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MG TD TF 1500 - water temperature. what should it be?

Is it safe to assume that the temperature in the header tank will be cooler than that of the engine and if so by how much?
What should the temperature at the probe in the header tank be? I have fitted a modified thermostat but the temp. seems to be low at 60 degrees or 70 at the most.
What will other indications be if it is running cooler than it should?
j c rathbone

In the spring and fall and cool nights I run 70/75 degrees... on a hot day 80/85 Only on a hot day stuck in traffic will it get up to 90 or +
gblawson - TD#27667

Ditto. Watch out for the upcoming vapor lock season.

Tom Balutis

Well pretty much like the measurment from Gordon spring and fall and cool nights 70/75 degree hot day 80/85 and a hot day in the summer 90+
with the supercharger shrieking.


"Hot Summer Day" is a regional relative term. A hot Summer day in Texas is when the eggs you were frying on the pavement burst into flames :-)


L Karpman

Our hot summer days (really hot) are the same I drove down to Gatlinburg in... 90 to 100 degrees...and humid!
gblawson - TD#27667

Gordon: That's what we get when a "cool front" comes thru :-) It's 8:20PM now, the sun is down, it's not summer yet, and the outside temp in still 92 degrees F!

L Karpman

Much better running too cool than too hot. If it is running well not to worry. My TF runs at 75 all the time, winter and summer, and performance is great.

Another related question: This past weekend, we had a great Brit show here in Edmonton, and one Shorrock-supercharged TD had a pressurized rad cap at 4 pounds and a catch tank neatly tucked down on the left hand side of the firewall [a right-hand-drive car]

Since I'm still at the stage of being able to do things like this, what are the general feelings of the group regarding cooling and supercharging - with my Judson will it be advisable to build a catch tank and pressurize the system? I agree that it's better to run too cool than too hot - you can always change a thermostat to deal with that problem, correct? But if I'm going to be running too hot to start with at 6 pounds boost, then perhaps better to engineer pressurized cooling system now rather than after a catastrophic blow-up?

Thanks for the thinkin' on this one,
Dave Jorgensen

Thanks for the comments. It would seem to be time to change the thermostat! Would running cool result in plugs that foul up after 800 miles?
j c rathbone

Over the long haul running too cool is as bad as too hot -- a cool engine doesn't drive off contaminants (fuel and water) from the oil as quickly so you get accelerated wear. T cars are worse in this regard because they don't have positive crankcase ventilation systems to help remove contaminants. So for the best longevity, you want to get the engine up to full operating temperature as quickly as possible, and you want the that temp to be as hot as is practicable.

With a 50/50 mix of water and antifreeze, boiling will occur around 230F (110C). If the system was pressurised, you'd gain an additional 3F for every 1 psi, so that car in Edmonton wouldn't overheat until about 242F (117C). 90C (about 194F) sounds good, but 60C (140F) is way too cold....

Rob Edwards

Dave Jorgensen,

One can't deny the laws of physics. If you extract more power from your engine than the design spec, it follows that you'll produce more heat.

No matter how you slice or dice it, you're going to encounter more heat from a supercharged engine. For the record, the TF hs a pressurized system - abt. 4 psi.

So better take any sensible precautions to disperse any excess heat, including:-
water-wetter in the summer (+5% anti-freeze)
engine oil cooler
electric fan
bonnet louvres
larger water pump pulley

Gord Clark
Rockburn, Qu.
Gordon A. Clark

"Hot Summer Day" is a regional relative term..." You've got that right Larry. Here in the Puget Sound area of Western Washington state, westart whinnng when the temperatures edge above 85. Cheers - Dave
David DuBois

Absent running water wetter, unless stored in a space that will go well below freezing, a 25% mix of antifreeze in water will cool better than a 50% mix, as water has superior heat transfer capability compared to antifreeze.

A 25% mixture will freeze at 10F

A 33% mixture will freeze at 0F

A 50% mixture will freeze at -34F

Here in Minnesota, we whine at 90F and -10F respectively.

Dave Braun

Our car runs at a consistent 83 deg. winter and summer.
I does not overheat in traffic and only when I have run it a 4000 rpm on a 90+ deg day did the needle get past the 90 deg level. Slowed down to 3200 rpm and heat went down.
I use 50/50 antifreeze (orange type) and distilled H2O and a half bottle of water wetter.
Colin Stafford

Water does have superior heat transfer properties, but inferior boil-over (overheating) protection. So it will cool better until it hits 212F, at which point it overheats. A 50/50 mix still has another 18F to go before it overheats....

Rob Edwards

Our current TF(Aramis),behaves the same way exactly temperature wise as per Colin Stafford's TF.


Colin or Rob
Do you know what your thermostat temperature is stamped as. If I can get your performance I will be happy!
j c rathbone

how long should it take to get up to 70 degrees C? i suspect my thermostat is open cause it seems to take too long.
thanks and aloha,
J.L. Hossellman

If your thermostat was stuck open, and provided your temperature sensor is in the top of the radator as the factory placed it, you will see a temperature indication start rising very soon after you start the engine, eventually making its way to operating temperature.

If the thermostat is operating normally, you will see no increase in temperature after start for quite a while, as it takes a while to get up to thermostat opening temperature (depending on what degree thermo you have in there). Therefore, no increase in temperature from ambient, until the engine is fully warmed.


L Karpman

My needle starts to rise(well, you know what i mean) about 5 minutes after starting...maybe 4 after... You can tell when the thermostat opens then it gets to 70 about 5 minutes later. (this happens about 5 miles from home with a minute or two warm up)
gblawson - TD#27667

John R.,

It was a while ago when I restored the current TF's
motor when doing a total car restoration. but I seem to remember 74 degrees was about the mark.


Thanks for all the comments. I changed the thermostat to an 88 degree one and no difference! I checked the gauge and it might be news to most but water boils at 90 degrees according to my gauge. The distance on the gauge between 90 and 100 is about 3/4 in but between 30 and 40 about 3/16 in ie. non-linear. Is 50 actualy 70 or 55? I am of to buy a thermometer to test over the range. It was a fiddly job which may have been for nothing but at least I was in the garage and not in the garden!
j c rathbone

Hi John, my car has a small old temp.gauge under the dash board and even with some fast driving the hand on dial is between 205 and 212 that's around 90 Celsius I think? Even with checking the ignition timing at idle for some 5 to 10 minutes it doesn't go up. I even put a long temp.meter and stick it in the radiator and at 82-83 C. it stops, so all is well here...

Good luck!

JJ Joop

This thread was discussed between 11/06/2007 and 29/06/2007

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