Try and source a product called Water Wetter. https://www.redlineoil.com/waterwetter This will help immensely. I use it in my 998 which had suffered the same problems as yours and eventually blew a head gasket (happily repaired under warranty). It’s stressful enough watching the needle climb relentlessly without being able to do anything about it. I don’t use the bike very much these days and certainly not in traffic but when I did, this stuff had the added advantage of lowering my heart rate too!
Pressure. Increased pressure increases the boiling point of a liquid, a vacuum decreases the boiling point of a liquid. The system should be sealed, thus as it heats up the liquid expands, the pressure increases within the system and this elevates the boiling point. A leak will cause the boiling point to remain at what it is at normal atmospheric pressure which for 100% water is 100c and for coolant (50/50 water/glycol) is c.120c. Normal operating temp of the engine is 90-100c Waterless coolants are as high as 200c!
thank you very much for all your replies, is very much appreciated ive ordered a new header tank an ill try that first then go from there jus for reference, cool system is good, motors jus been built everythings clean an fresh, rad has a few bent fins but seen a lot lot worse ill keep this updated as I go but for now ive actually got to do some paid work rather than playing with my bikes ! does anyone know anymore about uprated fans or 996 fairings onto a 998 ? I got a funny look when I got my tape measure out in motorapido
Bear in mind that Ducatis are Italian and Italy is hot. It’s likely to be OK if your cooling system is working as it should be. Check your coolant level and mix and that your system is free from dirt and faults (inc radiator) and that the fans are working as they should be. They do pump out a lot of heat though. Makes you feel alive.
Fishead, the bike has a thermostat which will set the running temp for normal riding (open road for most of the year will be 65-70c), the two fans cut in at 101 and 102c for when driving in stop start traffic. The thermostat reacts to the fluid temperature in the system and progressively opens from 65c on wards to allow coolant through the radiator as it gets hotter. It is not fully open until 90c or so. Up to 65c the coolant circulates around the engine only. It is the thermostat opening that controls the engine running temp under most conditions and not the fans or the snake oil properties of the coolant (despite what some claim). As Fire3500 has said the bike is designed to work in climates 10 degrees hotter than the UK so before you start spending money on fans and faffing around with the stock set up you need to make sure what you have is working. The cooling system can easily cope with the engine on tick over at 35c but the fans will be on a great deal. You could have the biggest fan in the world and the wettest water that is possible, but if is not circulating through the radiator it is all utterly pointless. So take the thermostat out and see if you can check its function by putting it in a pan water on the stove(a thermometer is useful if you have one) or simply change it. Also there is a possibility that the system has an air lock or the connection for the temp gauge or coolant sensor is dirty giving a bad reading. It is very easy to test the temp sensors with a meter set for resistance (resistance drops with increasing temp) to discount them as a sensor error. To check the system is pressurizing you simply get the engine fully up to temperature (above 65c) and squeeze the hoses. To save you some money stick with normal coolant equivalent to oem at 30-50% but don't put it in whilst you are diagnosing the fault otherwise you will waste quite a bit. Unfortunately the tank has to be lifted to fill the tank and bleed out the trapped air but you can bleed out excess on the water pump drain screw once the problem is sorted. The system takes 3.5l from empty. Good luck finding the issue
thank you very much for your help ive rewired the fans they now both cut in at 93 and out at 80 thermostat is new an works good rad /cooling system is all gwo I rebuilt engine in march all waterways ect ect clean an clear slow moving traffic ect fans cut in but temp on gauge still increases an will go all the way to the 120 top reading when I was balancing bodies I wasn't keeping an eye on it an it jus cut out an wouldn't restart till it had cooled down [pre rebuild] to me this isn't right, even if it is normal for this bike in my head its not right, I do a lot on my bikes different events ect ect an I don't want to be worried its going to pop if I have to que to get into bsb or whatever, I jus want faith in her in my head [im no ducati expert yet, know my way around her now but still lots to learn] 996 had single fan I think, 998 has 2 im guessing ducati changed fairings then realised the problem an added a fan my theories at mo are fans jus don't pull enough air its got temi 45 cans on, may need mapping [don't really want to pay for mapping until ive scourced an fitted a full system] fairings without cut outs jus don't allow the heat out quick enough don't want to spend money unnecessarily but in my head shes not right an I would like faith an peace of mind thank you very much for your help, much appreciated
don't rule out that last summer and so far a few days this year, we are experiencing quite some hot days and if you don't ride the bike all year round then you might be looking for something that is perfectly normal. Some bikes are/were never built to be a commuting bike or used regularly in built up stop/start traffic. I have seen some classic car owners use evans waterless coolant but I'm not sure I've seen it so much in bikes let alone ducati's
Just a thought; in #27 above you say the fans cut in at the correct temp but that the gauge continues to rise until it reaches 120c; you have checked the gauge is displaying accurately haven’t you?
I actually haven't specifically, however I have fitted a lower temp fan switch, which the switch temp range does tally up with the gauge, so no alarm bells have rung so far good thought though, thank you is something ive taken for granted
Makes you feel roasted alive . I sort of had a " Baptism of Fire " . Brand new ST4 , bought in Bologna in a July that was very hot even by Southern Italian standards . Rush hour traffic in Milan had the fan running almost continuously and you could hear the water gurgling at every traffic light . Temperature rarely went below 100 , and I'm thinking " what have I just bought ? " But then a drive across the alps that was so good I just wanted to hang a U turn , and do the whole thing again ! I kept it .
It might be that the gauge is accurate up to say 100c but then goes doolally; worth checking out anyway. My 748 sin pieces at the moment so I can't trace the wires back but your temp gauge will be connected to one of parts 18/19/20 on the attached diagram. Which ever one it is I'd lay money on that it's a relatively cheap part and readily available. If it were me I'd purchase a new replacement one, swap it over, and see what the temp gauge reads afterwards.
A shot in the dark here ..... but does your model have two temp sensors ? I only have circuit diagrams for 748 , 916 , 996 and they all have two . One goes straight to the ecu , the other goes to the display . AFAIK , they are identical so it makes it very easy to swap them around and identify a faulty sensor without buying a new one , just to check . Just a thought ..... I don't know diddley about the newer models .
Out of curiosity , I looked at the parts schedule for my own bike . Those two sensors ARE identical , and the part number is 55240131A " Water temperature sensor " Mine was made 20 years ago , but I bet a dollar to a donut that they are still using it . A lot of the sensors and other electronic doo-dads have a BMW logo moulded into them ( or Weber ) And they are often cheaper to buy from BMW parts suppliers than they are from official Ducati parts dealers .
I rode my bike in to town this morning and had to stop to make sure it wasn’t shooting fire out of the fairing where it was so hot. In this weather, everything is amplified like mad, but it is good in the winter
748/916/996 have three temp sensors If you look at the bike from the left the there are 2 horizontal ones pointing at you 19&20 on the diagram The rear most 19 is for the ECU the front one 20 is for the fans. The vertical one not numbered on the diagram below the bolt number 27 is for the temp guage
done some googleing an it appears this is a very common complaint of 998s had a look about when i had it in bits doing other bits, imo the fans are shit, id prob be better off getting off of it an blowing on the rad, only just enough suck to hold a piece of paper on the rad ! my rad is clear internally and externally ! i spend ages fairly regular ensuring its clean [bugs] an straightening any fins next step im gonna start working out how to fit better higher cfm flowing fans if anybody has an old spare rad doesn't need to be any good, jus not mangled and pref 998 if poss so it has the twin fan fittings, that theyd loan or sell me so i can start working out what an how i can get something to fit would save me an ebay wait an be much appreciated
This is the nub of it for me. Threads about 998s running hot come around every so often and people get very animated about possible fixes, bigger / different fans / relays / fluids etc. I don't think it's worth the effort really. 998s run hot, and very hot in town, and one really has to try to avoid town.
