If I am to believe the sticker, there is a 15psi one on it now.
Given the PSI rating (as opposed to metric) and the apparent lack of Chinese markings (don't know what's under the yellow sticker), that's almost certainly an aftermarket cap. In my estimation, it should be replaced ASAP. We're only talking about a $4 part here.
We're talking about an engine that was designed around coolant temps between 70C and 80C. If you've got one of the old owner's manuals, you'll see commensurate winter instructions;
"
if the tractor will stop for a long time after operation, the water in the cooling system should be drained out",
"...water of 60C-80C can be poured into radiator for easy starting", etc.
Then consider that the (unpressurized) boiling point of plain water is 100C. A pressure cap merely raises the potential boiling point, and - assuming the correct thermostat and a clean cooling system - your engine
should seldom even come close to the boiling point. So why raise it?
Over-pressurizing the cooling systems on these low end Chinese engines will eventually - if not immediately - result in coolant seepage. Let's face it, the design tolerances are really pretty loose - and this is especially true of the pre-EPA engines (2006 and earlier). If you don't change the cap, be prepared to see coolant oozing out around both the upper and lower tank seals, past hose clamps, past the water pump seal, around the temp probe, gaskets, et cetera.
//greg//
