850 water pump failure

Danbot

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Sad time for my sled and my season.
Had a strange overheating issue, and an exhausting tow /extraction on the weekend. Was hoping thermostat, but I found the water pump not spinning with the engine. Must have ate up the plastic teeth.
Engine coming out, I'll learn as I go. Not new to this kind of work, just my first time opening up an 850 aside from replacing pistons.
Need to figure out if it was a cross-shaft lube issue, or the plastic gear simply failed.
 

Rhodesie

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i haven't had one apart but the crank gear used to be brass and the water pump shaft was steel. the impeller is plastic. you may not have to split the cases. it could be just the impeller needs replacing.
 

Danbot

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The gear on the water pump shaft is plastic for sure.
I got it as torn down as I can for now. Waiting on a flywheel puller along with the rest of the parts.

It def got hot but I was nice to it as I could be. Pistons, bearing etc all look ok so far.
I can't get the water pump shaft to come out, might have to wait until the cases are split.
 

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gedakbx

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If this motor is like the 700/800 dragon bottom end I think there is a tool to space the seal properly when you in stall it? You may want to check into that. I installed one and it leaked. Had to pull the motor again and have the dealer install the seal.
 

Danbot

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Somewhere around 3000km total.
-At about 800km my center cavity oil line popped off, dealer warranty partial rebuild (oil check valves, pistons, all bearings and seals). They said the internal oil check valve was not relieving from the water pump cavity.
-This fall I installed a new top end with a turbo kit.

Obviously the turbo kit is going to be a suspect, as the lube supply interrupts oil injection hoses. But, I have been researching how all the different brands of turbo kits get lube... they all seem to hook up to the oil hoses the same way, except the newer BD kits. (I didn't mention the turbo until now to eliminate getting sidetracked by turbo brand bashing)
I'll be testing all the check valves and replacing as needed. Perhaps one failed, or has a higher / lower popping pressure than others.
I also wonder if the water pump plastic gear took some non-visible damage way back when the oil hose popped off and the warranty work didn't catch it.

I'll know more when I get the cases split and get into testing / inspection.
 

Danbot

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Got the cases split and tested the check valves. All the external checks pop at about 4.5psi, and close at about 3psi. Very consistent.
The internal check that relieves from the water pump cavity is free flowing, so then I pull out the new replacement that is an updated screen covered unit on it will not flow, I tried pressure and vac. Seems like I got a faulty part?



The water pump shaft gear was shredded as expected. Bearings on the shaft feel fine, everything else is in the bottom end is ok.
Didn't really get my answer on why this happened which I don't like.
 

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Danbot

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I tested the oil injectors over and over again.
-all 5 external injectors "pop" at 4psi, close at 3psi. In factory spec.
-the internal water pump cavity injector (that relieves to crankcase) pops at 2psi, closes at 1psi. I did not replace it with the updated screen covered injector because it does not function. Faulty part I guess.
Engine is 90% assembled and almost ready to drop back in the chassis.
I did not find any definitive cause for the pump gear failure which I hate but that's where I'm at.
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I should get the engine and turbo kit installed in the next day or two between holiday visiting, and hopefully get a chance to do a shakedown ride.

This is my first time dealing with the polaris electronic oil pump. I purchased a diagnostic tool from Candoopro that is supposed to be able to do alot of what digital wrench does (oil pump bleed procedure needed). Interested tmto see how that goes.
 

gdhillon

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I’m following this closely because I find your testing interesting and very thorough

Are you a sled mechanic?
 

Danbot

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-To update the bearing, the cases would need to be machined for the ring so that wasn't gonna happen.

-Not a sled mechanic, but previously was an auto mechanic. I have also been working on my own sleds and dirt bikes since I was a kid. Most of my testing is outlined in the service manual.

My water pump seal install tool hadn't arrived in time, so I had to bring the motor to my polaris dealer to have them install the seal. With that taken care of, the engine was installed and almost ready to go.
Bleeding the oil pump was done the "manual procedure" way, next gen power-up cables were required as well as a "doubler connector" that I made to be able to power up more modules. This is all in the service manual.


Got it all done and put 2.2 hours of local shakedown riding before heading to BC for two days. All seems good!
Still don't know the cause of the water pump gear failure, maybe its only got so many revolutions before the plastic fatigues. I hope some of this may be useful to someone someday.
 

DRD

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Shoulda ran the cases/jugs through the dishwasher when the wife wasn't home. They come out pretty spiffy...
 

Danbot

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Do you have to pull the engine to change the water pump seal.
With the engine still installed I could get the wp cover off, but I don't think it would be possible to work on seals. Maybe with the mounts un-bolted and tip the engine back? at that time your so close to just pulling the engine.
 

Danbot

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Shoulda ran the cases/jugs through the dishwasher when the wife wasn't home. They come out pretty spiffy...
lol, I was in panic repair mode
 
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