We just got an Apex MX 100 ATV this week and took it for testing and break-in. It had a problem of overheating a bit -- boiling coolant into the overflow bottle. I didn't have any coolant with me and added water which, of course, seemed to make it happen easier.

I'm assuming that maybe I didn't get all the air out when I filled it? I burped the hoses and kept re-filling it at the radiator cap after a few mins of running. After some periods of longer riding is when we saw air bubbling and coolant steaming out of the overflow bottle.

Any ideas out there? I'm used to the air-cooled stuff so this is a bit new to me.

FOR THOSE OF YOU WONDERING ABOUT THE APEX...
Wow! What a little machine. It's a really nice little quad with great features. Once we get the bugs worked out of this cooling issue, I think it will be a home run. My son loves it...he doesn't race, but this is his second ATV and it's perfect for that next step of performance.

 

Hey there jcarpentr2 congratulations on a great quad,getting one for my son in 2weeks time.it may seme as you have some air in your cooling system,lift the front end high to let the air out and fill coolant repeat if neded.also check your owners manual trobleshooting if you dont have this you can dowload this at apexatv.com under tecnical suport
Hope this helps.

 

Thanks for the reply.

I drained the coolant today and refilled. I raised the front very high at first and lower and lower as I filled. I burped the hoses and made a hell of a mess. :-) I also found a note about the bleed vent at the top of the cylinder, so I loosened it to get air out there also when it was flat on the ground again. After many times of burping the hoses and filling the radiator neck, I failed to produce any more air bubbles. I think it might be good now...we'll see.

For those of you who may end up with anything similar, here are some things to check from my experience:

1) make sure to get ALL the air out of the cooling system however you can. Take as long as you need to because if you don't do it right, you get to start over anyway. ;-) Squeeze the hoses, raise the front, open the bleed valve on the top of the cylinder...keep trying.
2) check your overflow bottle "straw" inside the bottle. Ours fell out and it seem to caused air to suck back into the cooling system. I put a wire clamp on it to help it stay on.
3) make sure to put some fluid in the overflow bottle in case your system pulls a little suction when it cools down -- I was told to leave it empty and I think that results in air being pulled in. I put mine about half full until I know it isn't going to pull any more into the system, then maybe an inch so that it covers the hose inside

Any additional tips would be appreciated, so please feel free to keep posting replies. Thanks!