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Plode's M923A2

plode

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South Jersey
So the other day I bought a 1990 M923A2 off of another forum member. It has the Cummins 6CTA 8.3L engine. Engine has a tag says it was rebuilt in 2011.


Been going through it the past two days to see what is wrong with it, and what could use work. I've been trying to follow the TM's but I'm more of a visual person, and the illustrations in the TM's aren't helping me much. I've been searching on here for info as well. I'm sure all of this has been addressed at one time or another, it just is very time consuming having to read through 47 page threads to find what I'm looking for.

What I've found so far wrong with the truck:
1. Coolant leaks. The heater core is leaking, so that is shut off(I saw there is one for a 93 Mustang GT that will fit with some modification to the lid. This is probably what I'll replace it with since it's only $20.
There is also the wye just behind the bottom radiator connection, which seems to have a bit of rust on it, not sure if the leak is coming out of that, or if the hose connections are leaking. I don't have any container suitable(big enough) to drain the coolant into yet, so I haven't messed with it. I'm working on getting a blue 55 gallon plastic barrel that I'm going to cut about 1/2 or so off of to use as a drain pan.


2. Fluid leak. Not sure if it is diesel or something else. There are like 18 million hoses all near it on the frame running to the rear of the truck.
This is looking from under the truck(leak is the pipe with the union, it is directly above the front differential):

This is looking down from above. It is the red/brownish color pipe that goes to a union and connects to a soft line. Again, directly above the front differential.


3. CTIS(of course!). CTIS box blinks all 5 lights. When I click a setting, the valve down on the floor will hiss three times like it's doing something, but then it goes back to blinking all 5 lights. I tried shutting the truck off, restarting it, checked connection to the controller...it must be one of the wheel cylinders. At this point, I'd be happy just disabling the system for now, until I get these other issues sorted out first.

4. Air system.
A. Have a leak in the cab. Apparently the windshield wiper control valve for the passenger side doesn't seal, because it's blowing air out a seal on the wiper motor when the control is in the park position. I tried getting the control valve out today, but there is just so much stuff behind that dash, I can't even get my hands to the back of the valve. I tried pulling the gauge panel out so maybe I could get a better angle on it, but the dash panel won't pull out more then an inch. Not sure what to do there.
It also sounds like the parking brake might be leaking, but a very tiny leak if it is.

B. Transfer case lever is locked down. The button was stuck in, I managed to get it to come back out, but pushing it back in does nothing. I know there is an interlock, but no idea about it.

C. When I shut the truck off, there is air hissing into the intake. I went around with some soapy water and hit all of the lines and connections, only saw two very minor leaks, which I took care of today. I have my dad bringing home fittings from Home Depot so I can connect it to my shop air so I can go around and spray all of the brake chambers without the engine running. The brake pedal also seems very "stiff", but the previous owner says it is normal. Not sure if that is true or not. The only other vehicles I've driven in the past with air brakes were Pierce fire trucks, and their pedals were much more like something you would feel in a normal car, stiffness wise.
When the truck is running, the pressure builds up to 120psi then you hear the thing blow off(more of a long dramatic whine vs what I normally hear on big rigs/fire trucks.)The pressure also drops on both the primary and secondary pretty quick with each brake application. 4 or 5 brake pumps and it's below 90psi and I get the low air alarm.

When the truck is running, something is constantly clicking near the rear axles. I'm guessing this is either something with the CTIS, or ABS.

5. ABS light.
The ABS light was not on when I got it, or for the drive home, but since moving the dash panel out an inch today, the light is on solid. I'm do hear three clicks when I turn the "ignition" switch to the on position.



Another random question- do these trucks have glow plugs? I started the truck up yesterday, it was 14 out. It fired right up but billowed white smoke for a couple of minutes(not coolant, had the diesel smell, not sweet at all). Enough smoke to leave a cloud in my neighborhood
 
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Suprman

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Looks like the power steering is leaking. Abs electronics and valve control is over a back axle. Unplug the ctis control till you work out the main problems. Coolant seeps from hose clamps you can usually snug them up a bit to fix it. I have not had an 8.3 smoke that much. Maybe some water in the fuel.
 

plode

Member
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Location
South Jersey
Looks like the power steering is leaking. Abs electronics and valve control is over a back axle. Unplug the ctis control till you work out the main problems. Coolant seeps from hose clamps you can usually snug them up a bit to fix it. I have not had an 8.3 smoke that much. Maybe some water in the fuel.
7F71D404-BD2A-418C-AFB2-705E23C091B0_zpsp5wrrlkt.jpg16B4D947-5BEA-4750-86CD-94C19D8CB1F3_zpsyhxx6jtg.jpgA825994C-A340-41F6-BC2B-D1C30783046E_zpsb3sozsv4.jpg

I circled the leaky hose(and the leaky fitting specifically in the one). Is that a power steering line? It looked like it goes back on the frame rail somewhere, but I could be wrong. Does that connection have O-rings or is it something I can put some teflon tape on to seal up?

I did disconnect the CTIS computer. I was wondering what specific fittings I will need to seal off the wheels from the rest of the system. In one post I saw the person said a 7/16" fitting, and a couple others said 3/8". Also, what size plug do I need for the hubs?

And as far as the smoke- does pumping the accelerator while the motor is off open the injectors and dump fuel into the motor still? I started it up today and there was barely any smoke, even though it was still pretty cold out(33 degrees?). I plan on changing all of the filters and fluids soon, but I'll have to do them individually so my bank account doesn't take such a huge hit at once. I'll try draining the fuel water separator tomorrow.
 
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Suprman

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That looks like the air line coming from the compressor going to the air dryer. The round thing above it is the steering reservoir and in front of that is the compressor. Clean everything off and look for leaks. If the steering reservoir is overfilled it can leak a little out the top.
 

plode

Member
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South Jersey
That looks like the air line coming from the compressor going to the air dryer. The round thing above it is the steering reservoir and in front of that is the compressor. Clean everything off and look for leaks. If the steering reservoir is overfilled it can leak a little out the top.
The top of the steering reservoir is completely dry. It really looks like it's coming out of that line, but that wouldn't make sense if it's an air line. I'll clean it all off and see if I can pin point the leak.
 

Suprman

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Air compressor has an oil supply for lubrication. Could be oil leaking from there. Follow the line back to the top side of the compressor.
 

Suprman

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I have had oil leaks from where the air compressor bolts in up front. There is an oil seal there. How much oil is coming out? Check the steering lines under the reservoir. Engine uses oil, steering use the same oil as does the trans. It's all the same.
 

plode

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It's leaking out at the connection where it goes from copper to rubber. Enough oil to coat the leaf springs, and there was a few drops on the bottom of that connection when I was under there today. The front of the line where it goes into the compressor is dry. I mean, it was honestly enough that I thought in my first few posts that it was a liquid carrying line :lol:
 

Suprman

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It has to be dripping down from somewhere. It would spray out if the line when the truck was on if that was the case. When you drain the air tanks does any oil cone out? Check the expello valve on the bottom of the air dryer is it oily?
 

74M35A2

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The 6CTA8.3 engine does not have glow plugs. It also does not have an intake air grid heater either. The only start assist your truck should have is an ether injection system. It may smoke a bit when cold on start up, but it should not be that much. You may be burning coolant if it is enough to cloud a neighborhood. I'd suspect a head gasket or leaking after-cooler. With the engine running, look for bubbles in the radiator surge/fill tank with the cap off.

Cummins had an issue with that block cracking at the top between cylinders, and they fixed it during 1990's production. If your truck is a 1990, it could have an engine in it that was built in 1989 calendar year. You could also pressurize the cooling system with the truck running and see if the exhaust blows white.
 
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plode

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Location
South Jersey
The engine has a tag on it saying it was rebuilt in 2008 or 2011(I forget which now). I'll have to check the coolant for bubbles tomorrow. I have the tool to pressurize the cooling system, but I don't think I have the right adapter for it.
It didn't blow much(if any) white smoke today at all(was 30 degrees warmer today then it was yesterday). Yesterday it was in the teens or low 20's.
 

plode

Member
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South Jersey
I tightened down the clamps around the wye where coolant was seeping. I also hooked up a fitting so I can charge the air system from the shop compressor and check for leaks. I found a couple pretty good leaks underneath, one on a 90 going into the transfer case, and the fitting coming off the front of the top air tank. Good news- none of the brake chambers are leaking at all.
3D924298-6378-43D0-A3B7-E1AC45F10571_zpsqcffazjp.jpg

There is a pin hole leak(just barely leaking) on the top tank, it actually really looks like the truck was shot with a gun.
702905B3-113C-4F32-A162-B73BC987FE8E_zpsz0rc4olz.jpg

The other good news is...I checked the coolant for bubbles with the truck off but air system pressurized- Didn't see any. I checked the coolant for bubbles with the engine running- didn't see any. So that is good.

Also after letting the truck idle for a good bit, the ABS light turned off. Don't know what that is about.

Now for the bad news:
The exhaust is smoking and it isn't a good color. Grey/blue. Got a whiff of it at one point and it smells like oil. The truck wasn't warmed up yet though, I only had it idling. It'll take years to get it to warm up at idle. I pulled the oil cap off and it doesn't seem like it has excessive blow by. I might try to have a friend of mine who went to school for diesel mechanics come by, and take a look at it. I think he works at a Caterpillar dealer now.
EDIT: He apparently moved to San Francisco. He recommended a garage that does truck repairs, but doesn't charge as much as a dealership. I can see the dollar signs piling up already :(

It also seems like the engine is idling a little low, right at about 500rpms.

I went around and got the passenger side parking light working, and two marker lights on the drivers side. Both marker lights were corroded up, so I cleaned the bulbs off, and used some Deoxit(love this stuff) on the sockets. The one marker light is very, very bright, so I'm wondering if I put in a 12v bulb? It didn't say on the bulb, it was a 623 I think.
The front marker lights(next to parking lights/turn signals) don't work at all, so I'm going to have to dig into that wiring. The turn signals don't work now(but they did on the drive home). All of the black out lights work, not that I'll really be using them. I have to buy a license plate bracket with a light that I found at Napa, and wire it up. Gotta switch the bulb in it to 24v.
Passenger side headlight is out too, looks like the filament is broke, so I have to get one of those from Napa as well.



Might go out in a while to work on the air leaks that I found, but it is starting to rain here(beginning of this snowstorm we're supposed to get).
 
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Rifleman

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Just a question, in your first post you said your engine was overhauled in 2011. So was the overhaul done by the Red River Army Depot?
 

plode

Member
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South Jersey
Just a question, in your first post you said your engine was overhauled in 2011. So was the overhaul done by the Red River Army Depot?
I have no idea. Does it say somewhere?
There was a tag on the engine that had a rebuild date. There are only two MWO tags in the door jam. One MWO is for the ABS, and the other I can't tell as they didn't list the entire number.
678956EF-FF76-4D64-ABB0-AEEF926B3244_zpsatjvsn9y.jpgC489C135-356D-48F0-ABB8-BC206C49108B_zpsmkug9svr.jpg
 

BKubu

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Just a question, in your first post you said your engine was overhauled in 2011. So was the overhaul done by the Red River Army Depot?
Man, I'm glad you said it first because that was exactly what I was thinking. Did anyone see that "rebuilt" NHC 250 in GA on GL that went off on last week's sale? It had a fist sized hole in the block right next to a nice, clean data plate that said it was rebuilt at RRAD! I think the date was in 2011 or 2012...you can't make this stuff up!

PLODE, I applaud your interest in fixing the truck up. That's what this hobby is about. Check to see what is wrong with your engine, but don't sink crazy money into it when John Appel on this list has verified running take out motors for $1,500...before any negotiations! He is in PA, near DE, not far from you in south Jersey. Where in south Jersey are you?
 
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