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Generator Overheating (sometimes)

March 30, 2012, 10:30:59 am

We've got the 10KW gen run by the Isuzu 3LD1 engine. It's running fine - oil full, coolant full and no leaks, electric sqirrel cage fan operating and blowing, engine fan belt intact and no visible leaking at the water pump. Sounds pretty good, heh? Until... Running fine and the little guy shut down with a high temp fault light.

Checked the temp at the thermostat with my handy digital thermometer and sure enough, it was over 220 when I checked it. (The book indicates auto shutdown at 230.) Hmmm... This thing has very long coolant hoses which are actually two hoses each. I noted that one of them (out from thermostat) was soft at the connecting point. Could the hose have been crimped? I had had the genny slide out several times so it could be (always looking for the easy solution).

Waited for it to cool, restarted and got hot again. Another restart later and no heating issues. It ran around 185 at the thermostat with no load, slightly higher with one AC and about 195 or so with both ACs. Ran it for two hours or so. The next day I ran it for awhile, maybe an hour, and the temp began creeping up again, this time to about 212, then back under 200, back and forth.

So I'm thinking occasionally sticking thermostat or a slipping fan belt on the engine. Any other ideas? We're dry camping and I'll probably have to take it somewhere. Thanks.
jor

Just thought of one other thing. It was puking a tiny bit of coolant from the overflow. Never has in the past.

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Re: Generator Overheating (sometimes)

Reply #1 – March 30, 2012, 12:09:30 pm

John,

Likely the thermostat is 13 years old.

They are not expensive-- that is where I would start with an intermittent overheating issue (assuming air flow through the radiator).

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Re: Generator Overheating (sometimes)

Reply #2 – March 30, 2012, 12:51:48 pm

Could be a bad thermostat. They do fail or only open part way. Especially after long term storage.  Easy to check the belt. Mine was fairly loose when I got it. You should be just able to turn the belt 90 degrees with your fingers. Good rule of thumb to see if it is loose.  If you can't tighten it where you are you could use some belt dressing on it and see if that fixes the problem. The hose routing design looks a little suspect on mine where it makes some sharp turns. Old hoses could be a obstructing the coolant flow. You might try running the generator pulled out and see if that makes a difference. Have you checked for a gradual buildup of crud in the radiator fins? Sometimes an engine will pull a certain load but a little additional draw or higher ambient temps will bring out the faults in the cooling system.

Pierce

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Re: Generator Overheating (sometimes)

Reply #3 – March 30, 2012, 11:13:30 pm

Thanks, guys. I'm thinking' thermostat. Pierce, the fan belt is under a full shroud and I haven't a removed it yet. I guess most of the radiator cooling is done by the squirrel cage. Not even sure why it has a fan at all. I need to do a little disassembly and see how this thing works. I'll post when I have it fixed.
jor

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Re: Generator Overheating (sometimes)

Reply #4 – March 31, 2012, 08:10:04 am

There's no fan there - the fan belt drives the water pump.

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Re: Generator Overheating (sometimes)

Reply #5 – March 31, 2012, 09:53:32 am

Thermostat is a great starting point indeed, if that does not solve the issue, look for a very soft inlet (bottom) hose, that without a spring inside to hold it open, might be sucking shut when the thermostat is wide open. 
Are you certain the cooling system is full ? no air lock, radiator is full ? Remote radiators need checking at the top vent screw.
Another thing have seen on a Kubota engine (Onan DKD) the vibration damper, is rubber mounted and have seen once where it would start slipping / not turning the water pump / fan.  (The DKD has a belt driven fan) Was a b@#ch to find that one.
I would try to rotate the engine using the damper pulley to see if it is slipping.  I do not know the Isuzu engine.
Some times the hardest problem is the simplest to fix.

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Re: Generator Overheating (sometimes)

Reply #6 – April 02, 2012, 08:40:13 pm

Well, Dave's "simplest" solutions seems to be holding true. The genet has a little overflow bottle,which was at the proper level so I had assumed the radiator was full. After the unit cooled down I popped the cap on the little holding tank and it was just about dry. For the time being I topped it off with distilled water (about 3/4 of a gallon, burped the radiator by opening the upper petcock while running, retopped the little tank and all seems to be well. This remote radiator setup sure complicates the process! Might be fixed. When I get home I'm still going to change the thermostat, hoses and coolant. Thanks to all.
jor

Anyone know what the radiator capacity is on this engine (3LD1) including rhe little aluminum tank?

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Re: Generator Overheating (sometimes)

Reply #7 – April 02, 2012, 11:03:34 pm

I kept having to top off radiator. Got a new radiator cap and no more fluid loss.

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