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MG MGB Technical - Strange Temp Fluctuation

Hey Folks -

I have a strange temp fluctuation that I have never seen before except with a stuck thermostat.

I have replaced the thermostat and still see the temp drop down almostt to the "C" when at speed. It will then climb back up to the left hand leg of the "N" at the slower speeds.

All other gauges are working fine - so I dont think I have a voltage problem. I will check the new thermostat and make sure it isn't sticking. Hoses seem fine - but I don't think a weak lower hose would cause this - that would cause warmer temps I would think.

Any thoughts,

Jeff
J Delk

What temp thermostat are you using?
Kimberly

Start from a cold engine and feel the top hose and top of the radiator frequently as the engine warms up. Whilst they will warm up slightly, it is not until the needle gets close to N that the thermostat should open and they will suddenly get much hotter. Is this an electric temp gauge? If so it could be a loose connection or a bad sender.
Paul Hunt 2

Kimberly - its a 195 thermostat...but normally that wouldnt account for the vast fluctuations.

Paul - connection on sender is firm. Unit worked perfectly until about 3 weeks ago. I'll check on that.

Thanks folks!

Jeff
J Delk

Have you tested the thermostat? Sounds like it could be stuck open.

Guido
G.D. Perrone

"Unit worked perfectly until about 3 weeks ago"

Ah well, they've all got to go some time :o)
Paul Hunt 2

Still sounds like a bad connection - sender or ground.

I would think a stuck thermostat would just give one constant bad reading (usually toward the "C" side), as you say. It's possible, though, that it is failing - it just hasn't completely checked out.

That leaves PH2's suggestion: Bad sender.

You've already checked the connections, so that's likely out. Do you have an infra-red or other thermometer you can monitor things with externally? If your gauge shows fluctuations that just don't show up at, say, the head adjacent to the sending unit - voila! Bad sending unit.

If the IR thermostat shows the same fluctuations as the gauge, then your t-stat is likely the culprit.

Assuming, of course, you don't just need a flush-and-fill to get a few years' worth of crud out of the system.

R.
Rick Stevens

This thread was discussed between 02/12/2006 and 04/12/2006

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