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Discussion Starter #1
My '95 916, (35k on the clock) which has always run dead center 180 degrees, is overheating. After about 10 minutes, it will slowly but surely climb to 210 while cruising (quicker if it is over 70 degrees outside). If I then hit a red light, it will climb to 220, and if it is over 80 degrees out, it will inch toward 250 pretty quickly. It is very, very slow to come down once it has gone that high and I am underway, and will not come down lower than 210, even if it is cool outside. There is no obvious loss of power, but I know this bike's habits, and this is NOT normal. Fan comes on at 212 and goes off at 200. I flushed the system, changed the thermostat, thermistor, and temperature sending unit, which did nothing but lighten my wallet. So then I took it to the dealer, and they changed the water pump seal (which was allowing oil seepage into the reservoir), replaced the temperature gauge (because they said it was reading high compared to their infrared and ECU readings, "confirmed" that the water pump is working, flushed the hoses (thought maybe oil had impeded flow) and the system again, replaced the cap, did compression tests (155 ea. cylinder), swapped out the radiator with a spare I had, and scratched their heads a lot, because none of that did anything to change the overheating pattern. They now suspect there may be a micro-crack in one of the heads or a small head gasket failure to the water outlet, though they have no direct evidence of either, and say they would have to tear into the engine to know for sure, i.e., major $$$. Except for replacing the water pump seal, which does seem to have stopped the oil in the reservoir, everything else has been a complete waste of money...plus they had the bike for over 2 months. At this point I don't have much confidence that authorizing them to open up the engine to 'see which head might be cracked' will do anything other than lighten my wallet $1000 or so (their estimate). So I am wondering if anyone has any other ideas of what might be the problem. (The only other Ducati shop in the area is owned by the same place and they conferred by phone, so going elsewhere is not so easy, plus the current dealer claims he will try to give me a break on pricing given the history of paying for nothing) . If I could be guaranteed the problem would be fixed, I'd bite the bullet and do it, but I really hate pouring money in without getting a solution. But at this point I am limited to riding it around the neighborhood until it starts to overheat, just to run it, which is less than thrilling. Any constructive thoughts would be very appreciated. At least I still like looking at it in the garage. Thanks.
 

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I'm no expert but until they chime in here's my 2 cents worth.

mine has always run hot but never goes above 110C (230F according to google) Except in the middle of winter when i stuggle to get it to 80C.

Running lean could cause it to run hot or maybe spark plugs with wrong heat range.

Have you changed anything recently?

What colour is the carbon in the end of your exhaust? what did the plugs look like?

You could try checking exhaust manifold and everything on the intake side tight.

A dyno run to check your air/fuel ratio would tell you for sure.
 

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Old Wizard
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Over time, the cooling fins on the two radiators become bent-over from road debris kicked-up by the front tire — thereby reducing the surface area available for cooling. Carefully straightening them and optionally add window screen mesh or similar material to prevent future damage.
 

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Discussion Starter #4
Nothing was changed on the bike before the overheating began, though the dealer did, in the course of having the bike, put in new plugs also. The exhaust, if anything, looks rich to me, i.e., pretty dark, sooty, but that too has been the case right along. Shazaam, do you think a less than optimal radiator could by itself produce this sort of slow, inevitable, overheating pattern? Swapping radiators didn't have any effect, but I suppose since the replacement also was used, with of course some bent fins, it too was just as suboptimal. I was thinking of maybe taking my original radiator to a radiator shop that can clean out the corrosion for $50. Do you think that is worth doing? (I can also try to straighten fins but I already had done a bit of that on the spare one that is now in the bike.) Thanks guys.
 

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Old Wizard
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If you regularly experience high temperatures at speed and live in a place where you don't see freezing temperatures — such as San Diego — consider using Red Line WaterWetter added to distilled water alone as your coolant.

Water Wetter is often used because it reduces the surface tension of water (the property that makes it bead-up) thereby improving further water's superior heat transfer ability while also adding the necessary lubricants and corrosion inhibitors.

Water Wetter will reduce coolant temperatures under all operating conditions. Across-the-board temperature reductions of 15°F under all riding conditions are commonly experienced.

http://www.ducati.ms/forums/showthread.php?t=82248
 

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Did this start suddenly or did it gradually start running hotter? Did it sit for a while and then start or do you ride it consistently?

I had a leaking head gasket on a car and found that with a leak down test - it would blow bubbles in the coolant when I looked in the top of the radiator. In that case, I was getting lots of scum on the radiator cap before I found the bad head gasket. I suppose your shop would be saying that the possible leak is so small it might not show up on a leak down - other normal leaks would prevent it from being seen.
 

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Head gasket

With 35K on the clock, I vote for head gasket.

A compression test won't show this, but a leak down test, when warm, might.

Try a good independent shop in your area. Dealers are good at servicing newer models, but usually suck at fixing older bikes. The good mechanics leave and start their own shops.
 

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Radiator

My 748 did the same and I did the same as you except I never changed the radiator.

My opinion not backed up by any fact is that the radiator was slowly clogging internaly causing the rise in temp because it could not get rid of the heat.

Make your your plastic overflow is not cracked. That will cause it not to hold pressure and you then get the temp rise.

I never did figure it out and parted the bike out.
 

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Discussion Starter #9
Re whether it was sudden or not, weirdly enough, I don't know for sure. The reason is that for several months the bike was running at an indicated 150 or so. It was winter and so i didn't think much of it, but then it got to be warmer out and it still was running cold. So that is when I swapped out the thermistor and bang, the gauge instantly indicated that bike was running too hot after about 10 min (verified by dealer infrared probe). So it may well have slowly gone bad without my knowing it. When I first detected that it was running too warm, I did the Water Wetter/water deal - it maybe helped a little but that didn't solve it. My plastic reservoir seems to be okay in that there is no evidence of cracks or leaks, and supposedly the dealer verified it is okay. Rather than surrender the bike and $$$ to the dealer at this point, I'm starting to think it might be worth taking a shot at getting the radiator cleaned out really well and doing the Water Wetter/water again. I think I can manage that myself (not a great mechanic) and if it doesn't do anything to reduce the temperature, I can rule out the radiator as the cause for not too much more $. Then I can take out a freakin loan against my house to return it to the dealer and let them look for micro-cracked heads or a too-small-to-see head gasket leak. Don't have a good independent in the area that I know of. T8KC, do you know of one in Costa Mesa area? Thanks all.
 

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You can test for a cracked head/ blown gasket yourself easy and cheap by testing a coolant sample.
[ame]http://www.amazon.com/Lisle-75500-Combustion-Leak-Detector/dp/B0007ZDRUI[/ame]
 

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Discussion Starter #11
Hey, thanks, Davy.J. Never heard of this! I'll have to look into it. I wonder why the dealer doesn't have something like this...maybe because there is no money in it compared to ripping the engine apart?!
 

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the radiators have a divider plate in the lh tank, which sometimes fails. warm it up with the fairings off and feel both ends of the rad to make sure they get hot. i've had rads where you can put your face on the rh side while the lh side is so hot it'd melt it off.
 

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could be a bad thermostat, or the fans not working.
 

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I know you said that you swapped radiators, but the swapped one was also used. Consider cleaning out the radiator. I was impressed how much stuff came out of my radiator when I cleaned it this January. Mine runs cooler now. It now takes a bit to get to 180 (straight up). Granted, it was 54 degrees F outside when I ran it, but it would have heated up more quickly prior to the clean. I was previously running water/Water Wetter, and now I'm running 35-40% coolant mix. I have a low temperature fan switch from Motowheels, as last summer, my first summer with my 996, I was uncomfortable with how warm it was getting, even with Water Wetter.

I took the radiator off, covered the outlets, and poured vinegar in. I let it sit for a couple days, every now and then going out to the garage to shake the fluid in the radiator. When I poured out the vinegar, I flushed with distilled water. That is when gunk came out of the radiator. It looked like globs of goo for lack of a better way to say it. I was impressed enough to try again. When I flushed the second time, here was nothing else that came out of the radiator except the water.

I'm pretty sure it had never been cleaned in its 15 year life.

Anyway, worth a shot and won't cost you anything except a little time (and whatever you choose to clean with).

Good luck!
 

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Discussion Starter #16
thanks, yeah, I'm thinking of going at the radiator for sure. I know my original one had never had the sort of flush you describe, and the spare, which is what is on the bike now, was off eBay so who knows on that one. Fingers crossed. Thanks.
 

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I modified mine for a second fan as well. Runs cooler.
 

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By all means try the radiator flush, vinegar is cheap and works well if you don't want to take it to the radiator shop. Checking for combustion gasses in the cooling system is a good but not foolproof way to check for headgasket leakage. Your radiator shop probably has a tester and it is simple to use but the bike has to be there and running. It could be that the gasket only seeps at a certain temperature due to head warpage/thermal expansion differences.
 

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a couple of things...

1 You said you had changed the temp gauge, as it registered higher than the external thermometer test, dd you change the temp sensor as well? These parts ar known to fail, and I personally changed it before I had spent the coin on the new gauge. What was the max temp the shop got with the external test?...

2 While it is unlikely to have two bad radiators, it is not impossible. before I ripped into the cooling system again, I would check for the head gasket leak, using either a leak down test as mentioned, or the chemical test. A good parts guy at an automotive parts house can help you with this...

3 A sometimes overlooked potential cause of overheating, is improper ignition timing. It will affect things as much or more as a lean condition...

$ If the fan is indeed cycling properly as you said, that leads me back to the faulty sensor, if the engine is getting past 220 degrees, the fan should not shut off, it shuts off, when the engine temp cools down. something is askew here, let us know what you find out...
 

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Discussion Starter #20
Well, here's some new info. Understand that this saga has been going on for about 18 months, so my memory is a little hazy. But fortunately, I'm decent about logging what I or others have done to the bike. So...going through my notes, it indicates that at the start of all this, I put in a new thermostat, a USED temperature sensor, and a used thermistor (sourced from a reputable online company, but nonetheless, used). Yes, I am a cheap SOB. I apparently did NOT change the temperature sender (so my original post is incorrect on that point). The dealer ended up installing a new thermistor and a new temperature gauge.
Reading the report more closely, they also did a leak-downiest and found 0-2%, which I guess is why they were not thinking head gasket originally. So, to summarize, leak down results seem okay, bike has new thermostat and thermistor, but used temperature sender and used temperature sensor.

I had the same thought about the odds of two bad radiators, but now with this "new" info., I'm wondering if I should try replacing the sender and/or sensor with new OEM? I don't like throwing money at parts needlessly, but I personally can handle replacing the sender or sensor (no labor charge). On the other hand, the dealer's notes, after they had done everything, says, "still running hot at 190-200 on gauge with infrared and ECU confirming at 185-195." (that presumably is at warm up because it goes way above that as I've noted after 10 min. or so). So that implies there IS some overheating going on rather than just a misleading sender/sensor issue right?

My head is starting to hurt again, which is why I've let the bike sit in limbo so long. Going to go do my short weekly ride to run it now after which I'll feel the radiator to see if both sides are hot. Thanks for continued help.
 
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