Temp gauge dropping!

Went out for a 3 hour ride yesterday, mainly motorway riding and then 'A' road and town riding for the last hour.

Occasional glancing at the gauges and lights during the ride all showed normal until about 1 minute from home when I noticed that the temp gauge had dropped to two bars. When I stopped outside my garage (engine still running) the gauge popped back up to three bars straight away, back to normal.

What on earth could cause the engine temperature to 'drop' while riding? The ambient air temperature was about 10 degrees but I've ridden in minus temperatures many times and the temp gauge has never moved.

Any ideas

Sticking open thermostat?

Good point oldwingguy and I hope it is something fairly simple like that. I always thought that once a thermostat was 'open' after a cold start that it would just stay open until the engine cools right down after stopping.??

Does a thermostat open and close during riding? I have never thought about that, till now.

Loosemarbles wrote:

Good point oldwingguy and I hope it is something fairly simple like that. I always thought that once a thermostat was 'open' after a cold start that it would just stay open until the engine cools right down after stopping.??

Does a thermostat open and close during riding? I have never thought about that, till now.

I too would have thought that but it's mechanical so all bets are off The cooling fan acting normally? It cycles as we know.

Mmmmmmm.......cooling fan? I suppose if it was running when not needed it would cool the system prematurely. I'll make that my first investigation. Weather here is not looking too good for the next few days so I'll wait till it improves.

Whilst on the subject of the fan I have previously considered installing a dash light to show when the fan is running rather than trying to listen for it. Shouldn't be too difficult to do.

oldwingguy is most likely right. Thermostats do go bad they start to hang up a little open or don't open at all. Honda makes good parts but they do wear out.

Fan running all the time would not cool the engine if thermostat was working correctly. It opens and closes but slowly as coolant heats or cools it. Once you stopped no airflow through the radiator temps. came back up. Replace it. I hope that's 10° C not F. Burrrr.