743 running a bit hot

[Chris 8603]

So I've had a issue all summer long. In the evenings starting around 3, my 743 starts to overheat. If the temps or above 90 it will do it ever time. I have cleaned both the hydro cooler and the radiator, flushed the radiator, removed the thermostat and it still does it. The water pump is a little over a year and half old. All filters have been changed. I thought maybe the fan blades may some broken, but there all good. But it still wants to get hot once the even heat gets the hottest. It just doesn't make any sense. Runs fine the rest of the time no matter how hard I run it. Took the radiator cover off to do the exhaust fluid test and that was good. I left the cover off and went back to work and the dang thing didn't over heat. So I ran it the next day and same thing, didn't heat. Put it back on and the @##$ started to get hot. Does this make sense to anyone or has anyone had this issue. I can't leave it off, I don't want to run a limb into the radiator. Any thoughts????

 

[foton]

could the fan belt be glazed and is slipping and not spinning as it should?? a 160 degreee thermostat is as cold as I would use. diesels like 180 degrees usally. good luck a head scratcher for sure.

 

[Chris 8603]

I've changed the fan belt too, sorry I forgot to add that.
It's running with no thermostat. That was the first thing I thought of. Changed it and did the same thing. Pulled to ses if it would run any cooler.
Yeah, I have a new one for it, all I could find was the factory thermostat to put in it. I agree with you on no lower than 160. Rule of thumb is 175.
That's what has me stumped on it???

 

[laurencen]

when the motor gets hot what is the temperature? does the radiator hoses and radiator get hot also?, any oil in the radiator when you take the cap off

 

[Chris 8603]

No oil visible in the radiator. I've put test equipment on the upper and lower hoses, and also front and back of the head and block. Just short of 200 is when I shut it down so as hopefully not to crack the head. I put a new bourbon style gauge on it when this started so I could see what it was doing for sure. When it's doing it the temp at the radiator is pretty close to the same in and out. There is no difference in the temp of the radiator to make me believe it could be partially stopped up. Plus I ran a good cleaner though it. It has good circulation watching though the cap. There's 30 or so degrees difference in upper and lower hoses. All this though without the radiator guard off. With it on is the only time it gets hot. Then the upper and lower hoses get within a few degrees of each other. If it was a issue with something engine wise, it seems like it would do it either way??
I'm scratching my dang head!!!

 

[brdgbldr]

I'm just throwing my thoughts in here.

It sounds to me like an air movement problem. For some reason with the radiator cover on the air is not moving properly past the radiator.

Is your blower housing in good condition?
A hole or a crack would cause bad airflow.
There are also two covers that should be on it. I have seen these missing or loose on some machines.

Take a look at the parts catalog and make sure all of the parts of the housing are in place:

Bobcat Parts Catalog - Find Diagrams for Your Equipment - Bobcat Company

Locate all parts and component information about your Bobcat equipment with detailed visual diagrams and illustrations with parts numbers and add to your list.

partscatalog.bobcat.com

 

[Chris 8603]

I'm just throwing my thoughts in here.

It sounds to me like an air movement problem. For some reason with the radiator cover on the air is not moving properly past the radiator.

Is your blower housing in good condition?
A hole or a crack would cause bad airflow.
There are also two covers that should be on it. I have seen these missing or loose on some machines.

Take a look at the parts catalog and make sure all of the parts of the housing are in place:

Bobcat Parts Catalog - Find Diagrams for Your Equipment - Bobcat Company

Locate all parts and component information about your Bobcat equipment with detailed visual diagrams and illustrations with parts numbers and add to your list.

partscatalog.bobcat.com

Any thoughts are better than none at this point, so thanks. I'm thinking air flow too but just can't fiqure it out. I know the service panel are in place. I didn't check the blower housing when I checked the fan blades, so I will do that. With the panels removed the air coming from the blades will blow you're hat off your head. But there is definitely not anywhere near that much coming through the radiator. The cooler and the radiator have been cleaned. I also used a light to make sure I could see though the whole surface of both. I will check the housing and post back. Thanks

 

[Tazza]

How does your engine start, have you had the head off at all? not everyone knows that in diesels, you need to make sure the gasket you use is the same thickness, top clearance is very important, differences of .1 or .2mm makes a big difference. If your clearance is too small, your compression is too high and you get too much heat.

Generally there are only a few reasons an engine will run hot, exhaust gasses getting into the cooling system, be it a cracked head or failed head gasket.
Not enough coolant flow
Stuck thermostat
blocked radiator
not enough air movement.
Compression that is too high.

If your radiator was in good shape, the outlet side should be a fair bit cooler than the intake. If it's not transferring heat, you may have sludge or something in it, sure, you can run cleaners, but if it was already plugged, you stand little chances of it cleaning it, like a blocked injector, you add cleaner to the fuel system, but it's too little too late.

 

[foton]

that makes sense radiator did not clean up with the flushing, is there places that still rod out radiators or replace cores,or is it another lost art of repair. Of course if that radiator is aluminum it is a throw away anyway.

 

[DirtRodeo]

How about getting longer bolts for the radiator cover and adding spacers to move it away from the radiator? An inch might be a big help with airflow.

 

[haymaker]

Very basic question but I didn't see it addressed.
Does the radiator have the proper pressure when hot?
Second, did your water pump have a metal or plastic impeller.

 

[Chris 8603]

The machine starts and runs fine, as long as that cover is off. That's when I have a issue. The engine is factory except for glow plugs and water pump. The radiator isn't stopped up, there's no temp difference across the core. I ran flush though it just to make sure there was not any sludge in it I couldn't see in the water causing thermo issues. It was left in over night and nothing came out. If the radiator was plugged just taking the cover off wouldn't change it enough to cool properly. With the cover off and thermostat out, it barely reaches 180 with the cover off unless I run it hard. Then it will cool down to 170ish.

 

[laurencen]

I had a 743 that had a cracked head, it would overheat quickly and after replacing the head ran fine, if you have no oil in the water and no bubbles head may be OK, take a good look at the rear behind the motor, there are covers that deflect the air from the fan to the radiator, if a cover is missing or not located correctly air will not go thro the radiator, another possibility is the fan, it may have damaged blades removing the radiator cover likely improves the air thro radiator by convection but its not the answer.

look at the service manual or Bobcat parts on line and you will see the covers behind the motor

 

[laurencen]

here is bobcat part for the cover, be simple to fabricate but possibly its just fallen down, with the motor running you should feel air blowing out the top of the radiator cover, the fan moves a lot of air

Blower Housing Cover for Loaders, 6565196

Blower Housing Cover for Loaders, 6565196 is commercial quality hot rolled steel, 14 x 9 inches.

shop.bobcat.com

 

[Azhayseed]

It sounds to me as though it is an air flow problem. The radiator may be partially plugged by dirt or debris. Or is the out side of the radiator fins coated with oil ? You should routinely clean out radiator fins and straighten out bent fins.

 

[Chris 8603]

Very basic question but I didn't see it addressed.
Does the radiator have the proper pressure when hot?
Second, did your water pump have a metal or plastic impeller.

I do not know what pressure it is hot, I never thought about checking that. It does push water back to the overflow tank when hot and pull it back as it cools.
As far as the impeller it was the metal impeller on both the old one and the new one.

 

[Chris 8603]

here is bobcat part for the cover, be simple to fabricate but possibly its just fallen down, with the motor running you should feel air blowing out the top of the radiator cover, the fan moves a lot of air

Blower Housing Cover for Loaders, 6565196

Blower Housing Cover for Loaders, 6565196 is commercial quality hot rolled steel, 14 x 9 inches.

shop.bobcat.com

Yeah my covers are in place. That's what I don't understand. It blows your hat off though the cover holes, but when you put them back on you don't get that much air though the radiator. I checked and cleaned the radiator just to clean it because the cooler had some dirt in it. Both or clean to the point you can see light from every inch of surface. It's like when there's back pressure on the fan it doesn't move air properly. It moves plenty out the cover holes, so???
Got me completely stumped, it's just not moving enough air.

 

[Chris 8603]

It sounds to me as though it is an air flow problem. The radiator may be partially plugged by dirt or debris. Or is the out side of the radiator fins coated with oil ? You should routinely clean out radiator fins and straighten out bent fins.

It and the cooler are clean. I clean my machine after every job and sometimes during. I mean it's airflow, but why it won't push though the radiator like it should is beyond me, because the fan moves plenty of air though the access door.

 

[laurencen]

there has to be some restriction between fan and radiator, have mice got in and blocked the duct? the top cover can not restrict the air flow its basically a gration,

does the duct from fan to radiator have any insulation inside

 

[Wayne440]

The hydraulic cooler is thick enough to appear clean but actually be somewhat obstructed. If you are cleaning the machine by spraying the radiator from the outside, the loosened mess can fall onto the hydraulic cooler and it will end up more obstructed than it appears.