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MG TD TF 1500 - Boiling after stop

Last evening after turning off the key I heard a heavy boiling. Do I have to check some things? Coolant is okay. My TD is not equipped with a thermometer.

Maybe check the thermostat. Not that difficult to remove. If it was frozen in the shut position that could cause the coolant in the block to boil yet there would be no apparent loss of coolant in the radiator. Cheers
Peter TD 5801
P Hehir

It is just heat transfer after the circulation stops. If it was boiling while running you would lose your coolant.
My TF has always done this for a short time after shut down, As I have had the car for 43 years I am not going to worry about it.
Ray TF 2884
Ray Lee

Thank you

my thermostat is absent. A new one is stored on the shelf - waiting to be installed.

I'll have attention if it is boiling while running.

It might not be a bad idea to prepare the thermostat for retro-fitting a temperature gauge before you fit it.

Declan Burns

Running without a thermostat is not a good idea, the water can circulate too fast and won't have time to cool in the radiator before re-entering the engine. A thermostat not only lets the engine run at the proper temperature, it also slows the coolants flow down giving the radiator time to work. Now, that's assuming the radiator and block are clean. PJ
PJ Jennings

Good advice from both Declan & PJ re fitting a thermostat. Bore measurements taken here by an owner of 3 T Types on a number of blocks show that those that have run for a while without a thermostat show more wear on #1 cylinder.
Peter TD 5801
P Hehir

Thanks for the advice!

Declan - I think a fitting must be welded. I don't have such a equipment. Or is it possible to make it with a thread? Now the car must be grounded because the clutch is broken. I'll install the thermostat soon.


You can install the guage sender in the elbow from the head using a taper tap.

The casting wall is around 3-4mm thick, but there is no pressure there - see picture below of the installation on my YT.

Wiring is protected in a steel tube mounted off the rocker cover.

Good Luck



Before you fit a temperature gauge, you could buy one of those infrared pistol type temperature measurement devices and check around the car when it's doing the boiling and see what's hot and what's not and make a decision as to whether you really have any serious issue.
John Quilter (TD8986)

Do it now just as Tony has shown above. I can lend you either a 1/8" BSPT (R 1/8"),a 1/4" BSPT (R 1/4")or 1/8" BSPP (G 1/8")or a 1/4" BSPP (G 1/4") tap if you want.
You can always plug it and fit a gauge later.

Declan Burns

It might actually be better to tap 3/8" and use an adapter demending on the gauge you choose. Electrical gauges operate at 10V so you will need a voltage stabilizer and new ones are polarity sensitive.
Refer to:
Declan Burns

I have an electric fan fitted to my TF with the sender in the rad header tank. The fan frequently switches on a minute or so after the engine is turned off.

Jan T
J Targosz

I really ought to do that, as I have an electric fan in addition to the regular one, and it never comes on unless I switch it on. A sensor jammed between the radiator fins just isn't sensitive enough.
Dave H
Dave Hill

My TD has boiled a bit after hard driving on a warm day forever. Make sure you have 50/50 water/coolant as that raises the boiling point. Make sure timing not retarded. Great article in one of the recent Totally T-type issues about modern fuels burning hotter. If it runs fine and doesn't boil while driving, just drive and enjoy. Also, is the bypass blocked off? The original thermostats did this with a moveable sleeve. If it is wide open, much of the circulation is going in circles. George
George Butz

Dave Hill, I've had one of those thermostatic switches for the cooling fan on my '65 Jaguar 3.8S and it has worked well for many years. It looks like a large aluminum nail and its output runs through an adjustable potentiometer. It was made by the fan maker, Hayden. But as they say, your experience may differ.
John Quilter (TD8986)

While checking everything, I would also look at your ignition timing. Slightly off can increase temperature.

Thank you all for those useful hints!

This thread was discussed between 27/05/2017 and 29/05/2017

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