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gilkeyb

WR400 Over Heated, Coolant in Oil

7 posts in this topic

All,

 

I realize this is a hopeless stab, and that i'm avoiding reality, BUT:

 

Sunday I attempted to get my new (to me) 2000 WR400 to run.  The float valve was leaking, so I rebuilt the carb.  Once I put the carb back on, I also installed a PMB Insert in my uncorked exhaust.  I could not get the bike to start.  I realize that this is because I changed too many things when i rebuilt the carb (float height, idle speed, idle mixture, exhaust insert).

 

Well, finally by bump starting the bike on Sunday, I got it to run.  I was attempting to tweak the idle mixture (in order to keep it running I had to have the idle very high), and the bike *presumably* overheated and coolant spilled onto the ground.  At that point I shut it off immediately and called it a day.

 

Flash forward to today, Wednesday.  Based on Sunday's results I do some further tweaking.  I get the bike to catch on the second kick and it is idling almost like new!  My relief was short lived, however because I decided now that i had it running, it was a good time to check the oil level.  Well, that is when i  found that the oil was VERY runny and ready much too high (bad sign).

 

So, I dropped the oil and it looked as you see pictured.  DANG IT.

 

So, my question is: Is there a chance that it is NORMAL that when the bike overheats some coolant gets in the oil?  I realize this is 99% unlikely, but as a street bike guy I continue to be surprised by how tolerant of abuse dirtbikes are.

 

TLDR; overheated the bike, ran it a few days later for 60 seconds, checked oil level and found coolant.

 

I suspect I will be told I have something internal going on (blown head gasket?). But heres hoping...

photo (4).JPG

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Your bike probably overheated because the coolant was in the oil.   The coolant is not in the oil because it overheated...   understand?

 

Your problem is most likely the water pump seal.   It separates the oil from the coolant.   Its toast.    You need to replace it ASAP. 

 

More importantly, the water pump shaft gets pitted and corroded and the seal will never seat properly.    So my advice is to replace both the water pump shaft and the seal(s).   I think there may be two, but I had a 450 and not a 400.

 

Try this before you go looking at the head gasket, which I think is not likely the problem.

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Your bike probably overheated because the coolant was in the oil.   The coolant is not in the oil because it overheated...   understand?

 

Your problem is most likely the water pump seal.   It separates the oil from the coolant.   Its toast.    You need to replace it ASAP. 

 

More importantly, the water pump shaft gets pitted and corroded and the seal will never seat properly.    So my advice is to replace both the water pump shaft and the seal(s).   I think there may be two, but I had a 450 and not a 400.

 

Try this before you go looking at the head gasket, which I think is not likely the problem.

If my water pump seal was leaking, should I have seen it coming out of the bottom of the WP cover?

 

I will have to investigate this further.  I haven't yet pulled the head, so if this is the case it could save me some work

 

Brian

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If my water pump seal was leaking, should I have seen it coming out of the bottom of the WP cover?

 

I will have to investigate this further.  I haven't yet pulled the head, so if this is the case it could save me some work

 

Brian

There are actually two seals as part of the water pump assembly, along with a couple of important washers.   Its possible that the outer seal, which primarily handles coolant  is fine, but the inner seal has been compromised.  The inner one separates oil and water.    Remember, the water pump shaft is gear driven, so there is obviously oil on the other side of it.  The coolant is leaking through.    I think that the inner seal leaking is definitely a problem with the water pump shaft.   Its gets a little pitted from the coolant and doesn't seal the way it should allowing the water to seep past it into the crank case.

 

Change out everything... the gasket, shaft, both seals and the shaft.   Don't mess around.  The impeller is rarely bad in my opinion.    You are looking at $40 in parts.       http://www.ncy-motorsports.com/fiche_section_detail.asp?section=3959838&category=Motorcycles&make=Yamaha&year=2005&fveh=177671

 

 

Loosening and tightenin the impeller can be tricky.    You may need to get the uber expensive lockup tool (a.k.a.    "a penny")  and strategically place it where it will stop things from turning.     

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I pulled the crankcover.  This is what the water pump shaft looks like.  Does this strike you as:

 

 

A) Hmm, that looks perfectly fine

B) I guess that could be your problem

C) Wow, I can't believe it didn't leak sooner...

 

At any rate, I will order the new seals, bearing, and shaft.  Hopefully have it back together in time for a track day on Oct 5th!

 

 

photo (5).JPG

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Pay very close attention how those seals came out so you can replace them right. I did this last spring and read many posts where it was still leaking because of how the seals were put in.

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MauriceDorris appears to have been correct.  I replaced the water pump seals/bearing/shaft and all appears to be ok.

 

I got the WP back together in time to hit my first SM track day.  I had a great time and its definitely something i'd like to do again.  Although, I have to work on getting the bike to start first kick. Not sure if it was just the temperature that was making things difficult (mid 40s when the track opened) or if my technique is off or if the carb just needs adjusting.

 

My bike is still smoking a bit under decel. So I may have to do valve guides/seals this winter. Time will tell

 

Thank you for the advice.  And help!

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