Help Grayracer or anyone!! Coolant leak from overflow tube


17 replies to this topic
  • icon27

Posted December 31, 2009 - 08:51 AM

#1

I don't know what to do!!:moon:
I had a coolant leak that was coming from the overflow tube of the radiator. i posted on thumpertalk and came to the conclusion that I had to change out the head gasket. Over the last few months I have rebuilt the top end of my YZ450F 2004. Parts replaced... Cylinder, all gaskets including head gasket (which i thought would solve my original problem) Piston and rings, Radiator cap and checked the water pump which looks like it is functioning just fine. Started up the bike yesterday and the leak is as bad as it was before the rebuild.:cheers: I don't know what to do next. I already spent hundreds of dollars and many hours to fix nothing...... HELP!!!!!!!! trying to get the bike working for my son for a xmas present before he returns home on January 4.... thanks

  • grayracer513

Posted December 31, 2009 - 09:15 AM

#2

Under what specific circumstance does the bike push coolant out of the tube? How long does it have to run? Are you riding or idling? Are you certain that it's leaking from the tube, and not from the water pump? Did you ever have the cap tested?

  • devo1

Posted December 31, 2009 - 10:39 AM

#3

If mine is idling, it will lose a little coolant. That's normal.
Did you go thru the torque procedure? It's a little different. Read the manual very carefully, I missed it and had to replace the head gasket a second time.:moon:
If you still have problems, let me know.

  • icon27

Posted December 31, 2009 - 12:41 PM

#4

Under what specific circumstance does the bike push coolant out of the tube? How long does it have to run? Are you riding or idling? Are you certain that it's leaking from the tube, and not from the water pump? Did you ever have the cap tested?

it leaks at idle a lot (I can watch it start flowing out at the cap). it takes 15 to 30 seconds for it to start leaking. the cap is new (i also tried the old one). I did do the "special" yamaha torque specs. Im afraid to ride it if it leaks at idle.. thanks for the quick replies guys

  • tech24

Posted December 31, 2009 - 12:52 PM

#5

I was gonna say junk cap but its new so...was it aftermarket? Could it be junk? Sounds like there is still combustion gas getting into cooling system...maybe cracked head? Do you have any way of apply pressure to cylinder, leakage tester, rigged air hose or something?

  • icon27

Posted December 31, 2009 - 03:02 PM

#6

I was gonna say junk cap but its new so...was it aftermarket? Could it be junk? Sounds like there is still combustion gas getting into cooling system...maybe cracked head? Do you have any way of apply pressure to cylinder, leakage tester, rigged air hose or something?

I replaced the cylinder also.. should be fine. the cap is actually rated a little higher than stock

  • Brad_Aus

Posted December 31, 2009 - 06:10 PM

#7

How high are you running your coolant level?? If its full or near full, of course it will spew out coolant as the water expands.. Once its been hot, that will basically self set the water level..

usually just 5-10mm over the top of the tubes is enough

  • husqy360

Posted December 31, 2009 - 06:30 PM

#8

How high are you running your coolant level?? If its full or near full, of course it will spew out coolant as the water expands.. Once its been hot, that will basically self set the water level..

usually just 5-10mm over the top of the tubes is enough



you might be right, but my 06 wont spew out any coolant even after 5 min when feelling right to the top, bike is standing still, it will lose the extra coolant only when ridden hard for a couple of minuts after the engine been warmed up.


maybe the internal radiator passages clogged , making the extra pressure. :moon:

  • eazrider

Posted December 31, 2009 - 08:42 PM

#9

My '04 will puke coolant if left at a high idle from cold after 3-5 minutes...My '06 will overheat while taking a break of more than a minute or so on a trail ride...set a good size fan in front of the radiator and let the bike idle and see what happens...It should not overheat with any sort of airflow across the radiators at idle....but if there is no airflow, even at idle, they will puke coolant...

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  • icon27

Posted January 01, 2010 - 05:01 PM

#10

you might be right, but my 06 wont spew out any coolant even after 5 min when feelling right to the top, bike is standing still, it will lose the extra coolant only when ridden hard for a couple of minuts after the engine been warmed up.


maybe the internal radiator passages clogged , making the extra pressure. :moon:

checked all passageways before re-installed the top end. I have never had a problem like this before. Its 15 degrees here right now so I don't believe over heating is a issue after a few minutes at idle.

  • mikedabike

Posted January 01, 2010 - 06:35 PM

#11

checked all passageways before re-installed the top end. I have never had a problem like this before. Its 15 degrees here right now so I don't believe over heating is a issue after a few minutes at idle.


Ambient temp doesn't matter. If you are not moving air through the radiators it will start to overheat and puke coolant. It just might take a extra minute if it only is 15 degrees.

  • grayracer513

Posted January 01, 2010 - 06:40 PM

#12

Ambient temp doesn't matter. If you are not moving air through the radiators it will start to overheat and puke coolant. It just might take a extra minute if it only is 15 degrees.

Plus, they don't really circulate well at idle, either.

  • icon27

Posted January 01, 2010 - 09:07 PM

#13

Plus, they don't really circulate well at idle, either.

guess I'll try breaking in the top end and see what happens

  • Birdy426

Posted January 01, 2010 - 10:55 PM

#14

With my WR, I did a head gasket without surfacing the head and cylinder mating surfaces (I know, I know...but I was trying to get it ready for a big ride) ad it leaked again very, very quickly (maybe 5 minutes of run time). When I pulled the head off again, I could clearly see the leak path...

I surfaced the head (figure eights on emery paper taped to a 1/4 in thick piece of glass method), and it's been together for several hundred miles without issue...might be worth a shot...

  • icon27

Posted January 02, 2010 - 10:08 AM

#15

Plus, they don't really circulate well at idle, either.

is there a proper way to circulate the coolant when the radiator is empty? (I.E. run the bike with the cap off and fill as it circulates?) Is prepping the mating surface of the head and cylinder a common practice? I thought cleaning the surface from old gasket material etc. was enough.

I was just comparing the radiator caps and the new ones spring mechanism seems to extend further than the stock cap that I replaced (about 1/4") and the relief valve dangles when its pressed down. Could that be an issue? I do have a extra cap that is rated at 0.9. can I try that? would that cause problems if the stock is rated at 1.1?

  • grayracer513

Posted January 02, 2010 - 03:36 PM

#16

The right way to refill the cooling system is to fill it full, cap it up and run it for about 5 minutes and let it cool a bit 'til it's safe to remove the cap. Then fill it to the top again. Any trapped air should work itself free in that amount of time.

Yes, prepping the head surface is common. Enough so that it's in your manual. You do have one, right?

And yes, the cap configuration should be the same as OEM, or it may very well affect the sealing ability and the pressure rating. On a side note, I have seen it posted that '80-'85 Toyota Corolla caps will interchange, but I can't vouch for that.

  • icon27

Posted January 03, 2010 - 08:15 PM

#17

The right way to refill the cooling system is to fill it full, cap it up and run it for about 5 minutes and let it cool a bit 'til it's safe to remove the cap. Then fill it to the top again. Any trapped air should work itself free in that amount of time.

Yes, prepping the head surface is common. Enough so that it's in your manual. You do have one, right?

And yes, the cap configuration should be the same as OEM, or it may very well affect the sealing ability and the pressure rating. On a side note, I have seen it posted that '80-'85 Toyota Corolla caps will interchange, but I can't vouch for that.

Went to see if the 80-85 Toyota Corolla cap would work for a replacement. The size looks right but is rated at 13psi. Stock is rated at 1.1 = 15.9psi I believe. If anyone knows what car radiator cap would replace stock Yamaha yz450f? Im going to post a thread to see if anyone else knows.

  • grayracer513

Posted January 04, 2010 - 12:17 AM

#18

Went to see if the 80-85 Toyota Corolla cap would work for a replacement. The size looks right but is rated at 13psi.

You can buy caps for most automotive applications in a variety of pressures. The source of the info on the the Corolla cap fitting stated he bought one at 1.3 bar (18.5 pounds)





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