P700 Missing Coolant Mystery

[fmjnax]

I've got an '11 MUV700 (same engine as the P700). For quite a while now, I've been losing coolant and have to add almost a 1/2 gallon after each use. The leak is seemingly internal. I have never seen even a drop of anything under the machine. I've lifted it and ran it while looking for any evidence of a leak (unsuccessfully). The engine does not smoke at all. Putting paper against the tailpipe, it doesn't get wet. No coolant in the oil and doesn't seem like oil is going to the coolant either. No steam coming off the engine itself and nothing looks wet. I cannot figure out where the coolant is going!

A couple of months ago, my kids ran the machine and didn't top the radiator off. It overheated and started smoking. Rings were stuck. I ended up replacing the cylinder, piston, rings, and gaskets with new parts. The machine runs greats again aside from the coolant disappearing.

Where could my coolant be disappearing to?

 

[Glock21user]

Do you see witness marks on anything that may look like coolant is moving along a surface and possibly evaporating while in use, and residue in a location that seems odd?
It is either losing it or ingesting it if continually low.
Have you pressure tested the system to see if a pinhole leak shows itself or possibly a bad cap seal.
Coolant escaping under pressure can make a very fine mist that is hard to detect.
Antifreeze and water sometimes are hard to track just look for little indicators that are out of place.
Good luck and keep us updated.
Oh yeah before Barney gets here POIDH..lol

 

[osobad]

Are you sure you got the coolant full?

 

[fmjnax]

Yes, osobad, I'm sure I got the coolant full. As much coolant as I have put in it since I last flushed it, there's no way it's that simple of an issue. I just don't get that kind of luck around here. LOL!

I couldn't see any blatantly obvious recent tell-tale witness marks but did see some possibilities. However, I just couldn't tell with the accumulation of time what might be new vs old. I just got back inside from giving it a good wash so after it's completely dry I'm going to run it again and see if anything new will present itself. When I was taking the seat/plastics off, it looked like maybe the t-stat housing gasket was leaking at some point so we'll see if that might be the culprit.

If it's not the gasket at the t-stat and I still don't see any signs of a leak, I'll get a coolant system pressure tester and give that a try. I'll also snag some pictures to upload to see if anyone else can spot something I'm not seeing.

 

[osobad]

Understand. I know this can get a lot of air in the system when empty you would think if it was internal you would see it in the oil but head gasket will sometimes do that and smoke or leave other traces. Hope it turns out to be simple

 

[Glock21user]

Yes, osobad, I'm sure I got the coolant full. As much coolant as I have put in it since I last flushed it, there's no way it's that simple of an issue. I just don't get that kind of luck around here. LOL!

I couldn't see any blatantly obvious recent tell-tale witness marks but did see some possibilities. However, I just couldn't tell with the accumulation of time what might be new vs old. I just got back inside from giving it a good wash so after it's completely dry I'm going to run it again and see if anything new will present itself. When I was taking the seat/plastics off, it looked like maybe the t-stat housing gasket was leaking at some point so we'll see if that might be the culprit.

If it's not the gasket at the t-stat and I still don't see any signs of a leak, I'll get a coolant system pressure tester and give that a try. I'll also snag some pictures to upload to see if anyone else can spot something I'm not seeing.

Nice work.
Keep us in the loop and together we will solve this

 

[fmjnax]

The mystery might be solved! After the wash, I topped off the coolant and we drove the machine for a few hours. This morning I tore it back down. Radiator was still full but the overflow had dropped a bit. It looks like the t-stat gasket might be leaking and for sure the hose going to the t-stat. The worm clamp is in bad shape. It won’t tighten any further. So new t-stat, gasket, and clamp are on the way. We’ll see if that does the trick.

 

[Glock21user]

Looks promising.
Make sure the t-stat housing is good and clean as well.
Any imperfections in either the hose mating surface or the housing will create a leak path.
Good luck with the repair.
Keep us updated