Adding a thermostat and housing using pipe fittings

[vtmetro]

I added a thermostat to my Metro 6/1 using pipe fittings. There are other ways to do it -- a thermostat fitting is available from Utterpower, and there's a nice mod to the factory outlet flange you can do with a die grinder or lathe in another thread here that will accept a thermostat.

I did it with pipe fittings (before I saw the die-grinder version thread). Maybe someone will prefer to do it the way I did for some reason, so I'm including it here.



Here are the main items needed --
 
1.) a thermostat (I used a Parts Plus #P3839, (which I believe is also a Gates part number) It just fits outside a 2" pipe ID, and inside the OD of the threads. It is a 192F thermostat with a jiggle pin (which I removed later).
2.) a 2" to 1" pipe bushing
3.) a 2" Pipe cap
4.) a 1" to 3/4" pipe bushing
5.) a 3/4" pipe nipple
6) JB Kwik or JB Weld epoxy
7) a 1-1/8 hole saw








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[vtmetro]

The first step is to drill out a 1-1/8" hole in the pipe cap with the hole saw. Then sand or grind all bonding surfaces:

[vtmetro]

Apply epoxy to the rim of the 2" pipe bushing.

[vtmetro]

And assemble the thermostat to the bushing.

[vtmetro]

Next, place a piece of packing tape over the inside of the pipe cap's hole. Be sure that you sanded the inside and outside of the hole for a good epoxy bond.

[vtmetro]

Apply epoxy to the end of the pipe nipple (also well sanded for bonding), and set it into the pipe cap.

[vtmetro]

Here are the two thermostat housing pieces ready to assemble.

[vtmetro]

Here is the completed housing.

[vtmetro]

And here it is installed on the Metro 6/1.

[vtmetro]

During the first trial run, I checked out the engine head, fittings, thermostat housing and hoses with a non-contact thermometer as the engine warmed up.

Because the thermostat is not installed in the head it needs a small hole in it to initiate enough thermosiphoning to bring the head temperature water to the thermostat. Then it can respond to the engine warm up.

I found that the existing hole with the jiggle pin did not do this quickly enough for my liking, so I removed the pin and drilled out the hole to 3/16".



I reinstalled the thermostat and restarted the engine. This time, hot water traveled up, and when the temperature was hot enough, the thermostat opened.

Thermostats are designed to open gradually over a range of temperatures. The 192 rating is near the top of the range of opening, though not the very top. Since this thermostat was designed for an automobile with a far greater heating capacity, and since the Lister is so easily cooled, the equilibrium point was reached on my setup before the 192 F rating was reached.

I estimate that the running temperature of my engine in our cool weather now (70F) to be about 165-180F. At least that's what the thermometer registered. Hard to tell with a non-contact thermometer, since the outside of a pipe is generally cooler than the water inside. It's possible it may actually be as high as 190, but I'll need an accurate inline thermometer to tell.

Anyway, it seems to regulate very well -- quite steady within a couple of degrees. and it's now a lot warmer than the 100F return temperature I was getting before I added the thermostat. If higher temperatures are desired, it may be possible to drill a smaller hole than the 3/16" version I used. Perhaps just removing the jiggle pin would have been sufficient.

Good luck if you build this pipe version of a thermostat for your engine, and let us know how it works out for you.

[JMW]

That is a fantastic solution. It looks so neat.
I presume that the use of epoxy to fit the thermostat, is optional?
With the right tap and die, the top pipe could also be fitted without epoxy.
Well done.

Mark

[ronmar]

The use of epoxy can be avoided alltogether by using a female to female pipe reducer instead of a pipe cap.  That is how I fit the thermostat into the secondary outlet of my heat exchanger.  Instead of epoxy to hold the thermostat in place, a large coil spring works pretty good.  You could also use a stack of large washers to hold the thermostat in place.  It dosn't really have to be a tight fit, afterall you are drilling a hole in the flange to allow leakage anyway...  You can also do it with a extended pipe nipple cut in half, and rejoined with a piece of hose and 2 hose clamps.  The thermostat gets sandwitched between the two pipe ends where they meet under the hose.

I don't know how comfortable I would be with the epoxy holding up on a hot oily thumper.  Cast iron is ultimately porus, and if it were going to fail anywhere, I would expect it to fail at the epoxy butt joint, as that is the weakest mechanical bond...

Doyou have an overtemp shutdown system?

Good Luck

[vtmetro]

Thanks, Mark!

I think the pipe cap might be too thin to get a good thread with a typical pipe taper. You might not be able to tighten it without cracking, plus it probably wouldn't end up flush with the inside of the cap for nice flow. You could use a light screw fit and a sealer I suppose, and grind back the inside protrusion of the pipe. Instead, try a bell reducer instead of a cap. They're bigger though, and not as neat.

You could certainly braze the pipe cap and nipple together. I don't know if it would weld well, since the cap is cast iron -- maybe flame weld it with a cast iron stick. Might need to tap it to relieve tension and cool slowly -- don't know, haven't tried it. I'm sure others can "pipe in" here about welding to cast fittings. Might be easier than I think.

I was going to braze it myself but ran out of oxy/acet. So I just reached for the old tube of JB Weld epoxy. That stuff has done some amazing things for me before re. cast iron. I have a '51 John Deere model M tractor that 8 years ago had a big egg shaped hole in the cast frame forward where the front axle pivot pin goes through. The original bronze bushing was long gone and the cast iron itself was worn egg shaped.

I bought a new pin, new bushing and filled in around the bushing with JB Weld. It has stood up for the last eight years of house building, snow plowing, earth moving, log hauling, etc.

On this thermostat I used the JB Kwik -- not weld -- it doesn't have as high heat resistance: 300 F instead of 600 F, but I figured that's enough. I hope I don't run 300+ F steam through my roid, and if I do, elastic relief in the stat housing will be the least of my worries, if not a possible benefit.

[vtmetro]

Ronmar, simultaneous post. Didn't see yours.

No problem with doubts. I'll let you know when/if the epoxy fails.

EDIT:

If anyone is interested, here's a good review of JB Weld in cast iron/oil/gas/steel/engine coolant tractor applications, pros and cons, etc. In fact I've seen it used successfully to repair block cracks, including a freeze cracked thermostat housing on a JD-440 diesel crawler. Of course, please build whatever you are comfortable with, no need to do what I do.

http://www.ytmag.com/reviews/review0398.htm

JB Weld is basically an epoxy glue that does an exceptionally good job of bonding to cast iron and steel along with several other materials.

[WGB]

That is a nice small unit.
You could tig the nipple, gasket the thermostat.
This is what I did for mine.
http://www.Flickr.com/photos/39282821@N07/sets/72157622508133940/show/