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09 foaming coolant question


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I am trying to find a good used 09 crf450. I looked at one tonight and noticed that after a few minutes of running there was coolant coming out of the over flow hose. I took the cap off and there was foam. I restarted it without the cap and the foam started building up and out of the cap hole. The bike has about ten hours on new top end and he claims there has been no issues. It has pro honda coolant in it now. I would love to buy this bike but am not sure if this is normal or if i should run the other way. I tried using the search feature but found very inconsistent results. Please help!! Thanks

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The only time IMO when foam could be considered somewhat normal is if you just drained a lot (or all) of the coolant out and had just filled it back up.

It shouldn't foam enough to come out of the filler cap though. That suggests either very poor coolant quality, or the head gasket is blown and its pumping combustion gasses into the cooling system. You can rent a combustion/exhaust gas in coolant tester from Autozone.

The other possibility was that it was just overheating. These bikes will being to overheat within a few minutes of idling, and start dumping coolant out the overflow. If you took the radiator cap off while it was still hot, that could be the reason. The cap holds in pressure to raise the boiling point of the coolant, remove the cap and the boiling point instantly drops - that is why coolant tends to explode out of the cap if you take it off while the engine is hot. Some of the coolant is flashing instantly to steam.

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I would be more inclined to think the coolant may have been mixed with water that may not have been distilled.

If the seller wants to sell the bike it should not be too much to ask if you offer to bring new coolant and drain and change it... It doesn't hold much, and it will answer the coolant question.... If the owner doesn't let you do that, than maybe he is hiding something??

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there are WAY too many used thumpers for sale out there to settle on one that has issues or makes you wonder. Move on and find a cherry out there.

+1 :banana:

My thought would lean towards the head gasket, especially since it was just taken apart for the top end work. Idling will cause it to heat and shoot coolant over the overflow, but foaming coolant is indicative of a leaking head gasket pressurizing the coolant passages.

Not a huge deal, about $30 for an oem head gasket, and a few hours or so to install it, but I would still pass....

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+1 :banana:

My thought would lean towards the head gasket, especially since it was just taken apart for the top end work. Idling will cause it to heat and shoot coolant over the overflow, but foaming coolant is indicative of a leaking head gasket pressurizing the coolant passages.

Not a huge deal, about $30 for an oem head gasket, and a few hours or so to install it, but I would still pass....

I agree. This happened to my '09, head gasket was blown, although the cause of that seemed to be a warped head.

I agree with the post that said there are to many options out there to buy a bike with obvious problems.

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