I have a 2002 Yz 125, antifreeze is coming out of a small hole behind the water pump under the bike. Does this mean the seal behind the impeller is bad? If this is the case, can I just replace this seal? Thanks Dom
I think its the mechanical seal thats bad. Because there should be another seal, looks like a regular oil seal and if it was bad oil would leak out of that hole, so since its antifreezse leaking it should be the mechanical seal on the pump shaft thats bad. Any one else agree?
Not sure about this particular model, but the hole sounds like a "weep hole", which is put there to let coolant leak out as an indicator that the shaft seal is going bad. Replace the seal ASAP before it gets worse and you lose all the coolant causing very big problems! Also a good idea to give the impeller shaft the once over for any small nicks or burrs that might be eating seals.
I had this exact problem on my 2001 YZ 125. I ended up completely rebuilding the water pump. The only part that I didn't replace was the impellar. The driven gear shaft was eaten up beyond what I thought possible. The good news is that the parts weren't that expensive and it wasn't too difficult a job. The cause of the problem (as explained to me) was the coating they put on the factory bearings. The coating (which is very hard) came off and ate the seals. No problems since the rebuild.