I have had this problem for a couple months now and can't figure out what is going on. I have an 06 Vee with 15K miles. After about 10 minutes I get bubbling in the overflow tank but the bike is at 2 bars, not hot. Another five or 10 minutes pass and the bubbling increases and fluid level begins to rise in the overflow bottle and temp goes up to 3 bars. I don't want to keep on riding because I am worried it will totally overheat. I have replaced the radiator cap. Flushed and replaced the coolant. Removed all air bubbles. Checked that the fan comes on and it does, usually when the bike hits 3 bars. Nothing else wrong with the bike that would indicate head gasket. I plan on replacing the thermostat next. Why would I get bubbles at 2 bars? Should I go for the sending unit? What about the water pump? The service manual says "replace water pump", what part of it? Any help would be great. I talked to my mechanic and he basically said he will just start ordering parts and replacing things until it get fixed but I can only imagine how much that will cost.

Check the cap seat surface and test the cap. Coolant leaving the radiator at 2 bars is an indication the cap is passing pressure it should be holding.

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Pat- 2007 DL650A was ridden to all 48 contiguous states. 2012 DL650A is just getting started.
Nicknames for posting ease on my part, Vee = all DL1000s. Wee = 2004-2011 DL650s. Glee = 2012+ DL650s

I agree with Greywolf on this. If the temp indicator is at 2 or 3 bars and the engine doesn't seem to be hot then there is no way the coolant should be able to bypass the cap and flow into the reservoir more than just enough to slightly raise the level. Is it actually filling the reservoir and overflowing from it?

Carefully check the sealing surface in the radiator neck. Carefully check the radiator caps rubber seal for ANY defects ( cuts, slits, holes ).

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This is exactly the problem I had earlier in the summer, inconveniently a long way from home.

It was the radiator cap. I replaced it with a new one, problem seems to be solved.

I also think that my thermo switch went bad, resulting in the fan not coming on. This put additional pressure on the cooling system, which resulted in the rad cap failure.

I have a replacement thermo switch - swapping it out is on my very long to do list.

When this problem first started I took it to my mechanic. He said he pressure tested everything and it looked fine. I replaced the radiator cap anyway because its cheap and easy. I will take a better look when I put the thermostat in.

It has filled the overflow tank one time and leaked coolant down into my skidplate. I think it went to 4 bars on that occasion. It was 100+ outside and I had been riding about 30min in town. That makes me think that if I ride it long enough it will overheat but it does not explain why I would get bubbles after 10min and only 2 bars.

2 bars is not overheating. If the cap doesn't hold the pressure, coolant will expand past the cap, boil at a lower temperature than when under pressure, and lower the volume of coolant in the radiator. Those actions will, in turn, allow the temperature to increase to four bars.

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Pat- 2007 DL650A was ridden to all 48 contiguous states. 2012 DL650A is just getting started.
Nicknames for posting ease on my part, Vee = all DL1000s. Wee = 2004-2011 DL650s. Glee = 2012+ DL650s

Had the same problem with my vee, turned out to be the radiator had a split in the fins and when it heated up it would cause the water in the overflow to bubble over. Was hard to find the leak as being alloy it would expand under heat and seal up when it was cold. Replaced the radiator and all is now fine. Hope this might help.

Do you remember how you figured out that was the problem?

For future reference, if you do end up finding a radiator problem, you can have it repaired by Myler's quite inexpensively.

Myler's Radiators, Motorcycle Radiators, Radiator Repair, Radiator Sales, Offroad, ATV, Street, parts, accessories, apparel, service, jacket, glove


But please -- just replace the cap first. Odds are good that's your problem, and it's less expensive than what sounds like an incompetent mechanic.

A pressure test probably would not have uncovered a problem with the cap simply because the cap wasn't part of the test -- most pressure tests are done with a fitting that replaces the cap.

The pressure test does tell you that the rest of the system is sealing well, so it's likely everything else is OK.

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2002 Suzuki DL1000 V-Strom, Dark Metallic Space Blue
1983 Suzuki GS850G, Cosmic Blue
2005 KLR650, Aztec Red - Turd II, the ReTurdening

OP states cap has been replaced. I still question how the head gasket was eliminated as an issue?

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2007 Blue SuperVee 1000
2002 White HD Road King Police
2000 Red Honda XR 400r
2003 Green Honda Rincon 650 ATV

If it is not broken, it can still be fixed