Hello; New to the bobcat/skidsteer, however, somewhat mechanically inclined, and have so far been stumped. So here goes: Older bobcat 743 maybe from the 80's has a 30 HP Kubota diesel motor (engine model V1505-T-E3B) has had several modifications over the years so just keeping it running is a challenge. Here is the issue... At idle, it runs fine, for as long as I am using it. If I kick the RPM up a little (maybe 500 RPM from idle) and use it for more power it runs for about 10 minutes then the RPM drops down to the point where it barely idles. Bucket & boom both move barely, and hardly moves out of its own way. Here is what I have done: First thought it was overheating so I added an aftermarket radiator fan, and connected the regular fan (both 12v) directly to the battery. (it has an electrical issue where none of the gauges are working at all, will get to that later). That was not the solution It had an exhaust tube from the motor to the muffler (flexible exhaust) that was broken and was leaving a black stain on the inside of the back door, replaced that.. thinking that the intake was getting too much exhaust fumes back to the intake side of the motor... That was not the solution Changed the hydraulic filter and added about 3 gal of fluid to the tank That was not the solution There was a "funky" setup for the air intake filter (rubber radiator hoses cobbled together to a large 3" intake and 10" rectangle aftermarket air filter, the filter was black from the exhaust leak) removed that, ran with no filter (until I can get a proper replacement) still had same problem. (no intention of running it for long without an intake filter, very bad, I know...) That was not the solution I am suspecting that it might be some sort of a fuel/heat issue since I have repaired/replaced everything else, but if it was something like a filter, then my suspicion is that it would run with an RPM issue all the time. Is there some sort of pickup, or filter in the tank or fuel line issue that I can look at? I know that this thing sounds like a POS, but I got it on a trade for an airplane, and I am only using it for personal use on my land to modify and build a shooting range. Other than the RPM issue which has been an on-going issue since the beginning, it is a pretty good little machine. Has done some really good work for me so far. I have no intention of using it for hire, I would just like to be able to run it for several hours with no issues so I can blow out the work that I need done over a couple of weekends. (I know, I am dreaming..) Any suggestions? Thanks for your help
Is that really your unit? hard to believe it would be so well taken care of on the outside and so "jethro'd" inside??? That sure sounds like fuel to me. Overheating is usually easy to diagnose, it boils over, uses coolant, and the radiator gets hotter than it should. Get a non contact thermometer and check the temperature of the top of the radiator, if you're worried about overheating. There's several ways to go about the fuel issue. You could diagnose it, that is test it out to see if the fuel pressure is dropping after 10 minutes, or see if there are air bubbles in the fuel lines, or just check to see if the smoke is much less when the rpm drops, no smoke no fuel. With those symptoms (and the history) it would be just as reasonable to assume the fuel is the problem and go through the fuel system piece by piece, from the tank through to the injection pump, visually inspect and blow each piece out separately. There's common problems on some bobcat tanks and pickup tubes, you could take a good look at your fuel tank and lines, and then search this site a little to see what the most likely fuel system problems are.
I "understand" your theory on the filter but.. at idle it requires very little fuel to run.. at higher rpms it requires a lot more.. therefore if the filter is dirty.. it WILL run at idle and not at full or partial rpms. Does it have the push-on plastic see thru filter in-line?? you could take it out and plumb the lines together and see what happens.. How about a weak or non operating lift pump.?? That's the little pump that helps the fuel from the tank, get to the injection pump.. Just follow the fuel line FROM the inj. pump, backwards towards the filter and to the tank.. you'll run into something that is causing that problem.. Keep us posted..
OH, forgot to mention the fuel shut off gizmo before the injection pump inlet.. it may be partially on/off.. I think there might be a filter in it also. its about 3-4" long with an on/off lever on it..
Problem solved!!! I started with something simple, filters... There was a metal screw in filter into what looked like a fuel pump, and another filter that was inline with the fuel line, and had a little "bowl" on the bottom. While I was at it, I replaced the belt since it was looking a little "ragged" (I know that this has nothing to do with the RPM issue but I thought that I would mention it anyway). She ran like a BEAST for more than 5 hours with only a **** & quick water break (and to add more fuel) about 15 minutes total. No drop in RPM, even ran full throttle for more than an hour... got lots done today.... Thanks to all of you that had suggestions. I never did find the shut off valve thing, maybe it does not have one.. I will check in, in the future. I will post a picture of the "jethro'd" air intake system that I took off, and show you what I did as a replacement...
A lot of times there is a fuel shut-off on the metal bowl gizmo.. Glad you found the problem.. and thanks for keeping us posted..
if thats a pic of your bobcat. 74X series had 8 lug wheels.... 64X series had 6 lug wheels... that being said.... the most common overheating problem is lack of airflow through the radiator and hyd cooler, the cooler is located below the radiator inside the shroud. theres a couple of access plates in the engine compartment, pull them off and check between the cooler and the underside of the radiator for debris. the 2 plates need to be there to direct airflow, without them, it will over heat. kubota's are great engines, as long as you dont overheat them repeatedly. guarantee'd the head will crack. :drinkup
I solved this problem, by adding an aftermarket 14" 12v fan on the top of the metal grate above the radiator. I installed it directly to the battery and added a disconnect "blade" to the positive terminal of the battery. I connect the power, and the fan runs the entire time, pushing air down into the engine compartment. That along with the other fan that was already installed, I don't believe that it is too hot. What should the radiator temp be? I am going to get a laser temp reader and check it after running it for a few hours... to see what it is doing temp wise... Also, any suggestions about the best place to get a new set of tires? The ones that I have are not good for the mucky/soft stuff that I have been working in, summer is coming and it is going to start raining every day, I would like to be ready.. Thanks
Just an fyi, those machines were ment to be ran at full throttle all the time. With 36hp it is what it is, newer machines in that class are 50+ hp, they don't need to run balls out to get the job done. The only time I 'll cut mine back is when using the backhoe attachment. The pic of your machine shows 6 lug wheels........ Ed
200 is fine, 210 is probably fine, that's the hot end of the radiator, or the "thermostat neck" that the hose is attached to on the engine. Make sure it's a painted surface, non contact thermometers will read low on a metal surface that's not painted (reflective/emmisivity). The main thing is if the cooling system stays full. If it's not losing coolant, then it's close enough.
Just checked mine (1989) the engine is a v1703, I think you have a repowered 643. You should call the dealer and have them run the serial number. Ed