We have a 6415 with a hydraulic issue. The hydraulic temp warning light blinks after a few hours of operation. We recently had the radiator worked on due to a leak, and after the repair this problem came up - it was fine beforehand. We had asked the local JD place about using aluminum radiator stop leak in the radiator and they said it would cause problems. So is this true? I think somebody (not me, I'm inclined to take their word on things like this) may have put some in it after the radiator was patched.