Onan 8000 QD

[Ken Sair]

I am coming up on 1,000 hrs on my generator. The 'manual' says I have to take it in to an Onan dealer to replace the engine V-belt, thermostat and coolant hoses.

As belts on my coach at 1500 hrs are in excellent shape, is this overkill? What have all of you done at this interval, if anything? Seems to me if all is in good shape, this is not necessary at this time. Belts and hoses on my cars have routinely lasted 7-8-9 years.

Opinions?

Ken Sair 2007 Contessa

[Edward Buker]

Ken,

I would think that a little time inspecting would give you some insight. I would examine any hoses that could be reached with easy cover removal. Squeeze them to see if they are pliable and look for any weather checking. If they pass that test most likely tou have substantial useful life left in them. Thermostats do not fail very often so if the system is cooling well then you could take a pass on changing that item.

I would run the generator under significant load, whatever you can use in the coach to stress it a bit. After it has run for 1/2 hr to 45 minutes under load take an IR gun and shoot the radiator face, the engine block, and oil pan to get some temperature readings. Run it just enough time with the removable cover off to get the readings given that will affect cooling.

On my genset with a good belt I read 118F on the radiator face, 144F on the oil pan, and 187F high on the block. Your numbers will vary some from mine but they should be somewhat close. With a slipping belt my radiator reached 216F, oil pan 207F, and the block was 215F. You will not hear any squeal from a slipping belt in this application.

 My belt failed at 350 hours at 9 years old and caused an overheat shutdown. I think your belt is in the ballpark of when it should be changed but I would check the cooling profile with an IR gun as discussed and every 3 months or so. It is good to have that data. Run the same test and change the belt when you see your cooling profile temperatures rise.  Hope this helps.

Later Ed

[Gerald Farris]

Ken,
The fan belt on most Onan generators does not have an automatic adjuster (tensioner). So as the belt wears it will start to slip and the generator will overheat from a lack of air flow.

The 1,000 hour line is a guide line, and it is not set in stone. My 10K Onan started to overheat at 1,350 hours from a slipping belt. I replaced the belt myself in about four hours. I know of another owner who had to replace his fan belt at 500 hours because it was slipping and causing the generator to overheat.

If your generator starts to overheat it will shutdown automatically to prevent damage. So you can replace the belt now as preventative maintenance when it is convenient, or you can wait until it starts to slip and replace it the when it may or may not be convenient. However you may get a couple more years out of the belt if you wait.

I change the coolant in my generator every 3 to 4 years, but the hoses have always looked good, so I have never changed them to date, and my generator is 11 years old with 1730 hours.

Gerald  

[Ken Sair]

Thanks all. I am going to inspect it next week. Gerald, what is your opinion on replacing the thermostats? Also, does all the coolant drain at the bottom plug or is the overflow reservoir done separately. Onan told me that (they drain separately) and caught me by surprise.

tx, Ken

[Gerald Farris]

Ken,
In my opinion, replacing the thermostat as preventative maintenance on your generator is normally a waste of money. Thermostats seldom fail today, and I have seen a surprising number a new thermostats that were defective, so I do not see how it is cost effective to replace it.

On your model generator, I am not sure if the surge tank (overflow reservoir) drains when you drain the cooling system, however on the vast majority of cooling systems it does.

Gerald  

[Ken Sair]

Thanks Gerald, thats where I'm leaning. I'll open it up next week and give everything a good once over. FYI, I did call Onan in northern Ca. today. Engine belt was $10.67. Labor, if all went well was 1.5 hours. Labor was $150 an hour. OUCH!!!!! When I get it open I'll decide but right now I'm leaning towards a new belt and replace the coolant. If I think I can do the belt by myself later, I'll just carry a replacement (my mechanic friend is nearby to help this week).

tx Ken