Loosing coolant liquid when engine gets hot.

[bubblebeat]

Hi,

I have noticed that my 690 SM looses coolant when running hot. The first time I saw it do it was last week when I stopped the bike. Some coolant dropped on the floor via the overflow pipe. It did loose a few cl, maybe the equivalent of a shot.
When I checked the coolant level after it cooled down, it was just above the min level.
It did it again that day on my way back home. I added some more coolant over the week-end (less than max) and monitored the expansion vase while I was driving. I can see the level of liquid raising in sync with the temperature meter (the temp meter does not reach the max, maybe 1 or 2 bars below).

Has anyone experienced the same? I'm a bit concerned about this and I think it may be safer to bring the bike in...

Cheers.

[bajadog]

Just a thought.

If you have added a performance modification to your bike and not changed
your ignition/FI mapping, maybe you are running lean?

[vivianm]

I'm pretty sure that its normal operation to expand and contract with the heat...as that is why they install the overflow bottle and tubing etc.

The issue really is related to how hot the bike is running. you mention that the bars are near the top...which means that it is hot at the point in time. If you are riding around town, this is normal.

If the bars are above normal (halfway) when on motorway and riding normally...then I'd get it checked.

I felt I was loosing fluid etc, so I replaced the radiator cap as they release naturally under pressure so if they are playing up...more fluid escapes...plus temp can rise because of that

[wilmar13]

Originally Posted by bubblebeat

Hi,
I have noticed that my 690 SM looses coolant when running hot. The first time I saw it do it was last week when I stopped the bike. Some coolant dropped on the floor via the overflow pipe.

Originally Posted by vivianm

I'm pretty sure that its normal operation to expand and contract with the heat...as that is why they install the overflow bottle and tubing etc.

In order to diagnose your issue it matters if the coolant is flowing into the reservoir when hot(a), or overflowing out the overflow reservoir and onto the floor(b).
A: If into the reservoir, you can get a radiator cap with a slightly higher spring (which will allow a higher pressure before going into the overflow)
B: If it is flowing out onto the floor, you probably have a head gasket failure so combustion pressure is leaking into the coolant circuit.

Originally Posted by bajadog

Just a thought.

If you have added a performance modification to your bike and not changed
your ignition/FI mapping, maybe you are running lean?

Yes, this here is the most likely cause of both scenarios above.

I was running a PCV with AutoTune on my Husky SM530R and I had a short in the Autotune and it leaned out my A/F so bad the bike would hardly run and it was Hot. I solved the problem but a while later I had coolant boiling out, and there was a bit of soot in the coolant so I knew the head gasket was bad.

Because it is a 501cc and I have the factory 532cc kit(bigger bore), the gasket is thin from the cylinder to the water channel in the cylinder/head so it had a minor breakdown, either due to heat or slight warpage from heat. Either way even when I tore the head down, the gasket had only slight signs of damage, but it was the cause.

If you don't work on the bike yourself, tell them to look at the EGT's(exhaust gas temps) and verify the air fuel ratio is good. Then to look for signs of soot in the coolant. If all is good, get a higher pressure radiator cap (probably something like 1.8Bar) and see if your issue is solved.