Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Oil Cooler / Oil Pressure

I plan to install an oil cooler on my 1500 before the hot weather arrives again, but I'm wondering what that would do to the engine oil pressure, since the pump would have to move a volume of oil the through the filter, hoses & cooler instead of just through the filter & then to where it was intended.

Should a higher volume pump be installed, tweak the oil pressure relief spring or just install the cooler & run it?

Any ideas?

Dave Rhine

Dave Ive never heard of this being an issue, but Id install 1st, see what it does then tweek the oil pressure valve if needed...I cant imagine you would need a new oil pump


It shouldn't have any effect at all, other than needing to add some more oil to the engine due to the increased capacity!
Dave O'Neill 2

It's clear the oil cooler will provide additional resistance to oil flow. For moderate oil temps, it may slightly reduce the oil pressure at the bearings but the reading on the (upstream) gauge should increase slightly.

However, the cooler will prevent excesive oil temps and so:

- prevent breakdown of oil and additives
- avoid the very low oil pressure due to over-thin oil whereby the bearings are not fully protected

This is the reason to use a cooler; the other effect is less significant. No need to change pump etc.

Anthony Cutler

Thanks guys...I didn't think it would adversely affect OP, but I'm still on a Spridget learning curve!

Also, does anyone use an in-line oil thermostat? I've seen them advertised & it makes sense to me.

Dave Rhine

I have an in-line thermostat, it is strongly advised 'cause cold oil is no good either.
Unfortunatly I can not yet comment on its influence as one of my hoses' nipple (?) broke off and I fitted an oil temp gauge (sump temp) in the same session.
So at the moment I'm running without cooler...
Alex G Matla

You shouldn't need an in-line thermostat if you buy a MOCAL sandwich plate from Think Automotive because it comes with a built in thermostat. It also allows you to fit a spin off filter with an anti-drain valve which is beneficial in that oil is prevented from draining to the sump overnight.

From The Think Auto website:

Customers in the USA requiring Mocal products should contact:
BAT inc. 2263 Industrial Boulevard, Sarasota. FL 34234
Tel. (941) 355-0005 Fax. (941) 355-4683

With respect to oil pressure, then the way to go is to fit a longer oil pressure relief valve spring - these can be obtained from Moss. Alternatively the oil pressure relief plunger can be shimmed.

There is no 'High Flow' oil pump for the 1500 engine. However, consideration should be given to using the later spec pump which has an angled pick up which sits deeper in the sump (oil pan) and resists surge better. You should also check the oil pump rotor clearances and endfloat are at the minimum quoted figures:

Inner Rotor endfloat 0.0004
Outer Rotor endfloat 0.0004
Rotor Lobe clearance 0.010
Outer Rotor-to-Body clearance 0.008
Deborah Evans

Thanks Deborah

I haven't worked on these cars since the 70's. I'm on a re-learning curve at present.

You've given me a wealth of good, expert information.

BTW, what oil filters do you use/recommend?

Dave Rhine ('78 1500)


"Should a higher volume pump be installed, tweak the oil pressure relief spring or just install the cooler & run it?"

Typically when we refer to an engine having low oil pressure, then we are talking about hot oil at slower engine speeds. Under these conditions the system is working well under the relief valve set point, i.e. the valve is fully closed and 100% of the pump displacement is going round the engine. Under these conditions no increasing of the relief valve spring force is going to change this. So I would advise this is unnecessary.

However what is regulated by the relief valve is the faster running cold oil conditions, now if you want this to be exactly the same post cooler fitting as it was prior, then yes shimming the spring would be an option, although it's probably unnecessary, as cold oil simply isn't your engineering 'worse case'.

I'd also check you realy need a cooler, because it does represent another thing to go wrong on your car. If the hoses rub through you'll dump the oil in under a minute, and a road side repair will see you thumbing a lift to the nearest garage to buy more oil.

James (Lubrication Product Development Supervisor for Ford Euorpe)
James Eastwood


Thanks for the input...

I'd feel better running an oil cooler due to the weather conditions in my part of the world. It is generally hot here from April until October, with 95F+ through the middle of summer!

To me, a cooler would be a little added insurance for the engine bearings...the 1500 doesn't have that great a reputation for bearing life anyway.

I'll install the cooler & monitor oil pressure...make adjustments if needed.

Thanks again,
Dave Rhine ('78 1500)

The 1500 engine in the midget is very close to the limit vis a vis oil film breakdown for a number of reasons as I stated in another thread.

This is exacerbated in the Midget (relative to the 1500 Spitfire) owing to the fact that the Midget is shorter geared coupled with the fact it runs a far hotter engine bay.

For ANY sort of 'fast rod' work an oil cooler is essential.

Deborah Evans
(Building successful competition and fast road engines for over 25 years)
Deborah Evans

With an oil cooler fitted (no thermostat) my cold oil pressure isnt quite so high ( I assume the flexy hoses are the culprit here ) but the hot oil pressure is better
neil munn

All the new Mocal sandwich plates have that integral thermostat now so if you have a Marina/Ital sandwich plate you might want to upgrade to the later plate.

I think the only difference between the Marina/Ital Plate and the 1500 plate is the fixing bolt 'thing'.

Daniel Thirteen-Twelve

I took Deborah's advice & installed an oil cooler.


Dave Rhine ('78 1500)

Got the kit from Moss, very easy & neat installation.

Dave Rhine ('78 1500)

I opted for an external thermostat in case I want to bypass it for our sweltering (95 to 100 degree) Summer months down here.

I'll keep an eye on the oil pressure & tweak the pressure relief valve if necessary.

Thanks for the input & advice.


Dave Rhine ('78 1500)

Dave - what's with the in-line thermostat when the sandswich plate already has a thermostat?
Daniel Thirteen-Twelve

The sandwich plate I used doesn't have a built in thermostat...straight through, open ports.
Dave Rhine ('78 1500)

Looks like the same thermostat I run on my 1275. Working well thus far. As far as OP issues with the cooler, I don't believe BL made any changes to the A-Series engines that got the optional oil cooler vs the ones that went to miserly owners who did not spec a cooler, so I would not lose any sleep over it. IMHO, there is no downside to running an oil cooler with a thermostat. Lookin good!
David "not that BL can be considered authoritative..." Lieb
And we won't go into my just having had to splice the wires leading to the hatch of my 2002 VW GTi that had broken off in the rubber sleeve. German quality appears to be an oxymoron! The insulation on the wires used simply was not suited to sub-freezing temperatures; doesn't it snow in Germany???
David Lieb

I got the cooler location idea from this:

Dave Rhine ('78 1500)

But the more I look at it, the more I can see a stone ruining my day!

I'll come up with some kind of screen on the backside of the valance panel holes.


Dave Rhine ('78 1500)

The bride asked me again yesterday: "Aren't you about through with that little car?"

I just laughed...

On to the next project...

Dave Rhine ('78 1500)

David Lieb: had to do that myself on the golf although i found the loom on ebay for not much. first the door open warning goes, then central locking goes, worryingly the heated rear screen wire was about half way through too... 'quality'!
If you need to do it again, and can find the loom, the connectors are just beside the rear seatbelts, left hand side - half hour job to replace. simples!

C Robertson

This thread was discussed between 01/02/2010 and 22/02/2010

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.