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MG MGB Technical - Cooling in traffic update

Some time ago I posted that I had trouble with my ´63 MGB overheating as soon as I had to stop in heavy traffic, but never at speed. Following good advise on this BBS I have now checked that the ignition timing is spot on, reduced antifreeze from 50% to 40% to improve the efficiency of the coolant, and closed the gap between the header tank and radiator panel with a strip of foam.

Temperature still reaches 212 F in 10 minutes when I stop and let the engine idle at 1000 rpm. But the big news is that if I then increase revs to 2000, temperature drops to 195 F! That did not work before, and I believe the strip of foam is the main reason for the improvement.

When I then stop the engine, I can hear the coolant boil inside the top radiator hose after a minute or two. Is this normal?

Tore
Tore

Tore,
There must be a tight relation between the closed gap
between header tank and radiator, improving this way the airflow crossing the rad core itself. For the rest of history, all temperature in the block climbs up into the head at engine stop. But from me 212F is a bit too hot. Did you get back any positive info relevant to the pump gap you asked for some time back?
Have fun.
Renou

Hi Renou,

Yes, I believe the improvement must come from the fact that more air is now forced through the radiator, and not above it. Of course there is still the large hole in front of the carburetters...

Opinions were divided as to how important the impeller gap is for the water pump, but I believe the one I have, with the correct gap according to the workshop manuals, is quite efficient. I never have any cooling problems when the car is in motion, even climbing long hills in high summer temperature.

Tore
Tore

Tore,

All early MGB's came to the USA with an oil cooler as standard, I am curious (as you are in Norway) if your car equipped with this option? I would worry more if you also see a drop in pressure when the coolant temp rises?

I have installed a (12" dia.) 'pusher fan' on the outward face of the radiator of our B/GT with a remote switch inside that I can energize in traffic, or low speeds. This keeps things in check until we are moving again.

Regards,

Larry C. '74 B/GT
Larry C.

My car used to do that, I changed the radiator cap and it stopped.
Stan Best

Yes, my car has an oil cooler. But then it has spent most of its life in California!

I will have a look at the radiator cap. Of course if it is leaking, the system will not be pressurized as it should.

Tore
Tore

Tore, does switching the heater on help?

While you say increasing the revs from 1000 to 2000 helps have you tried reducing the idle from 1000 to say 700.

I can't remember all the detail from your earlier thread, but have tried flushing the radiator.
David Witham

The B series engine in my Cambridge used to overheat in traffic and after changing thermostat, pipes, radiator cap, radiator fan (blade missing), water pump checking the timing and reducing the idle speed I pressure cleaned the waterways around the block. The gunk that came out was incredible and it cured the overheating instantly.
D Dunlop

I strongly agree with Mr. DUNLOP point of view. And checking the block free flow output through the bottom tap is the final test that will help in deciding to clean the internal block waterways. switching on heater may reduce emergency but won't definitively fix the issue.
Regards.
Renou

hi
two points id like to make. I fitted a smaller size pump pully that reduced the temperature throughout the range.In bygone days the b pump was fitted to lots of different Leyland models and the scrappers had lots to choose from.
I have a 78 b and i found that the electric fan didnt kick in until the gauge was over halfway - 3/4 ive bypassed the thermo and fitted a kenlow switch and adjusted it to come in before the gauge is midway.
Now in traffic the fan kicks in nice and early before the tic-over gets lumpy and erratic due to the overtemeperature. I advice this mod it does work well
R S Clark

It was late summer, I was 19, my 'B was new and I took great pleasure in pushing the limit and beating my contemporaries on the back roads of rural Alabama. It was Thunder Road - British style. My 'B was responsive, took revs to the extreme and cornered like it was running a rail. It was Thunder Road - British style.

In contrast to the open road, however, my little 'B did not like being put in slow going city traffic. The temperature gauge would approach combustion, oil pressure would head toward zero and the fuel bowls were passing gas. The year was 1966 and my only cure for pushing down the temperature while stuck in traffic was cranking up the heater adjust with the blower on. They didn't have auxiliary fans for the 'B in those days. Because my 'B was too new to have clogged channels in block or radiator, one can assume that it's just the nature of the beast.

I'm doing a restore on a '66 now and will be fitting one of those large auxiliary fans (with manual override) - I would strongly recommend the purchase of one for yours.
Steve Buchina

This thread was discussed between 09/07/2007 and 13/07/2007

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