Dreaded coolant leak

[ecopter]

I've got it again on the Vmax 700. Son of a gun! I changed out the mechanical seal last season and changed the oil seal, too. In fact, it even leaked a bit after I changed it last year but I rode it anyway (2000 miles). It actually seemed to only leak (weep) after shut down and I didn't really lose a whole lot of coolant.

I just got the sled out of storage today and fired it up. I warmed it up real good and then shut 'er down. Sure enough......drip, drip, drip, drip. Using a mirror and flash light, it is coming out of the weep hole behind the mechanical seal. What's up with these things? How do these seals work and is it possible something else that's suspect? I've read somewhere on here that some have put loctite on the impeller bolt. I realize that's probably to keep the bolt from spinning off the shaft and causing the impeller to come off. But would loctite also prevent any possible leaks from getting back to that weep hole?

I'm at a loss. I have a hard time believing that the seal went out again after one season. I do not want to have to change that sucker again since it was a pain in the arse. This just might be something I finally give in and pay out the waazoo to have some service guy do.

This has been an awesome sled and the engine has been great, but this has been an irritating problem that's plaqued many a 700 triple. Anyone?

Jon

 

[yamaholic22]

You wont know for sure until you get it opened up, but i would be willing to bet that if you did not replace the shaft and impeller when you replaced the seal last year (most people do not replace the shaft and impeller because usually it is simply unnecessary), that now the tolerances between the shaft and impeller are too great, and the impeller has a slight wobble. This wobble from too much tolerance makes it impossible for the ceramic on the back of the impeller to seal against the rubber cup of the mechanical seal, causing a leak. The only way to really be SURE that it won't happen again is to replace the shaft and the impeller if they have any play in the splines, as well as the mechanical seal and the rubber sealing washer between the bolt and the impeller. Did you replace that washer when you changed the seal last year? If not, was there any noticeable damage to it? I have also seen these leak because of that little washer allowing a small amount of coolant to get down the center of the seal. Loctite is important on the bolt to keep it from backing out, allowing the impeller to come off and rub against the cover. I have also seen this failure before. Just make sure that if you don't replace the shaft and impeller, that there is really no play at all between them so that a good seal can be made on the back of the impeller. Sorry for the long winded response, but this is such a common problem, and material may be getting hard to find as the majority of the posts on this subject were a few years back.

 

[ecopter]

Thanks for the long winded response. Anything is good to know. I did change the small washer, however I didn't change the shaft or impeller. I did check that and all was good. The only thing I didn't do/change was loctite, or a new gasket around the housing. Although, after watching it leak with the mirror yesterday, it's not leaking around the gasket, but rather the weep hole.

I just hate having to tear into that again, especially the way I did it by keeping the engine in the sled and working in such tight spaces.

Jon

By the way, how does that mechanical seal work? Why would it quit leaking when it gets really warm?

 

[yamaholic22]

the mechanical seal is just a spring loaded rubber cup that pushes against the ceramic on the back of the impeller to make the seal. The rubber and ceramic seal tight enough to not let coolant through to the center of the seal. It is a radial seal, the center is open. If the sealing faces get damaged at all (such as a scratch in the ceramic or a small gouge in the rubber cup) the seal may leak. The coolant is also the lubricant for the seal, keeping the rubber soft and cool so it doesn't melt or harden. When the coolant gets hot the rubber expands and may band aid the damage to the seal. You may not even see any damage on the seal at all, it doesn't take much of a gouge to make a seal like this leak. I personally dont even touch the sealing faces with bare hands when installing, acids in the oil on your hands may damage the rubber.