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MG Midget and Sprite Technical - Too Many Holes?

So I've put on the head which does not have a bypass hose and drilled four 6mm holes in the thermostat and blocked off the water pump.

I have had an issue with my daily driver so am using the Midge (with the roof down) for work and have notice that when running at 70mph the temp gauge is reading close to the C when stopped at traffic lights it goes to 'N'.

To get it run closer to N I am going to fit a new thermostat - should I bother with the holes in it?

Shaun

Yes. I assume your current 'stat worked OK earlier. Check what holes this has and copy.

A
Anthony Cutler

The current stat is the one that worked fine with a different head which had a bypass hose so no need for holes in it.

I just modified it with the 6mm holes as suggested in the archives.

I was going to try a new one without drilling any holes. Is this wise bearing in mind no bypass hose.
Shaun

Shawn, in my experience, you only will need one hole to allow it to 'bleed' coolant whilst warming up, it appears the 4x 6mm holes would appear to be allowing too much circulation.

Mark.
Mark T. Boldry

In the colder weather these last few days mine has been running too cold as well. I put an MG head on earlier this year (no by-pass) and so I drilled a couple of 5.5mm holes in the 82 deg thermostat. I think for my car that is actually too much.
I am going to change it for the winter to an 89deg stat with just one by-pass hole.

Guy
Guy Weller

Shaun mate,

Mini spares do a sleeve, that should have the right number of holes.

Another way would be to let some oil out of the engine, that would bring the temeprature up a bit. You could drain it all actually, then add oil until the temperature is correct that would be a good way to do it.
Brad
Brad (Sprite IV 1380)

Brad, Oil...?

Mark.
Mark T. Boldry

Brad - WHAT are you talking about!?
Steve Clark

Shaun,
I didn't think you were allowed out to play just yet! I hope Mum and babe doing ok. When I put my MG Metro head on I put 1 hole in the 'stat about 4mm I think. Not noticed any difference in running temp.
Whats up with the day car? Never trust a car with a red line at 9k, I say.
Steve Church

Talking about size. Normally drill 1 or 2 3 mm holes in the flange.

Just to let air escape and create some flow for earlier opening and if anything goes wrong there is also some margin.

5,5 ot 6 mm holes and more then one seems a bit steep to me.
Bas Timmermans

Brad

Got no need to empty any oil to get it hotter, with the bore wear I've got it burns out quick enough but has not improved the heat. I find it's easier to burn it instead of coating the underneath with it like you!!

Steve

Babe and Mum are good thanks, nearly 20 days now....The S's battery went fut and not holding a charge had a suprise when I asked the dealer how much a replacement was!!! A massive £47 was not worth phoning around apparantly Honda have made sure they have competitive prices for that item and got one next day.

It is now replaced but I have enjoyed driving the Midge so much I have used it for the rest of the week only putting the roof up today.

Been bloomin cold without the heater though, I have been thinking of ways of improving the heat well so it can be directed to the screen/footwell independently.

Rest

Seems obvious that I have drilled too many holes in my stat so will order another and drill just a couple of 1.6mm holes in it.

Shaun

Steve C / Mark T,

just giving Shaun some light hearted advice, he knows what i'm like.
Shaun,
at least i can mop up my garage floor & reuse the oil, i quite like the gritty texture, perhaps you could give it a go for me.

As for your heater have you got all the air out of it, i fitted (honestly this time) a bleed valve on the heater rad outlet, on the Sprite.
Brad
Brad (Sprite IV 1380)

Im pretty sure BRAD is talking about using Veggie oil, like in the post with the citron 220,000 mile car that had the blown up engine...LOl


SERIOUSLY----
If you go to mini mania, or mini spares to tech articals there are several articals on how many holes and what size the holes need to be in the stat for a non by-pass coolant system, I want to say keith calver wrote them, Im pretty sure they where talking about certian holes and diminsions for differant weather extremes...like 8 small holes for hot weather and 2 large holes for cold weather...intresting read to say the least.

prop
Prop

Thanks Prop,
This is what Keith Calver says about it:

<<I would strongly advise using a thermostat in ALL road cars, of at least 82 degrees to make sure the correct running temperatures are achieved. Fit a thermostat that has had six or eight eighth-inch (3mm) holes drilled around the periphery. These holes allow water to circulate before the engine is up to temperature and the thermostat opens>>

He also says that the optimum temperature for a road-going A series is "85 to 90 deg"

Guy
Guy Weller

Didn't thermostats used to have a bleed hole in them at manufacture? (with a little pear shaped brass blob that jiggled about in the hole)
I haven't looked at one for some time.

Dave
Penwithian

Aren't the temperature and operating conditions for transverse A series different to inline engines such as the Spridgets

ISTR reading that having the rad by the edge of the wing and with the side of the block in the full airflow (except the plastic splash cover) made Mini temperatures different from those our cars operate under

I have one hole in Lara's stat and I don't get any problems (cue O/H and HGF next run out after the apparent complacency)

I am running an unmodified VDP/MG Metro Head with factory big valves

Which will be in line for a little gentle Vizarding this winter and a raise in C/R and some advanced Megajoltery stuff to run it (courtesy of Toby)

Bill

Bill,
I don't understand how transverse and in line operating temperatures would be different.
Yes I can see that the transverse may dissipate its heat in a slightly different manner as you describe. But why would the methods of heat dissipation mean that the actual operating temp should be different?

Guy
Guy Weller

Wasn't there a problem on early Minis due to the temperature gradient between the front and rear sides of the transverese engine?
Or is that what Bill is saying.

Dave
Penwithian

Dave seems to remember what I thought about too

I cant remember where it came from but it's just a vague memory the thread has woken up...

I wonder if the number of holes would differ under differing heat loading is all, Mini blocks running a bit cooler than inline-to-airflow Spridgets thus requiring more holes for the head being hotter than the block.

Just my head having a "bluesky" moment for a change

as I say, so far, and including temperatures in excess of 100F at Le Mans a couple of years ago having one hole only hasn't affected Lara
Bill

6 to 8 3mm holes? Is there any flange left with so many piercings?

IIRC the reason for drilling a hole or 2 is just to get air out and to open the thermostat earlier because hot fluid gets around. AND if its sticky with 1 or 2 holes its not a disaster.

If you drill 8 3mm holes you should better use a blanking sleeve. warm-up time in cold weather will be a lot longer so does the wear.
Bas Timmermans

Driving into work yesterday and the temperature behaved itself except when I pulled away from a set of traffic lights.

So for most of the 10mile drive at 70mph the temp gauge was 3/4 of the way to N.

Pulled into the supermarket petrol station to discover it was closed. (How annoyed was I that no signs mentioning this as I pulled into the supermarket!!!!)

Sat at the lights and the gauge went all the way to 'N' I pulled away and the gauge shot straight to 'C' s if the engine had not been started.

Could this be sign of a faulty gauge?

What is the easiest way to check.

However still going to get another thermostat and only drill one 2mm hole in it and take from there.

Shaun

Shaun

Shaun,
Put the end in a cup of hot water with a thermometer, like you would use for making beer :-) see what the gauge reads compared to the thermometer.

Your wasting your time though as your head is probably full of rust & the water ways are solid, so no water flow.

cheers
Brad
Brad (Sprite IV 1380)

Sorry Shaun,

i was mistaken, it's probably just a piece of head gasket from between cylinders 2 & 3 lodged on the water way.

cheers
Brad
Brad (Sprite IV 1380)

Oh great, I shall have to take the head off again and put it on with the lights on this time so I can see what I'm doing
Shaun

Shaun,
ah, that explains it, i think it's a simple mistake, with the lights on check that the head thermostat end is nearer the radiator than the heater.

LOL
Brad
Brad (Sprite IV 1380)

This thread was discussed between 29/10/2008 and 08/11/2008

MG Midget and Sprite Technical index

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