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MG MGB Technical - Good stat bad stat

I have two thermostats rated at 82*. The first has been in the car for a couple of years, since the introduction of a Kenlowe fan. With it the mechanical temperature gauge sits a good quarter inch left of N and well to the left on frosty days. The fan is set to come on just past vertical. The gauge read much the same with the stat that was in the car when I bought it so I've always assumed it reads a bit low. Fitting the new stat, the car runs hotter, with the needle almost touching the N, and this is confirmed by the fan is cutting in more frequently. The temperature is cycling more and the fan seems to have a job cooling things off, running for longer than usual.

I've put the two stats in water with a thermometer. They both start to open together with the temp in the mid-80's, both reach max opening together, but as things cool down the old stat stays open for a lot longer than the new, which shuts off quite smartly at around 82*. The water has to cool a few degrees further before the old stat is fully closed. So now I can understand how the new stat could be holding the water in the block at a higher temperature. I don't follow how this keeps the Kenlowe working harder, as its sensor is the radiator side of the stat in the top hose. More importantly, I don't know which stat to use. Which would you go with?

Many thanks,

Steve
Steve Postins

The new stat is the correct one to use, the old one is allowing the engine to run cooler than it should. IMHO you have your Kenlowe set too low, the factory fans typically cycle on and off about half-way between N and H. By having them set too low the stat could have closed before the fan has cut off, the fan is cooling the rad not the top hose, so keeping the fan on even though the rad might be cool.
Paul Hunt

I agree with Paul about your Kenlowe setting. If your gauge is like mine then you'll see a tiny white dot between N and H - I set my Kenlowe to come on at that point and it then shuts off just above N. I also use a hot stat - 88 degrees from memory.
Miles Banister

Thank you. Re-reading the post it seems daft to have even asked, so I appreciate your patience as well as the explanation!

Steve
Steve Postins

This thread was discussed between 22/05/2003 and 23/05/2003

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