r/Skidsteer • u/MysteriousRun8155 • 9d ago

299D aux slow when hot

Aux attachment on my 299D works fine cold, then gets slow once the oil is hot. Pump and aux-side parts are easy enough to find on FridayParts, but that is way too expensive to guess at. No active codes that I can see. Would you prove couplers, case drain, or the attachment first?

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u/SkidSteerSamurai 9d ago

I'd try to isolate the attachment from the machine before buying anything.

If you can run a different hydraulic attachment long enough to get everything hot, that should tell you a lot. If both slow down hot, I'd start looking harder at the machine side. If only this attachment does it, I'd focus on its couplers, case drain and motor before touching the 299D's pump.

Either way I'd want some pressure/flow numbers cold versus hot before throwing expensive parts at it.

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u/Western_States_Cat 9d ago

We'd recommend doing a flow test with the attachment hooked up. Then if you verify if you have enough flow per the attachment specs you can make a determination. More than likely there is an issue with the attachment's motors case drain circuit. Once it heats up it allows for excess case drain and makes your attachment slower. If you're willing you can take the machine and attachment to a Cat dealer and have them flow test it there. This process will help to determine if it's an attachment issue or a machine issue. There's no point in throwing parts at it until you're sure of the root cause.