Hi All, Posted a thead yesterday about high water temp due to being caught in slow moving traffic. Temp up to 101c. Had a few replies saying that their bikes quite often got to 104c and that the hand book says its OK up to 120c. Not had a look to see if this is correct. When this happened the first time, on holiday last year with ambient of 30c, my bike got to 104c also. Big panic and strip the fairing off to replace coolant once at hotel. However coolant still full. Did the same yesterday still full. My question is once it goes past 100c it becomes steam and that equates to high pressure so presumably it vents somewhere? Why no loss of level. As there is no loss of level it follows that it does not vent. Please explain. Also is 120c OK? Regards Steve
No it don't turn into steam cos it's pressurised if you was to open the rad cap so the hot water could mix with the cold air it would turn into steam
Indeed, my 916 will soon hit 102 - 105 in traffic and I have seen it at 110+ with no ill effects, also antifreeze/coolant has a higher boiling point than water.
Most sports bikes i have owned all run hot in the summer, its not nice when the bike reaches 100c. plus, My 749s did overheat a few times in traffic, My ST3s was fine in all weathers, My current bike Aprilia rsv Mille, is the same, normal temp 75c, in traffic 100c and the fan cuts in. Only thing is you right leg gets cooked. The 749 and 999 cooked you butt.
There is an expansion tank on the 1098 and I would guess on all water cooled Ducati's. Most fluids are incompressible (for real world applications). No tank and the expanding fluid would force the system to a crazy pressure and something would give for sure. The pressure relief valve is the rad cap, but that should never lift normally its a safety to stop the system exploding. Antifreeze/Corrosion inhibitor and fluid under pressure raises the boiling point so even at 120C the coolant is still in the liquid state, as others have pointed out. Its also why the dire warnings are printed about removing a rad cap on a hot engine, you depressurize the system to atmosphere, (this in itself can spray hot fluid) the boiling point drops, fluid flashes to steam and you stand a very good chance of getting scalded. Pressure cooker works on a similar principle John
My 999 reached 120 in Italy last year, riding in city traffic, the temp indicator flashes to warn you you're at the danger zone. I stopped and switched off and it boiled over, probably due to the latent(stored) heat and the pump not circulating.
Good point. If the engine gets very hot and you stop the engine, but leave the ignition on and watch the temp gauge, it will go up sharply for a couple of minutes after stopping. The heat in the cylinder head casting is still soaking into the coolant, but the coolant is no longer being circulated. If you start the engine and run it for 10 seconds or so then off, temp will drop rapidly. Some cars have an electric auxiliary water pump and fans which stay on for a bit after ignition is off, to deal with this very issue.
Ok thanks lads I should have worked that out myself really. Elementary physics but it is worrying when you think baby is about to explode. Regards Steve
bit of a hijack but I have a question that's kind of related. I have just bought a 749r and I noticed it getting warm today on my first ride on it. I didn't let it get as high as 100 as i figured the fan should have kicked in by then. Maybe I am missing something but what is the normal temperature for the fans to kick in.? I'm sure it was mid 80s on my KTM and I can't say I ever noticed on my old 749bip so I am a little concerned that the temperature sensor/thermostat for the fans is broken.
Having come from air-cooled engine on my Superlight to fitting a ST3 water-cooled engine with a small custom rad, I was also concerned about high engine temps, so currently trying some Engine Ice coolant to see if it has any affect on engine temps. Has anyone experimented with other coolants??? Cheers Pablo
I did read the replies, that's why I knew what the thread was all about. One person said theirs kicked in at 100 but I wondered if there was a definitive temp the switches were set to kick in. I get all the stuff about pressure and steam/ boiling points. My was blowing a little coolant out of the header yesterday hence my concern. I've removed about 50ml from the header and put it back in the rad. Thanks NZdave I'll run it to a slightly higher temp today before I go making a call to the dealer.
The Mutli 1200 fans come in at 103 this can be set to a lower temp but that means re-setting the ECU.
Good good, just the excuse I need to get it out of the garage and ride it til it's hot....... Quick edit. 102 the fan kicks in but only the left hand one. Next question, is the ECU set up to split the left and right fans depending on temp?
Just did this test on my 749R (see thread in Superbike section "749R Wierdness") - fans kick in at around 100 - left one first then right. Just so happen to have the Workshop Manual open right now and it states the following: First Fan: 101degC Second Fan: 102degC Hope this helps. R X
