evening all. Noticed that on the last ride out and also today, the temp gauge suddenly drops to 40 or 50 degrees while riding at a quickish pace. One minute it would be showing 70 or 80 degrees then while moving at the same pace shortly after, would drop right down then would go back up to showing normal running temp? When this happens, there is no change to the RPM showing so thinking it might not be due to the battery which is probably due a change anyway... Anyone seen this before? Cheers, Ian
Air in the system can be a possible cause of this. I have had this on bikes and cars, as the water flows if a an air bubble flows over the temperature sender then the temperature sender will show a drop as water will not be in total contact with the unit. Try bleeding out the system and also after a run remove the radiator filler cap and see if you get water bubbling up into the header tank. Check that you system is not too pressurised before releasing the cap and leave the engine to cool slightly before releasing the cap as above. You can also run the engine with the cap off to see if any air escapes. Check the air bleed valves on the bike and let a bit of water escape from them as well to be on the safe side.
Also check the wire on the sender for the temp gauge I had the same on my 748 was a bit corroded so cleaned it up was fine after that.
Yes, I wondered about air trapped in the system causing this but shouldn't it find its way out eventually??
Thanks lads. I'll have a look at it later. I cleaned up the contacts on the temp sender but maybe didn't do the wire... but the temp needle doesn't drop to the resting point so maybe it's not that... Red, when you say the bleed valves, are you referring to the drain plug on the water pump housing? If not, where are they located? Cheers, Ian
Based on my experience yes normally they often do, but if you get a bubble that gets trapped or circulates without finding it's way up to the header tank then it can be more difficult to get out. I have had situations where I have had to have several goes at getting all the trapped air out of some systems. The tube to the Ducati header tank is quite narrow and I suspect at times that when water flows around the system it finds it easier to follow the main route of flow and therefore does not always go up to the header tank. Conversely I have filled some systems and ran them and thought all the air was out and then taken them on the road only to find the level drop quite a lot as all the air finds it's way out eventually via the header tank. It can be a real pain at times bleeding a system completely.
Some Ducati models have air drains on the elbow of the water pipes that supply the heads, they vary between models as the elbows themselves differ. I know the 998 uses a hose that is the same as a 748R but I have never looked to see if the elbow it is attached to has a air bleed on it. I know that 748E's do from my experience. If you don't have\cannot find one then just slacken the drain on the water pump and see if anything comes out there. I have found pinching the radiator pipes where they enter to the top of the radiator sometimes dislodges air and can push it up to the header tank and therefore lose any air bubbles. Pinching a hose can give you a good idea of the possibility of trapped air. I do this always when refilling a system and in fact try pinching all the hoses as I slowly top up. Check also that your thermostat is opening fully, I had one case where the thermostat was only opening about half to three quarters of what it should have been, It caused me a bit of a headache for a while and also in my case started to affect the cold starting and also it was upsetting the fuelling as the engine ECU was getting misleading information from the engine temperature sensor. I was also getting frothing from interrupted water flow resulting in air belching in the system. In the end I had to replace the thermostat, the temperature sensor and also the temperature sensor for the ECU, only then was it finally cured. Having said all that it could be something entirely different, and another thing that springs to mind if you cannot get air out of the system is that a head gasket could be leaking and air can be pumped in via the engine running. I seem to remember someone had this problem once on this very forum (or the old one!) and commented on it.
I'd be surprised if it was but I know of two cases of head gaskets going, only one being in the 748-9** range. I think the forum mention was for a 1098. I only mentioned it as something to be aware of.
Thanks again lads. Going to see if I can get any air out of the system first. The thermostat could also be a cause. But I think the engine runs slightly rough only between 5,5 to 6k rpm... If it were the thermostat, wouldn't the air/fuel mixture be upset throughout the rev range? Cheers, Ian
Don't know about the head gasket. I'm not losing any coolant but there's always a bit of liquid, (tiny drops) at the bottom of the rear cylinder.
Aye that'll be it, fooked, need to get shut of that old bag of nails mate, I'll take it off your hands I need a conservatory ornament
Is it water, oil or condensation? If there is any sign of a leak, it just may, be the sign of a potential problem. I don't want to start scaremongering you but some fairly innocuous things can turn out to be major or minor. My new 998 at first service leaked oil from a valve access plate and this had to be sorted under warranty, this should not have happened but I soon realised that this was nothing new if you want own and run a Ducati. I feel it has to be said that resilience wise Ducati don't score as highly in my book as Japanese bikes, but call it character or whatever you do have to get used to it, know the foibles, and deal with it if you want a bike of character(!), And i do love them, they are very unique and a privilege to ride, when, in my case, I get the time to ride them. They can be costly. Just work through the options and figure out what you think it could be and eliminate it and move to the next aspect. Fundamentally, from my experience, you should not have any water leaks and you should not find yourself either losing or using water. My three bikes have no problems now and remain constant and predictable and do not use water or get over pressurised on the water cooling front. I assume you have checked for the dreaded failing header tank which can lose water mostly, but could potentially suck in air as well. Some of my comments may be a bit out there, but experience has shown that all potential problems need a thorough looking at. I have learnt the hard and expensive way in the past.
Hi red. No leaks from the header tank as of yet. The water or oil at the bottom of the rear cylinder doesn't seam to get any worse but TBH, I haven't really got into that yet. Can't see it being much to do with the temp reading but just a separate issue to be sorted. Cheers
It could simply be a bit of oil blow by and a bit of\or condensation and maybe a combination thereof. Just try and narrow it down, go through the logical and the illogical and work from there. It is highly likely to be nothing but from a few (very!!) costly experiences what can seem like nothing can amount to something, if there are problems try and nip it in the bud and save some cash. I lost a replacement alternator case on my 748R when the main bearing went on my 4,000 mile engine and I didn't suspect it or narrow it down enough, upshot a £1400 bill and £900 was for parts. It's all good now but a stitch in time etc, and of course a bit of bitter experience. I have been there more times than my wallet can remember!!!
