Air in coolant. Sometimes.

[Dimebag]

Hi,

A buddys MCX 290 nytro is overheating, and when we open the radiator cap there is air coming out. Its a MTX with the rear cooler.

It did the same thing a couple weeks ago, and we filled coolant and let it idle without the cap until all air seemed to be out. Rode several miles with no problems, and checked that no air came out when opening the cap. We repeated this step several times.

Today it overheated again, and there was definately air in the system.

What is happening? Could a blown head gasket cause air in the coolant?

Or is it simply that we did not get all the air out of the system last time?

Thanks

 

[TurboTime]

You would know if you had a blown head gasket. I think your not getting all the air out of the system. Try leaning the sled opposite of the the rad cap and try to lift the front end a bit. You want the rad cap to be the highest point on the coolant system. Start the motor and message the lower coolant tube located between the brake cal and oil res tank, this will help push the bubble through the system

 

[raginyamaha]

X2 front end really high to get all the air out.

 

[Dimebag]

Thanks guys, we will try that for sure.

The strange thing is that it works as it should for several miles... Like a whole weekend. Then next week it becomes a problem again.

Thats why Im starting to find it hard to believe that its only air in the system, and not something that is actually causing this.

 

[Sled Dog]

Park the sled in a very steep ditch and let it run there for a minute or two go for a rip and do it about 5 or 6 times.

 

[shadow44]

just ride it...it's a self bleeding system, it will burp itself out.

 

[Dimebag]

After about 300 kms, it does not seem like its gonna burp out..?

I was also under the impression that was the way its gonna work, but it does not seem that way. In fact I can't even see the coolant overflow bottle... It seems like they remove them when installing the bigger mcx kits. Either that, or its hidden below the intercooler.

Could it be that the "overflow-hose" is plugged, and that air isnt getting it like its supposed to do?

We will try parking it in a steep hill tomorrow and see if we can get the last air out.

 

[grizztracks]

just ride it...it's a self bleeding system, it will burp itself out.

I like to run the engine through several heat cycles without overheating it and normally the air will work it's way out. If it doesn't, I'd be looking for a pump or restricted coolant hose problem and because there have been several reports of blown head gaskets I wouldn't rule that out.

 

[1975FA]

A yamaha tech also sugested to us, raise the rear of the sled and pull the tunel exchanger drain plug to get air out. It got some air out on mine. Could a hair line crack in the radiator let air in? We are questioning that on my sled.

 

[LSXM3]

Being that it is an MCX sled and is/has been boosted heavily I would bet that the head gasket is toast, i would pressure test the cooling system at the caps pressure and see if it drops. If it passes that i would do a leak down test to insure it is not the head gasket, water getting into the cylinders can be catastrophic if left undiagnosed. If you really want to be sure get a 4/5 gas anaylizer and check for hydrocarbons in the cooling system as anything over 15ppm would indicate a bad head gasket...but typically you will see 200-1700ppm on the hydrocarbon side of things if in fact the head gasket is bad.

 

[Dimebag]

We parked it in a steep hill today, and let it idle for some minutes with the cap off. There was a lot of air bubbles in the beginning.

Filled it up. And took it for a spin. Repeated the hill procedure, and this time there where no air bubbles. It seemed like the coolant was flowing normally.

He is gonna take it for a test ride this evening, and if there still is air in the system its going back to the dealer that did the engine work, as this problem has been present since he got it back from them.

I will report back what we find out.

Thanks for all help so far guys.

 

[canoehead]

IMO if it keeps re-occuring I'd be swayed to believe it's the head gasket. Check for white smoke and odour of glycol. Did they shim the head for his Turbo? Might want to try a retorque if so. Good luck

 

[Dimebag]

The head has been of when they ported it. No unusual smell or smoke.

We'll see what happens the next ride. Probably he will take it back to the dealer that did the engine work to have them check it out.

 

[arteeex]

Make sure there's ample coolant in the res and that tube going to the radiator is buried in it. When the system cools it can pull in air thru the tube.

 

[bradb]

i seem to be having a similar problem, when sled is idling the temp light is blinking on/off sometimes i get a code 21 and engine light but the moment i lift the front end just 4" or so it goes out. i tried bleeding it but don't seem to get any air out.