2007 yz 450f losing coolant

10 replies to this topic
  • 88motoman88

Posted January 03, 2016 - 01:52 PM


So im losing coolant, twice now topped of ive lost about 1/4 of the coolant. The oil both times wasnt grey or lighter at all really. My son said he saw smoke for a second but i had just went thru a puddle. Riding at the track yesterday i lost the same amount again and oil was fine. Do I check for bubbles while running with the rad cap off? Starting seems ok still not to bad. Runs fine no smoke what so ever. I am running water wetter with regular not distilled water. I meant to drain it i know itll corrode.

  • stevethe

Posted January 03, 2016 - 03:01 PM


You could just be loosing it through overheating. You should be running 50/50 or a coolant mix that can stand heat not to mention corrosion protection.

  • Bass Mechanic

Posted January 03, 2016 - 03:25 PM


You could have a minor leak in the head gasket that is sending exhaust or pressure if you like into the water jacket. Pressurizing the coolant system and pissing it past the radiator pressure cap.
Or the radiator cap could be defective or have s bad seal

  • 88motoman88

Posted January 04, 2016 - 08:31 AM


Ok ill flush it. Is engine ice a good brand to use? Ive heard bubbling coolant means exhaust gases leaking thru the head gasket. I just hope thats not it. Maybe it is overheating and spewing it out.

  • stevethe

Posted January 04, 2016 - 09:19 AM


Ok ill flush it. Is engine ice a good brand to use? Ive heard bubbling coolant means exhaust gases leaking thru the head gasket. I just hope thats not it. Maybe it is overheating and spewing it out.

I don't use engine ice. This guys spitted out quicker with engine ice. http://www.thumperta...est-no-airflow/

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted January 04, 2016 - 11:13 AM


There is a difference between bubbling coolant and the normal foamy nature of the stuff.  It's also normal, if you fill to the top, to push out coolant until the tops of the tubes in the radiator are just covered.


  • Have the cap tested for correct pressure
  • Check for leaks, including around the weep hole under the water pump (might need to dust up the area with foot or baby powder to spot the leak, and water pump seals may not leak under every condition)
  • There is a test that can be done for the presence of combustion gasses in the cooling system. 

  • 88motoman88

Posted January 09, 2016 - 08:36 PM


So i flushed the radiators and put green 50/50 premixed coolant in amd riding today i lost alot of coolant again. Totally forget to check for bubbles. Autozone rents a kit to check for rad exhaust gases. Ill prob checkl that.. And my oil again. Idk how it not changing the oil color...??.. The cap seems fine but maybe a new one wpuld solve this. Who wants to put in head gaskets and the like..... It has a new top end less than 6 months ago

  • 88motoman88

Posted January 10, 2016 - 12:34 PM


Just found the leak!!!!... Weep hole!!! Whats the fix? Just rhe two gaskets? Ones oil side ones punp side??? Thank gosh its not the head gasket man im so relieved thanks again for tt guys an help...couldnt do it with this help an knowledge...i was straight up thinking about going back to 2 stroke..

  • grayracer513

Posted January 10, 2016 - 03:41 PM


The fix is to remove the right side engine cover (drain the oil and the coolant) and replace the water pump shaft seals and bearing.  You may also find that the coolant seal has worn a detectable groove in the shaft, in which case you'll need to replace the impeller shaft as well.  


Read: http://www.thumperta...0-coolant-leak/


While you have it apart, you'll want to check that the balancer shaft, which both drives the impeller and supports the inboard end, is OK.  More than 2-4 thousandths of an inch up/down play (perpendicular to the shaft axis) is a sign of a worn bearing, which will cause the impeller shaft to run off center in the seals so much that they will leak.  



  • 88motoman88

Posted January 13, 2016 - 09:05 AM


Ok, ill ride it again before i do the work probably. Can you actually feel that 2-4 thousandths? When i take the cover off what am i doing to determine the up and down play?

  • grayracer513

Posted January 13, 2016 - 09:23 AM


The best bet is to set up a dial gauge on the shaft, then attempt to move it vertically, up/down, and see the clearance the bearing has. 

Related Content


Should I buy this bike? help....... by Numsa Hul

Dirt Bike   General Dirt Bike Forums   What bike should I buy?
  • * * * * *
  • 10 replies

Yamaha YZ450F 2017 by Chris.GVS

Yamaha YZ450F 2017
  • * * * * *
  • 1 review
  • Last review by Tommyk_55
  • On January 15, 2017


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  30 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies

05 yz450f not fast enough by RedeyeYZ

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  38 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.