NHC250 metal in oil

[WillWagner]

There ya go. Swing type fan hub. In the pic, kinda hard to tell, but MOST of the oil leak looks to be concentrated toward the lower part of th acc drive pully, I don't see a large amt of oil on top of the acc drive ear and data plate.

The oil leak looks to me to be from the accessory drive seal. When the swing style fan hub is used, it is extremely easy to over tighten the fan belts to the point that the accessory drive shaft is physically pulled up into the bushing in the front cover and makes it impossible for oil to do it's job.

If I were a bettin' man, I'd bet your next paycheck that your mystery metal is an accessory drive bushing that has failed due to incorrect belt tension.

The repair can go 2 ways.

You pull the accessory drive out, this entails removing the belts and drive pulley then pull the drive/compressor out as a unit, yes, it can be done easily and w/o the pump, it makes it easier! Inspect the front cover. IF the bushing hasn't spun or the shaft hasn't been pulled up into the cover so bad that the bore is now egg shaped or has massive amounts of metal transfer, you can polish the shaft, install a new bushing, and it is a press fit, re assemble and be on your way.

OR

You pull it apart and find that the shaft is FUBAR, and the cover has an oval hole instead of a round one. If that's the case, you either get a new/rebuilt accessory drive assy or a shaft and you rebuild it, they are easy to do, BUT, if the shaft has been pulled on so hard it totally knocks out the bushing in the cover, it usually takes out the bushing in the accesory drive housing, so a new/exch one is better. I forgot, I takes a special tool to remove the spline drive from the shaft too. Then you take the front of the truck apart, remove the front cover and replace it. The pan might need to come down, depending on how hard the pan gasket is and how it comes apart from the ft cover. You can transfer the cam end play shim set from the old cover to the new one with no issues.

If you pull it apart, make sure that the "TDC" mark on the pulley is aligned with the pointer on the cover....for reference, the pin in the acc dr shaft will be at 12o'clock when you pull the pulley off. That is for the timing of the drive, The engine will still run just fine if it is not put back in time, the only thing it times is the overhead set. The next guy will thank you when he sets the overhead.

 

[FourthGenSS]

The serrated grooves are not unlike a chip as metal is turned from a lathe. Either something really bad happened or this is debris left over from manufacturing. If the engine runs without unusual noise and full oil pressure I would guess the latter.

Pressure looks good. Seems to run fine. Not sure what “unusual” noise is for one of these. Always describe the HMMWV as angry dwarves with hammers.

 

[FourthGenSS]

There ya go. Swing type fan hub. In the pic, kinda hard to tell, but MOST of the oil leak looks to be concentrated toward the lower part of th acc drive pully, I don't see a large amt of oil on top of the acc drive ear and data plate.

The oil leak looks to me to be from the accessory drive seal. When the swing style fan hub is used, it is extremely easy to over tighten the fan belts to the point that the accessory drive shaft is physically pulled up into the bushing in the front cover and makes it impossible for oil to do it's job.

If I were a bettin' man, I'd bet your next paycheck that your mystery metal is an accessory drive bushing that has failed due to incorrect belt tension.

The repair can go 2 ways.

You pull the accessory drive out, this entails removing the belts and drive pulley then pull the drive/compressor out as a unit, yes, it can be done easily and w/o the pump, it makes it easier! Inspect the front cover. IF the bushing hasn't spun or the shaft hasn't been pulled up into the cover so bad that the bore is now egg shaped or has massive amounts of metal transfer, you can polish the shaft, install a new bushing, and it is a press fit, re assemble and be on your way.

OR

You pull it apart and find that the shaft is FUBAR, and the cover has an oval hole instead of a round one. If that's the case, you either get a new/rebuilt accessory drive assy or a shaft and you rebuild it, they are easy to do, BUT, if the shaft has been pulled on so hard it totally knocks out the bushing in the cover, it usually takes out the bushing in the accesory drive housing, so a new/exch one is better. I forgot, I takes a special tool to remove the spline drive from the shaft too. Then you take the front of the truck apart, remove the front cover and replace it. The pan might need to come down, depending on how hard the pan gasket is and how it comes apart from the ft cover. You can transfer the cam end play shim set from the old cover to the new one with no issues.

If you pull it apart, make sure that the "TDC" mark on the pulley is aligned with the pointer on the cover....for reference, the pin in the acc dr shaft will be at 12o'clock when you pull the pulley off. That is for the timing of the drive, The engine will still run just fine if it is not put back in time, the only thing it times is the overhead set. The next guy will thank you when he sets the overhead.

It looked to me like all the oil was coming from the power steering pump has the entire bottom of it and the bracket and all of the stuff directly below it are covered. The fan belts themselves are not tight at all but the power steering belts are. It’s gonna be a couple weeks before I got the time to tear that all apart and check

 

[WillWagner]

Well, to me, it looks like the oil is starting at the acc drive and being blown out the back of the pulley. Notice that the area at the PS pulley isn't that wet, but the bottom of the mounting bkt is very wet. Where is it the cleanest? Oil leaks wash dirt and debris away, dirt and debris stick to the non leak, oil soaked areas. Yeah, I get it, slinging oil is tough to pin point. But, if the PS pump was leaking, the area behind the pump would be wet and clean. It isn't.

First pic clearly shows a sorta dry data tag. 2nd and 3rd pic show oil out of the center of the shaft area and is wet behind the pulley. Classic acc drive leak. If it were a PS pump leak, the oil would be behind the PS pulley and pushed back from there. What is in the PS pump? Oil, PS fluid, or ATF?

Again, I'd bet you next paycheck on it.

But what do I know?

 

[FourthGenSS]

Well, to me, it looks like the oil is starting at the acc drive and being blown out the back of the pulley. Notice that the area at the PS pulley isn't that wet, but the bottom of the mounting bkt is very wet. Where is it the cleanest? Oil leaks wash dirt and debris away, dirt and debris stick to the non leak, oil soaked areas. Yeah, I get it, slinging oil is tough to pin point. But, if the PS pump was leaking, the area behind the pump would be wet and clean. It isn't.

First pic clearly shows a sorta dry data tag. 2nd and 3rd pic show oil out of the center of the shaft area and is wet behind the pulley. Classic acc drive leak. If it were a PS pump leak, the oil would be behind the PS pulley and pushed back from there. What is in the PS pump? Oil, PS fluid, or ATF?

Again, I'd bet you next paycheck on it.

But what do I know?

PS Fluid, at least that’s what it looks like and I found a big jug of it in the truck when I got it. I’ll definitely look into the acc drive as soon as I get a chance. Thanks for your help man I really appreciate it!

 

[WillWagner]

Amy progress on this? If you are doing the acc drive, I have tools to remove and install the pulleys and a tool I made to remove the old bushing from the pulley.

 

[FourthGenSS]

Amy progress on this? If you are doing the acc drive, I have tools to remove and install the pulleys and a tool I made to remove the old bushing from the pulley.

Not yet, I have an OHV/camping trip coming up so all focus has been on the HMMWV and my kids Trailblazers, so it’s going to be a few weeks. I will for sure follow up with what I find and really appreciate the help.

 

[FourthGenSS]

Not yet, I have an OHV/camping trip coming up so all focus has been on the HMMWV and my kids Trailblazers, so it’s going to be a few weeks. I will for sure follow up with what I find and really appreciate the help.

Not yet, I have an OHV/camping trip coming up so all focus has been on the HMMWV and my kids Trailblazers, so it’s going to be a few weeks. I will for sure follow up with what I find and really appreciate the help.

So obviously the PS pump did not sluff off metal in the oil but I cleaned the whole thing up and took it for a drive to see if I could see that accessory drive leaking and the power steering pump blew up and let all it’s fluid out the front so now I need to see about rebuilding it also. I see kits for servicing them, how do you get them apart? Will hopefully be tearing into the accessory drive this weekend.

 

[FourthGenSS]

So obviously the PS pump did not sluff off metal in the oil but I cleaned the whole thing up and took it for a drive to see if I could see that accessory drive leaking and the power steering pump blew up and let all it’s fluid out the front so now I need to see about rebuilding it also. I see kits for servicing them, how do you get them apart? Will hopefully be tearing into the accessory drive this weekend.

Never mind a little bit of light on on the bench and I can see the threads