Coolant hose collapse on MCX Nytro

[Linc]

Anyone seen this, been fighting overheating issue, thinking it was a head gasket, I replaced the shim and gaskets, threw in some studs while i was at, the gasket showed some leakage, so I was confident that this was the repair, but it's still overheating, I pulled the clutch off and ran the engine and noticed that the coolant hose from the heat exchanger to the water pump collapses at high RPM. Now the old MM700 had a spring in the hose, this doesn't have one, is it missing? Has anyone seen this before? Also the noise coming out of the clutch side seemed excessive, so I pulled the water pump out, and found that gear and the pins had a lot of play from excessive wear, so combine the water pump and the clutch rattle, I think I've found the noise.

Linc

 

[Mountaintech]

To have a hose collapse like that tells me that there is a restriction in the system. The front heat exchanger isn't damaged, is it?

 

[Linc]

Nope, it's good, that was my thoughts too, checked the thermostat, I'll totally drain out the system and check for blockages, very strange.

 

[Mountaintech]

No spring in my hose. Does it collapse with thermostat removed?

 

[Linc]

I couldn't find anything wrong, other than the coolant level being low, which might do it, I filled right up and I'll try it again without the spring, I might still put the spring in through, just for insurance.

 

[red]

Is this a lower hose? Rap caps can cause a hose to collaspe, its worth trying as its a quick check. Im guessing you checked that already thou.

 

[Linc]

Lower hose to the water pump, I think if the water is low it will do it too, I'll light her up tomorrow and see what happens, I was shocked at how much play the impellor had on the shaft though.

 

[Mountaintech]

How many miles on this bad boy?

 

[SylvanLaker]

The only reason you should have water pump gear wear is if your head stud was hitting the gear. Is there clearance from the head stud to the gear? Better check this while you are at it.. I've repaired a few that were done by home mechanics..

 

[Linc]

The gear wasn't worn, the pins and the key way in the gear is worn, the old Vectors used to to do this, Yamaha changed the designed for the Nytro by adding another pin to the pump shaft, so now there is two pins instead of one, there is plenty of clearance to the stud.