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MG Midget and Sprite Technical - thermostat in or modified

Hi there

I run a heavily modified 1275 (EFI, supercharged) and modified my thermostat a bit (few holes in the ring).

What are your experiences with thermostats, especially regarding the bypass / heater
a.o. arnold

Hi

If you do decide to run without one (not that I would want to do this for a non-race car) you might want to fit one of these: http://www.minispares.com/product/Classic/Cooling_heating/Water/11G176.aspx?0703&ReturnUrl=/shop/classic/Cooling~heating.aspxBack%20to%20shop

Also would not want to block off the heater connection as apparently this can cause head cooling problems (but there are plumbing options to protect your head while deleting a heater)

Wiser advice should be along soon.

Cheers
Mike
M Wood

The thermostat offers temperature control, within its range, allowing a faster engine warm up and it helps control temperature within its range.

You could try a stat that opens sooner to see if that gives what you want/need.

Much more powerful cars producing, and holding, much more heat have a thermostat fitted.

What's required and good for track cars isn't necessarily good for road use cars the circumstances and environments of use are different.

Unless you're going to restrict your use of the car to limited times when the thermostat would be doing very little you might as well keep one fitted.

The more power you have the more (wasted) heat you will have, what other modifications have you made to get cooler air in and hot air out?

Nigel Atkins

https://www.calverst.com/technical-info/cooling-how-it-works/

This is about the mini, the engine is the same

Flip
Flip Brühl

Thx guys. Car doesn't fully warm up in the winter (70 degrees max)
a.o. arnold

Quick thoughts -

oil cooler
. do you have an oil cooler fitted
. does it have an oil thermostat fitted
. do you blank off the oil cooler in winter

which 'water' stat is fitted - 74c/82c/88c

is your gauge accurate when showing 70c

do you have an engine driven cooling fan fitted

do you have an electric cooling fan fitted

do you have an engine driven fan plus electric fan

what temp is shown on the gauge in summer.


My current and past C-N-H gauges have always had the needle showing lower than 'N' summer or winter, see photo two.






Nigel Atkins

Most important question is:
Do you have a bypass hose fitted?
If yes than just fit a normal thermostat
If no one 6mm hole will suffice
O K

Good point, I took it a bypass and heater were fitted by the wording of the original post but I could well be wrong.

A few holes in the ring though, painful!
Nigel Atkins

Surely the point is that if it doesn't heat up beyond 70c in the winter then the thermostat won't be opening and radiator, fan etc are all irrelevant at that stage, with no circulation taking place. The implication is that the engine would be self-cooling with little or poor pumped circulation even within the block.

I'm not convinced. Where is the 70c being measured, and has the guage been checked?
GuyW

Actually, the holes in the stat ring aren't going to help with warm up of the engine. If the stat has the jiggle pin or small nick out of it that would be enough (for standard set up at least).

We covered this in a recent thread, I'll see if I can find the photo.
Nigel Atkins

Guy,
that's the whole point, how accurate components are, the gauge, the stat. A 74c, or other stat, with loads of holes is partially open.

I've little faith in any standard water temp gauge readings on these cars, with the probe just before the stat it ought to show about same as what the stat is allowing, the last three gauges on my car never have.

An oil cooler without oil stat will be cooling the oil especially if not covered.

Depends on the driving and conditions but I'd have thought a supercharged motor would get warm at some stage even over winter.
Nigel Atkins

I know "thats the point", Nigel. That's why I asked!

If the engine genuinely isn't warming to 70c and the thermostat isnt therefore opening, then even with holes drilled in it the circulation in the block would be be compromised and likely to be resulting in hot spots. But with a performance EFi engine it seems surprising to me that the engine is producing so little waste heat, irrespective of the ambient winter temperatures.
GuyW

Yes dear, that's why I asked (even) earlier! :)

Are you sure it was your sister that fell out of the Mini Countryman and not you, parenting was so different in the last millenium. :)

Nigel Atkins

As promised, example of (92c Delco with debris) stat with jiggle pin circled.



Nigel Atkins

Hi guys, a few answers as far as possible:

Quick thoughts -

oil cooler
. do you have an oil cooler fitted >> YES
. does it have an oil thermostat fitted >> NO
. do you blank off the oil cooler in winter >> NO

which 'water' stat is fitted - 74c/82c/88c >> NOT SURE

is your gauge accurate when showing 70c >> GAUGE IS RUBBISH, I READ IT OUT WITH THE COMPUTER AND MEAGSQUIRT. A SENSOR IS FITTED

do you have an engine driven cooling fan fitted >> YES

do you have an electric cooling fan fitted >> NO

do you have an engine driven fan plus electric fan >> NO

what temp is shown on the gauge in summer. >> AROUND 80

I ADDITION, I HAVE NO OVER HEATING ISSUES


Do you have a bypass hose fitted? >> NOT SURE
If yes than just fit a normal thermostat
If no one 6mm hole will suffice >> IN WHAT?
a.o. arnold

My 20 cents worth--and probably worth 20 cents as well-----
If it runs at 80c in the summer, you're a lucky man and obviously your cooling system is working well
If it's not getting up to temp in the winter, the only thing that controls that is the thermostat, by adjusting the coolant flow--you are getting too much flow that the thermostat can't control by having too many holes in your thermostat
IF you have the bypass hose fitted then a single little 2mm 'max' hole in the edge is enough to let any trapped air through without compromising the operation of the thermostat
I suspect you have too many holes in yours
How many holes and what size are they in your stat.
It'd be interesting to know exactly what temp the thermostat is rated at-
On a friend's Targa midget (highly modified) he had issues with coolant circulation with no3-4 cylinders blowing the gasket between and the only fix for it was to keep the heater tap turned on to get some circulation back there, eventually modifying the heater hose layout with an inline heater tap and a cross link like a capitol H with the hoses so that he still had circulation with the heater turned off

willy
William Revit

It would be very useful to have photos of the cooling/rad/stat-bypass set up to be sure of what you have and how to proceed.

A quick easy thing to help straight away is to securely fit a blanking panel on the front of the oil cooler (see below for why).

Next I'd just fit a 82c stat with a jiggle pin but without extra holes in it (see Willy's post and below for why).

Having an oil cooler fitted without an oil stat means the oil is being cooled when it is already cold or very cold, the blanking plate is fitted in winter to reduce the cooling on the oil cooler.

The oil stat does the same as the water stat (in broad, basic terms) in that it opens and closes when the oil is at a certain temperature, so not cooling when not needed.

If you 74c water stat fitted then this will open at a lower temperature slowing the warm up of the engine.

The standard engine driven fan is running straight from start up and before the the engine warms, when it not needed or wanted.

As Willy has put the holes in the water stat will bypass it.

Adding all of above together would mean a longer warm up time at least and lower temperature running if heat can not be built up enough and retained.
Nigel Atkins

I'll check coming weekend. I use EFI coolant sensor to measure temp
a.o. arnold

no need to shout
I don’t check the BBS daily but will reply.
To clarify:
If you have no bypass hose the fit a thermostat with a 6mm hole in the edge of the thermostat (where Nigel has pointed out the jiggle pin)

And help the poor car a bit, 82 or 88 degree thermostat and wrap some cardboard around that oil cooler in winter .
O K

Where is the sensor located in the cooling system?

Don't worry too much about figures or comparing figures, as long as the car is running well then those are the figures to your sensors and gauges/readouts. Yours might say 70 and 80 mine might show 65 and 75, someone else's shows 82. As long as your readings operate your systems correctly for your other electronic systems.

You could use your standard Spridget gauge as just that, a gauge, where ever the needle points is fine as long as the car runs well. Only worry when the needle remains at some showing different to usual, or moves more than usual, for no good reason.

My water temp gauge (and the previous) normally shows where the white line is in summer, as you can see it is well before the 'N', if it was on the 'N' the car would be running (too) warm.

I could move the needle so that it normally sits on the 'N' or blank out the 'N' and put another 'N' where the needle is now. Or blank out the 'N' and just have 'C' and 'H' on the gauge, as some later gauges had (a different example as photo).






Nigel Atkins

Hello O.A. Arnold,

I wrote an article (In Duch) for The dutch Healey magazine about (under) cooling. If you are interested I 'll send you a copy

Flip Bruhl,
mail: flip at bruhl point nl

Flip Brühl

Great Flip, I'll email you

Numbers are important when one uses EFI. I also do use the gauge, just as an indicator

My (EFI) sensor is in one of the hoses to the heater. I gues a better location would be in the housing of the thermostat?
a.o. arnold

a.o.,
perhaps I did not make myself clear previously, the numbers are important to the EFI, but exact numbers on the standard Spridget gauge for road use a lot less so, which is perhaps one of the reasons they dropped the numbers on the gauges later.

The usual location for the water temp pick up on a standard road car is the cylinder head just before and below the thermostat.

That is where mine is located but still the gauge reading does not tie in with what temperature the stat would begin to open at.

The best location for your EFI temp sensor would depend on the cylinder head you have and the plumbing arrangement and components of the cooling (heating) system you have, hence the request for photos.

I barely understand the basic system so getting into EFI gets beyond me but others on here will know but the basics are that the sender and receiver should be a match to each other and the location of the sender and the plumbing arrangements could make a difference to the readings given.

I would have thought that a supercharged engine driven in a spirited manner even in winter would get warm quite easily.
Nigel Atkins

I checked. No bypass. I run the MG Metro head.

Sensor is in hose from the pump to the heater
a.o. arnold

This thread was discussed between 08/01/2021 and 17/01/2021

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