Actuator, Air Fan Clutch for M923a1

[juanprado]

Hi Mark,

I hope the picture helps. It screws into the top front of the motor by the top radiator hose passenger side and has an airline going to it from the front drivers side all the way across the motor.

Juan

 

[TiGWolf]

I just ordered a new one myself...

VALVE,FAN CLUTCH M939 P/N: CA200046
www.memphisequipment.com
$147.50

Hello Guys,

We're working on an M923a1 right now, and the Fan Clutch Actuator is shot. I'm running into problems finding a new one. The numbers on the side of the Actuator are:

19207-11669644
11-84
CAS190

I'm looking around trying to find one so that I can replace it, but using those numbers (11669644 seems to be the part number) I am having trouble tracking one down.

Anyone know of another number they go by, or a 5 ton whiz that I could talk to about it?

 

[1StumpJumper]

Thanks to all, I need to perform this repair as well. The whistle is quite loud when it bleeds down.

 

[rronning84]

I have a new one of these I am 90% sure. I will look. If anyone needs and other I will do a sweet deal for them.

 

[1StumpJumper]

rronning84, PM sent

 

[rronning84]

Holy crud. I did not know these are so popular. I only have one if I can even find it and I have had 6 people PM me for it. .I will have to see if I can score any more of them

 

[rronning84]

I found the one I was thinking of and it turns out it is for a hmmwv. Sorry guys.

 

[goldneagle]

I would strongly suggest you try to repair it before you go spend lots of money on a replacement. It is easy to take apart and clean/lubricate. I am sure you can get replacement o-rings from NAPA or other auto parts store if they are needed. Mine just needed cleaning and lube.

 

[nf6x]

Looks like I need to dig into one of these now, too. When I shut down my M936A1 after doing some work on it today, I first heard an air leak coming from the engine air intake. Not the vent tube along the side of the intake pipe, but the actual air intake. It stopped after a minute with a humming sound like a diaphragm valve fluttering as it closes, and then I found that there was still an air leak sound from the engine compartment. I tracked that down to the fan clutch actuator discussed here, with air coming out of the holes in the end cap.

The next step will be for me to remove it, disassemble it, and see if I can repair it, or else order a replacement. I hope that the air leak sound from the air intake is related to this valve's failure, and not a different coincidental failure. Have any of y'all seen this symptom before, where a failing fan clutch actuator valve somehow manages to dump air into the engine air intake?

 

[TiGWolf]

Looks like I need to dig into one of these now, too. When I shut down my M936A1 after doing some work on it today, I first heard an air leak coming from the engine air intake. Not the vent tube along the side of the intake pipe, but the actual air intake. It stopped after a minute with a humming sound like a diaphragm valve fluttering as it closes, and then I found that there was still an air leak sound from the engine compartment. I tracked that down to the fan clutch actuator discussed here, with air coming out of the holes in the end cap.

The next step will be for me to remove it, disassemble it, and see if I can repair it, or else order a replacement. I hope that the air leak sound from the air intake is related to this valve's failure, and not a different coincidental failure. Have any of y'all seen this symptom before, where a failing fan clutch actuator valve somehow manages to dump air into the engine air intake?

I'm not sure how that could be possible. The only two lines going to the fan actuator should be the supply line, and then to the clutch fan. Is your exhaust port to the atmosphere or is it piped elsewhere?

BTW: Just buy a new actuator. They wear out, and there's not much you can do.

 

[nf6x]

Well, that's what I was afraid of. Since the compressor draws its air from the engine intake manifold, maybe I also have an issue in the compressor head that's causing it to leak back into the manifold when shut down? It just seemed like a weird coincidence that both symptoms appeared at the same time.

 

[TiGWolf]

Well, that's what I was afraid of. Since the compressor draws its air from the engine intake manifold, maybe I also have an issue in the compressor head that's causing it to leak back into the manifold when shut down? It just seemed like a weird coincidence that both symptoms appeared at the same time.

Does your air safety valve pop at all or are running over 120 psi on your tanks?
If so, it may not be as bad as it seems... Your problem may be the air governor, a relatively cheap part, and would be worth replacing before shoveling out a barrel of cash for a rebuilt compressor. I don't recall of the top of my head if there is a check valve on the top of the compressor or not..

 

[nf6x]

I'll check on that stuff next time i fire up the truck. If my governor failed and caused an overpressure, then maybe that's what took out the fan clutch actuator at the same time?

 

[nf6x]

Thinking on it some more, I do not recall hearing either of the pop off valves venting. I still need to fire it back up to take a close look at the pressure gauges. I checked the P2P, and it only shows the compressor and filter restriction gauges tapping off the engine air intake, which makes me awfully suspicious of the one way valves inside the compressor head. Have any of y'all done a do it yourself rebuild of the compressor head? Are rebuild kits available? Off to the TMs and Google...

I think I need to partially drain the coolant before I pull out the fan clutch actuator, so I want to make sure I do any engine-running tests before I do that so I can figure out what parts I will need to order.

 

[nf6x]

Hmm, it gets stranger now. I disconnected the air input hose at the fan clutch actuator to get that problem out of the way while I look at the other one, and I plugged the dangling hose with a pressure gauge. That pressure gauge tracks the gauges in the cab, the governor cuts out just above 120 PSI like it should, and I don't hear any pop-off valves opening. I noticed that I could also hear the air leak from the engine air intake mushroom with the engine running once I knew it was there.

Next, I disconnected the air inlet elbow from the air compressor head so I could see if that was where the air was coming from. I could hear a pfft and feel some air coming out of the compressor intake on each compression stroke... but then I noticed that I could still hear the air leak from the engine air intake mushroom. So, the air is coming from somewhere other than the intake port of the air compressor. So it's good that my compressor may still be OK, but something is wrong elsewhere.

On shutdown, the intake air leak sound continues for up to 30 seconds or so, and then gradually stops over a few seconds with a humming diaphragm valve sound which seems to come from the vicinity of the air tank under the driver side of the cab.

So, now I need to figure out what else could put air pressure into the engine air intake. I checked the vent line that runs up along the snorkel by plugging the end with my finger, and that's not where the leak is coming from.

While I was waiting for air to build up, I investigated my non-functional tach. First I disconnected the tach cable from the top of the electrical RPM sender on top of the injection pump. Cable turns freely, but the driver in the RPM sender wasn't turning. Next I pulled off the electrical RPM sender, and found that it's bound up and the tach drive shaft in the IP is rusted, broken and not turning. So I'll need a new tach drive, and optionally a new electrical sender (I think it's just used for the diagnostic port, and could probably be left out). Oddly, there's an open 4-pin connector next to the 2-pin one that the electrical RPM sender plugs into, and I haven't figured out where it goes yet.

 

[TiGWolf]

Hmm, it gets stranger now. I disconnected the air input hose at the fan clutch actuator to get that problem out of the way while I look at the other one, and I plugged the dangling hose with a pressure gauge. That pressure gauge tracks the gauges in the cab, the governor cuts out just above 120 PSI like it should, and I don't hear any pop-off valves opening. I noticed that I could also hear the air leak from the engine air intake mushroom with the engine running once I knew it was there.

Next, I disconnected the air inlet elbow from the air compressor head so I could see if that was where the air was coming from. I could hear a pfft and feel some air coming out of the compressor intake on each compression stroke... but then I noticed that I could still hear the air leak from the engine air intake mushroom. So, the air is coming from somewhere other than the intake port of the air compressor. So it's good that my compressor may still be OK, but something is wrong elsewhere.

On shutdown, the intake air leak sound continues for up to 30 seconds or so, and then gradually stops over a few seconds with a humming diaphragm valve sound which seems to come from the vicinity of the air tank under the driver side of the cab.

So, now I need to figure out what else could put air pressure into the engine air intake. I checked the vent line that runs up along the snorkel by plugging the end with my finger, and that's not where the leak is coming from.

While I was waiting for air to build up, I investigated my non-functional tach. First I disconnected the tach cable from the top of the electrical RPM sender on top of the injection pump. Cable turns freely, but the driver in the RPM sender wasn't turning. Next I pulled off the electrical RPM sender, and found that it's bound up and the tach drive shaft in the IP is rusted, broken and not turning. So I'll need a new tach drive, and optionally a new electrical sender (I think it's just used for the diagnostic port, and could probably be left out). Oddly, there's an open 4-pin connector next to the 2-pin one that the electrical RPM sender plugs into, and I haven't figured out where it goes yet.

I think some pictures are in order to help diagnose. Can you take pics of your intake, with the attached lines? I'm wondering if something is in the wrong place.

 

[nf6x]

I think some pictures are in order to help diagnose. Can you take pics of your intake, with the attached lines? I'm wondering if something is in the wrong place.

Sure, here are some pictures. Nothing looks wrong to me, but I'm still new to the world of M939-series trucks.

Note that the tach cable and the air supply to the fan clutch actuator are both disconnected and tied off to the windshield washer fluid reservoir bracket, and the air supply line is plugged with a pressure gauge. The air intake elbow is also disconnected from the air compressor.

The only things I see plumbed into the engine air intake pipes are the compressor intake, ether injector, and filter restriction gauge. I don't think this leak was present before yesterday, but maybe I just didn't notice it before?

I think I need to fire it back up again to see if the noise is playing a trick on my ears, but it sure seems to be coming from the intake mushroom on top of the snorkel.

 

[nf6x]

I ran it again, and that leak sound still sounds like it's coming from the engine air intake mushroom.

I popped both the oil fill cap and the coolant reservoir cap after shutdown while it was still making the air leak sound, and neither the coolant system nor the crankcase appears to be involved. No sense this makes to me, says I.

 

[jonesal]

I see you have the fuel tank ventilation MWO update/upgrade. Could it be that? Trace the lines from the fuel tank to the stack. Could it also be a restriction that might cause the air noise (vent kit again)? My kit was installed poorly and had rubbed itself until it was restricted in one spot and completely wore through in another.

Just a thought.

Al Jones
'84 M923

 

[nf6x]

Isn't the fuel tank vent that tube clamped along the side of the intake stack? I verified that the sound comes from the intake mushroom rather than that small tube by plugging the end of the small tube with my finger. I guess I can try loosening the fuel tank lid to see if the sound is caused by pressure or vacuum in the fuel tank...