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MG MGB GT V8 Factory Originals Technical - V8 cooling system

Hi

I know you've seen the title and you're thinking "Not this again!" but mine runs too _cold_. (77 roadster with a P6 motor)

It takes ages to heat up, then it is ok during normal driving but a gentle run on a dual carriage way at 60ish will send it back down to (say) 1/3 rd of the temp scale (a '77 has no numbers or markers on the gauge).

(I replaced the thermostat and noticed that the new one is marked 82 Centigrade. That seems a bit low to me??)

Anyway, it still takes too long to warm up. Has anyone used a thermostat in the oil cooler circuit to overcome this problem? Indeed, does anone else suffer from this?

Thanks

Nick
Nick Wilson

82 C sounds just right to me. For those of us on the other side of the pond, that's 180 F. You may want to verify that the thermostat opens at the correct temperature. Cheap thermostats often do not open at the advertised temp. I usually heat some water in a microwave and use ice cubes or more boiling water to get the temp to 180 degs, then drop the thermostat in to see if it opens. On another note, I always had to close off the air supply to my 78B (4cyln) radiator during the winter. On my brothers 70 B, we had about 75% of the radiator blocked off with cardboard. You can also try a 190 F (87.8 C) thermostat, but you would need to change back to the 82 C in the summer.

Mike
Michael Hartwig

Hi

I never did understand about blocking the airflow to the radiator. Surely if the thermostat is working it will reduce the flow of water through the radiator to keep the motor warm?

It's obviously not as simple as that, or people would not block their radiators - can someone explain my misunderstanding??

Nick

Nick Wilson

It's not so much blocking it from the radiator which will be shut off by the thermostat as you say, but from the block. On a freezing cold day an engine - particularly a 4-cylinder - will get a significant amount of cooling from the air flowing over the block and the hoses that have hot water circulating through them. Likewise in on a boiling hot day there will be significantly *less* surface cooling than average. It is my contention that the hotter stats for winter (open later) and cooler for summer (open earlier) that used to be recommended were for this very reason - to try and maintain something like an average temperature inside the engine. You only need to look how high the temp gauge goes *after* you switch off - particularly on a V8 - on a hot day and compare that with on a cold day to realise just how much variation there is in the internal temperature of the engine. Some people say that once the stat is open it is fully open but I disagree - in most cases. Under very hot ambient condition that may be so - when the radiator is cooling to its maximum capacity, but in that case any increase in load would would generate additional engine heat that could not all be dissipated by the radiator which would cause an immediate increase in indicated temperature. On my cars, on all but the hottest days in the UK and then only in the V8, that is not the case.

PaulH.
Paul Hunt

A V8 that runs 'too cold' is a very rare beast indeed. So rare, I would definitely not touch anything on the basis of 'if it ain't broke don't fix it'. FWIW I would suspect the temperature gauge is under-reading....
David Smith

Water temperature at 80 C sounds just right to me, more important is does the oil get hot enough to drive off water from condensation ( and there must be plenty on this in the various technical archives!! ). With a 19 row oil cooler my oil temperature is about 10 C above the water under road conditions, it does go higher when stationary but there is no fan on the oil cooler.

Dave
Dave Brooke

This thread was discussed between 27/09/2000 and 28/09/2000

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