Stalling when overheating

Hi All,

First post here so hoping I've posted this in the correct place!

At the weekend I took my 1967 MGB on a 400 mile round trip (up Friday back Sunday). It was absolutely great, no issues at all. Until I got about an hour away from home and the famous killer hill near me, I decided to be unsympathetic and try and boot it up. She held 60 mph the whole way up to my suprise only to puke coolant when I got the top. Initially lost lower and then stalled out as I pulled into the layby. Why do cars do this? I can't in my head figure it. It is on twin SU carbs.

My thoughts are super hot air being drawn in through the pancake filters, coolant through the intake manifold getting so hot it's evaporating the fuel or maybe a temporaty heat seize?

And the other question, as I want to drive it more around cities and have it ready for all situations I want to fit an electronic fan. Should I remove the exisiting engine driven fan and fit a single spal fan drawing through the radiator or shall I keep the exisiting fan and add a push Spal fan in the front of the radiator? As it will happily sit in 20*C weather at 170/190*F (car measures in *F).

Hope this makes some sort of sense!

Cheers :)

What was the coolant temperature - if it went high, then localised boiling could have forced the coolant out. if it stayed around mid-range then there may be a head gasket leak - the engines use 3 bolts per cylinder, and that can be a problem on olded engines as the gaskets age.

If it did run hot, and the inlet is coolant heated, it could have picked up enough heat to cause vapourisation - localised boiling - of the fuel, which would be consistent with the vehicle stalling. Add in ambient air around the filter that is also "pre-heated", and...

When it was allowed to cool down a bit, you probably found it ran, as normal, after a little cranking as the (IIRC, electric) fuel pump refilled the float bowls.

Just to be safe, and ensure there's no head gasket issues, I'd suggest a sniffer test on the coolant for CO.

I expect it to have a fixed pitch, solid hub, cooling fan, and removing that and replacing it with an electric SPAL, or similar, fan should give a small increase in power and economy. While doing that, I'd have the radiator checked/cleaned, too, as the engins houldn't have got that hot, unless it was a VERY steep hill. Hmmm, might also be worth checking the engine tune.

Something to watch out for, especially if it is still fitted with a dynamo, usually around 22A at best, is that the fans can draw quite a lot of current, so there is an increased risk of a discharged battery if idling with the fan on.

Back in the day, I used 3 position ON-OFF-ON switches for the fans on my old Pontiac. FUSED power to the fan, from the fan to the switch centre contact and from there I ground it through a thermostatic switch on one "ON", directly to ground through the other, and centre position was OFF, of course. this meant I could leave it to operate normally through the 'stat, have it run continuously which is handy if wanting to cool it down more, or just turn it off entirely which was handy if I needed to balance electrical load vs temperature, or just run a single fan.

Forgot, if the radiator matrix - the centre bit with the fins - is looking past it's service life and needing replacement, it's usually only a small additional cost to fit a three row core instead of the two usually fitted, and this can make a significant improvement in coolant temperatures in hot weather and/or heavy loads and/or slow speed running.