NH LX665 won't maintain high rpms (drops even with throttle full on)

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bengarland

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Joined
Nov 27, 2009
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Hey everyone, I'm a skid steer and construction equipment newbie. Just got a '99 NH LX665 that appears to be in pretty good shape. It has about 1600 hours and the guy I bought it from said he just had all fluids serviced a month ago. He said the only thing he didn't do was change the air filter (looks pretty clean to me) and the fuel filter (not sure of the status). He had it for 14 months, I just bought it from him a week ago. When I got it home, it worked fine for a couple days. I took down a few small (4-6") trees with it and moved some dirt around. It seemed to have good power most of the time. A few times it would cut itself off when under a big load (such as when lifting tree roots out of the ground with the bucket and moving forward at the same time) -- I've never used a skid steer so I'm not sure if this is normal or not. I just cranked it back up and kept on going, no problem. Then I left it sitting out in the woods overnight and it got rained on. I figured this isn't any big deal, since I thought construction equipment is built for outdoor use. But I thought I'd mention it since the problem started after getting rained on. Not sure if it's a coincidence or? Anyhow, the problem is this: When I start it (at 1/3 to 1/2 throttle) and then bring it up to full throttle, it sounds "fine" (like it did prior to the problem) for about 10 seconds, then the rpms begin to fall so that it sounds like I moved the throttle down but I didn't touch anything. I checked the digital display and it shows 3170 rpm at full throttle, then 10 seconds later it slowly winds itself down to about 2560 and stays there. I can get it to go back up to 3170 ONLY if I bring it down to idle, wait 3 seconds, then jam it back to full. But then it does the same thing, ramping itself down after 10 seconds or so. I tried leaving it idling for 10 minutes to warm it up more, but it had no effect. What could be wrong? It was 60 F outside when I tried this so I don't think temp is the problem (it was the same temp a few days before it got rained on and it worked fine). I ordered a manual from NH but it's not here yet. I'm not really sure what to check. The engine oil and hydraulic oil are at a good level. No warning lights are coming on. The only thing that looks kinda empty is the coolant reservoir located on the inside of the back door. It just has maybe 1/2 cup in the bottom of it. What goes in here? Regular antifreeze like I use in a car? What is the antifreeze/water ratio? How much do I fill it? I don't think this is related to the problem but I thought I'd mention it. I called the local dealer and he said "Check that the throttle cable isn't stretched" then suggested that I bring it in (of course) for them to look at. I checked the cable and it looks fine. When the rpms drop, the throttle is at the same position in the engine compartment and at the lever in the cabin so the cable is not actually moving (at least that's what it looks like to me). Any suggestions? Thanks!!! Ben
 
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