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Dan_187

Excessive coolant dripping out of overflow

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So, my bike has been slowly loosing coolant, i have overheated it twice. I was out at the dunes this weekend and saw that as i stopped and killed the motor coolant would be dripping out of the overflow tube. I do not idle it for long periods of time or anything. my friends yz450 does not do this.

Could this be happening due to a warp cylinder head, it could have gotten warped when i overheated it.

What is causing pressure in the coolant system to force it out the overflow tube??

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So, my bike has been slowly loosing coolant, i have overheated it twice. I was out at the dunes this weekend and saw that as i stopped and killed the motor coolant would be dripping out of the overflow tube. I do not idle it for long periods of time or anything. my friends yz450 does not do this.

Could this be happening due to a warp cylinder head, it could have gotten warped when i overheated it.

What is causing pressure in the coolant system to force it out the overflow tube??

Exactly as you said, its overheating. Your radiator cap could also be faulty so check that. You would know if the head was warped. You would more than likely have a mix of water and oil with most blown head gaskets, or you would be burning coolant. Pull the cap off the radiator and have a look if there are lots of bubbles? And check the colour and level of your oil too.

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Lean jetting will make it overheat. Maybe you had your air screw to lean. Ask your bud what % coolant he is running 50-50 or 75-25?

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Heat creates the pressure; that much is normal. What is not normal is coolant loss and an excess of pressure forcing coolant out the overflow.

You need, in troubleshooting this, to determine if it's getting hot and loosing coolant, or loosing coolant and then getting hot. The three most common culprits in coolant loss leading to overheating are leaking water pump seals, faulty radiator caps, and head gaskets, although leaking hoses, radiators and gaskets can be a problem. The water pump seals can be difficult to spot, because they may not leak constantly. But if there's a build up of oily looking dirt around the area under the pump, be very suspicious. The residue should smell of coolant if there is any present.

You might also want to examine the area around the joint between the steel tubes at the water pump and head for leaks.

One thing would be to run the engine up to nearly the point where it would start blowing coolant, let it cool off, and see how much is in the radiators. If the level's gone down, it's leaking. If it hasn't, it's getting hot, possibly due to a blocked radiator or something interfering with circulation.

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Also , check your water pump impellor to ensure it hasn't lost any tines. Have you crashed and possibly damaged either one of your radiators to restrict flow? Have you changed any of the hoses and created a crimp in one of the lines? No mud or debris affecting air flow? Just some additional thoughts?

More times than not, just change your radiator cap, as they like cars, can eventually fail at less than operating temps.

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Thanks for the help guys,

when i was out riding this weekend i swapped caps with my buddy's 08 450 and had the same problem and his bike was fine with mine.

The oil does not appear to have coolant in it, it is not gray or anything.

Maybe the head gasket at the combustion chamber is bad so a bit of coolant is getting burned and some pressure is getting into the coolant system.

I have never seen bubbles or anything strange in there either...

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