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How did a MGBGTV8 cope with high temperatures

Postby V8webmaster » 01 Sep 2017 19:02

When Andrew Collins first started making plans to join the Club’s European Event of the Year in Portugal this year, his planned route added up to about 1,500 miles in Spain and Portugal in July and August. He thought about engine cooling, and decided that at the least he needed some way of accurately knowing the temperature of coolant leaving the engine. To provide this information he bought a small LCD temperature monitor which attached to a remote sensor element. The sensor element is housed in a stainless tube, 4mm in diameter and about 15mm long. He drilled a 4mm hole in the V8 thermostat housing and fitted the sensor. The LCD monitor was fitted in the centre console inside the car. In an article he has contributed which has been released on the V8 Website this evening he describes his preparations and the information the sensor provided on how his MGBGTV8 coped with the very hot conditions.

His article concludes saying “I have often heard the assertion that “the V8 cooling system is marginal”. After the run in Spain and Portugal I don’t agree. The cooling system on our car is totally standard, but in good order throughout. The radiator flows well, the coolant pump works properly, the pressure cap works, the fans work, the thermostat is correct, the coolant passages in the engine are clear and the coolant is a 50:50 mix. After the experience of a fortnight which included a good deal of ‘hot and high’ driving, I cannot see the need for holes in the bonnet, waterless coolant, baffles around the radiator etc”. ... es-AC2.pdf

Nic Houslip commented “what a splendid experiment, you confirm what I also believe that the cooling system on the B V8 is not marginal and never was, the biggest problem being, usually maladjustment of carburettor or ignition or some part of the cooling system not working. The amount of Loud pedal you use determines how much heat the engine develops”.

Thinking ahead to the colder months, Nic adds “something I discovered only recently, an antifreeze and water mixture has its lowest frost protection at 50/50% mixture, but if you increase the amount of antifreeze, the protection point (that is the freezing point of the mixture) rises from -37 deg C at 50/50% to only -12 deg C with pure antifreeze. This interesting fact I discovered in a book called What Einstein Didn’t Know, by Robert L Wolke, Professor Emeritus of Chemistry at the University of Pittsburgh”. Continuing Nic adds “many people believe that the thermostat regulates the engine’s temperature constantly, but in fact it only does so during warm up phase, when it restricts coolant flow until the engine has reached a minimum operate temperature - for the V8 its 82 deg C. Changing for a lower opening temperature just means your heater won’t start working so soon, and the engine will take longer to reach it minimum operating temperature in winter conditions”.

Tony Lake commented "I’m not surprised by these findings, exactly what I would expect from a well prepared and maintained engine cooling system. Plenty of ram air to remove the heat during high speed cruising. V8s don’t overheat they just get hot. Given the high ambient temperature I’d be interested in how the coolant temperature fared in city driving at low or no speed; that is where the fan shroud benefit is evident in reducing the spilled air volume".
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Re: How did a MGBGTV8 cope with high temperatures

Postby Mike Howlett » 02 Sep 2017 06:36

That's most interesting Victor and mirrors what I saw with my V8 while in similar temperatures in France in 2015. Only I didn't have the definitive coolant temperature gadget. When in traffic, my gauge showed well above the normal boiling point for water, but the engine was absolutely fine and didn't lose any coolant. The fans were on pretty much all the time if I was below 40 mph, but went off once the speed built up. I have a tell-tale light on my dashboard to let me know when they are running. The sensor for my gauge is plugged in between the RH cylinder head and the thermostat housing. I am using 4-Life coolant which is claimed to have a boiling point of 180 C.

EDIT: Something else I wondered about. How well did Andrew and his passenger cope with the temperature in the GT? Catherine and I found it pretty unpleasant and had to pull off the motorway at one point as we were feeling ill with the heat. You really can't drive for hour after hour at 80 mph with the windows wide open. The buffeting and noise become too much, and yet with the windows shut the cabin was like an oven.
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Re: How did a MGBGTV8 cope with high temperatures

Postby Bob Owen » 02 Sep 2017 10:22

Well, whether the cooling is deemed adequate or marginal depends on the conditions. I agree that for most conditions the original V8 cooling system is adequate. But as Tony says the key factor is the air ram effect. The other factor is how hard the engine is working. If idling in traffic the engine is not working hard and the power to be dissipated is relatively small so the fans cope even in hot weather, as evidenced by their cycling. If driving along the air ram is usually sufficient to obviate the need for the fans. The worst conditions are if the vehicle is travelling slowly but the engine is working hard for a significant length of time. This is rare but can happen when for instance ascending a mountain pass in hot weather. The typical string of hairpins dictate a low average speed and acceleration out of the hairpins plus the ascent require high engine power. Typically for a petrol engine about a third of the energy in the fuel must be lost by the cooling system (a third is mechanical energy and the other third lost via the exhaust). So if the engine is running at an average of say 70hp this same power must be lost by the cooling system - in more usual heat units this is around 50kW - or 50 bars of an old fashioned electric fire. That's a lot of heat. In the early years of using my V8 in northern Italian passes in the summers of the late 90s I found that I suffered some water loss, especially if I stopped at the top, as is common (admiring view, talking to others). This means that there had been boiling in the block which is a possible definition of "over-heating". So the measures I took were to fit a Clive Wheatley enhanced performance radiator (this is not aluminium - just has more effective radiating area), to re-jig radiator and fan positions so the fan blades were within 2mm of the matrix, and to re-wire the fans so that they could run with the ignition off (reduces post stopping water loss). These measures improved the cooling such that passes in hot weather no longer cause water loss. No doubt Tony's shrouding of the fans would be an additional useful improvement.

I should say that my engine is not quite standard but nearly so - it has a 3.9 cam and K&N filters with a richer needle. So it has a bit higher power output so in some circumstances might demand a bit more cooling.

This year we, like Andrew, travelled to Portugal, in our case driving from Northern France and then through the Pyrenees (because we hadn't done it before) with no problems in the passes with ambients in the 30s. Similarly, earlier in the year going to Croatia for the MG Italia meet, we went via the spectacular Grosseglockner pass in Austria (8000ft at the top) with no problem (the tick-over was 450rpm at the top due to the thin air).

To respond to Mike's point: On our journey through central Spain there was a heat wave and we suffered temperatures up to 40C. This was an ordeal but the V8 IMHO is generally as good as any other non AC vehicle. True, if the front windows are wide open you can't go at 80mph. But if the BACK windows and the air vents, including the valuable footwell vents, are wide open with the front windows closed or only open half an inch the buffeting (low frequency resonance) is absent and the wind noise not much higher than with all windows closed. Then the cab temperature is more or less as ambient and you can drive at 70-80mph. Moreover, if leaving the car in a car park, leave the back windows open (at minimal security risk) and a towel over the steering wheel (or you can't hold the wheel firmly enough to get out of your parking space) and you're good to go. So IMHO the V8 GT is an excellent touring car suffering relative to a modern car only in lacking AC, power steering and the aerodynamics to give low wind noise.

Incidentally the fuel consumption for the 3800 mile round trip to Lisbon and Oporto, return via Cornwall, was 29.4 mpg. The engine has done 140 000 miles and used under a litre of oil for the 3800 miles.
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Re: How did a MGBGTV8 cope with high temperatures

Postby David Macadam » 02 Sep 2017 13:28

Climbing severe mountain roads is a rare activity for most drivers including MGBGTV8 enthusiasts, but clearly when the engine is working hard with a lower ram effect than you would get on a less inclined road, the cooling system will be working hard and getting quite hot! Even driving at moderate speeds on motorways or A Roads followed by a slower pace on minor roads to a stopping point will often result in the risk of the coolant being very hot. When I come to a halt what I often do in that situation is to run the fans for several minutes after the engine has stopped, restarting the engine for a short while to circulate the coolant and repeating the routine, and usually after three or four cycles the coolant temperature reduces so the car can be left parked up in a slightly cooler state. I agree with Nic, I found Andrew’s experiment was an interesting way of getting good information on coolant temperatures in various driving conditions. Andrew's conclusion is sound that if the various component factors that have an effect on the efficient cooling with an MGBGTV8 are all in good condition there is no need for some of the fixes and mods, often suggested as good ideas. Both Nic Houslip and Tony Lake also highlighted that in their concise comments. For example simple maintenance like renewing a pressure cap with a good quality replacement part with the right pressure rating is just one of those factors. But really how often do pressure caps get replaced before they may be beginning to contribute to a reduced cooling efficiency?
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