F series Engine RPM's

[yellowdogsvc]

My F series Toolcat has about 250 hours +/-. About three months ago I noticed that the RPMs dance all over the place at low to mid rpms when the machine is in gear and moving forward. It's not at every throttle position but rather a few but those happen to be where I like to set the throttle for running around or light grapple work.
At idle or when I'm running my chipper, it idles just fine at low, mid, and high rpms.

When I press the accelerator, at those lower rpms, it almost sounds like the engine is surging. It doesn't seem to have power loss but you can hear and see the rpms dancing as much as 50 rpms. I know my Bobcat will go up and down in rpms but you can't really hear anything or feel anything different..just runs like a normal machine would. I've had several people tell me the Toolcat doesn't sound right or that it sounds like it is revving up and down (but not above where the throttle is set).

I had my Bobcat dealer send out a very experienced tech and he said nothing was wrong yet it still does it. The next step is taking it into the shop but I'd rather not if I don't have to.

My B series didn't do that. Where you set the throttle, the rpms stayed and only moved up and down under load but it was consistent.

Does anyone have any ideas or what other info should I post about it?

 

[Xfaxman]

Change the Horsepower Management setting to see if that makes any difference.

 

[yellowdogsvc]

I will give that a try!!!

 

[yellowdogsvc]

I think that worked. It was turned to the on position. I will know more when I get a chance to work it but a quick up and down my hills seemed to feel different. Thanks for the reminder. I had forgotten these machines had that. I think I set it when I got it and forgot all about it.

 

[Xfaxman]

Good, let's hope it is not a flaky RPM sensor.

 

[yellowdogsvc]

Don't say that. Warranty just expired!
I have actually been kicking around the idea of selling my Toolcat. I've had one since '07 but around the ranch, I mostly use it for mowing, loading attachments on my flatbed or running to the back 40. I have 2 mules for the running around and it seems a waste to have such an awesome machine not being used much. I need 2 machines so I have been kicking around getting a second Bobcat. I used to run two identical ones so that I never had downtime but switched to the Toolcat back in '07. I'm not sure I wouldn't miss it, though, but I have more attachments for large skids than I do a TC and I still have an excavator that needs to work.
Uggh. Decisions!

 

[yellowdogsvc]

Well, had to take it to work yesterday and it's still doing it. Only when I press the accelerator about halfway or when it's under load. No noticeable power loss but the RPMs jump up and down and you can hear the motor going up and down.

 

[yellowdogsvc]

I tried it out today. It's the hydrostatic pump making the noise. The rpms do go up and down quickly while under load.. not sure if that's normal. I've owned 12 or 13 Bobcat machines with the Kubota and this one just sounds different. I tried dead heading the hydraulics at different rpms to recreate working under load and I can hear/feel the pump. Maybe it's because of where the engine/pump is located. My old machine had rear engine and I think the pump was slightly to the middle right. This one, I think the pump is under the driver's seat or partially under the middle. I know my F series is louder than my B series in the cab.. probably due to motor placement.

Before I take a trip all the way into Bobcat, I am going to ask my salesman to drive/listen to it. It has plenty of power and I run hydraulics so maybe this is normal sound. Just sounds odd and my wife said she thought it sounded different recently.

 

[SSdoxie]

have you readjusted the Drive Belt tension spring lately? If not, try that.

 

[yellowdogsvc]

I only have about 225 hours or so on it. Could it be loose already? Thanks for the advice. Will check on it.

 

[yellowdogsvc]

Update:

Dealer didn't find anything. Everything spec'd out and flow meter showed it was on the mark as well as having a belt adjusted correctly. Still doesn't sound right and I can feel it surging. Related to when the accelerator is about half-way down and rpms in the 2100-2350 range mostly.

It has plenty of power, does good on fuel, runs fine, etc. so maybe it's just normal. Wish there was someone else nearby with an F series so I could get a second opinion but it doesn't sound the same as my B series.

 

[Xfaxman]

If you get up near Oklahoma City, you can come drive ours. :thumbsup:

 

[yellowdogsvc]

I'd like to try the 5610!

 

[yellowdogsvc]

Re: F series Engine RPM's -Update

I contacted Bobcat on the recommendation of my service manager.

Spec-wise, everything checks out but everyone I work with says it sounds like it is revving or "chugging" like a choo-choo . I know it doesn't sound right. It's got plenty of power but when it starts, it rough idles more than my other kubota motors (s750, 335 ex) and smokes. It smooths out after a minute or two. I was thinking it's not getting a complete burn of fuel when it starts but it's not white smoke like my big cummins diesel belched when it first started up.

Anyway, I'll post updates as I get them in case anyone else is troubleshooting a similar issue.