Hello all,

I have a small bit of coolant leaking out of the weep hole below the thermostat housing on the left side of the engine. It's a cold leak - it doesn't leak while hot or running, but only after left overnight and cooling down. It ranges from one to about 3 drops, approximately. The fluid is green and doesn't appear contaminated with oil. Anyone had this before? How serious is it? I looked around the forum for similar problems but didn't stumble onto any similar threads -- if they are already out there a redirection is appreciated.

The bike is a 2006 KLX250 with 3,300 miles.
Thanks,
Scott

 

Would pay to fix it before it become a major problem

 

One of the knowledgeable people will be along soon, but, from ALL the previous bikes I've had, it means your water pump seal is failing. Usually it's not a big problem to fix, just the cost of the new seal, and some semi-delicate wrenching. Usually it's the impeller nut torque that requires careful touch, as they historically strip easily if you don't have a torque wrench on it to monitor applied force.

Again, wait for someone with specific experience with this bike before you count my answer as correct....

 

Looking at my bike, the thermostat is in the head and water pump is near the crank.

David

 

That is correct...and the thermostat housing has no weep hole. I think the poster must be referring to the "drain" hole that allows fluid to escape from the spark plug cavity...like during a rain or when washing the bike. If coolant is coming from there, I'd suspect one of the following. Worst case is a cracked head...unlikely but remotely possible.

More likely is a dribble of coolant from the thermostat housing o-ring, cracked housing, or a dribble of coolant from the hose where it clamps onto the housing. These possibilities could make it look like the coolant is coming from that drain hole. It's going to be hard for coolant to actually be in that spark plug cavity and then be draining out of that drain hole. Coolant could be wind driven from the rad cap or top of the radiator somewhere and pooling into the spark plug cavity, but I think you'd see evidence of this on other parts of the bike...not just the drain hole. Even a bad head gasket would make it difficult for coolant to pool in this cavity without being quite evident elsewhere on the motor. Coolant in the combustion chamber would have an extemely difficult time getting past the spark plug and into that cavity.

I'd look first at the thermostat housing integrity and/or the hose clamping at that spot. Of course, I'm assuming the poster knows left-from-right on the engine, and the difference from the water pump and the thermostat housing.

 

Of course, you are correct! I should have read the OP more closely.

 

All I see listed in the parts is an elbow. No thermostat. I ASSume there is one.

David

 

There's a thermostat under that aluminum hose elbow on the countershaft side of the engine at the cylinder head. If you look at a parts diagram over on Bike Bandit under the cylinder head, it is listed.

 

Found it
Thank you.

David

 

Yes, the poster...IDRIDR...let's call him Scott ('cause that's my name) knows right from left and top from bottom...at least on most days...but admittedly not on every day......because of course there are __those__ days.

okay, joking aside now.

It sure looks to me that the fluid is coming from the below-thermostat weep hold. Looked fairly closely at the spark plug basin tonight with an inspection mirror and didn't see any fluid. But tonight's real project was my first real mod for her (not yet named, still waiting to get to see her real personality). Installed her 49 tooth rear sprocket and 110 chain leaving the front at 14T. We're looking ahead for some sweet technical riding this weekend or next. A few walk alongs at idle RPM and _easy_ wheelies from a stop out front tell me this is the right gearing for now.

But from what I can see, the leak is still coming from that darn hold. Will dive into the thermostat gasket and housing soon as I'll be digging deeper to install Watt-Man's Thermo-Bob very soon.

In the meantime, I'm sure hoping this doesn't turn out to be one of the possible bad problems like a cracked head.

IDRIDR...hrd