Series Two radiator – is mine up to the job?


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According to the temperature gauge, my 1972 2000 TC runs hotter than it should – mostly at the top end of the green section, and past the 85-degree mid-point. I have renewed the thermostat (82deg), the temperature sender and the voltage stabiliser (now a solid-state one), and the reading hasn't changed. The engine runs fine and doesn't give the impression of being excessively hot, but I'm wondering if the radiator might not be as efficient as it should be. (Or the gauge could be faulty, which I will attempt to check with an infra-red thermometer.)

The gentleman from whom I bought the Rover had the radiator rebuilt in 2018, and it's free of sludge and scale. It has a surprisingly thin core, though. Might it be too thin to do the job?

Could one of you with a crossflow-rad four-cylinder Series Two please measure the thickness of the radiator core? If mine (1 3/16in) proves to be thinner, then I could think about getting the radiator rebuilt with a thicker core.

A further thought. The factory manual says that the 2000 was originally fitted with a 77-degree thermostat, nowadays hard to find. Might it be a good idea to fit a 74-degree one, which would be fully open at about 79 degrees, rather than the more commonly used 82-degree one? A hotter engine is a more efficient engine up to a point, but assuming my temp gauge isn't lying I'd rather the needle sat in the middle or just below once the engine is fully warmed up.

Many thanks, John
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The core on my horizontal flow rad is about 1.75” (original unit). Have you used an IR thermometer on the thermostat housing to see if the gauge is off? I’ve noticed that modern rads are far more efficient these days.
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Thanks – that's significantly thicker than my rad. But yes, I'll try an IR thermometer before leaping into changing anything else.
How confident are you that your water jackets are nice and clear? Mine where full of sludge when I changed the side plates.
Good thought, thank you. But I rebuilt the engine in 2020, which included acid-dipping the block, so no sludge. There was quite a lot pre-rebuild, though. I've just checked with Geoff at Wins and my radiator core is correct for a Series Two. Seems it's all pointing to an inaccurate gauge. I'll borrow my son-in-law's IR thermometer tomorrow and find out what is really going on.
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Hi, A quick check is to run your hand over the rad core to see if there are any cold spots, engine up to temp but off of course.

I have seen a note that more than 3 rows of tubes in a rad is counter productive.....doesnt improve the cooling.
I have now checked the temp with an IR thermometer aimed at the temp sender (the hottest external part other than the exhaust manifold). After a good and vigorous drive the temp gauge was towards the upper end of the green, well past the 85deg mid-point, but the IR thermometer recorded 80-82 degrees. So all is fine apart from an inaccurate temp gauge. Mild panic over.
What colour is the plastic around the connector of the temp sensor in the head? There are two versions, I think the correct one will be red. The wrong sensor will make the guage read high.

In my Austin the red sender made the gauge read high, the black was the correct one.
However i am not sure what colour is the current one in the Rover, which reads correctly.
In my Austin the red sender made the gauge read high, the black was the correct one.
However i am not sure what colour is the current one in the Rover, which reads correctly.

It would be good to know which sender you have. The one in my car, supplied by JR Wadhams so I assumed it was correct, is red.
I've just ordered a black sender. £10.95 inc postage so worth a try. If the temp gauge needle goes off the end of the scale I'll know it was a bad buy…
That's quite the treatise. Fascinating.
The P6 parts specialists don't seem to differentiate between Series 1 and 2 for temp senders, which means the black one may end up being right for my car. Will report back.
I've just found the original temp sensor for my car in a pile of stuff I've been meaning to throw out. I changed it a month or two ago because the gauge had started to under-read dramatically. The colour code of the original sensor is… black. So why do the Rover parts specialists sell only red ones for the P6? The new black one should arrive soon, and with luck normal service will be resumed.
New black sender now fitted. Gauge still reads high, but not as much as before. I shall check the resistances of the new red and the new black senders and see if there's actually a meaningful difference.
Just as a thought, how's the fuel gauge looking? Could the voltage regulator be playing up with age?