Kawasaki FD590v - Coolant Geyser!

[TWG1572]

I've got a Deere F725, with the Kawasaki twin liquid cooled engine. I bought it non-running, and just got done replacing the stripped cam gear. I've probably put about 10 hours on it since, but have recently noticed that I've got bubbles coming into the coolant overflow tank. It may have been doing this all along, I just noticed it when I pulled the cap off the tank a couple weeks ago to top it off. It bubbles when the radiator is cool/engine cold, and also does it when the thermostat is open.

So today, I decided to top off the radiator since it's not sucking coolant back through the overflow tube. Completely cold engine. I pop the radiator cap, bring the fluid back to the top of the neck. For some reason, I thought it would be a good ideal to turn the engine over while the top was off. Before the engine even caught, I had a stream of coolant shooting out the top of my radiator which literally hit the roof of my garage. No kidding. Had to get a ladder to wipe it off the ceiling.

So at this point, what I think I know is that something is pressurizing the system with air. Even when the radiator is cold and thermostat closed. At this point, I'm leaning to a head gasket but I'd appreciate more expert opinions. I don't smell anything other than exhaust when it's running, I've heard that a blown head gasket has a distinctive sweet smell. But I don't know.

So where would you guys go from here? I'm assuming I'd need to do a leakdown test to confirm the head gasket failure? I don't have that tool, but can grab one from Harbor Freight tomorrow if needed. Is there any chance it's a bad radiator cap? I don't see how, but it would be a pleasant surprise vs. having to do the head gasket.

 

[Chris142]

Head gasket or a hole in a liner

 

[JTK]

Weird that just under the starter's power you'd get that much pressure/flow. That would be one heck of a HG leak.

I do know when I used to follow these things a lot more years ago, water pumps were an issue on these liquid cooled V-twins, but the issue then was external coolant leaks from the WP.

 

[TWG1572]

Now that you say that, I think my memory might have been a little foggy on the engine not running yet part. I do remember jumping and turning the key off, I think the coolant flying up in the air had me pretty distracted. I'd expected some bubbling action, but not what I got.

The WP is new OEM and replaced when I did the cam gear. It SHOULD be good, but you know how these things go. I should have just proactively done the HG at the same time when I had the engine up on my workbench and torn down - not sure what I was thinking.