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YZ250F Coolant problem :(

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Hey guys!

I have a problem with my 2001 YZ250F. I recently bought the bike with a leaking waterpump seal. I thought " No brainer, just change the seal and braaaaaaaaaaaaaap away"

This was not the case. I changed the seal 4 times. With a maximum ride time of 4 minutes each. So I flushed the radiators and changed the radiator cap. Thinking that the bike was building up pressure and blowing the seals.

I took the bike out last weekend and guess what! DIDN'T BLOW A SEAL

This story is not all rainbows and butterflys. The bike was relieving alot of coolant out of the overflow! So much that I could only take it for 10 - 15 minute rides in fear that i would empty the tanks.

I was told that the radiator cap may be for a bike with a coolant reserve. I then rang my local bike shop and they said that it sounds more servere then a radiator cap and I should take it in for a check up! PSSSSSSSSSSSSSSSSSH! (it is sooooo hard to find a bike shop that doesn't see dollar signs everytime they see you)

The bike doesn't seem to be showing signs of a blown head gasket. I.E no bubbles in the coolant and no sounds of escaping air.

My question is.....WHAT CAN IT BE ??? i wanna go out this weekend. It's been raining all week

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Check your engine oil and make sure its not leaking into the crankcase. Also, did you replace the waterpump bearing with the seal, or just the seal? If the bearing is worn, it can allow a new seal to leak.

If the seal is not working properly AND it is getting pressure from the crankcase, that could be pushing the fluid out. Check your crankcase vent and make sure its not plugged up with mud, especially if you've been riding in the MUD. Buddy of mine also got his carb vents plugged up with mud and caused some wierd running characteristics. Good luck.

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Check your engine oil and make sure its not leaking into the crankcase. Also, did you replace the waterpump bearing with the seal, or just the seal? If the bearing is worn, it can allow a new seal to leak.

If the seal is not working properly AND it is getting pressure from the crankcase, that could be pushing the fluid out. Check your crankcase vent and make sure its not plugged up with mud, especially if you've been riding in the MUD. Buddy of mine also got his carb vents plugged up with mud and caused some wierd running characteristics. Good luck.

The seal isn't leaking anymore since I changed the cap. It is now leaking coolant out of the overflow. I'm affraid if I put the old cap it'll blow another one.

I had the old one tested and its venting fine.

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swifty,

there are only a few ways you can puke coolant via the overflow:

1) motor too hot

2) blown head gasket

3) bad cap

you say the cap has been tested and is ok. so #3 is out.

you claim #2 is not occuring.

so that leaves #1.

put a candy thermometer in the coolant and see what it shows. or use a thermo strip or infared temp gun.

or it really is #2 and you are simply not able to see it doing that. which i think is your real issue.

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swifty,

there are only a few ways you can puke coolant via the overflow:

1) motor too hot

2) blown head gasket

3) bad cap

you say the cap has been tested and is ok. so #3 is out.

you claim #2 is not occuring.

so that leaves #1.

put a candy thermometer in the coolant and see what it shows. or use a thermo strip or infared temp gun.

or it really is #2 and you are simply not able to see it doing that. which i think is your real issue.

If it was a head gasket. It would explain blowing the waterpump seal all those times.

Im really guessing its running too hot. Just feels like its runs too hot. Even has a red header at dusk :blah:

I don't know how to tell if its too hot or not. I don't have a thermometer! Should go buy one :thumbsup:

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Are you runing a Rekluse or do you slip the clutch a lot? Either can run the temp up on the water pump side and cause the seal to go bad. Friend of mine had that happen and he took the Rekluse off the problem went away.

No Rekluse as far as I know. Only just bought the bike. As for making the seals go bad. I only got about 4 minute rides on each seal. Then they would just piss coolant out.

UPDATE: Put a cap off my brothers 250 onto mine and didn't spill coolant (till it was really really hot, as it should)

Went and bought another cap and didn't seem to overflow :thumbsup: Meaning my other new cap may of been faulty. see how it goes. Will keep you updated.

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so the "tested" cap seems to have been the issue. well, the overflow issue.

not the seal issue.

I tested my original cap (when I first had the seal issue) and it tested fine. However, I purchased a new cap for good measure and started having the overflow issue. :thumbsup: I couldn't understand why as it was a cap for a overflow system and not a reserve.

So yesterday, I purchased a new cap to see if it was a faulty cap and it wasn't overflowing (until it was at the brink of overheating, so doing its job correctly)

As for seal, I haven't blown a seal of late. I took it for a 2 hour ride last weekend and it held up good. Just leaked coolant from the overflow.

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You should not over fill the system. Just cover the tubes. Any excess will come out the overflow. You can add a catch can, and it will suck the excess back in as it cools off, I've done it. The WR comes with a tank and so does a KDX200/220.

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Still sounds to me like you might have a blown head gasket. A couple of the times I have had it happen I didnt see bubbles in the coolant while it was running.

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Im affraid of that. However, its not showing any signs at all. Runs and idles perfect.

We will see how it goes this weekend!

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it wont show any signs, if i were you id pull that head off and have it checked at a machine shop.theyre only gonna soak you 15 bucks or so to check it with a dial indicator. my 04 did the same thing except it didnt pop water pump gaskets, just the overflow. i bought a 40$ oem radiator cap and that wasnt the issue, no milky oil, no bubbles in the rad. after doing the top end over twice i finally pulled the head and took it to my welding teacher. we blocked it up on our bridgeport and it was .007" off from one side to the other. the tolerences in your manual say anything over .002" is out. i took it to the machine shop and they milled the head .010" and i think it only ran me like 60 bucks. your compression will be higher but there will be no issues with valve clearence or anything like that. i started running race gas just to kinda reap the benefits ya know......good luck.

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Well, new cap held up fine! 4 hours of riding and didn't lose much fluid!

Waterpump seals intact.

:thumbsup: Problem solved! For now.......

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