Hi, I have a 2003 Scrambler 500 and the coolant keeps overflowing out of the coolant reservoir bottle. I know that it is not overheating my fan cycles on and off fine and the overheating light never comes on. I have replaced the radiator cap and tried to bleed the air out of the system several times and have had no luck. Some times this happens right away and other times it takes an hour. This has stumped me and my dealer and was hoping you guys could help. Thanks.
Jason

 

A few things that could be going on are:
1. Bad thermostat
2. Leaking head gasket.
3. Cracked head.
4. Cracked cylinder

 

Hey, I forgot to say that i did also check the thermostat and it opened and closed at the specified temps. I don't think that there is a leaking head gasket, cracked head or cylinder because it dosn't so any kinds of white smoke or any coolant in the oil, but how would I know for sure? Thanks for the response.
Jason

 

The head gasket (most likely problem) or crack is only leaking at pressures above 15 psi. Since the radiator cap spills coolant back to the recovery tank at 15 psi, the coolatnt does not leak into the cyclinder or crankcase. But cylinder compression is way over 15 psi on the compression and power strokes. During one or both of these stokes is when the gasket or crack is leaking. The leakage enters the water jackets, pressurizes the coolant and cause the rad. cap to spill to the recovery tank.

Quick test is to remove the radiator cap and start the engine. If water shoots out the rad cap neck then it is time to tear the top end down.

A better test is to remove the rad cap and than apply a leakdown test over 10 minutes. Any sign of bubbles at the rad cap neck indicates a leaking head gasket or cracked head.

 

ok, thanks for all of the good info. I just tried removing the radiator cap and reving the engine and nothing happened. I will do a leak down test tomorrow. If i do need to get a top end gasket set what brand should i use? I used moose last time (about 4 months ago when i tore it apart for crak end paly) and everything was great until the last few days. I want to get this thing going again. Thank you for all of the help!!!! You guys are awsome and suggested more ideas than the dealer!!!
Jason

 

Is your 500 stock bore and piston? I would use only a Polaris gasket on the 500 engine, unless it was modified. Then I would only use a gasket that was suggested by who ever modified it. Lastly,the Polaris 500 gaskets require a very specific torque sequence. Was that followed when you assembled it last time? I have definitely had a head gasket leak with no other symptom than an over flowing coolant bottle. At least until it catastrophically failed monthes later. This was on a modified 500, but still the same problem.

 

When you had it apart before, did you torque the cylinder down with the correct procedures? If there is any doubt, I suggest that you check the cylinder and head to be sure one or both are not warped. This would cause the head gasket to leak.

The moose gasket will work if nothing is warped.

 

I went through this with my scram a few months back. It was spitting water out the over flow as well. I can agree also that it is most likely a head gasket. Use the factory head gasket!!!!!!!!!!!! I went cheap and bought the after market kits and it left me with a failed head gasket at windrock. It started leaking coolant into the cylinder. I cut it off and liked to never got it to start back. It ended up being a bad gasket and went with factory and no problems at all. If you are on abudget you can RTV the valve cover and timing chain cover.

 

Ok, thanks for all of the good info. I found out it was bored .20 over when I took it apart last time. I did use the suggested torque pattern in the polaris service book. I will check the head and make sure that it is not warped when i take it apart. So aftermarket gaskets or OEM? I will be ordering them tuesday and I like your input on what has and hasn't workerd! Thanks again.
Jason

 

I have used aftermarket and OEM with success. I do prefer to OEM though.