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Discussion Starter #1
Sled is a 2015 ZR6000 RXC, approx. 2,000 miles on it, have owned it since new.
Long story short, I noticed towards the end of last season that the sled would occasionally be hard to start after siting for a day or 2 or more. By hard to start I mean the motor would feel like it would hydro-lock after a couple pulls. I also noticed the level in the coolant bottle would need topping off every once in a while.
So just pulled the sled out of storage and the coolant bottle is empty and engine hydrolocks after only 1 pull.
Pulled the plugs and exhaust and pulled the engine over, the clutch side cylinder had a bunch of coolant in it.
Got it all cleaned up, cleaned the plugs and put them back in and still won't start. Plugs are both covered in a greyish-black sludge after only a few pulls.
Repeated this about a dozen times, and engine will barely bark, but won't start. Plugs both still come out wet.
Have 165psi on both sides but the crankcase is full of an oily-coolant mess. It shoots out the exhaust too.
Have done some searching and can't find anyone having this issue on a C-tec2.
Anybody have any ideas? Could it be a head or base gasket or?
T.I.A., Jay.
 

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I think your going to have to open her up no matter if it’s base or o rings just to suck coolant out with shop vac. Coolant and water sitting over the summer on those bearings can’t be good. Duck tape a 1/4 inch plastic tube to your shop vac and try to suck everything out than get some 2 stroke oil in there and give bearings a bath. Let it sit overnight and than suck oil out. Hopefully there’s no bearing damage
 

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Discussion Starter #3
I've received replies on another forum saying the issue is the mechanical seal on the water pump. Apparently when it fails it causes the coolant to leak internally. Great design on AC's part!
I know it's obviously not a good thing to have coolant in the bottom end, but I'm thinking it should be fine after I get it flushed out. Realistically metal doesn't rust in coolant, almost all vehicles used to have iron blocks and heads and they didn't rust. Water-pumps are also lubed by the coolant that runs through them.
I also had about a 70/30 coolant/water mixture, and it's mixed with all the oil that was in the engine as well so hoping for the best.
Either way, anobodu else heard of this water-pump seal failure on C-Tec2 enogines?
 

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I'm not familiar with the C-Tec, but that mechanical seal will have the same results on whatever engine it is, regardless of make/model. It's typically a spring loaded ceramic or carbon seal, and when they go, it really doesn't have anywhere else to leak. I've had this happen on a few engines. I usually try to replace it any time the engine is removed just so I don't have to worry about it, lol.
 

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First thing to do is stop pulling it over.
Second is tear it down.
In the time it takes to poll multiple websites you can have the motor out. It sucks but having the satisfaction of having it back together right is worth something.
 

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back from the dead, but there are 2 seals on the water pump shaft, the mechanical seal that keeps the coolant in the cooling system, and an oil seal that keeps oil in the center cavity. Between these 2 holes there is an air space, and a weep hole. If the mechanical seal fails, coolant drips out of the weep hole, it doesn't go into the engine.
Also there are oil seals on the crank shaft to keep the oil in the center cavity.
It is pretty much impossible for coolant to get into a cylinder from the water pump seal. You woudl have to have 3 or 4 seals fail at the same time, and the weep hole plugged. Even if that magically happened, the sled would likely burn up the water pump drive gears from lack of oil, long before you couldn't pull it over from a hydro lock
 

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Discussion Starter #7
back from the dead, but there are 2 seals on the water pump shaft, the mechanical seal that keeps the coolant in the cooling system, and an oil seal that keeps oil in the center cavity. Between these 2 holes there is an air space, and a weep hole. If the mechanical seal fails, coolant drips out of the weep hole, it doesn't go into the engine.
Also there are oil seals on the crank shaft to keep the oil in the center cavity.
It is pretty much impossible for coolant to get into a cylinder from the water pump seal. You woudl have to have 3 or 4 seals fail at the same time, and the weep hole plugged. Even if that magically happened, the sled would likely burn up the water pump drive gears from lack of oil, long before you couldn't pull it over from a hydro lock
Thanks for clearing that up, I had my doubts the issue was related to the waterpump seals.
Anyway, I ended up putting the motor back together with new head and base gaskets and it's been running good so far, although I haven't been on a trip yet to properly test it out.
I also pressure tested the coolant system to 18-19psi before filling it back up with coolant and it held, so that's a good sign IMO.
We think the coolant could have been getting past the base gasket judging by the witness marks from the jugs. Maybe the cylinder base nuts weren't torqued properly from the factory or possibly rattled loose?
Either way, I made sure to torque everything properly and used blue locktite on the base nuts.
Hopefully issue resolved.
 

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Thanks for clearing that up, I had my doubts the issue was related to the waterpump seals.
Anyway, I ended up putting the motor back together with new head and base gaskets and it's been running good so far, although I haven't been on a trip yet to properly test it out.
I also pressure tested the coolant system to 18-19psi before filling it back up with coolant and it held, so that's a good sign IMO.
We think the coolant could have been getting past the base gasket judging by the witness marks from the jugs. Maybe the cylinder base nuts weren't torqued properly from the factory or possibly rattled loose?
Either way, I made sure to torque everything properly and used blue locktite on the base nuts.
Hopefully issue resolved.
If it passed the leak check, send it!

Glad to hear you got it all back together and didn't even need to pull the motor.
 

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Discussion Starter #9
Back from the dead, again... lol.
So as I mentioned at the start of last season, tore down the top end and replaced all gaskets and seals, no more coolant leaking into the engine, awesome.
Only had a chance to ride about 4 or 5 days last season, but they were decent 180 to 200 mile days. Sled ran great.
Only issue (once again coolant related) was that at the end of each one of these days, the coolant level in the reservoir was way down. Like an inch or two below the "cold" level line. I'd top it up, ride the next day and it would be low again...
There aren't any signs of external leaks anywhere, and the engine hasn't shown any signs of being "hydro-locked" after sitting for a bit, like it was before I changed the gaskets... It fires right up 1st pull.
It's not like the rad cap is easily accessible either, losing hope with this thing...
 

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Back from the dead, again... lol.
So as I mentioned at the start of last season, tore down the top end and replaced all gaskets and seals, no more coolant leaking into the engine, awesome.
Only had a chance to ride about 4 or 5 days last season, but they were decent 180 to 200 mile days. Sled ran great.
Only issue (once again coolant related) was that at the end of each one of these days, the coolant level in the reservoir was way down. Like an inch or two below the "cold" level line. I'd top it up, ride the next day and it would be low again...
There aren't any signs of external leaks anywhere, and the engine hasn't shown any signs of being "hydro-locked" after sitting for a bit, like it was before I changed the gaskets... It fires right up 1st pull.
It's not like the rad cap is easily accessible either, losing hope with this thing...
On my 2016 6000RR I noticed the same thing. It seems to settle in an inch or so down from the cold line but still in the reservoir. When I take the cap off it comes back to the cold line. I quit adding any coolant.

Keep an eye on it. As long as it is still shown in the bottle I would say you are ok. If it keeps going down and you no longer see it in the reservoir then I would be concerned.

If you are real concerned about it do a pressure decay test on the coolant system and see if it drops at all overnight. Chances are you are perfectly ok.
 

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Discussion Starter #11
Ya I was kind of thinking this as well, especially since I didn't really notice any change in my water temps, regardless of the level in the bottle.
The thing that concerns me is that I've owned the sled since new and I'm pretty sure the coolant levels always stayed in-check, up until I started getting coolant in the engine 2 seasons ago. Why the change now?
I'll definitely have to do another pressure test on the coolant system as well.
How many psi should I set it at?
 

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Who knows why it would do that. Just keep an eye on it. You should be able to check it daily through the side panel with a flashlight.

For the pressure decay test set it to what the reservoir cap relief is at. I think that is in the 12-15 psi range. It doesn't take much. The big thing is it should hold pressure overnight without dropping.
 

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My 2015 xc was losing coolant and chased it around for a yr.
The plugs showed one cyl was washed /burning an orange color while the other was normal dark brown
Removed the motor and filled with coolant and pressure and found a small drip coming down the transfer port seen thru the reed openings
Turned out the cylinder has a small crack/porosity failure in the transfer port near the exhaust port.
Soapy water and high presssuer air when cyl was removed verified.
Used cyl installed and the coolant has not wiggled off the full mark since,
 

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pic shows the soapy bobbles in the bottom of the transfer port after a quick blast of air in water jacket with soapy water sprayed in ports
IMG_6814.JPG
 

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I've received replies on another forum saying the issue is the mechanical seal on the water pump. Apparently when it fails it causes the coolant to leak internally. Great design on AC's part!
I know it's obviously not a good thing to have coolant in the bottom end, but I'm thinking it should be fine after I get it flushed out. Realistically metal doesn't rust in coolant, almost all vehicles used to have iron blocks and heads and they didn't rust. Water-pumps are also lubed by the coolant that runs through them.
I also had about a 70/30 coolant/water mixture, and it's mixed with all the oil that was in the engine as well so hoping for the best.
Either way, anobodu else heard of this water-pump seal failure on C-Tec2 enogines?
Mechanical seal leaks through a weep hole in the casting. Not internally.
 
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