Hiya, I ride my XT660X all year round here in Italy where we get fairly high summer temperatures and I have never felt excessive heat from my engine even in city traffic riding. I have also never heard the fan cut in. So your case sounds very strange.

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(Now sold on, sob) 2011 Blue XT660X with gold wheels, was 26,500 km.
Engine mods: K&N Stage 1 filter, DNA Stage 2 filter, snorkel removed, Kev fuel mod fitted.
Plus: smoked Puig screen, Yam aluminium sump guard, Yamaha / Acerbis handguards, Givi Trekker aluminium side cases, Leo Vince X3 cans plus Kev front fork mod and Fender Xtender. Just fitted Michelin Road Pilot 3 tyres.

SOLD the XTX for a Super Ten 1200. And just bought a Raptor 700 so staying on here for some tips....

You really need to remove the sensor in order to check it with a multimeter to get any degree of accuracy or useful data. Using a guesstimate of cold/hot engine and comparing the readings with a top hose temperature reading just isn't going to be accurate enough. The sensor resistance needs to be checked/compared with temperature at/or in very close proximity to it. The temp on any top hose reading gauge will lag considerably from that of the actual engine temp sensor; it will also be affected by operation of the thermostat, whereas the engine temp sensor reads before the thermostat and reacts quickly to cylinder head temperature.

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Thanks cya

Thanks cya

You are (in your own words) making the assumption that the temperature gauge fitted is correct and the gauge in question is fitted to, and measuring the temperature in, the top hose.

My point is that, although you may well get 140ish ohms when the fan cuts in, you have no idea what the actual temperature is at the sensor in order to make a comparison. Yes the fitted gauge may say 109, but the temperature could be, and is highly likely to be, much higher in the water jacket itself? For example the sensor might be sending a reading of 140 ohms to the ECU so the fan is switched on, but you don't know whether it is the right temperature. In other words, the range of resistances produced by the sensor may well be within spec on the multimeter, but you won't be able to confirm whether the correct temperature range corresponds to those resistances when relying on the fitted gauge in the top hose. The crucial thing to test is whether or not you're getting the correct resistance at the correct temperature. Just checking the resistance is not enough to ascertain wether the sensor is good or bad in itself, unless you can cross-reference it with temperature.

As you say, the only reference temperature you can be 100% sure of is the ambient. The rest is based on assumption.

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Thanks cya

I know, but to be fair you didn't mention that before! Originally you only mentioned taking out the thermostat to test it with a thermometer...

Not the sensor, which you originally implied was best to test in situ (no mention of testing it against a thermometer?)

Man this is hard work!

All I originally said is "you'll need to take the sensor out to test it", which indeed you will have to do to measure the resistance against temperature with a glass bulb thermometer as you quite correctly say in your last post. You don't need the diagnostic tool to do this - I never said you did for this. All I said you'd need a diagnostic tool for was to "check the coolant temperature that the ECU is reading".

Anyway, in a nut shell, I think we have finally established/agreed in a roundabout way that, to test the engine coolant temperature sensor on an XT you need to:

1) Remove it
2) Heat it up in water with a glass bulb thermometer
3) Measure the resistance against temperature

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Mate you are seriously insecure about your abilities and so not worth the effort. What a great forum but not worth the effort trying to assist when only ONE opinion is allowed. For the record no.. Only a retard would feel they need to remove the sensor to get an adequate reading of its serviceability, which you never thought to allude to till I explained it to you.
All the best.

Pleiades was only trying to help you based on the facts he was given, I think a little cool it down period (no pun intended) would do wonders to this discussion if we all walk away for a day or two and come back to it with refreshed mind.

May I remind all forum users that we provide this platform not to measure each other's "bits" but to friendly participate in discussion to try and help with our experience, we welcome those of you who have more experience then others to share those with the people who has had less experience. So it's a exchange of valuable info that we pass one another.


Please never get irate or offended in the process of these discussion taking place, realize that often either one of you has not made themselves clear to the rest or given contrasting info.

The Latins got it right when they said: "Errare (Errasse) humanum est, sed in errare (errore) perseverare diabolicum.", attributed to Seneca. which translates to: "To err is human, but to persist in error (out of pride) is diabolical."

Take a few minutes to reflect and then come back in a few days times and see if you can see the argument from a different constructive approach.

Thanks in advance for accepting my suggestion and if you are still pi$$ed and want to leave the forum of remove your profile I can do that, but... who will lose then?

For Brad, or anyone else wanting to test their coolant temperature sensor, here is the correct procedure to follow, taken from the official Yamaha Service Manual:

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