[Gert]

Is the overflow bottle filling up when bike overheats?
What happens when you run the motor with the radiator cap removed?
I'm thinking along the lines of a possible damaged water pump which is not circulating the coolant or perhaps a faulty / stuck thermostat.
Have you check the temp of the upper and lower radiator hoses?

 

[PeteW]

Valves need adjusting would be my guess. Not saying Gert's guesses are wrong, simply that valve wear does happen even on DL's

 

[Oily]

Is the overflow bottle filling up when bike overheats?
What happens when you run the motor with the radiator cap removed?
I'm thinking along the lines of a possible damaged water pump which is not circulating the coolant or perhaps a faulty / stuck thermostat.
Have you check the temp of the upper and lower radiator hoses?

Ran the bike with cap off to get all the air out.
Could a a stuck thermostat but at 62k and 2 years old it doesn't sound right.

 

[Oily]

Valves need adjusting would be my guess. Not saying Gert's guesses are wrong, simply that valve wear does happen even on DL's

I did all the valve clearances at 40k and all were in spec. I will do again at 65k.

 

[Marmora]

Have you been wrenching on bike prior to this? Check hoses & wiring for discnnect or crushing.Does the cooling fan come on? Both ends of fan wiring intact & connected? Critter damage,blocked fins on rad, plastic bag in rad?Air in cooling system.

 

[Rolex]

Is the cooling fan kicking in ?

Does the fan run ?

Did you change the coolant after the problem showed up or before ?

Infrared thermometers are quite cheap, buy one and run it over all parts of the cooling system looking for hot and cold spots, it can also tell you what temperature the thermostat is opening at.

Pull the thermostat, drop it in hot water and check the opening temperature.

Have you had any fuel supply problems or changed fuel type or exhaust, the air filter the same as removed ?

 

[Oily]

Is the cooling fan kicking in ?

Does the fan run ?

Did you change the coolant after the problem showed up or before ?

Infrared thermometers are quite cheap, buy one and run it over all parts of the cooling system looking for hot and cold spots, it can also tell you what temperature the thermostat is opening at.

Pull the thermostat, drop it in hot water and check the opening temperature.

Have you had any fuel supply problems or changed fuel type or exhaust, the air filter the same as removed ?

Cooling fan does kick in and working fine.
Air filter OEM Suzuki
I have a infrared thermometer so I run some spot checks.
Would it be common for a thermostat to fail after 2 years 62k klm ?

 

[STCorndog]

Two things you can check

• the thermostat
• the temperature sending unit (it tells the dash gauge what to display.

 

[Griff]

I agree with Corndog.

A thermostat or sender can fail at any time regardless of make or bike brand.

I also once had an issue on a former KTM where the overflow bottle was not partially emptying when the bike cooled. The return valve on the rad cap was to blame there.

 

[Rolex]

A guy at my work had the thermostat fail twice on his Toyota they told him they have a service life of 2 years.

My experience is most last the life of the motor but I have seen some fail much earlier, never on a bike.

Cold on one side and hot on the other will tell you, it should start out that way then even up.

Often this can be done just with your hand, but also search the radiator to ensure even heat on all fins.

It can also tell you if the reading on the dash is right, there is a chance it is not getting hot it just looks that way.

It could be risky but you could unplug the fan and see if it gets even hotter.

Poor fuel delivery or condition, plugged or more free flowing exhaust can also lead to a hotter running motor, has anything changed in that department.

I would first prove it is hot then investigate further like a leak down test, they are quite easy to do and can tell you a lot.

While you have the thermometer out check both exhaust pipes near the head to ensure they are the same.

 

[Motorpsychology]

Does the bike smell hot? Any change in engine noise when it's showing 5 bars? is there an odor of burnt oil, hot aluminum, hot rubber ? I had a car that had a frost plug heater dislodge, expelling all the coolant. Had to drive several blocks before I could safely pull over, and by then the temp gauge was almost at full hot, and all the above smells were present, and the motor didn't sound normal.

Thermostats mostly default to the fully open position. If it were to stick closed, you will not be able to squeeze it.
Can you notice it being hotter than normal on your legs? The water pump is gear driven, and dirt reliable; a failure here would be noisy and/or belching coolant out.

Being as how none of the other things is going on and no master caution light or messages, my guess is the temp sensor located in the fairing (left side in 2017, they might've moved it) or the driver in the instrument cluster are faulty.

 

[14ozarkstrom]

This is a pain but put a clear hose ( get at a hardware, plumbing supply ) you can see the coolant flow. Also is the lower half of the radiator warmer than the top. Would indicate a clogged radiator not likely but possible. Or a water pump impeller loose and slipping may be the issue.

 

[Oily]

Ive pulled the radiator guard off and given the radiator a good clean. There were a few bugs and grime in the fins so I will see if this make any difference if not it looks like it maybe the thermostat which is not a job I will look forward to.

 

[Hans471]

You can buy a new thermostat and it can be defective. There is no rule in life that it will last a certain amount of time. I have seen them last for well over ten years, seen them defective when new coming out of the box. In fact, I learned long ago to always check them before installing them. What I normally do is put the old one in water and heat it up to observe the old one as I heat up the water to the boiling point. (A can of water and a propane torch makes quick work of this. Then I check the new one under the same conditions to insure it works properly. Often I just put them both in the water and compare them. I don't like doing a job twice so I always like to double check things. Thermo check is fast and accurate. I would not blame valve adjustment, spark plugs and all those other things people like to point out until I first made certain the thermostat, one of the most common causes of overheating, was eliminated as a cause of the problem.

 

[Solo]

I had to replace the new, just replaced T-stat in my Civic. It was being intermittent, sometimes not warming up. I suspect same manufacturer as Japanese bikes.

 

[Rolex]

I can't see how a thermostat can fail open.

When you park the ts will close as the motor cools what drives it open again if it is stuffed ?

Every one I have seen failed closed and the small bypass hole, hose or valve has allowed some coolant movement

 

[Dark Angel]

The thermostats found in most engines are the wax-pellet type. They always close when cold and are supposed to open when the pellet is hot enough. When they fail it is almost always in the closed position. They also don't completely seal as there is a bleeder/bypass hole in them. This means that when they are closed you can still squeeze the hoses. The hoses only get hard when the engine is hot and the coolant is pressurized.
One thing I've seen people do that kills cooling systems is using the wrong fluid to top them up. Anything but pre-mixed coolant or distilled/demineralized water is a no-no. That includes rain water as it is acidic and carries dissolved minerals. Tap water and river/stream/lake water are worse and bore water is just asking for trouble. The result is mineral build-up inside the radiator which ends up blocking it and corrosion that eats away the aluminium in the engine casing and fittings. The other thing is people mixing glycol and organic based coolants. Don't do that. Ever. If you want your cooling system to work efficiently use ONLY the specified coolant. Don't try and be clever or cheap.

 

[Hans471]

Having worked over four decades in the automotive field I have seen more failed thermostats than you could count. The most common failure is the wax leaks out and they won't open completely, or at all. However, that said, I have seen more than one fail stuck open. I would suspect this might have happen on a very hot engine and the seal on the shaft came apart under pressure from the wax and jammed the shaft of the valve while it was wide open. Anything can, and will, happen.
I have also seen some very nasty failures due to people mixing incompatible antifreezes. We lost an engine on one of our historic LCVP's on our LST ship when the cooling system got stopped up from the excessive debris in the engine's cooling system. The boat operator ignored the temp gauge and kept running the engine harder and harder. It finally seazed up a couple of pistons and ripped itself apart internally. What an expensive mess! When we tore it down we had to scrape out all sorts of semi-solid multicolored goo left from all the different anti-freezes that had been poured into it over the years. Trust me, they didn't mix and in fact can wreck an engine.

 

[Rolex]

Someone earlier said thermostats fail open but that is not the norm.

If you buy a new thermostat and it is closed when you buy it that would be the normal fail position.

We had a pair of Aussie members on here that got their coolants mixed up, the result was a clogged up radiator, even after changing the radiators they were consciously having over heating problems, this was on 2 bikes.