Cooling Question

Did some serious hike-a-bike yesterday on my old KDX200 in San Manuel, AZ and caused my bike to over heat a few times. I realize now that I am going to have to put a fan on it. Anyways, I get back to the staging area and check my bike and I see my sight glass is fogged over with moisture. Now, as some know, I rebuilt this bike completely (frame up!) almost one year ago and it did get a brand new water pump shaft, bearings, and seal at that time.

My question, have any of you experienced water getting into your trans after overheating it? I just really can't believe that the seal went out in less than a year.

No I have never had coolant get into the trans from overheating.


Thanks. I just don't understand how I got the water in there. I have had no problems whatsoever with loosing coolant and/or coolant in the trans oil. I had just changed the oil the night before and I always check it for water and other contaminants and it looked normal. It just seems funny that I overheat it and all of a sudden I have water in my oil. Hmm...

I trust no1clyde. For me, it is as good as:

"So let it be written. So let it be done."


What pressure radiator cap are you using? Not sure if it makes a difference, but it would seem more likely to leak by the seals if you were using a very high pressure cap.

Just a 1.6 bar cap. Eh, I guess I'll try to tear in to it later this week and see what I find.

One thing you could try is to put a radiator pressure tester on it and pump it up to 1.6bar and leave it on over night and see if it forces and coolant into the trans or if the coolant level changes.


Hmm, I'll have to see if I can find/borrow one of those.

I have one but I'm not very close to you.


I have one as well, but not that small.

With a little bit of ingenuity you could make one. Use an old radiator cap, pull the inner seal off the cap. Then use the overflow tube to pressurize the system. If you had a small valve laying around you could rig up a bicycle pump and fill it, then close the valve and wait. Or better yet use an air supply with a low pressure regulator to keep constant pressure in the event of a small leak.

I didn't think of that. Great idea.

Well, I finally got around to draining the oil today. Not a trace of water could be found. Weird. Anyways, I filled it back up and will see how it does tomorrow. Thanks for the input, fellas!

Do you hear bubbling in the system after it heats up and you shut it down? Maybe you could have a leaking head gasket? It may leak into the combustion chamber but not to the outside.

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