Kohler Generator Question
 

My boat has Kolher 5ecd generator and it keeps overheating. Things I have done to this point:

Cleaned the sea strainer
Changed the impeller (old one looked just fine)
Back flushed the heat exchange
Flushed the coolant and put new coolant in

It was still over heating. There is plenty of raw water running through the system and the heat exchanger stays cool but the manifold is getting very hot.

Finally I pulled out the thermostat and tried to run it without the thermostat and it's still over heating.

At this point I'm thinking it might be the coolant pump but I can't find anything in the manual on replacing this. Has anyone been through this? Is there something that I missed? I know for sure it is overheating and it is not just a sensor. I have a call into the Kohler Mechanic in Destin but I figured it was worth a shot to ask on here.

Thanks,
Aaron

What is it doing when it overheats? How long does it take to overheat? Does it start/run fine until then?

Starts and runs fine... Takes maybe 5 minutes from the time it is cold to get hot.. It then shuts down and give me a "HE" code (over heat). I know the fluid is getting hot because it starts to steam and boil over into the overflow. I'm told there is a way to bleed the system so I'm going to try that next. I'm also told that getting to the Coolant pump is a major pain in the ass.

Had the same problem with a 7 series kohler , was a real head scratcher. Ended up having a air pocket in the system. If you have acess to one of those radiator style funnel with the adapters put that on first, and open the bleed in the u hose. At the top .

Definitely have air in the coolant system. I had a 7.3 that I ran around for a couple yrs trying to figure it out. I had small screw/plug on the top of the heat exchanger that was the bleeder or air escape for the coolant system. I would take a syringe and put coolant into this hole until the coolant flowed over the top. Then put the plug back in. I would still have problems time to time. Then I realized one more thing. When the boat sat in the water, it would sit nose up higher than the back. This would essentially make the generator sit in the boat higher in the front than in the back. My generator sat behind my bench seat cross ways in the engine compartment. I realized that if you grab the back side of the generator and pull on it toward the front, the rubber mounts would allow the generator to be more level. I would repeat the filling process over again. This fixed my problem. There cant be any air bubble in there or it will over heat.

^^^ agreed. Purge air out of the system. Fought it before on my 5E

Good info guys, I really hope its not the coolant pump. I'll get back to the boat sometime this week to give that a try, and report back.
thanks,
Aaron

Air bound . There is a service bulletin. Remove 1/8 pipe plug and purge keep filling w antifreeze . For some reason tiny air bubbles get trapped at the heat exchanger and mine did the same thing . 5.0 kohler. Boat was 2001 w 200 hrs gen only had under 20 hrs since new and then we figured out why after changing everything.
Frustrating.

Final got back to boat yesterday and topped off the coolant through the vent like was suggested and the generator ran great all day, no overheating issues.
Thanks guys!
Aaron

I love happy endings!

Best kind of massage there is!:whistle:

Ok, new issues, sort of... Tried to run the generator last weekend and this weekend and more problems. Here is what it's doing this time, the overflow hose (runs from the top of the fill cap to the overflow bottle) keeps falling out. I'm not sure how that is supposed to attach since the hose just slips down into the bottle. I tried to tape it and tried to use some heat shrink with a hose clamp and eventually it still works it's way out. Once that happens it starts dumping coolant and over heats. Another thing that I noticed that seems weird is that the overflow bucket is always full... Any new ideas? I'm about to just call the Kohler Tech and tell them to get it fixed..

Any chance you got a blown head gasket, or a warped head, from it over-heating ?

I agree, it sounds like you have a blown head gasket, or compromised heat exchanger, or another part of the system; and you are "making" coolant.

Given your location, I am assuming that you are in salt water. If this is the case, I would address this absolutely 100% immediately; as you have now mixed salt water into the closed part of the system.

The first thing I would do with drain all the coolant, fill and run it or freshwater to warm it up and are certain that thermostat and the system is open. Then drain it and fill it with freshwater and run it again.

Ok, went down to the boat and drained the overflow bottle down to about 1/4 full and topped off the coolant I the engine. Started the generator and ran like a champ for over an hour with a heavy load. That was all the time I had. I'm really not sure what's going on since through this entire process I feel like I haven't found a "smoking gun".
I don't think I'm "making coolant" since it ended up in the overflow and in my bilge. The coolant chamber was low. Also for the hour or so I ran it today it ran like a top, no coolant leaks, plenty of water coming out of the exhaust, no overheating...

Damn Kohlers... Year before last I somehow ended up with fresh water in both of the cylinders over the winter on my 5E. Don't ask how... It had run flawlessly all summer long. Long story longer, I rebuilt the top end and re-rigged the muffler set up (think the hose was holding water causing the water in the cylinders) and it now runs fine. However, once I shut it down after a full weekend of running (12+ hours) and put the boat up for the week, all the coolant from the overflow bottle drains out and ends up in the genset tray. Ironically, the heat exchanger remains full. Top it off to the cold line and go boating... This happens every weekend. No signs of leaking on the engine, runs fine, no overheating or leaking while the engine is running. Go Figure...