GX390 Oilsplosion

Hey all,

I have a few Pressure Pro GX390/General Pump HP4040 belt drive machines. A few weeks ago, one of them decided to shoot oil all over the place.

Here’s where it gets weird…

There’s no evidence of a leak. The oil was dark black, and we had just changed both the pump and motor oil, so they were running clear. It only happened once.

I couldn’t replicate the issue or figure it out, so I took it to my small engine guy, and he couldn’t either. Seals and gaskets are also in good shape. We all had a not-so-serious idea that someone got tired of hearing the machine running and threw a cup of oil in the vehicle to make it look like something was wrong, but considering where my employee was parked, that would have been a struggle for someone to accomplish.

Has anyone ever come across this issue?

Oil can turn black quickly, especially in engines without a filter. How are you measuring the oil? If you’re using the dipstick, the oil level is likely low. It should be filled until it reaches the oil filler neck, which is significantly higher than the dipstick’s range. When you say “shoot oil,” do you mean it sprayed everywhere or just formed a puddle on the ground? If it sprayed everywhere, it’s likely that something, probably the filler cap, was tight enough to allow pressure to build but not tight enough to contain it once the pressure was high. If it was just a puddle on the ground, it’s possible that some oil was spilled during the last change and went unnoticed, accumulating on the skid plate. As the vehicle was driven, the oil spread. This explanation is more plausible than someone deliberately pouring oil on engines, as there are more effective ways to damage an engine if one were so inclined. I’d be willing to bet the filler cap was just left a little loose… also would explain why nobody else could figure it out since thats an easy piece to adjust without thinking about it… after having 2 or 3 people look at it and move it the evidence is gone.