Need help with Powertech generator and cold weather noise

[belfert]

I have a Powertech 8KW generator with Cat (Perkins) engine.  When it is cold outside like in the 30s it has always made some strange noises that go away when the generator warms up.  The generator also tends to vibrate at cold temps until warmed up.

This past winter I started the generator up at around 30 degrees and it was making some really horrid noises (worse than normal) like the blower wheel was hitting or something so I turned it off and left it.  I started it up in 60 degree weather a few weeks ago and it was making the same horrid noises so I turned it off again and left it.  Today, I finally got around to working on it.  I crawled underneath the generator and looked at the blower assembly and the wheel is not close to anything.  It is 75 degrees today and when I started the generator I expected to the hear the horrid noise again.  Strangely enough it sounds just like normal with no noise and it has been running a good 20 minutes just fine.

Any ideas why I would have a horrid rubbing/hitting type noise at temps of 60 degrees and below, but it works just fine at 75 degrees?  The bus has not been moved since first starting the generator this past winter.

[wg4t50]

Will give it a go as to the ruff running when colder, that cat engine is actually a Perkins, it is a pre cup engine, if a glow plug is not working, but starts on other cylinders, it surely will sound bad and vibrate.
As to the mystery noise, my guess is a loose panel that  shows when cold before engine warms up enuff to run on all cylinders. Could be the exhaust vibrating.
All guesses, but the Perkins diesels seem to do a good job, but the glow plugs are a weakness on all glow plug / precup engines, mostly the are burnt u from excessive use of the pre heater/ glow plug use.
Dave M

[belfert]

That would be bad if a cylinder doesn't run.  The glow plugs really can't run too long as the little ECU inside the unit controls the glow plugs.  I'll have to see if I can determine if a glow plug is bad.

[junkman42]

Very possible that the support bearing in the gen head is bad!  It is a permanently lubed bearing and requires replacement at some interval!  I removed mine and using a grease needle injected some electric motor grease into the bearing.  Just My way.  Regards John L

[belfert]

Would a bad bearing suddenly sound fine once it got to 75 degrees as compared to 60 degrees?  The noise sure sounded like something hitting, but I am no expert on mechanical noises.  How long does the bearing typically last as I have around 650 hours on my unit?

Replacing that bearing is a complete pain in the rear as the entire unit has to come out and half the unit dismantled.  I had to replace the brushes last year and it was a total pain in the rear.  I wasn't able to get the end plate off because the head has to be unbolted from the mounts and raised about one inch to get the end plate off.  I ended up just reaching in to replace the brushes.  It would have been easier with the end plate off.  If I had managed to get the end plate off I would have replaced the bearing.

[wg4t50]

While anything is possible, I doubt it, normal, that end bearing needs relaced about 5 k hours, when it goes bad, most likely it will let the rotor rub on the stator, then you need both.  I put 6,500 hrs on a Perkins 12.5 kw 3 cylinder with a Marathon Pancake 12.5 gen end, and it never showed any signs of getting warm.  That combo of Perkins aned Pancake, I married up, made suspension and controlls, ran remote radiator, never any issues unless thegrass/hay seed plugged up the fins, then blow them out and keep getting up.
Dave M

[luvrbus]

It should be in your Powertech manual mine says replace or inspect every 2000 hrs on the 8 and 10 kw I have replaced a few with less than 600 hrs, didn't Jack Conrad's Powertech bearing fail at around 500 hrs most Powertech owners carry a spare bearing   

[belfert]

I can't find anything in the manual about a replacement interval for the rotor bearing.  The manual says "If signs of abnormal wear or leakage are observed, the bearing should be replaced."

If I have to take the generator apart again to deal with the head again I'll replace the bearing.  My plan right now is to replace the bearing at maybe 1,250 hours if not before then.

[wg4t50]

Generally you can detect when the bearing is starting to get ruff if you are paying attention to it, it will start to feel a strange vibration that starts getting worse pretty quick, if not replaced in time, the rotor and stator are at risk too.

Power Tech uses  different makes of generator heads, at one time they used the Maraton Pancake, but the last one I handled was an off shore mystrey, it is still going but no warm fuzzies with it on my part.
Yes I am opinionated too.
Dave M

[RickB]

Brian

Any chance when you put the new brushes in the motor something went wrong in the installation? If it started right after you installed the new brushes maybe their connected.

RB

[FloridaCliff]

Brian,

I had one fail, lucky for me was covered under warranty.

Pull the stator off and you will be able to tell by the side to side movement on the rotor.

You don't want to have a full failure, mine ate the stator and rotor.

Not hard to replace, just a pain in the A$$.

Cliff

[belfert]

Brian

Any chance when you put the new brushes in the motor something went wrong in the installation? If it started right after you installed the new brushes maybe their connected.

I certainly could have done something wrong.  I did put about 50 or 60 hours on the generator last fall after replacing the brushes and it worked great.  I had a electrical motor shop in Hudson install new brushes in the holder.  No issues until it sat all winter.  It appears to be working fine right now, but who knows how long that will last?

For Dave, my generator does have a Marathon pancake head, but it also says made in China on it.