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New to me M1078A1 - Flew into Houston yesterday - What have I done

2Wheels

2Wheels

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Hey everyone,
I decided at midnight Sunday / Monday to book a flight to Houston and Pick up this 2003 M1078A1 Truck. I left Huston about 1:30 pm. It had under 5.1k on the clock. Have a little over 500 miles on it since then. Just waking up from a ~1.5 hour nap a the Buc-ee's between Mobile and Pensacola. ~380 miles to go to Jacksonville for the holidays. Then back to North Carolina. My first military vehicle. So far it is great! I hope it continues to be so. I just thought I would share.20221220_043236.jpg
 
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GeneralDisorder

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Rear main seal. That is the drain hole - the bell-housing fording plug (to the lef) is in it's stowage position. It should be in that configuration unless you are fording deep water.

Although it looks like there's oil forward of that port on the bell-housing also. More pics needed.

Also the vibration might be an imminent tire failure. You have the Michelin Maypops on there and I'm betting they are from 2003. By the time they stopped using those it would have been within their usable life so those are 20 years old. Very dangerous IMO. Keep them inflated to 75+ psi and keep your speed down. The vibration could be many things and one of those is a tire failure in progress. You'll want to change those immediately when you get to destination.
 
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Ronmar

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Yea oil-line-o-death is a 3116 thing. You have oil forward and above. I think this may be something less sinister than a rear mainseal. You can of course confirm this by moving that plug from its stowed position and putting it in the drain port and drive for a bit and see if any oil comes out when you remove it later.

This block design(3116/3126/C7) have some weak spots. The way they integrated the oil pump into the front of the block/timing case makes this area prone to leakage where the oil pan seals over it. since the oil pan appears to be coated as far forward as your pic shows, it could also be that your oil pan bolts are loose due to vibration/age.

Another weak spot is where the compressor attaches to the timing case. They hung the power steering pump off the back of the air compressor. The HEUI pump is above all of this. That is a lot of overhung weight on that aluminum case. They put a steel support bracket that ties from where the hydraulic pump attaches, over to the engine block inboard of the starter. It is vital that this bracket is installed properly and undamaged. If it has been removed or it is damaged/loose this allows the compressor weight to crack the timing case, especially with vibration…

On these big tires, they rotate about 6 times per second At highway speed. So if the vibration is slow enough to count in a second, it is probably tires. An axle issue would be double that at 12hz, which is about my limit to count in a second. Driveshafts would be 3X that and too fast to count at highway speed.
 
2Wheels

2Wheels

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Apologies for taking so long for the followup.

How much oil is too much oil coming from the rear main?

I put the fording plug and drove ~600 miles. Dropped the plug today after warming the truck up and received right at 4oz. of oil.

After cleaning the engine last week and running a bit it seemed like the leak is coming from the oil pan gasket. Last week I checked the oil pan bolts and 2/3 of the bolts were at least 1/4, or more, loose.

According to the service records the previous owner paid a tire shop in Houston to change the oil and replace the gasket in May this year. It appears that they used a ton of orange RTV and did a really crummy job. After cleaning and inspecting multiple times I am 90% sure the seal at the oil pan is the main culprit for the leaking oil. I will be reading the TM on the oil pan gasket replacement procedure.

This weekend I will be making sure that the bottom of the front timing cover is not leaking.

Any additional input is appreciated.

After more driving I am not concerned with the vibration. The tires are new as of May this year. I am pretty sure it was the fact I was not use to 4-wheel drive steering around bends at 50mph on large aggressive tires.

Thanks everyone-
 
Mullaney

Mullaney

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2Wheels said:
Apologies for taking so long for the followup.

How much oil is too much oil coming from the rear main?

I put the fording plug and drove ~600 miles. Dropped the plug today after warming the truck up and received right at 4oz. of oil.

After cleaning the engine last week and running a bit it seemed like the leak is coming from the oil pan gasket. Last week I checked the oil pan bolts and 2/3 of the bolts were at least 1/4, or more, loose.

According to the service records the previous owner paid a tire shop in Houston to change the oil and replace the gasket in May this year. It appears that they used a ton of orange RTV and did a really crummy job. After cleaning and inspecting multiple times I am 90% sure the seal at the oil pan is the main culprit for the leaking oil. I will be reading the TM on the oil pan gasket replacement procedure.

This weekend I will be making sure that the bottom of the front timing cover is not leaking.

Any additional input is appreciated.

After more driving I am not concerned with the vibration. The tires are new as of May this year. I am pretty sure it was the fact I was not use to 4-wheel drive steering around bends at 50mph on large aggressive tires.

Thanks everyone-
Click to expand...
.
There really shouldn't be any oil coming out of the Fording plug.
I think you have already answered your own question on the oil pan gasket. :-(
 
simp5782

simp5782

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2Wheels said:
Apologies for taking so long for the followup.

How much oil is too much oil coming from the rear main?

I put the fording plug and drove ~600 miles. Dropped the plug today after warming the truck up and received right at 4oz. of oil.

After cleaning the engine last week and running a bit it seemed like the leak is coming from the oil pan gasket. Last week I checked the oil pan bolts and 2/3 of the bolts were at least 1/4, or more, loose.

According to the service records the previous owner paid a tire shop in Houston to change the oil and replace the gasket in May this year. It appears that they used a ton of orange RTV and did a really crummy job. After cleaning and inspecting multiple times I am 90% sure the seal at the oil pan is the main culprit for the leaking oil. I will be reading the TM on the oil pan gasket replacement procedure.

This weekend I will be making sure that the bottom of the front timing cover is not leaking.

Any additional input is appreciated.

After more driving I am not concerned with the vibration. The tires are new as of May this year. I am pretty sure it was the fact I was not use to 4-wheel drive steering around bends at 50mph on large aggressive tires.

Thanks everyone-
Click to expand...
3126b's do have issues of cracking blocks on the ones cast in France. This leaks at the oil pan. Just to be sure to check for hairline cracks when you take the pan off.
 
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GeneralDisorder

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Or a valve cover from one anyway. o_O

Just to introduce another layer of confusion and uncertainty.

Bolts don't look molested though so yeah - probably a 1999 production engine. The engine on my 2008 was made in 2008 but maybe in the earlier years they had engines sitting around for a while before use? I don't have any statistics on that unfortunately. We will have to survey members.
 
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