Best way to get air out of your cooling system?

[/infamous/]

I have air in my radiator/hoses/etc somewhere causing some small problems with coolant flow. Whats the best way to get air out? Ive drained and flushed the radiator, Let it idle with the cap off and some other things but i am still stuck with the air. Any ideas?

[miles Machine]

you must make the radiator spout the highest point of the atv...stick the right front tire on a goof size piece of wood or anything to make it higher

[/infamous/]

Okay do i do that then let it idle with my cap off?

[miles Machine]

yes but make sure you take your cap off before it gets hot or you will get burnt

[/infamous/]

Yea haha no doubt.....how long should i let it idle before i take my cap off? Or should i take it off before i start it?

[eastside 400]

take the cap off before you start it, ive never had problems with air in the system and ive drained my bikes countless times, are you sure you dont have another problem? what is the problem you are having now?

[deathman53]

air bubbles in the coolant(that won't go away) usually means a blown head gasket. I had this happen on my 250r(I know its not a 4 stroke), remove radiator cap and it bubbles away, pressure builds up and comes out of the radiator(or overflow from radiator if you have the cap on). Its the same principle, blown head gaskets leak between cylinder and head and/or pressure the radiator with air bubbles and cause the radiator to boil over quickly. I had both happen. You can also look at the color of the coolant and usually can tell if there is gas/oil in it also. Thats a sure way to tell if you have a blown head gasket also.

Many times, I've filled the radiator, ran it w/o the cap on and watched the level drop. This even happens while filling when not running. Run it for several minutes and then re-check, usually the coolant is somewhat lower, refill to the neck and its perfect and doesn't bubble or lose any coolant. My ktm dirtbike has 2 screws you remove to bleed the air out, I'm guessing that air can get trapped in the cylinder head and right radiator.

My money is on it that you have a blown head gasket.

[/infamous/]

Well what happens is...my radiator and coolant bottle will be at the right levels, ill ride and when it gets hot it will fill the overflow bottle up untill it starts blowing out of the overflow hose thats on the bottle. it does this even if i run it with no coolant in the overflow bottle. My quad can even set all night and cool completely off and the next day ill take the cap off and it releases a ton of pressure like it was just running.....i just had it rebuilt a couple months ago and it never did this before, then i ran the Alabama national and it started. I didnt think the new head gasket would already have blown but do you think thats what it is? There is no wet spots anywhere around the gasket and i dont seem to be at a loss of power. I already tried a new cap, thermostat, and impeller

[deathman53]

same thing happened to me with my 250r, not a 4 stroke, but same principle. When it ran, boiled quickly, alot of pressure, it blew out the overflow bottle, next day, take off cap and a gas bubble and coolant level is down. I didn't have any coolant leak around the head either. Of course with a 2 stroke its much and much less costly if you have to pay someone to replace the headgasket. Do this test, start it w/o the radiator cap on and watch the coolant. You should be seeing a flowing stream going across the neck of the radiator. If the headgasket is bad, you will see air bubbles and the coolant level rising quickly. Mine did the same thing. First indicator is I seen a film of oil on the top of the coolant and then the level starting rising quickly and it was bubbling away and didn't stop.

Now when you take off the head , if the headgasket is going, you will see part/total of the piston will the really clean. That is the coolant washing away the carbon. Mine started showing on the edges of the piston being nearly carbon free and working toward the center. I don't know how to work on the top end of a 4 stroke motor, nor have the patience for it, so I can't guide you with help replacing the headgasket. I'm suprised more people didn't say, headgasket, immediately. If you put this question in the 250r section, most would say that immediately.

When I refilled my crf450r hybrid, I filled the radiator, left the cap off and watched air bubbles come up. several minutes later, the level dropped pretty good. Then refilled it, level stayed pretty good. Started it and ran it w/o radiator cap and saw some air bubbles, mostly huge ones. Shut it off, refilled(very little) and ran it w/o cap and no bubbles and level stayed the same. Put cap back on and got it nice and hot. when cooled off, checked level again and it evened out to ~10mm below fill up neck. My ktm dirtbike, similar, except level dead cold was ~10mm above radiator fins, as manual says.

[/infamous/]

i have let it idle with the cap off, and the coolant level does not drop unless i hit the gas. it will drop then come back up to the normal spot it was in. there has been no oil in the coolant and there has also been no coolant in my oil when i change it

[metalman101]

Have you tried standing the bike up on the rear bumper and leaning the bike over on each side to get the air bubble to pass thru ?

[Ruf Racing]

If, when you ride, the coolant is blowing out the overflow hose.
You are pressurizing the coolant system. Main cause, blown
head gasket. :(

[/infamous/]

Okay ill try a new head gasket, Mark Baldwin told me to take the coolant bottle off and just run a hose from the radiator to the ground like he does Uppermans bikes

[eastside 400]

sounds like a headgasket pretty much 100%

[deathman53]

always use a overflow bottle. If you overheat and blow coolant, w/o a bottle its gone. With a bottle, it can/will suck it back in. Racers typically don't use overflows, they run laps for a short time and later on go for more laps. WE don't do this for the most part, WE ride for several hours, with some breaks between, usually can be several-20 miles from our trucks. If we do lose coolant, once it gets colder it will suck it back in. There is a reason why most the atv's and 1/2 the bikes come with them stock. With ktm's and motocross Jap bikes, the first aftermarket purchase is a overflow bottle. I have mine setup so the hose from the overflow goes right over the pipe, same thing that baldwin wants.