Infamous Coolant Overflow

[Willasan]

Rode again today, all through the heat of the day. I believe it got close to 90 degrees. Pushed her hard, never saw the temp go into the last block when stopped. No overflow.

 

[Deleted member 351]

I would take pictures or video if it happens next time. Take a picture of the temperature gauge as well as any coolant that is spilling on the ground. This will give the dealer and idea of the extent of the problem. I would note whether the fan was on or not before turning the bike off and take a picture of the coolant level with the bike level to show it is at the proper level and not overfilled when cold.

Thanks, i am making sure to take video when i shut my bike, So far I rode it around for an hour up in the twisties and no overflow when I shut my bike off. When I got the bike back the coolant was just a little bit about the min line. I'm not sure if its a combination of the new coolant and the level that is making the difference. it hasn't overflowed so I'm happy.

 

[gbabyracing]

For some of you with apparent over heating:

I talked with another RC390 tuner this last weekend who found their bike to have a slipping water pump impeller. He retightened for the fix. I would suggest that while under warranty, if you are have real cooling issues you contact you dealer as soon as possible.

 

[reenmachine]

I don't think so. I think it's the altitude affecting us. I'm going to try and find a 1.6 bar cap locally so I can try it this weekend. It's 105° up here too so I'll get it plenty hot here in town at low elevation before and after the swap and then head for the mountains.

After further thought, I've changed my mind about the altitude affecting it for now. The cooling system is a closed system so the difference in external air pressure shouldn't make a difference within a normally-operating cooling system. The pressure relief the radiator cap offers is resisted by a spring, not some device that relies on a balance of air pressure that would be thrown off by the altitude. I now think I (and other pukers) just have caps on the low end of the quality scale, which wouldn't be too surprising.

I rode hard today under the same conditions as usual, but I paid a lot closer attention. The bike never ran hot -- always sat right at 2 bars below the break, which is completely normal for me since I switched to distilled water & MoCool. The cooling system appears to be functioning normally. I'd shut the bike down but key up so I could watch the temperature gauge, and the highest it ever got was 1 bar below the break. Not hot at all. However, the reservoir would start bubbling rapidly, followed shortly thereafter by a decent puke out of the overflow hose. I reproduced this three times back to back.

So, pressures shouldn't be all that high in the system at the temperatures I'm seeing and thus the radiator cap shouldn't be releasing, causing all this, but it is. This is what leads me to believe my cap isn't holding the rated 1.4 bar.

As a result, I was thinking I'd just buy a better 1.4 bar cap from Moose Racing and see what changes. But frankly, does anyone see a downside to just going to a 1.6 bar cap while I'm at it?

 

[reenmachine]

After further thought, I've changed my mind about the altitude affecting it for now. The cooling system is a closed system so the difference in external air pressure shouldn't make a difference within a normally-operating cooling system. The pressure relief the radiator cap offers is resisted by a spring, not some device that relies on a balance of air pressure that would be thrown off by the altitude. I now think I (and other pukers) just have caps on the low end of the quality scale, which wouldn't be too surprising.

I rode hard today under the same conditions as usual, but I paid a lot closer attention. The bike never ran hot -- always sat right at 2 bars below the break, which is completely normal for me since I switched to distilled water & MoCool. The cooling system appears to be functioning normally. I'd shut the bike down but key up so I could watch the temperature gauge, and the highest it ever got was 1 bar below the break. Not hot at all. However, the reservoir would start bubbling rapidly, followed shortly thereafter by a decent puke out of the overflow hose. I reproduced this three times back to back.

So, pressures shouldn't be all that high in the system at the temperatures I'm seeing and thus the radiator cap shouldn't be releasing, causing all this, but it is. This is what leads me to believe my cap isn't holding the rated 1.4 bar.

As a result, I was thinking I'd just buy a better 1.4 bar cap from Moose Racing and see what changes. But frankly, does anyone see a downside to just going to a 1.6 bar cap while I'm at it?

Just as a final update, I fitted the 1.6 bar Moose racing radiator cap after flushing the coolant 3-4 more times (until it ran clear) and filled with distilled water and MoCool. I ran the bike hard today on the same route that causes boiling and puking 100% of the time and I experienced no boiling, no puking, nothing.

I'm very pleased. Again, I think I just had a faulty radiator cap and the 1.4 bar Moose cap would probably have done the trick, but I won't mind the added efficiency of the 1.6 once summer rolls around again. I'll update if anything changes, but I think I'm good to go.

 

[Willasan]

Reenmachine, I believe I also had a defective cap, same situation as you. I'm glad your fix was as simple as mine.

 

[reenmachine]

Reenmachine, I believe I also had a defective cap, same situation as you. I'm glad your fix was as simple as mine.

You just replaced yours with a new OEM cap?

 

[Willasan]

You just replaced yours with a new OEM cap?

That's correct.

 

[ShinySideUp]

I've never had this problem & I frequent the mountain roads in los angeles canyons quite often. lil over 3k miles on it.

 

[reenmachine]

I've never had this problem & I frequent the mountain roads in los angeles canyons quite often. lil over 3k miles on it.

I'm not surprised -- there are many people putting the bike to heavy track use without issue either. It looks like there are just some bad radiator caps out there and I got one of 'em.