A $5 part *****kills***** a $4000 Generac generator

[Smarty]

I personally installed a Generac natural gas stand-by generator 5 years ago, after a freak October ice storm knocked out electricity in this area for nearly 2 weeks.

The Generac has worked flawlessly over the last 5 years, including the weekly exercise it does to ensure integrity, except for one HUGE problem:

Every year or so, a $5 rubber part which Generac calls a "bellows" ruptures without warning, leaving the generator totally unable to start / run.

This rubber bellows is nothing more than 2 inch long corrugated and flexible connector which provides a flexible hose connection between the carburettor air input and the air filter's air output. Once it ruptures, the air/fuel ratio is grossly changed, and the engine will neither start nor run. The rupture is not especially visible, and only has to be the size of a pin-prick to spoil the mixture and prevent combustion.

Generac uses a flexible coupling of this type to absorb vibration which the engine and attached carburettor create, and dissipate it and isolate it from the separately mounted and isolated air filter, which sits in an adjacent chamber next to the engine.

No doubt the heat and vibration of the engine do a real job on this rubber part, and I have been replacing them as they fail, only to have the replacement fail less than a year later.

I spoke with Genrerac's local parts distributor, and then with a factory Generac parts manager, hoping to find a replacement part with a better life expectancy. When the first one failed during the warranty period in the 10th month, I was told by the Generac service technician that this was a common problem, and that Generac has issued a newer and better bellows to fix the problem. He assured me that I would NOT see this happen again.

He lied, or was ill-informed...... I am now on my 4th one, and was told today by Generac that there are no new or replacement alternatives they are aware of.

The one and the only part they sell to do this job can be seen at:

Now that those of you with the patience to read this far know and understand my predicament, I am posting here with the following questions:

1. Are there any high-temperature hose materials which can withstand the engine compartment temperatures and vibration which I might use instead, which would allow me merely to make a direct 2" long connection? The ID of the hose is 1.5", and should be a pretty standard, easy-to-find size.

1. If I use a replacement coupler which has the flexibility of a "bellows" to allow it to dissipate vibration in the same manner as the current part, are there other flexible couplers which exist which would allow a more permanent / durable connection?

2. If there are no superior parts to be purchased because options 1 or

2 above do not exist, is there a 3rd option to treat this rubber bellows in some manner to strengthen it and make it far less vulnerable to heat and vibration?

Presumably somebody must make a flexible coupler for 1.5" diameter connections which can take the heat and vibration better than this $5 rubber part.

To avoid digressions, I want to point out here at the onset that the Generac is otherwise working properly, the engine is not vibrating excessively, the temperatures are not rising excessively, and the usage is extremely light, nearly all of it being the weekly check-out self-test. Unfortunately 10 months of self-test seems to be enough to destroy this part. I am very much aware that replacing this part on a preventative maintenance schedule every (let's say) 9 months would quite possibly solve the problem, but I am really not interested in doing so if there is some reasonable alternative, even if the part cost is much, much higher.

I am open to any ideas and suggestions, and much appreciate your time in reading this, and possibly replying. Thank you very much.

[David Nebenzahl]

On 7/21/2010 5:12 PM Smarty spake thus:

Just a shot in the dark here: any chance that flexible corrugated metal duct, like the stuff used for old VW fan hoses, might work? Dunno what sizes it's available in or how long it would last, but it would at least be a lot cheaper.

[Oren]

A short piece of radiator hose? Takes heat, vibration and you might find the ID you need. Auto supply store...

[The Daring Dufas]

I install a bunch of the older 8kw units that had the Vanguard engine, yours must have the newer Generac manufactured engine. Have you ever seen the silicone radiator hoses installed on taxi and police car engines? You might ask an old wrinkled up parts counter man at a real auto parts supply house if he can find one for you.

TDD

[Nate Nagel]

That's what I'm thinking. Also sold at your FLAPS as "heat riser hose" (think the hoses from the heat stove on the pass. side exhaust manifold up to the snorkel on the air cleaner on your typical 70's-80's American sedan.) Clamp on with regular hose clamps. Defroster hose might be more flexible, seal better, etc. but might not be any more durable than the original "bellows."

Alternately, a piece of radiator hose the correct diameter would probably never, ever fail although it might not do quite as good of a job of isolating vibrations.

You might want to look at a junkyard, because I think the air cleaner on my old Ford pickup has a pair of flexible ducts something like that to connect it to the throttle body ('93 with the straight six) although I don't know the diameter off the top of my head.

nate

[The Daring Dufas]

Oh yea, I forgot, look at the hump hoses at the link I posted.

TDD

[Nate Nagel]

They're also sold for custom air intakes for ricers for that matter, and that might be the best idea I've heard yet.

something like a "hump hose" is probably what you want, for better vibration isolation. I don't see them that small on Pegasus' site, but I did get a couple hits when I searched online, just nothing from a brand I recognized. For $20 or so, it's worth a try. Just use a

*lined* hose clamp at each end; silicone hoses don't like the "teeth" on typical worm drive hose clamps, it tears 'em up.

Pegasus *does* sell lengths of straight coolant hose in all sorts of sizes, so that's an option too.

nate

[Pete C.]

If you can find something in the correct size, the hose sections used to couple turbo outputs to intercoolers and intakes would seem to be sufficiently durable.

[Larry Fishel]

Since no one else has asked... Is the hose exposed to direct sunlight? If so, can you easily remedy this? Nothing (well, relatively little) destroys rubber as fast as the sun...

[Gordon Shumway]

I would replace that failure-prone bellows with a length of hose that would be available at an auto parts store. I don't believe heat is a big concern because it is on the intake side rather than the exhaust side.

Is there is the possibility of shortening one or both of the tubes in question to lengthen the "flex" area? If yes, the replacement hose would have the vibration/mis-alignment spread over a greater distance and therefore, reduce the probability of failure.

It sounds like the engineer that designed this part must have had his head where it didn't belong.

[WW]

Just an idea. Get a tube of silicone sealer and coat the exterior of the hose. This will still let it flex but be sealed. WW

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[Smarty]

Thanks to everyone for your generous and extremely useful advice!

I was entirely unaware of the availability of these automotive couplers and hoses, and will go out tomorrow to local suppliers to see what I can find.

I am particularly tempted to go with the idea of the silicone "hump hose" since it offers the deliberate design to flex, and is made of a material which is vastly better than rubber in terms of high temperature performance.

I hope to find something locally like this one:

I also intend to ask about and see if I can find the hose types used for risers, intercoolers, and other stressing vibration environments, in particular if anyone has anything intended for heavy duty use. I am not as attracted to a piece of hose since the very short connection (approx. 2 inches total) cannot be widened. I think a hose will transmit way more vibration to the rest of the enclosed air cleaner assembly.

The part is not exposed to sunlight, and lies inside a cabinet housing the generator covered on the top by a part which Generac calls the "roof". UV bleaching and deterioration is not a concern here.

Thanks again for the great assistance here. It is very much appreciated.

[Smarty]

Thanks Nate and will definitely get lined clamps. Never knew there was such a think until I read your reply and did some Google searching! Of course I would have used the wrong type which apparently extrude the silicone of the hose........

[ransley]

Does the air filter align itself 100% without the rubber connect piece, does it fit properly and easily together, thinking maybe something is wrong with its alignment that would cause alot of stress on the rubber. Does the air filter have brackets to keep it from moving, is it stable and attached to the motor so they vibrate together. If something is defective and loose, out of alignment or missing, that could account for all the failures. Have you googled for complaints on this model. It could be a factory defect from a sloppy build, my generac came with a bent muffler bracket and dented muffler it was hit hard at the factory , generac sent me a new asssembly. I think initial build quality inspections can be lacking, build quality poor and mistakes covered up or missed by unhappy employees. I would have a good look at a cause of failure rather than the part just being bad. On another issue how does it hold and what is voltage under load and at startup, mine was not adjusted right at factory but is a portable generac not a standby unit.

[Jeff The Drunk]

DING!

At least give this a try.

[Smarty]

Thanks Mark, Jeff, and Smitty for your help. As best as I can tell, the pipes / nipples I am connecting to are aligned as well as they can be, and that the stationary air filter assembly is pinned independently of the vibrating engine nearby. I will take another look at it today since I have not really been careful enough on this point, and the bottom line truly is that the premature failures may have a lot to do with some form of misalignment that I have overlooked.

The very short distance between the two connecting points, less than 2 inches, makes it very difficult to put merely a piece of hose in there and expect it will take up the vibration. Even the hump connector may not have enough damping to absorb the energy. And getting a large loop may be a way to avoid the issue, and something I will take a look at this afternoon also. In the final analysis, the large loop may be the very best solution, even though it may look a bit weird. It is certainly an easy one to try.

Other than this issue, the Generac has worked fine. Mine produces nominal voltages under load of around 110V on each leg, and the voltage regulator allows this to be adjusted nicely. Frequency stability is good, and I have put a counter on it and assured myself that it remains stable under load. The only minor issue is the waveform, which is not especially sinusoidal. My appliances and electronics don't seem to mind it. The unit runs both hot and noisy, but I was expecting both. I am also not entirely happy with the transfer switch logic, which makes the crucial decision when to throw power back to the pole when power resumes after a blackout / failure of utility power is corrected. It should wait a bit longer, in my opinion, and I have seen one intermittent power interruption here causing the transfer to oscillate more often than I would like. If I did the design, I would have chosen at least a couple minutes for street power to return before switching back to it and shutting down the generator.

Thanks again, and I will report back.

[chaniarts]

..snip..

home depot has 1.5" diameter silicone water tubing. if it's not too high a temp, that may do you. it'll be far cheaper to just buy a few feet of it and cut off lengths a few times/year as pm.

[Bill]

Can the air filter be moved further away? In which case a long radiator hose with a 90 degree bend would provide the flex needed?

Or perhaps even longer and an S type hose would provide quite a bit of back and forth movement?

Or perhaps dump that air filter and go to the automobile wrecking yard and see what is available with the same size tube...

[Jeff The Drunk]

There should be several options. I know the space is limited inside the housing but there's got to be a better solution. Maybe look at some of the high performance auto type filtration components. That bellow/intake arrangement has got to have some type of pressure sensor that won't allow the natural gas valve to open if the bellow has a leak. That would prevent the thing from catching on fire if a leak occurred.

[WW]

One more thought. Since it is a short distance cut up a NITRAL (spelling) glove by removing the fingers and clamping remainder in place. I use these gloves in wood shop when using stains and thinners and they hold up fine. The gloves are Blue in color and I buy from Harbor Freight. WW

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