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MG Midget and Sprite Technical - Oil Cooler

Hi,
I am thinking about fitting an oil cooler to my 1275 mk3 midget.
The engine is producing around 90bhp and I suspect that the oil is getting a little too warm.
I would like to fit an oil thermostat too.
I have heard that the Mocal thermostats open too soon at about 80C. Is this too soon and what options do I have? Having one that opens at 80 must be better than allowing flow at all temperatures.

Also does anyone know what size and length pipes I need and what threads are needed on each end?
I was thinking to replace the solid pipe between the block and oil filter head rather than fit a take off plate on the oil filter head.
I am thinking of a 13 row cooler. Is this over kill? What do you recommend?

The car is used for road use only but quite spirited driving.

Are there any issues/problems that I should be aware of?

Thanks

Dave
Dave Brown

There are a number of Kits around which supply all the parts you need. An oil cooler was an optional extra anyway and the pipes replaced the solid pipe between the block and filter. The cooler was fitted just in front of the radiator, there are holes in the front panel to accommodate the pipes.

for what its worth, I have had a cooler for many years on my 1275 Frogeye and have never bothered with a thermostat on the basis there is less to go wrong! it was not fitted as an option as far as I know.

Bob Beaumont

I don't have a thermostat fitted. However, this does mean that under normal running the temp gauge never gets more than 3/4 of the way between C and N . I sometimes wonder if running cool in this way could be harming the engine in some way.
graeme jackson

Hi Graeme,
Are you talking about an engine water cooling thermostat?
I am questioning the need for an oil cooler thermostat.
I would be impressed if an oil cooler could keep the engine cool. Or do you have an oil temperature gauge?

Dave
Dave Brown

For road use a 10-row cooler should be fine in this country, and you may well want to blank it off with a cover in winter anyway.
IMO a thermostat isn't needed unless you do a lot of short journeys.
David Smith

I have found, on two 1275 Midgets that I have owned, that fitting an oil cooler improves the hot oil pressure. But you really don't want to prevent the oil getting hot, hence an oil stat is a good idea. If the oil takes an age to get up to 80 Celsius, which it will in cold weather, you are never going to evaporate off the condensed water and other contaminants that oil collects. The thermostat keeps the oil in the engine until it reaches over 80 C.

On my MGB I fitted an oil stat and was in the habit of checking the temperature of the oil cooler after a journey by putting my hand on it. To my surprise it took a really long drive on a warmish day before the cooler was allowed in the circuit. On most trips the stat never opened at all, which begs the question "does the MGB need an oil cooler in the UK?", and the answer is probably "no".

On the Midget the oil seems to get hotter quicker and a cooler seems to have some benefit, but I would definitely fit a stat.

On my MGB GTV8 with 3.9 litre engine I have no oil cooler with no apparent detriment. The MG-Rover RV8 doesn't have one either. I and the V8 experienced temperatures of 36 degrees recently in France and the engine was fine. (The passengers weren't!)

Incidentally, it is generally reckoned that if you are having over-heating problems, fitting an oil cooler won't help. It seems to make little contribution to the overall engine temperature.
Mike Howlett

Vote for oil cooler plus thermostat. Had both installed for 8 years and have found only on really hot days does the stat open but it is a standard engine whereas yours is not and likely to run hotter. For the cost (and peace of mind) it's not worth not fitting IMHO. (Apologies to those who so detest double negatives) :#)
Jeremy Tickle

High rpm pushes the oil temperature up more than pretty much anything else. So, if you plan on using more than 5000rpm for extended periods then you probably need an oil cooler.

Obviously the best approach is to fit an oil temp gauge and then find out if you need a cooler or not.

The Mocal coolers can be fitted with thermostats that open at different temperatures.
Daniel Stapleton

I've just fitted one to my Sprite after managing for 10 years without. It used to run at about 100 degrees c on a warmish day at about 60-70 mph (about 4k rpm), higher revs on track would see it up to about 120 degrees after about 3 or 4 minutes.

Not a problem for sprints and hillclimbs but I wanted to do a few trackdays so a cooler was needed. I went for a 115mm 10 row (half the width of the normal ones) and it seems perfect, on the road it stays at about 80 degrees and on track it was about 100. I've not bothered with a thermostat because I don't use it in the winter and for hillclimbs I'll either blank the cooler off or remove it altogether. I'm going to get a flexi hose to go in place of the metal filter pipe so removing the cooler should only be a few minutes of a job.

Having the luxury of a guage helps as you know exactly what is going on. Having had a cooler on a road car before I'd definitely fit a thermostat and I'd go for a small cooler. Take mine as an example, not an exact test but it looks like the 115mm 10 row cooler has reduced the oil temp by about 20 degrees.

john payne

A guage?! I think that should be gauge!
john payne

Dave Brown. I'm talking about a thermostatic valve in the oil cooler lines. Mike howlett's post, Posted 17 July 2015 at 14:30:10 explains things a lot better than I could.
graeme jackson

Hi,
Thanks for the information. All bits have been ordered and I hope to be fitting an oil cooler at the weekend (just in time for the return of autumn and cold weather!).

Dave
Dave Brown

Dave.

Here is a great install tip someone gave me and worth its wieght in gold

Coat all the threaded fittings with anti seizure compound ( same stuff for spark plugs)

Prop
Prop and the Blackhole Midget

I had one(10row) in when I still had the 1500 engine in but without thermostat.

Now have one(13row) in again with the K-series engine but with thermostat.
No need for it with normal driving but when doing high speed/revs for a while (track-motorway) the oiltemp got very warm(130C ish) hence the oilcooler+thermostat.

And yes , I only found this out because of the oiltemp gauge I installed a couple years ago.

Why not do it?
Its not rocketsience installing it and its always cool to have another gauge. ;)

For an oilcooler its very handy to have the extra 1500 cooling vents in the frontvalance


Arie

What Daniel says.

I have oil temp gauge and no cooler. On TDs, oil runs around 110-120. Recently at wet Pembrey, I was just tooling around in 3rd at 5K+ ish (light throttles), and was surprised to see the oil around 105/110C. Normally on the road in higher gears, the temp would be 90C or so.

I guess there's a deal of friction heat from the bores etc for each rev of the engine, regardless of power being produced.

IMO oil temp gauge more useful than water temp gauge - esp. without a stat, it gives a good indication of how much work the engine is doing. One of my sons has a 330i Coupe, and that has oil but not water temp gauge; there's a warning on the dash when the water temp is out of spec.

A
Anthony Cutler

I always understood that the engine's oil is responsible for roughly 1/3 of the engine cooling. It cools the bits that are not in contact with the water jacket. Crank bearings, little ends, underside of piston crown, cam bearings, rocker shaft and bushes and (not least) the oil pump itself.

It might be more than 1/3 in Midgets, which are notorious for relatively high underbonnet temperatures, reducing radiant heat dissipation.

So to me a thermostatically controlled oil cooler seems to be pretty much essential. And the peple who know these thing say it's the best way to get good oil pressure on a 1500.

I read on an American car site (I think for Corvettes, but not sure) that fitting one reduced the engine temp from (I think) 210F to 170F. (Don't quote me).

So that's why I bought one. Doesn't explain why I haven't fitted it yet, though!

I have a spare temp gauge and thermistor intended for a boat engine. I'll rig it up as an oil temp monitor if I can figure out a sensible way to do it. Then I'll record some numbers and have a baseline to find out what difference it makes when I do get around to making up the hoses and fitting the cooler. If I find anything interesting I'll let you know. Even if it's to say I wasted my money lol!
Greybeard

"Midgets, which are notorious for relatively high underbonnet temperatures"

Relative to what?
I've owned, driven and competed in Midgets since the 70s and I've never heard this before. Any source or attribution please?
David Smith

David the only source or attribution I have for this is what I have read on the internet, including the BBS archive.
I have the impression that the 1500 is worse in this respect than the A series, but it's all apocryphal - I have no empirical evidence. Only what I have read as I said.
For example I read that the 1500 Midget runs about 15 to 20 degrees hotter than a 1500 Spitfire. Same engine, different body.
This is an interesting conundrum. If anyone here really knows the chapter and verse I'd really love to know.
Thanks for raising the Q.
Greybeard

Ah, OK, maybe it's only 1500s - I don't pay a lot of attention to them haing never had one.
I was wondering if the A series Spridget runs any hotter than a classic mini for instance? Anyone?
David Smith

According to the Brother the "classic" Mini if tuned is hard to cool effectively.
Not only do they share the engine oil with the transmission, but the radiator is in a silly place.
The Brother likes them. I detest them and I've tried slapping him to no avail!
My Dad was a keen and very effective Mini tuner and he always used oil coolers. Unfortunately I can't ask him about it because he died 17 years ago.
Greybeard

Had an interesting day yesterday when my plans changed dramatically when the steering on my new mk2 Jaguar failed. Luckily, I was in Tescos car park.

That meant that I had some time on my hands as I couldn't get the Jag to the rolling road and couldn't change its gearbox oil afterwards.

So I started to fit the oil cooler in the Midget.

It didn't start too well as the bracket from MGOC was too big for the front valence. I cut the middle out of it thinking that the oil cooler could support itself.
So that is now in. Next I looked at fitting the pipes and noticed that one of the previous owners has run the front wiring loom through the oil cool pipe hole.
I now have to pull the front loom back through the hole and reroute it through the correct hole. There are a few dodgy connections in the front loom and a pair of driving lamps to remove, so I think it is an opportunity to make good. A job for tonight.

Not rocket science as Aria says, but as simple job has been highjacked by several others causing it to now take much longer.

Now, having seen Arie's valence holes and low mounted oil cooler, I am thinking I may need to change my plans. Do I mount it lower and cut holes in my valence? It has a valence with the indentations...

Dave
Dave Brown

On my 1500 engine I had the pipes run thrue these two holes, one was already there(factory original?) and created the otherone myself.
Because of the external oilfilter on my K I had to run the pipes/hoses lower so run them thru the heaterpipe hole (ive never used a heaterpipe anyway).


"It has a valence with the indentations..."

Dave, is your midget a pre 1500?
Don't know how you are about originality but if the indentions are already there it probably is a 1500 frontvalence panel and you might as well open it up there.
In this position it doesn't block/interfeer the coolantradiator much.

My bracket was an original Brittisch Leyland modificationpartnr and when I ordered it in the late nineties (pre cheap reproduction sh*t) it fitted perfectly.



Arie

Ive placed the thermostathouse just after the oilfilterhousing on the 1500 bumper-beam.
Could have replaced the oilfilter housing a bit to the rear but didn't bother much, it fits fine now.


Btw, on the top of the oilfilterhousing ive drilled a hole, fitted a 1500 electronic temp.sensor for the oiltemp. gauge.
Maybe not the most ideal place but found it too much hassel to get the engine out to drill one in the K-sump.
As the oil comes straight from the sump with only 15 to max 20cm pipe between it I think its a realistic temp.reading point.


Arie

for those intrested:


Arie

IN & OUT, oilpressure take of and tempsensor


Arie

Okay, forget about the sender on the photo.
After stiil having sone off-tempatures I visited a rollingroad and found sometimes the temp. was completely off: +130C on gauge to 95C in oilfilter...

Now found out that for an oiltemp. you need a oiltemp.snesor(not a waterone like mine) and a relay...
Smith tell on their site accept don't offer them for sale...
You sell the gauge, don't include a warning on whats needed, you do write on your page about it tho but don't sell it...
Anyway, now found a company who does(so they say).

Will be continued!
Arie

Conrad.nl sells al kind of sensors and gauges, I have this one in my midget..
http://tiny.cc/dp6b2x
Alex G Matla

Finally getting close to finishing mine now! Hopefully the engine will be going back in this weekend after a 6 year restoration!

However I have a few extra dials on my dashboard now so wondering the best place to put the oil temp sender...?

I have an oil cooler but there seems to be no place to put it with the kit supplied.

Is the best place to drill a hole into the sump and stick it in there?

It's a 1500 btw :)

Thanks

Simon
S J Dodd

On my set up... im using an electric oil pressure gauge

what i did was rework the oil sump drain plug so the sensor is the actual drain plug ... to drain the oil i just remove the electrical sending wire then then remove the sensor plug and out flows the oil... no drilling holes and welding in bunggies into the sump pan a

and i think you get a better reading of the temp of the oil because its measuring from the oils lowest point

prop
Prop and the Blackhole Midget

Thanks for that Prop,

I did consider that but then thought that if I hit one of the many speed bumps in this country it is likely to hit that area more than anything else... Glad to know you agree that the sump is a good spot for it though :) Thanks for that.

Simon
S J Dodd

how about one of these ?
just sandwiches between the oil filter and its mounting.
gives 2 tapped holes for oil pressure and oil temp sensors.
Available in lots of colours too..


Andy Phillips (frankenfrog)

Mine is in the sump, opposite side to the drain and high enough up so the sensor line misses the chassis leg. I just brazed the fitting into the sump.
john payne

Cheers for that suggestion Andy, nice solution but I don't think it will fit in my engine bay as I already have a sandwich plate in there for the pipework that goes to the oil cooler...

Cheers John, I reckon I'm gonna drill a hole in the sump and then fix it in place with a couple of washers and a nut... Fingers crossed :)
S J Dodd

Fitting an oil temp to a VW air cooled engine and the consensus appears to be to fit the sender/sensor in the sump for the most accurate readings.
Jeremy Tickle

I just drilled a hole in the sump, and then bought a couple of brazing rods and a camping gas type blow torch from my local DIY store. Probably not the neatest bit of brazing but has never leaked.

ps with the sump off the car of course.

Dave
Dave Barrow

S J

if you hit that high up on a speed bump... your going to have alot more serious issues and distruction then a damaged drain plug
Prop and the Blackhole Midget

where do you get those from Andy?
Rob Armstrong

Rob,

Source looks like www.vbautoparts.com from a google image search of the image posted.
David Billington

Yes VB autoparts is a local place in Bangkok.
However they are sold at many place over here.

I just checked Merlin motorsport website and Demon Tweeks and they both have them
Andy Phillips (frankenfrog)

This thread was discussed between 17/07/2015 and 05/03/2016

MG Midget and Sprite Technical index

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