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Discussion Starter · #1 ·
It's been a while since I posted...But I'm back with my cursed 1999 mxz 600.

The sled only had 3100 miles when I got it. shortly after the crank seal, that holds oil in the water pump shaft cavity, failed. Also causing the nylon gear to fail.
The sled got a new crank, pistons, rings, water pump shaft asy,seals,bearings,and new t-stat.

It ran good around the yard with no issues. But on the first trip out to the gas station it overheated again. The nylon gear is toast, but there was still oil in the cavity. Not really sure where I went wrong or why this happened.
Any input would be greatly appreciated.
 

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The bearing that we see in both pictures, was it pressed out at one point?
 

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It looks like the bearing is damaged also. Maybe the pump and shaft were not aligned/meshed properly upon installation? The thermostat could have failed and stayed closed. Can remove it and test it on the stove. Who rebuild the engine?
 

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Discussion Starter · #6 ·
It looks like the bearing is damaged also. Maybe the pump and shaft were not aligned/meshed properly upon installation? The thermostat could have failed and stayed closed. Can remove it and test it on the stove. Who rebuild the engine?
My dad rebuilt the engine. He was the one that took it out for the first ride. He said the coolant bottle had a hole in it and the t-stat was missing a peice. But I couldn't find any peices in the lines or the impeller. After replacing the coolant bottle and t-stat that's when he realized coolant wasn't circulating anymore.
 

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Discussion Starter · #7 ·
When I zoom in on the picture of the bearing cavity it appears something may be hanging down on both sides of the worm gear on the crankshaft. What am I seeing?
Sent from my moto g(7) using Tapatalk
I believe they are the seals that prevent oil from leaving the cavity. But I'm not entirely sure. This is the first time ive got into the bottom end on one of these.
 

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I think it can only go one way as one end has the threads for the bolt and other other is smooth.

The damage looks like the wrong gearing to me. Or it could be just to tight.

Or, if you put it back together without filling the cavity with oil it can cause the damage in the first minute or so of running. Service manual says specifically for that motor:

"Add chaincase synthetic oil (P/N 413 802 800) into water pump housing until oil level reach bottom of plug hole. See above illustration. Total capacity is about 14 cc (.47 U.S. oz).

This oil addition is needed only when servicing water pump. During normal engine operation, this oil can flow through engine. After that fuel/oil mixture will lubricate water pump bearings by scavenging."
 

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I think it can only go one way as one end has the threads for the bolt and other other is smooth.

The damage looks like the wrong gearing to me. Or it could be just to tight.

Or, if you put it back together without filling the cavity with oil it can cause the damage in the first minute or so of running. Service manual says specifically for that motor:

"Add chaincase synthetic oil (P/N 413 802 800) into water pump housing until oil level reach bottom of plug hole. See above illustration. Total capacity is about 14 cc (.47 U.S. oz).

This oil addition is needed only when servicing water pump. During normal engine operation, this oil can flow through engine. After that fuel/oil mixture will lubricate water pump bearings by scavenging."
Is the pump gear (the tan coloured part) and the metal drive shaft all one piece? or is there a keyway in it? IIRC its one piece and slide into a slot on the crank and the then the drive gears would line up, I THINK. Maybe the shft didn't get fully seated into position prior to assembly?

420837421. water pump assembly. Doesn't show the pump shaft as being available by itself.
 

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the bearing on the oil pump side hasn't been replaced, so it should be the original. The water pump shaft assembly was bought new, so that bearing is new. But I noticed some lite scoring on the side
It looks good. Thanks for this latest picture. From the two different angles I can tell the bearing was not pressed too far, so that's good. I imagine that it got the 50cc/ml of oil for the engine assembly. So far I don't see anything obviously wrong. The next step is to put the crank into the lower half of the case to see how the two worm gears are meshing. You'll need to help seat the crank bearings, but that's simple. The idea to find anything obvious and if there is then you will notice it. The two measures that I look for are: 1. <It seems good> or 2. <That can't be right> lol
 

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Is the pump gear (the tan coloured part) and the metal drive shaft all one piece? or is there a keyway in it? IIRC its one piece and slide into a slot on the crank and the then the drive gears would line up, I THINK. Maybe the shft didn't get fully seated into position prior to assembly?

420837421. water pump assembly. Doesn't show the pump shaft as being available by itself.
It is one piece as you remembered. On a bench I have tried to install the worm gears out of alignment and I just couldn't do it.
 

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Sounds dumb, ill trow it out for elimination or consideration.

Was the pump gear installed in the correct orientation?
Good thinking! I did check and it was fine. Google skidoo coolant pump shaft and switch to Imagines to see the orientation.
 

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Discussion Starter · #15 ·
It looks good. Thanks for this latest picture. From the two different angles I can tell the bearing was not pressed too far, so that's good. I imagine that it got the 500cc/ml of oil for the engine assembly. So far I don't see anything obviously wrong. The next step is to put the crank into the lower half of the case to see how the two worm gears are meshing. You'll need to help seat the crank bearings, but that's simple. The idea to find anything obvious and if there is then you will notice it. The two measures that I look for are: 1. <It seems good> or 2. <That can't be right> lol
I was told it did get filled with oil upon assembly. I ordered a used water pump shaft assembly from a 02 mxz 700. Should be here by the end of the week. When I re-install the water pump shaft where do I add the oil, the oil pump opening?
 

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Kinda looks like that gear was too deep in the cavity ??? Just the way its worn ?? Just an idea. Proper gear? Proper water pump?? Just throwing it out there
 

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Bottom line that pump gear got hot. I think you know the problem, thermostat and coolant bottle. If you don’t have a shop manual, I would get one. Easy find on internet and cost about $10. Good luck.
 

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I was told it did get filled with oil upon assembly. I ordered a used water pump shaft assembly from a 02 mxz 700. Should be here by the end of the week. When I re-install the water pump shaft where do I add the oil, the oil pump opening?
Will the cases be opened? Either way there are several accepted methods. I am currently transitioning to the vacuum method which I have seen in person and found it to be by far the easiest, fastest and cleanest.
 

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I pm'ed you but it appears motor was assembled wrong but hard to tell on my phone will look at pic at work tomorrow but it seems crank seals are sticking into water pump cavity and jamming the gear...I am laying in bed or I would go take a pic of a set of cases and show you what I mean ... maybe I will have time tomorrow

Michael M ...
 
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