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Discussion Starter · #1 ·
A few months ago I dropped my engine and pulled the rear engine cover to replace the grounded A/C generator stator. I ended up replacing all of the rear seals as well, enlarging the water pump seal opening and using the Yamaha seal set. After reassembling the engine and installing it I have ridden around 1,500 miles without leaking a single drop of coolant or oil. Just yesterday I noticed a small wet spot under my CX500 after parking it for the evening. Starting it today revealed a small but steady stream of coolant originating from the weep hole.



Since I just disassembled and reassembled my engine, I'd rather not do it again if I can avoid doing so. Does anyone have any ideas of why this problem would suddenly surface?
 

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I'd be inclined to give it some time and get more and more upset about it. That sucks. Was the rest of your cooling system good and clean. Perhaps something in the coolant wore out your new seal prematurely. I'd want to think getting 1500 miles out of it rules out a faulty seal. I'd be hopeful for that and not a bad cam surface. You can always do the shep replacement method and not pull the motor next time. I would.
 

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It is hard to tell what might have happened. Maybe the dome nut came loose and is allowing coolant past the impeller. Maybe the seal got some grit on the sealing surface. Maybe the new seal wasn't lubed and the disks locked and pulled the boots loose.



Good news is that you can replace the seal without dropping the engine. Just use Shep's method which should be detailed in the Quick Reference section of the General Discussion forum.
 

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Like Blue said, you can take the water pump apart with the engine in and replace just the rubber part of the seal if you need to, aka the Shep method.  If it's a stream of coolant and not just a drip you'll probably want to stop riding until you can fix it.
 

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Like Blue said, you can take the water pump apart with the engine in and replace just the rubber part of the seal if you need to, aka the Shep method.  If it's a stream of coolant and not just a drip you'll probably want to stop riding until you can fix it.


Correction, replace the rubber and the ceramic together.



I'd suspect a loosening of the dome nut here, I'd pull the cover and inspect, retorque.... and maybe re-anneal the copper crush washer.



OP, you've been running a proper 50/50 mix ja?
 

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Correction, replace the rubber and the ceramic together.



I'd suspect a loosening of the dome nut here, I'd pull the cover and inspect, retorque.... and maybe re-anneal the copper crush washer.



OP, you've been running a proper 50/50 mix ja?


There are rare occasions where my,"In-bike" seal method does not work but I've only seen one posted so far in over four years.It's not clear if the OP did a full seal swap or an in-bike one?



Anyway.The two common causes of any Mech seal inner failing after renewing is not using RTV correctly and or not lubricating the Mating faces of the Rubber seal Carbon face and the ceramic polo meet with something like soap/oil.
 

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Discussion Starter · #7 ·
Thank you everyone for your input so far!



@Abes_CW: Correct, I am running a 50/50 coolant mix; the previous owner, although, had been running greater than 50% water in the system which resulted in quite a bit of cleanup work on my part.



@Shep: I performed a full seal swap and used petroleum jelly to lubricate the mating surfaces.



I will be pulling the impeller cover tomorrow to check the status of the dome nut and crush washer. I am very much hoping that it is as simple as one of those as my new rear tire just arrived today.



Also, the leak only occurs while the engine is running. As soon as it is turned off the leak stops. Would this change the diagnosis at all? Sorry to not have mentioned this before.
 

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I'll bet a Pepsi that it is the dome nut. And the steady stream and quiting when turned off validates that too.
 

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Thank you everyone for your input so far!



@Abes_CW: Correct, I am running a 50/50 coolant mix; the previous owner, although, had been running greater than 50% water in the system which resulted in quite a bit of cleanup work on my part.



@Shep: I performed a full seal swap and used petroleum jelly to lubricate the mating surfaces.



I will be pulling the impeller cover tomorrow to check the status of the dome nut and crush washer. I am very much hoping that it is as simple as one of those as my new rear tire just arrived today.



Also, the leak only occurs while the engine is running. As soon as it is turned off the leak stops. Would this change the diagnosis at all? Sorry to not have mentioned this before.


When the engine is running a certain amount of pressure builds up as the coolant system as it heats up.This rarely if ever exceeds 13 PSI(0.9 bar) which is what the radiator cap/valve system is set at.

I doubt the seal has failed at the metal cup to engine as that would normally allow coolant into the oil much like if the Water pump O-ring seal inside the engine had gone ending with the old coffee coloured,"Milk-shake".



I have a feeling the inner Mech seal may have got damaged/split on fitting.If this is the case you can just renew it using my system,"In-Bike".



http://www.pdsrecording.site90.com/cxgl500/Mseal.html



Problem here is that it may be very hard to see if the inner was split from just taking the Water pump cover/assembly off but I would take the cover/assembly off and have a really bright light source/lamp at it and press it to see if I could see anything but be prepared to change the inner seal which all-in-all is way better than taking the engine out to do a full seal swap.
 

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I performed a full seal swap and used petroleum jelly to lubricate the mating surfaces.


I don't know if this is why your seal failed, but nothing oily or greasy should ever touch the mating surfaces of a ceramic to carbon seal assembly, not even the oils from your fingers. Old fashioned soap might work as an initial lubricant and not harm the seal, but oil or grease will not work.



My company used to use a very similar ceramic to carbon seal on a water pump assembly we used to sell in our industry (commercial HVAC), if a field tech greased or oiled a replacement seal it would never last. Our instructions were to install the seal clean and let the coolant/water lubricate the seal.
 

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I always lubricate the mating surfaces between the Ceramic surface and the carbon face and have never had one fail yet on any of my engines.One of which rear case has done over 18,000 miles.



My 10 penn'th.
 

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If you are worried about running the seal dry at startup then lube the seal faces with a few drops of clean coolant during the assembly, but i wouldn't recommend using anything oil or grease based. Soap might work because the water would flush it away quickly.



The carbon part of our seal assembly is called a "wear nose", it is softer than the white ceramic and should wear in and sacrifice itself over time. Every instruction I have ever seen for this type of mechanical seal recommends against the use of petroluem based lubricants.



Looking for a better answer to "why" we would not want to lube these seals, I found this :

"The graphite in the carbon/graphite soft face is a natural lubricant. In operation the graphite separates from the mixture and transfers to the ceramic hard face. This means that the seal face combination you are normally running is carbon on graphite. The hard face of the ceramic is just some place to put the graphite. Moisture must be present for the graphite to separate from the carbon/graphite mixture."



And that's just my two cents worth.
 

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I always lubricate the mating surfaces between the Ceramic surface and the carbon face and have never had one fail yet on any of my engines.One of which rear case has done over 18,000 miles.



My 10 penn'th.


But Shep you use a soap, not a petroleum product. Interstater is probably bang on here. Vasoline isn't that slippery either in the big scheme of things either, IMO.
 

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Discussion Starter · #15 ·
So I managed to pull the water pump cover this morning and take a look under the impeller. My crush washer looks like it has seen better days. Also, I noticed some odd gray buildup covering both mating surfaces of the seal set. Could that be an amalgamation of petroleum jelly and any impurities floating around in the cooling system? My course of action from this point is to replace the crush washer and the outer seal and then use some fresh coolant as a lubricant. Hopefully this will stop the leak.



Picture of the crush washer:

[media]http://s837.photobucket.com/albums/zz299/Odenian/?action=view&current=crush_washer.jpg[/media]



Picture of gray buildup on the inner seal:

[media]http://s837.photobucket.com/albums/zz299/Odenian/?action=view&current=shaft_seal.jpg[/media]
 

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So I managed to pull the water pump cover this morning and take a look under the impeller. My crush washer looks like it has seen better days. Also, I noticed some odd gray buildup covering both mating surfaces of the seal set. Could that be an amalgamation of petroleum jelly and any impurities floating around in the cooling system? My course of action from this point is to replace the crush washer and the outer seal and then use some fresh coolant as a lubricant. Hopefully this will stop the leak.



Picture of the crush washer:

[media]http://s837.photobucket.com/albums/zz299/Odenian/?action=view&current=crush_washer.jpg[/media]



Picture of gray buildup on the inner seal:

[media]http://s837.photobucket.com/albums/zz299/Odenian/?action=view&current=shaft_seal.jpg[/media]




You my get away with a new crush washer(And it needs a new one) but also you can use a bit of RTV/Silicone gasket sealer over the domed nut area which may help.I had a running basket case engine I that had been hacked/bodged this way and didn't leak from the Mech seal.
 

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I agree with Shep, a new washer is in order. Also don't forget to put that small thrust washer on the camshaft before slipping the impeller on. It may be stuck in the impeller, I can't see it on the shaft. And I would wipe the seal surfaces clean and make sure that you can push the black seal back some against the spring pressure. There are little tabs on the cup that need to be aligned with the recesses on the black part of the seal.
 

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I agree with Shep, a new washer is in order. Also don't forget to put that small thrust washer on the camshaft before slipping the impeller on. It may be stuck in the impeller, I can't see it on the shaft. And I would wipe the seal surfaces clean and make sure that you can push the black seal back some against the spring pressure. There are little tabs on the cup that need to be aligned with the recesses on the black part of the seal.


Good call Blue F.

painted red on here,



http://www.pdsrecording.site90.com/cxgl500/Mseal.html
 

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Discussion Starter · #19 ·
I removed the buildup from both seals, the thrust washer, and the impeller. I then swapped the outer seal, found a new crush washer, applied some RTV silicone between the cap nut and crush washer as per Shep's advice, assembled the whole package using a small amount of soap to lubricate between the seals, and then torqued the cap nut. I have now idled the motorcycle twice for around 10 minutes and have not seen any coolant emerge from the weep hole. Hopefully it stays that way. There is definitely a bunch of garbage floating around in my cooling system so I'll be performing a cooling system flush this afternoon. Thanks again all for the help!
 
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