My furnace blower has begun to squeel, and I'm sure the bearings need lubrication. I removed the return air grill, but I can see nowhere to apply luberication? Any help will be appreciated.

'93 33' Breakaway

I have done both furnaces on the old 78 and it requires taking the motors out and apart. You can't normally lubricate that type of motor externally as far as I know. Some AC electric motors have oil cups that allow a couple of drops for lubrication.

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I haven't heard of any way to lubricate blower bearings short of removing the furnace, and the difficulty scale seems to vary depending on the make/model.

These fans use "permanently-lubricated" bearings (there's an oxymoron). This type of bearing is made from sintered metal, which means they consist of little particles of brass/bronze heated up to the point they "weld" to each other. This leaves a porous material. Simplified, the bearings are heated in a pressure vessel, immersed in oil. Temp and pressure are gradually lowered, and oil is pulled into the pores as the mess contracts.

When they're installed, and the shaft rotates, the bearing heats up, and the oil expands, forcing it to the bearing surface, and lubing the shaft.

Once the bearing has dried out. these can be surface lubed (drip some oil onto the shaft-bearing interface), but that's a temporary fix, although it should last a long time. Using this "fix", the motor should be run for several minutes (at least 15) to warm up the bearing, so that the oils will retreat into the pores when it cools on shutdown.

What I do (which is only a longer-lived temporary fix) is to remove the bearings (if possible; the entire endcap if not) and put enough synthetic oil (Mobil One) into a saucepan to cover the whole assembly. Then I heat (using a meat thermometer) to 300F, then remove from the stove and allow to cool to room temp (a couple of hours).

This will partially replenish the dried-out oil supply in the bearing, but with better stock than was initially injected. It's cheaper than buying a new motor, since bearings are rarely available separately.

An alternative is to grease the bearings with Super Lube Grease, which works very well: http://www.super-lube.com/product_description.htm

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Rusty

StaRV II, '94 28' Breakaway, 6.5L TD
2 Not-spoiled Golden Retrievers.

[This message has been edited by Rusty (edited February 06, 2006).]

quote:

Originally posted by Rusty:
What I do (which is only a longer-lived temporary fix) is to remove the bearings (if possible; the entire endcap if not) and put enough synthetic oil (Mobil One) into a saucepan to cover the whole assembly. Then I heat (using a meat thermometer) to 300F, then remove from the stove and allow to cool to room temp (a couple of hours).

This will partially replenish the dried-out oil supply in the bearing, but with better stock than was initially injected. It's cheaper than buying a new motor, since bearings are rarely available separately.

Hey Rusty, Do you still have your first dollar? Just kidding, I love the way you think man! I never thought of heating them. I just soak them in sythetics and reinstall them.

There is a company in town here called Bobker Bearings and so far there has never been a bearing that these guys didn't have for me. I have rebuilt many thing that the customer could not wait on. I have had to machine bore and installed oversized bearings in alot of things to get the customer going.

Thanks for the info, I'll try it out!

There comes a time when convenience trumps economy & DIY satisfaction. I tried various means of lubricating my furnaces in the motor home with limited success, and finally replaced one furnace in a friend's driveway in Yuma(expensive). I had the motor replaced on the other in a service center at home. That wasn't too bad cost-wise. I shudder to think how much either job would have cost if I hadn't done the R&R myself.

quote:

Originally posted by Bill:
Hey Rusty, Do you still have your first dollar? Just kidding, I love the way you think man! I never thought of heating them. I just soak them in sythetics and reinstall them.


Thanks for the info, I'll try it out!

I have the first dollar received by the insurance agency I just sold - I found it in the parking lot on my way in the door...



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Rusty

StaRV II, '94 28' Breakaway, 6.5L TD
2 Not-spoiled Golden Retrievers.

So is it then possible to obtain a new set of bearings for a:

Hydro Flame 8535-H

Rear Furnace has a "squeel" - Front Furnace has the definite sound of a "dry" bearing.

Both are intermittent and both furnaces work and heat just fine ...just the occasional irritating and offensive noises.

Your furnace symptoms are identical to what I suffered.

I doubt that you'll find new bearings. Like most modern small appliances the motors aren't designed to be repaired. As I recall, they're assembled with rivets, not nuts & bolts.

As noted in an earlier post, I replaced one furnace with a new one, & had the motor in the other one replaced by my local RV service facility. Can't recall the cost, & the bills are in the coach in storage.

I removed my furnaces & reinstalled them, but dismantling them was a challenge I chose not to face. There's a lot of sharp-edged sheet metal & wires.

I once fixed a heater squeal for good with a drop of a mixture of Anderol and molybdenum powder. Previous lubes with just Anderol did not last too long. I suspect any other synthetic should be good, like the Mobil 1 that Rusty mentions.

I have a 8535 that I took out of my Breakaway, has a tiny crack in the combustion chamber but the fan motor ran well and was quiet. I am sure I can let it go very reasonably to anyone that would need it for parts, etc. Just let me know what you think is fair.

What is the labor involved in getting to the bearings? Ours started screaming at the initial start of the heat cycle then as the furnace cycles off & on again it will squeak once or twice then about the third cycle on it goes away completely. Our furnace is an '82 surburban dynatrail propane furnace. I've never taken one out & since it is propane I want to take extra care in the process, as well as deciding whether it's somenthing we should undertake ourselves. Any suggestions.
Humbojb's wife

We have an '82 surburban dynatrail NT-30S. We are going to try the Mobile 1 recipe that Rusty mentioned so we have to get to the parts. We have looked at the installation & maintenance details & have a couple of questions. When removing the furnace do you remove the innards from the furnace box or remove the whole box? I am aware that several things have to be disconnected first. Turn off propane at tank, turn off thermostat, disconnect Gas line, 4 ducts, electrical connection, pilot lines? a couple of screws that are holding things into the box. Any more suggestions before we proceed?
Tere

My furnaces are Hydroflame, not Suburban, but I suspect there's not much difference. I found it somewhere between supremely difficult & impossible to work on them while installed in the Barth.

I removed them by disconecting the gas & electrical connections, drilling out the rivets in the exterior frame, removing that (the Hydroflame has sheet metal tabs that that locate the frame around the furnace. They have to be bent down to remove the frame.) The furnace was attached to a built-up plywood platform inside the M.H., held down by 2 screws.

Your Suburban installation may be different, but the difficulty of working on them in the M.H. is probably the same.

FWIW, mine were under a bed and in the bottom of a closet. Both were easily removed from the inside.

I will have to slide mine out into the kitchen. It is in a cabinet under the stove. My furnace is in a metal box. It is about 12" square by 28" deep. Do I remove the entire box or do I slide the insides out of the metal box? Do I need to unscrew the outside intake & out take exaust cover to take the box out? I'm having a little trouble with the installation instructions. There are no "removal" instructions.