Welcome to our Site for MG, Triumph and Austin-Healey Car Information.


MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Warm GT for the winter?

I live in Norway, where the winters sometimes can be cold. Only sometimes. I have two MGs, a TD 35 that is hibernating for 6 months every year, and an MGB GT 1953 (image). The latter is my winter car! Equipped winter winter tyres (no spikes). The big problem is lack of heat blowing in. Oh, I have heat, but it seems not to want to get into the car. An MG specialist is taken a look at it now. It is almost like there is a dead animal in there, hindering the airstream.
Any suggestions?
Someone will also fix the heat for the rear window, so I at least can look backwards.
I will not be using the car for long trips, and it will stay in a warm garage most of the time.
But there are those days when I will take it for a ride..
PS. I only have two cars!

Raymond Wardenaer

I just fixed mine after months of messing around. i released the connection between the flexible heater pipe connected to the waterpump and attached a hose to the other side. opened the heater valve and turned the hose on.

Using a digital thermometer with probe (£10 on ebay, useful around the house too) I had detected an air lock in the pipe leading from the heater valve on the cylinder head and the heater box which i just could not get rid of. There was a 50 degree C temperature drop within a few cm which just had to be air.

The hose cleared it and with careful reassembly trying not to allow air back in, i now have warm feet for the first time!

hope it helps.
Graham Moore


Have a look at:


J. G. Catford

Don't forget that with the doors and windows closed it's like asking the heater to blow up a balloon as there's no through-flow ventilation.

As a 1963 (sic) you can't do this but one way to boost throughput is to cover the intake at the base of the screen and open the fresh-air vents on the later dash, and get recirculation.

On a day with the ambient at 8C I measured over 60C from the screen vents of my roadster, a bit less at the footwell vents, but that is still enough to get our feet uncomfortably warm.

There are at least 10 areas that can contribute to poor heat output, you might like to have a look here
Paul Hunt

Tell me when you´ve got it right, Raymond. I would like some more heat output in my roadster, even if I don't use it in winter!

I think you messed up the years of your cars. It´s a 1953 TD and a 1973 MGB GT, right? Both are real beauties.


Thank you everyone for the input here!
Tore, of course you are right, I have an MG TD 1953 and an MGB GT 1973.
Raymond Wardenaer

Maybe I should add that the most important thing for me here, is to get the warm air reaching the front windows with some speed, since the windows of the car will mist up as it is now, with the heat just crawling in.
Raymond Wardenaer

Then as a 73 you can configure it for recirculation, i.e. pass already warmed air through the heater instead of external air.
Paul Hunt

some things you could check and do to help get more heat
. obviously have the cooling/heating system in full working order and in good condition
. have the correct water stat fitted
. follow coolant refill instructions from the Driver’s Handbook to avoid getting air locks or ‘hotspots’
. remove the heater valve and clean out valve and block water ways, lubricate the valve and refit the cable to fully open
. check and replace as required the fan belt and check the fan is clean and secure, metal fans have rubber grommets that can perish
. check the fins on matrix are clear of debris
. important - check the seal in the heater box and seal to heater screen are fitted correctly and in good condition
. exclude cold draughts to the screen from window and door seals
. fit a mesh to the air intake cover

Tip – to help clear the windscreen quicker angle the sun visors to deflect the fan assisted air back onto the windscreen and to prevent it blowing passed the visors to the roof
Nigel Atkins

Presumably the cold air "door" is shut? From his excellent web site that Paul mentions, have a look at the cutaway drawing of a BGT at Gaydon. You will be able to see the path of the in coming air and how it flows out. Might provide some clues as to where it is being lost. For winter (over here so not so cold!) I slide a piece of clear acetate between the mesh and the grille in front of the windscreen leaving about 1/4 of the original opening. Then use the re-circulation method suggested above.
Michael Beswick

I forgot about the fresh air flap good suggestion to check that, I can't remember now if that also has a seal on it
Nigel Atkins

It should have a seal. It serves a very important function. RAY
rjm RAY

Paul. just read your heater description. very useful.

noting your comments about the orientation of the pipes that input/output water to & from the heater, if it's more efficient to have input at the top, what is preventing one from swapping the pipes over with suitable extensions?
Graham Moore

makes sense that the fresh air flap should have a seal but for some reason I doubted it on some models, my mistake
Nigel Atkins

Graham - nothing, it would be interesting to do before and after comparisons. I suspect it won't make any measurable difference as the force from the pump should greatly outweigh convection.

When we first had central heating many years ago we had a thermostatic valve fitted to the hot water cylinder outflow i.e. the lower heating coil connection to control the temperature of the domestic supply, as that was purely convective. But because of the pipe runs turbulence from the pump was causing reverse flow in the hot water circuit, which shut off the valve almost as soon as the boiler came on, so no hot water. I fitted a thermostatic switch to the flow pipe by the tank, and wired that in series with the pump, so that the pump didn't come on until hot water had reached the cylinder, by which time it had enough of a 'head' to keep going.
Paul Hunt

Paul, very clever. RAY
rjm RAY

This thread was discussed between 20/11/2014 and 25/11/2014

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now