Cummins 8.3 fan shutter stat

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JamesH

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Well the fan isn't engaging so I disconnected the air line going from the shutter stat to the fan clutch and hit it air from my compressor, she started spinning immediately....sweet.
So I bled down the air system and proceeded to tear down the shutter stat. I didn't have a spanner wrench but channel lock pliers (gently :) did the trick. I had read here to use air to push the plunger out and that did work but I had to do it several times....each time the plunger came partially out, I pushed it back in with my finger and hit the inlet with air again. Took about 5 cycles to get it out completely.
I cleaned everything up, then lubed it all up and put it back together. Unfortunately I couldn't get the engine up to temp before I had to head out so I'll have to see if it working tomorrow.
 

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JamesH

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Well unfortunately the clean n lube of the shutter stat did not work :-( I guess that I will be tracking down a new one.
 

Alexsha

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Try replacing the o-rings first. There's a few threads on that. I think the big one is 3mm thick and 12mm id. Most of the replacement units out there are stupidly expensive. Worth it to try new rings.
 

Capehenery

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I just did the rebuild of the shutter and so far all is good. The fan used to be all the time and now It stays off. My shutter is labeled 200 and after running the truck for an hour I could not get it over 165. I even tested it with a digital sensor and no part of the system was over 170. So it is with guarded anticipation I will test more and hope it holds.

There were 4 O-rings on mine and I found all of them at NAPA except the larger one and it was a 3 x 12 metric that was the closest.
 

gimpyrobb

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Swampdonkey and I were talking today, he said he has learned how to refurbish them. Might try sending him a PM.
 

Swamp Donkey

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I appreciate the plug and Gimpyrobb is correct. This is an idea I have been throwing around. It started with just fan clutches but I decided to include the shutterstats, since they're in the same system and are a common problem. I still have some things to work out before I start making offers though. I know a lot of folks like to do this work themselves, and I support that as I'm the same way, but there are others that might not have the mechanical skill or desire to tackle things like this. Sourcing the parts is the other half of the battle that some might not be the best at. This would be more geared to them.

I'll start a thread when I'm ready to go.

To add to the thread though, rebuilding the shutterstat is a fairly simple procedure as has been posted many times before. There are a couple of things that can't be repaired from the end user standpoint though. The fan clutch can also cause symptoms of a faulty shutterstat and some of these are not addressed by the TMs or the manufacturer. JamesH, I know you tested the clutch and it is functioning properly. As Alexsha said, replace the O-rings and try again. If that fails to help, remove the whole thing and stove test it in a pot of water. This will verify the thermal capsule is working, which is not repairable by the way. Have you verified your engine is actually making it to activation temperature. Always verify your test equipment, your temp gauge in this case, for accuracy before troubleshooting. The factory gauges are well known for inaccuracy which is why I make the point. The shutterstat may not be working because it doesn't need to.

Hope this helps.
 

JamesH

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The O rings, in fact everything looked beautiful. I couldn't not see any problems at all other than it did seem to need lube. The O rings are so cheap to replace I will definitely do that. As far as temperature goes, I could not get it up to 200 on the gauge driving around the neighborhood so I took it up with ridge road by my house and it it hit 220 degrees on the gauge by the time I hit the top and turned around. The fan did not engage. As soon as I came down the ridge and got a little air through the radiator the temp dropped to the 175 range.

Did I remove all the parts that are removable?

When testing the unit in a pot of water, how do I tell if the thermal capsule is working?

thanks guys!
 

Floridianson

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[QUOTE=JamesH
When testing the unit in a pot of water, how do I tell if the thermal capsule is working?

Myself I might leave the whole unit together and if it is a NC when the correct temp. is reached it would open. So if you had a rubber hose attched to the in port and gave it a blow it would be open and if it was a NO you would be able to blow through it when cold but when hot you could not. Make sence?
 

Swamp Donkey

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Myself I might leave the whole unit together and if it is a NC when the correct temp. is reached it would open. So if you had a rubber hose attched to the in port and gave it a blow it would be open and if it was a NO you would be able to blow through it when cold but when hot you could not. Make sence?
This would be another test you can do. I use the stove because you can control temperature better to determine actual opening and closing points. Granted, most of the ones I've tested were already off the truck.

Another thing to check is that you are getting air flow to the shutterstat. There is reportedly a screen filter of sorts in the line between the engine and shutterstat, inside one of the fittings. My truck didn't have one but it's been visually confirmed in other threads as looking like a piece of steel wool stuck in there.
 

Swamp Donkey

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Did I remove all the parts that are removable?

When testing the unit in a pot of water, how do I tell if the thermal capsule is working?

thanks guys!
Missed this post somehow.

There is an O-ring on the capsule end that can be replaced but it requires complete removal. It is located behind the jam nut on the capsule stem.

To stove test you need shop air going in the supply side. Keep the capsule in the water and slowly raise the temperature. Use a good immersible thermometer to monitor water temperature. There should be no air passing through until the water reaches activation temperature. At this point air should exit the exhaust side. Make sure the exhaust air is not directed at the hot water.

Try it the way Floridianson suggested because like I said, the ones I've tested were already removed. Unhook the supply line and start the truck to verify you have full pressure coming to the shutterstat. Reconnect the supply line and bring truck to activation temperature. Air should not exhaust until that temperature has been reached. When you are at or slightly above activation temperature you should start exhausting air if the shutterstat is working properly. If you applied air to the fan clutch and it started operating, the shutterstat should be a normally closed unit.
 

Scott88M

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Sounds crazy but i had a coolant leak and didn't realize it was as bad as it was. My truck would get hot but fan wouldn't kick on. Make sure your coolant is topped off, i topped mine off and suddenly the fan would work. I guess want enough coolant to drench the probe on the shutterstat.
 

Strouty

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When diagnosing the problem, if the fan is working all the time, does that mean shutterstat is definitely the issue or can the clutch have an issue that would make it engage besides the shutterstat? I verified that the fan is not locked and when you start up the truck the fan does not move until it gets a bit of air pressure built up. While the truck is running you can hear and feel it leaking from the shutterstat. As soon as you turn the truck off, she starts draining until empty. I have tried rebuilding it with no luck, this was my 4th time. I have not ordered the mcmaster o-ring, I think that is my next step. I have not tested it in hot water, but I do not have the problem of engaging, I need it to disengage, so that seems like a waste of effort.
 

Swamp Donkey

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I'll update this thread since I've been getting some PMs on when I can start doing rebuilds. Basically I haven't made it too far with this. The main reason is time. I've accumulated several shutterstats and fan clutches with intentions of doing the rebuilds using a core system, but that's as far as I've gotten. I've just got to many irons in the fire right now to be able to make this happen in an efficient and reliable manner, which is the only way I would even consider offering it.
 

todds112

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When diagnosing the problem, if the fan is working all the time, does that mean shutterstat is definitely the issue or can the clutch have an issue that would make it engage besides the shutterstat? I verified that the fan is not locked and when you start up the truck the fan does not move until it gets a bit of air pressure built up. While the truck is running you can hear and feel it leaking from the shutterstat. As soon as you turn the truck off, she starts draining until empty. I have tried rebuilding it with no luck, this was my 4th time. I have not ordered the mcmaster o-ring, I think that is my next step. I have not tested it in hot water, but I do not have the problem of engaging, I need it to disengage, so that seems like a waste of effort.
Sounds to me like the shutter stat is stuck in the open position. Mine was stuck about half way between open and closed and just vented the air out like yours is doing. It might be the actual element that is sticking, though. If you take the element off make sure you note how far it is screwed on, as that affects the calibration.

PM me your address, I'll send you a McMAster O-Ring.
 

Floridianson

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I don't know about the 8.3 fan clutch and the one on the M925 250 Cummins I had needed air to lock up. So the shutter stats would be NC. and overheat it opens and the air goes in and clutch locks fan. Now Bendix makes a clutch called fail safe and it is locked up without air and unlocks with air. so the shutter stat would be NO. The fan would be locked up on starting the truck and as soon as the air built up it would unlock. Over heat cuts off the air and lock up happens. The fan clutch on my M920 is a fail safe and I don't know if it came that way or they changed out the fan clutch and shutter stat to match that set up. I am getting real bad memory loss and I am not kidding but thought the 250 M939 series had the bolts we put in if the shutter stat failed.
 
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