Water in cylinder. Water pump seal?

[Erics350x]

I have a 98 Polaris 400 that keeps getting water in the cylinder so bad that it dumps out the exhaust. Ive had the jug and head deck surfaces redone twice, honed, new gaskets 3 times, and new rings. I cant see any cracks so im lost. Id think that if it was a crack that let in this much water it would be easy to spot. Could it be getting in from the lower end like the water pump or something?

[TimSr]

Gotta be from the top end, cracked head or water jacket, if not the head gasket or surface. Need to pressurize the cooling system to check it. For cars, they used to use a hand pump that attached through its own raditator cap. Not sure what they use for bikes. Your dealer might might have a fixture to pressure test just the head.

[JasonB]

ya def sounds like a leak in the head somewhere. Water pump wouldnt have anything to do with it. Have you had it professionally decked or did you do it yourself somehow? I would talk to however has done that work several times for you, a crack in the jacket/sleeve can be hard to find. Is your overflow tank bloated or pressurized? I think when theres a leak in the head like that it pressurizes the coolant system. When you say its 'running out the exhaust', does the bike run after it gets to operating temp and coolant is flowing? I would think for there to be that much water getting in that you would have issues with having enough compression to run the bike right

anyone feel free to correct me if im wrong with anything above :lol:

[Scootertrash]

The water pump is sealed off from the cylinder/crankcase on these motors. My guess is a cracked cylinder or head. You could check your local auto stores for a rental radiator pressure tester. Some kits have an adapter that will fit the ATV radiator.

Full Disclosure: I've never done the pressure test on one of these but this is what was posted on another forum:


Put the piston at TDC w/plug removed and crankcase drainplug removed. Pressurize it and see where the leak is coming from. If it leaks at the spark plug hole-head or gasket problem. If it leaks at the case hole-base gasket, w pump seals or case problem.


If you determine that it's coming from the cylinder or head, there has got to be a way a shop can verify where the crack is.

Couple more questions:

Is there coolant in your counter balancer oil? (This won't affect your particular leak, but it could point to another problem-bad water pump seals-the 350 and 400 Polaris motors are known for this problem.)

(like Jason asked): Is your coolant reservoir bulging or are you getting bubbles in the reservoir when it's running? Are there bubbles in the radiator when it's running and you have the cap off so you can look inside? Sometimes it's hard to tell with the pump circulating the coolant.

Pull the crankcase drain plug and see if you get coolant out of there.

[Erics350x]

I was pretty sure the water pump was seperated, just didnt know if it coulda blew a crank seal and got in or something. I was thinking Its gotta be a crack in the head or sleeve also but i cant find it. Two machine shops didnt see it either. i guess ill just buy a whole used topend, i just hate not knowing.

[Scootertrash]

I know what you mean.

The water pump impeller is on the end of the counter balancer, on the recoil side of the motor. The counter balancer has it's own compartment separated from the crankshaft compartment, which is at the front of the motor. On a 98 I believe you'll have a dipstick or pull cap on the recoil side of the motor, beneath the carburetor. Make sure you check this oil regularly and change it regularly, This will let you know if you have bad water pump seals before you damage the bearings and/or counter balancer. The counter balancer runs about 500.00 from the dealer and good used ones are hard to find.

I would think you'd be able to find a good used head and cylinder on ebay or craigslist.

[Erics350x]

Just a update for others with this problems. It was the water pump seals, all the water washes out the crank seals and was letting it into the cylinder. Looks like the only right way to fix it is rebuild the bottom end. From what i've read its a common problem on the polaris 400. Wished i'd known before rebuilding one topend and buying another used topend. If i'd checked the oil at the start i'd seen it was full of water.