# MTH Smoke Unit Repair



## L0stS0ul (Feb 6, 2015)

I have a typical MTH PS2 engine smoke unit that is in need of repair. It's been over a year since I worked on one so I'm in need of some advice and a refresher. The engine has been running on my ceiling layout for about 8 months without the smoke unit turned on so it's been a while since it was used.

I believe I need to replace the motor soon as it was sounding pretty rough when I started it up. It had not been run in a while. I put a drop of oil on it which cleared that sound up. The impeller is tight on the shaft and when I test the motor with a worn down 9 volt battery it looks like the green wire + creates a clockwise rotation. I believe that is correct.

The smoke wick is charred but not the worst I've seen in an MTH engine. I've got a lot of that spare so will replace it with MTH rope wick. I don't think it was the problem.

I checked the resistance of the pair at the connector and it shows 8.5 ohms. For 2 ~15 ohm resistors that seems a little high? 

The main gasket looks ok but I believe my biggest problem is the rubber gasket that goes between the fan housing and the reservoir. It looks like it's so thin that it's not sealing at all and a ton of smoke is coming out from around there. What can be used as gasket material for it? I can't find any part numbers online or even a description of the gasket. Seems like MTH has used numerous things in the past for this from what looks like fiber board in one engine to this rubber thing.


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## HarborBelt1970 (Sep 24, 2015)

Do you have the MTH model number of this engine? There's not much difference between the smoke units I have seen in PS2 engines but in terms of replacement parts it could make a difference which model you have.

I've had problems with the rubber gasket you describe and I think some Lionel smoke units have a similar part. If you have smoke coming out in the space meant to be filled by that gasket it may not have failed but is just not properly aligned. I have resorted to gluing that part in place because getting it properly aligned when reassembling the smoke unit is tricky. 

P.S. I only expect the glue to hold the gasket in the correct position while reassembling the unit as it is meant to be compressed in its space between other parts. I've found that the gasket gets saturated with smoke fluid residue that it is hard to remove and as a result the glue (epoxy) won't stick as it would on a clean surface.

I can't help on the question about the resistance measured at the heaters - over to GRJ for that - although I think that they are wired in parallel and on that basis your measurement seems to be the right value. But I stand to be corrected on that.


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## L0stS0ul (Feb 6, 2015)

Thanks for the reply. The engine is this one http://mthtrains.com/30-1363-1

No parts list for this engine but it looks like all of the other PS2 smoke units I have. The rubber gasket looks like it has shrunk actually and it's definitely not thick enough to provide a seal. This one looks like it was glued on or had some kind of adhesive backing to it when it was installed on the smoke unit. I had to pull it off. I believe that fluid reservoir gets pretty hot so I need a replacement material that is resistant to heat and provides an air tight seal. I wonder if Michael's or some other craft store sells rubber sheets in various thicknesses.

One of the resistors is a little deformed but it appears to be working still.


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## gunrunnerjohn (Nov 10, 2010)

8.5 ohms is fine, the resistors are actually 16 ohm resistors. If you have it apart, I'd replace the gasket and the resistor that doesn't look good. You can buy 1/64" gasket material and roll your own, I have to do that for the smaller single element MTH smoke units. For Lionel and the standard MTH units, MTH has gaskets. The stock gasket isn't very thick, I measured a new one and it's .02" in thickness. The part number for the gasket is IB-0000006. The 16 ohm resistor part number is AI-0000018, and the part number for the braided wick is AA-0000001.


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## L0stS0ul (Feb 6, 2015)

Thanks John, I have a spare IB-0000006 gasket from when I worked one of these last time. That's the one between the circuit board and the shell. Is there a part number for the rubber gasket between the motor housing and the fluid housing or an alternative material that can be used? I assume it needs to be pretty heat resistant. This is the part I'm talking about









I'll go ahead and replace the resistors as well The unit on the left is the one I'm working on. You can see the front resistor is pretty well bent. They are also really tiny. The unit on the right is from a Locosound engine. Slightly different circuit board design but essentially the same thing but the resistors are quite a bit bigger. I can pull those from that board and stick it in this one and replace the gasket at the same time.


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## gunrunnerjohn (Nov 10, 2010)

That gasket between the chambers is the IB-0000024 gasket.

The Locosound board should be identical with the same 16 ohm resistors. The smart money is to simply swap the boards as you may do more damage taking out the resistors. The size isn't really significant, but the bent one has a broken core and will cause you problems down the road.


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## L0stS0ul (Feb 6, 2015)

Cool, thanks. I'll try to track some of those down. Here's the boards. The locosound on the right. Just slightly different but essentially the same thing.


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## L0stS0ul (Feb 6, 2015)

I found a big ol 1/16 inch rubber gasket sheet for $3.00 that could make a ton of these little gaskets. Going to give that a shot.

The original gasket on the smoke unit must have shrunk. It's currently .89mm thick and not even close to sealing. The ib-0000016 option which lists the 24 as a possible replacement shows as 1.5mm thick. The 1/16 rubber gasket material I found is 1.59mm thick so hopefully it will be a good replacement. If not I'm only out a few bucks and I'm sure I can find a use for it somewhere else.


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## gunrunnerjohn (Nov 10, 2010)

The 1/16 is way too thick, I tried that first. You really want the much thinner stuff, like I said, the real thing is .02" thick, so 1/32 is thicker than needed, and 1/64 is just about right.


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## L0stS0ul (Feb 6, 2015)

The rubber gasket that was in the ps2 unit originally is very close to 1/32 and it's not sealing at all. I can see the gap if I put a flashlight behind it and the amount of smoke that is coming out is a lot. Whatever the material is on the locosound one is really close to 1/16. hopefully the rubber I got is squishy lol otherwise it was a waste. Should be here thursday so I'll know then.


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## gunrunnerjohn (Nov 10, 2010)

I've never seen one close to 1/16, and I've taken a lot of these apart.  Let us know how you make out...


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## L0stS0ul (Feb 6, 2015)

We are talking about the rubber gasket that goes between the motor housing and the fluid reservoir right? IB-0000024


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## gunrunnerjohn (Nov 10, 2010)

Sorry, I keep thinking of the wrong gasket! hwell: Yes, that one is considerably thicker, they measure about 1/16" thick.


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## L0stS0ul (Feb 6, 2015)

oh good, I thought I was going mad which is entirely possible


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## L0stS0ul (Feb 6, 2015)

Just to close the loop on this one. The 1/16th rubber came in yesterday and I cut a piece of it off. for $3 I have enough to make probably 50 of these gaskets. I swapped out the circuit board for the old locosound one as John recommended and put it all back together with a new wick. Now it's smoking up a storm just like it used to with no leakage.

This is the stuff I found although the price doubled up since I bought it. 

https://www.amazon.com/gp/product/B0074II2K6/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1


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## gunrunnerjohn (Nov 10, 2010)

Love success stories.

FWIW, that stuff is $4 on eBay: Lasco 02-1048E Rubber Sheet 6X6-Inch and 1/16-Inch Thick


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