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Spitfire 1500. Temperature gradient across radiator. How much?


chrishawley

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Current efforts are to investigate poor running problems when hot. Spit 1500 mostly standard but has both mechanical and electronic ignitions (switchable) and Dolomite 1300 radiator.

But to ask about just a specific aspect for now: At a guessimate, how hot should the bottom rad hose be when compared to the top? Ambient temp was 30 degrees today but my impression that the 'out' from the rad wasn't very much less hot than the 'in'. Don't have an IR thermometer so can't be more specific than that. Let's say that the bottom was 'fresh-cup-of -tea hot'. So should I be suspecting that the rad is not clearing very much heat?

Tommorrow I'll replace the water pump and viscous coupling as I know the VC is well-iffy in any case. But it would be halpful, or even helpful, to have a clue of what is a 'normal' temp at te bottom of a rad.

Thnx in advance.

 

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I'd expect a moderate difference in temperature but whether you'd be able to notice it by touch is another matter. I'd say around 20degC difference as a ballpark, so if the engine's fully up to temperature then "hot cup of tea" isn't far wrong. The difference will increase when driving at high speed cruise in overdrive (lots of air flow, limited coolant flow).

If the bottom hose isn't any cooler than the top, then it's not a pump problem. It could be that the fan isn't spinning (though I think you'd notice that) but more likely it's a sign the radiator needs a good flush.

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at speed you get rammed air and the fan does little  

agree the thermostat and rad cooling should give around a 20c drop for cooler incomming coolant  

if the bottom outlet is as hot as the top then the rad is not working  and probably needs a re core 

the temp difference should be quite noticable with careful hand contact on the hoses 

an air lock will stop pump  circulation and then the temp builds up right across the radiator 

Pete

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Thanks. Got me a definite diagnosis regarding the viscous coupling: On removal it was evident that it was pretty much non-operative. On replacement tickover rpm notably reduced (=good).

Rad flushed with 10% HCl but crud was minimal, if any. So possibly hot running problems are principally due to lack of fan. Kempston Rads reckon they can squeeze an upgrade into the Dolly 1300 rad. So might consider that as one future option.

Thanks again.

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