W 50 is what the book says. FWIW my 1500 has a thermostatically controlled oil cooler and I never see the pressure drop below 70PSI, but my engine is fresh and I'm running 20W 60, which I put in because I wasn't sure what to expect after the long lay up time during the rebuild. Next change it goes back to 20W 50.
HTH Cheers
Rod
R W Bowers

Yes Richard, I changed the big ends, mains and thrusts with huge guidance from this site about two years ago.

Since then I have done 12000 miles in all weathers and conditions throughout the seasons as a daily drive.

Until now no problems with low pressure at all. Even when it is used by the missus for work in a nearby town that she has to crawl through.

Hi Rod, its 20w50 mineral. As I have a fair oil leak at the moment it is topped up as and when.

When I used some 10w40 way back (I was given some when I ran out of oil far from home 2 years ago) it seamed to percolate through every gasket and cause leaks although it cleaned the engine innards wonderfully. I have therefore stuck with 20w50 religiously since.
Dave Squire

The problem is identified and will be sorted.

Since last summer I put some pancake filters on so I could get to adjust the carbs easier. The low oil pressure only happens at low revs. That can be expected. The low revs only happen when engine hot and standing still. Therefore the engine is using very hot air when standing from the engine bay because of the pancakes.

Was in heavy traffic on M1 by Sheffield on Thursday however while engine hot we did not stand in traffic (at least walking pace most of the time) and no problems.

Old air filter box will be found and replaced on engine with tubes to the front grill as standard this weekend / asap next week depending on if I have some standard filters for it.

Thanks for all the help. Cheers, Dave
Dave Squire

Good spot Dave. I never thought of the air intake routing. I'd be interested to know how it turns out.
Greybeard

Gday Dave some time back I posted on this topic some improvements to the standard airbox and hoses which comprised increasing the tube diameter to nearly 50mm. (see pic)this worked a treat and now the motor revs freely to 5500 at which point I change gear, not wishing to confirm the "floppy crank" theory for the 1500. HTH
Rod

R W Bowers

Found part of it today. The rest is down behind the work bench no doubt.

Good thinking Rod. Its probably your initial post that came back to me about the hot air in the engine bay. Nice work btw.

Don't over rev the engine; its all true according to everything I have read. Good for 100 + bhp but at lower revs than A series.

Cheers, Dave
Dave Squire

This thread was discussed between 26/06/2015 and 06/07/2015

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