First off thanks Willie for the welcome! I'm not really new to here but long story short just bought a house 8 months ago and been tied up with all that goes with that mess and forgot my old password to my old S/N (3rdgendslwrench). Now down to buisness....a friend of mine has a Bobcat S250 with the bobcat engine in it. A few weeks ago I replaced the A/C compressor, reciever dryer, and expansion valve, made sure the radiator and condensor was clean and the hydraulic fan was working right. The fan starts out slow right at start up, once the engine coolant, hyd. oil temp heat up, or if the A/C is switched on the fan starts spinning faster...like a medium speed. A few days after I did all that work he called and said that the engine temp was getting up close to the red but would cool down within 5 minutes at an idle. I did the cheapest easiest thing first and changed the thermostat and gasket and once again checked to make sure the fan was working properly. My buddy even said once the temp gets up close to the red that you can hear the fan spin even faster than normal. Put the thermostat in and just sitting on the trailer after about 15 minutes the engine temp was reading 183 F and the gauge was normal. Both radiator hoses were the same temp and I opened the coolant bottle and you could see the water circulating. Pretty much covered the basics just short of the radiator being clogged. Two days later he said it was doing the same thing....cools down at an idle within 5 minutes and takes like 45 minutes to heat up again. I googled the problem one night and I'm hearing that this is a common problem for them which I think is B.S.! Anywho, he is running a hammer attatchment so I'm starting to think now that maybe he isnt giving it a rest every now. Has anybody else come across a problem like this before? There's a pretty good radiator shop around the corner from me and the wont charge a arm and leg to check the radiator out I'm just wondering if this is something somebody else has seen before on a similar machine.
I haven't seen that problem with any of our Bobcats, doesn't mean I've seen it all though. I've seen it happen when radiator gets clogged externally, but you've stated that's not the problem with this one. If you have a radiator shop that would go through the radiator for a good price, I think that would be a good thing to do. Even if it were not the problem, your friend would be confident that his radiator is good for some time.
check tht the machine doesnt have several oil, hydraulic, and regular radiators. A friend had problems with his 300 runnin a mulcher, turns out he had 3 radiators in the form of a hydraulic oil cooler, engine radiator and and aux. oil cooler that was part of the highflow package. Not all of the radiators were cleaned out, and it over heated. Does it overheat only when runnin the hammer?
I know its got the radiator, hyd.oil cooler, and condenser for the a/c. After I radiator blew air through the stack of coolers I took a rag across the whole assembly to make sure it was pulling air throughout the whole thing. His machine might be a highflow. I kinda remember seeing a button on the top left panel saying "Hi/Aux" or something like that.
I had this same problem on a wa500 wheel loader. It would take 45 min. before it would over heat. I blew out the radiator, checked for flow with the radiator cap off, checked for combustible gas in the cooling system. Everything seemed good. Come to find out the water pump belt was a little loose. At low idle it pumped coolant fine , but at higher RPM the belt would slip on the water pump pully. This might not be your problem, but sometimes the simple things are over looked.
My T250 had the same issue with slowly gaining temp, overheating and then quick cool down. The tensioner for the fan belt was wore out and wouldn't keep the belt tight enough to spin the fan fast enough. Replaced the tensioner and adjusted the belt and no more overheating. But I see the S250 in question has the hyd. drive fan like my S250. Funny thing is I didn't know my S250 had a hyd drive fan until one day I was servicing it with the cab up. I second mw85's suggestion and look at the water pump and belts.
as mentioned, check the alt belt for tension. check between the hyd cooler and radiator for debris. sometimes just blowing everything out doesnt help, but a good pressure washing of the radiator will flush out debris trapped in the fins. it sounds like the hyd system may be getting warm, breakers make a lot of heat very quick, especially when are being run constantly. :drinkup
The hydraulic fan will run constantly at a slow speed all the time until the thermostat tells it to ramp up when it gets warm. On the hydraulic fan itself there is an electric solinoid....pulling the electrical plug on this solinoid will allow it to run full noise all the time....do this and run the machine until your satisfied that it would have overheated by now....if she no longer overheats then the thermostat switch is your issue....i find it hard to believe that the machine overheats under normal conditions...You do not want to overheat them too much.
That's what I was thinking too Ryan. I know on a lot of Cat equipment if the solenoid goes bad or a wire gets broken to that circuit it goes into high speed default. I havent got to work on it lately because he's got it on a job kind of far from where I'm at so I'll have to wait. Do you know where on the engine the thermo-controlled switch is?
Okayyyyy just a quick update on my sitchyation. Took everything apart short of the block and the water pump. Used an O-ring pick to make sure the impeller was still spinning on the water pump shaft. Removed the muffler to take off the EGR cooler. No blockage in the coolant end. The cleaned the exhaust tubes with a small bore brush ( they aren't straight through, staggered). Put a new coolant Temp Sensor on it and pat in on the butt and sent it on its way for a test run. The only thing I did find wrong and I doubt this would cause it to overheat was the muffler-turbo up-pipe gasket was leaking...and leaking right onto one of the coolant tubes for the EGR cooler.