998 Overheating In Traffic.

I have a 998 and on the open road it will rarely get above about 80c. If you are getting up to 100c when the bike is on the open road then there is clearly something wrong.

Are both fans working as this model has two as opposed to the one of many other models in the 748-9** range.

The fans should run for a second when you switch the ignition on and then stop, one way of checking that they are at least turning over.

Obvious checks would be to the water temperature sender and also the sender for the ECU. After that is your water level correct and fully topped up in the header tank, do you have any air locks and have you checked and bled off the system fully.

You could simply have a faulty temperature gauge which is over reading and there may be no real problem, or if there is it could be a combination of one or more problems.

Check the header tank as these split and will cause water loss and overheating, a known Ducati problem.

My 998 only gets hot in traffic and never goes above about 105/106c as the fans keep it cool enough until I can get more air flowing through the radiator.

Check pipes for collapse or water flow restriction

If the engine gets hot then heat soak can cause the engine to start playing up as the ECU may not be able to cope with the signals it receives.

I have had heating and running problems on a 748 and it turned out to be a combination of the thermostat being stuck partially open all the time and the temperature and ECU temperature senders being faulty.

You may have a stuck thermostat that is closed all the time causing flow obstruction.

Checking these points and eliminating the problems as you go should see it narrowed down with any luck.

 

120 is not good.
Theoretically, if you have the correct 50/50 coolant mix and your radiator pressure cap is working correctly, the coolant shouldn't boil untiol getting on for 130c but if your fans are allowing the temperature to get as high as 120 then something is wrong.
One thing I've heard of is the fan blades becoming loose on their spindles, so the motors run but the blades don't turn. Worth checking for but if your motor is running hot on the open road, that suggests something else is wrong.
You say that both fans come on at 103 and 106 respectively, so that suggests both motors are working correctly and that the gauge is accurate.
80-100 on the open road is hot for these bikes, which tend to run too cool if anything - my 999 runs at 70 on the open road and that's at least 10c too cool imho, maybe 15.
As @Red998 says, check for levels and if they are ok, suspect an air-lock in your cooling system or collapsed pipes. Then the thermostat.
The 998 is a Testastretta like my 999, which has a relatively easily accessed thermostat, which should be simple to replace. Thermostats are designed to fail safe though, so should stick open rather than closed but you never know.

My money's on low levels or an air-lock...

 

You don't quite say that the fans are controlling the temperature and bringing it back down but let's assume that what you mean.
Impressive fault-finding with checking the temperature of the hoses and squeezing them to see if the level rises
If the fans are working to reduce the temperature, that means you have at least some flow to the radiator but maybe not enough.
Only way I can think of to check it is to take it out, heat it in a pan of water and see what happens.

 

The thermostat has three inlets\outlets and you will need to block off one and then test the flow. The thermostats are not that good and I have replaced two that have been faulty on my bikes over the years.

They are common to all the models including the 998 and are about £46 new when I last bought one, so it's not the sort of thing you would maybe want to buy just to see if it makes any difference or not.

First check that it is opening and closing at all and then take it from there as it could be partially stuck. One of mine was stuck slightly open all the time and it caused the bike to take a long time to hit running temperature but it was also affecting the fuelling as the engine was running cold and confusing the ECU thermostat, it would flood and kill the bike through running too rich.

Your bike could be running very weak and that causes the engine to run hotter, do you run standard pipes or do you have Termignoni's or some other aftermarket exhaust.

If you have Termignoni's do you have the correct ECU to run with those pipes. The standard 45mm Termignoni's use a 996R ECU.

When you start the bike check how quickly and evenly the water pipes start to get warm. My 998 reaches about 40c quite quickly and then moves up from there. If it takes a long time to warm up then you likely have an (stuck) open thermostat and then it will be a case possibly of is it stuck in a partially open\closed position.

I checked my damaged thermostat against a new one by simply covering a hole and blowing through it, you could feel the difference when they were off the bike and the damaged one was supposedly closed.

 

You could try reverse flushing the radiator and hoses to see if anything comes out. After that you could remove the water pump impeller housing and see if you have any broken or damaged fins.

I have only ever seen one bike, a 748, that was run with a few fins missing on the pump impeller and that seemed to make little difference.

Do you have anything obstructing the flow of air through the radiator or are the fins blocked with dirt or debris.

Having cleaned several radiators to repaint them it's quite surprising how much dirt collects in the small gaps between the fins and this could be enough to hamper efficient cooling.

 

There have been a few cases of the pump impeller spinning loose on the drive shaft.

 

(I am not sure this behaviour is so unusual, is it? 70-80 on the open road, then getting up to 100 quite quickly in town, sounds completely normal to me...)

 

A quick fix might be to use water wetter. If you look up Shazaams thoughts on Ducati cooling, he says he has tried using water wetter but it cooled the engine too efficiently, by about 15 degrees all round, so he drained it again.

 

My 996 hardly ever goes +80 on the open road. Try riding faster. Happy to test this theory for you if you wish.

 

I have used Water Wetter in a V8 Chevy engine that is in my Ford 1934 3 Window coupe and it does work.

In my case the engine is very large for the space surrounding the engine and it is fully enclosed under the bonnet, additionally I also had to wrap all the headers to try and keep the heat down.

The heat soak on the engine in warm weather is very high and in your case this could be some of your problem.

However as you state, the temperature should not continue to rise when the fans cut in as they are not doing their job as they should. Are they keeping the temperature down at all? as it seems they are either inefficient or, as mentioned, something else is wrong. I suspect there is a deficiency somewhere in the system, possibly however small.

My 998 does go to about 105c when I hit traffic and even worse come to a complete standstill. But the fans keep the temperature in check and as soon as I move off then the engine starts to cool and go back to it's normal running temperature.

As mentioned Water Wetter, 40 Below and Purple Ice are all coolant additives that do work, but if it was me I would rather find a solution permanently to the problem than try and skirt round it to keep the engine cool. Also the additive does lose efficiency with time, so it is not a permanent fix for all time, it has to be topped up and replaced at times.

My aim would be to find the problem and if you bike still causes problems and you have gone through every possible angle then I would use enough coolant additive to get the temperature down to the correct zone or fit a low temperature fan sensor. You don't need to use all of a bottle to get a result. I used only one bottle in my Chevy engine to make enough difference to get the engine running at the right temperature.

You may want to consider using a temperature sensor that will turn the fans on earlier as the other possible more permanent alternative. There are a few companies that make these, and that could be a better solution.

Mocool - A Motul motorcycle water additive (Cheaper then Water Wetter)
1x MOTUL MOTORCYCLE MOCOOL RADIATOR ADDITIVE ENGINE COOLANT FLUID CONDITIONER | eBay

Fan switch kit - Evoluzione went bust a while ago but this company seems to have stock of them, or maybe something like.

www.eurocorsa.com - EVOLUZIONEDUCATI998LOWTEMPFANSWITCH

This company, which is Australian also does a switch which is compatible.

UNTITLED | Tridon Australia

 

I'd be interested in what you find. Others have had similar problems and anything that helps collective knowledge is always welcome.

 

Check the header tank my 996 did something very similar
Turned out to be a hairline crack in the plastic

 

As above and then go for a lower temperature radiator switch. The fans will then cut in and start to cool the engine before it starts to get too hot.