Rear main oil seal leak?

[Rich Johnson]

Ive only had this 1008 for less than a month. Ive only drivin it a hand full of times, but yesterday I parked it and noticed lots of oil dripping from between the oil pan and the torqe converter houseing. I assume this can only be the rear main.
This truck sat for quite a while before I bought it, so it hasnt been driven hardly at all in recent years.
The puddle got to about 4 inches in diameter. Im kinda worried, I dont think it leaked like that the other times I drove it.
Is this something to worry about or what? I mean, is the seal kinda dry and will it seal back up or am I looking at huge pain in the ass to fix the dam thing.

I bought this truck to be a daily driver becasue it was cheap and had low miles, since my f-150 died. I really didnt plan on dumping money into it because it came from a friend of a friend that takkes good care of stuff. I know this couldnt be foreseen, but Im really bummed.

 

[OL AG '89]

seal is failing.... won't heal itself

I recently found an article about changing the rear main seal without removing engine from vehicle. The article was for a civvy model C30, but I think the concept would be the same.
Don't remember where I saw it, but will see what I find.
In a nutshell it discussed jacking up motor just enough to remove the oilpan and sliding the trans back enough to move the converter back.
Basics are you have to remove the rear main bearing and then you have access to the seal.
I don't know if the 6.2L is a 1-piece seal or 2-piece seal.
Not sure this method will work with 1-piece.........
Article made it look and sound easy enough......

I'll look at the TM and see if i can determine 1 or 2 piece seal before searching for article.....

For a "quick" fix you might get a bottle of "Motor Honey", but I am NOT a fan of quick fixes, unless needed "quickly"..... IT will cause ALL seals to swell in engine..... not sure I would give a 25 year old engine an uncontrolled shot of Viagra!!!

 

[OL AG '89]

TM -34P shows 2 part seal

Page 3-1 in -34P shows item 7 as a two part seal, so looks like the method I mentioned will work.....
I dig up the article and post it in here.

I realize the 6.2 is probably a little heavier than the 350 that the article mentions but still sounds doable for a weekend project with some buddies....

I would probably substitute the jacking up with a hoist for piece of mind.

Anybody recently replaced a rear main seal without removing the engine?

 

[beanman1]

you can also check out the cdr valve(the tuna can thing on the passenger side of the engine) if is stopped up it will cause to much engine block pressure and cause the seals to leak

 

[Barrman]

I agree with the CDR check first. To go from no leak to a flood is not normal.

 

[Warthog]

There is a writeup about how to replace the seal in the CUCV Wiki.

Cucv Wiki - Steel Soldiers::Military Vehicles Supersite

Here it is :
-----------------------------------------------------

Rear main seal replacement without removing engine
Autozone rear main ~ $22
Autozone oil pan seals ~ $12



Here are the steps I took:

1. Jack up front end frame, to raise frame slightly off axle. Even an inch will help.
2. Drain oil, remove filter.
3. Unplug batteries
4. Remove starter
5. Remove bottom access for bell housing, tricky since tranny cooling lines have to be pushed over a bit, no need to remove the lines though
6. Pull oil pan, may need to loosen a line for the front axle breather from frame rail, tends to block access to front bolts on oil pan. Use a screwdriver to gently pry the pan loose from the engine block if it sticks; which it should if RTV was used.
7. Remove oil pump/pickup
8. Remove rear main bearing cap
9. Remove old seal
10. Install new seal, carefully. I had a helper and with 4 hands we were able to hold it in place while applying pressure to push it in the grove. Take note of placement, mine was labeled which side points out. TM shows a shim which can be made to assist in seal install. I'd be wary though as you don't want to damage the seal.
11. Following the TM, use anaerobic sealing compound on the rear main cap as specified, install rear main cap and torque to spec
12. Reinstall oil pump/pickup
13. Clean old gasket from oil pan and engine block. RTV oil pan gasket to oil pan, let sit for 10 minutes, RTV top of gasket, let sit a few minutes; then reinstall oil pan while trying not to get RTV places it should not be.
14. Reinstall bell housing access cover and air breather line for front axle if removed.
15. Reinstall starter
16. Install oil filter
17. Fill oil, check level, etc.
18. Reconnect batteries
19. Start it up, recheck oil level after idling for a few minutes and verifying no leaks.

That is about it! If anyone sees a step I missed, please edit this. As long as you have another vehicle to drive in case the job takes longer than you hoped; you'll be fine to try it yourself. It took me two days, maybe 7hrs total. First day, I setup doing steps 1-5. Once you pull the oil pan, you will want to finish through step 13.

 

[Rich Johnson]

THe guy I bought the truck from replaced the CDR last year becuase he said they need replaced every 50K. Truck is at just over 50K right now.
How would I test the CDR?

 

[beanman1]

there is really now way to test take it off and clean it with gas and see how much trash comes out of it it really doesnt take much to stop it up mine was replaced last yr also then about 4 months later i thought the rear main was leaking and i also was told to check the cdr so i did and the problem was solved

 

[Rich Johnson]

You mean just wash out the cdr with gasoline and that will fix it if its clogged?
So then if that is the problem my engine is over pressurizing and blowing oil out the rear main?

 

[beanman1]

i dont wnat to give you a true diagnosis but try the cdr first(a good way to tell if it is stopped up is lokk inside the intake manifold anf if you see oil mist then time to clean the cdr). all the cdr is , is a screen the seperates the oil from the air when the engine is releasing pressure but if its stopped up the engine cannot release pressure so it blows seals
it sounds to me that you have seal blow by but i can be wrong

 

[raiburn]

Hey, make sure it is oil and not dirty tranny fluid. I had similar symptoms, and it was the front tranny seal (pump seal).
Also, if it is oil, make sure it is not coming from up higher on the back of the motor, and just running down and out of the inspection cover.

That is just my two cents.

 

[lavarok]

There is a writeup about how to replace the seal in the CUCV Wiki.

I wrote that..but I need to make one edit.

Per the TM, anaerobic sealant should be used on the bearing cap not RTV.

Page 3-112 in the -34 TM:

"Apply a thin film of anaerobic sealing compound (2) to rear main bearing cap (1) in pattern
shown."

 

[Warthog]

Correction noted. Changed my post.Thanks for the update.

 

[lavarok]

I updated the wiki as well. RTV can work in a pinch, but when I was rebuilding my last 6.2 I used the correct sealant.

 

[Rich Johnson]

Could I just use paint thinner mineral spirits to wash out the CDR instead of gasoline. I always see that you shouldnt use MoGas as a solvent.

 

[Rich Johnson]

Ok, well I pulled the CDR off and a bunch of oil poured out of the tube leading to the filler pipe. I cleaned it out with mineral spirits and a bunch of oil came out but no junk or crud. I reinstalled it then, so we will see what happens.

 

[91W350]

My first M1008 would puddle everyplace it went. The mechanic that had been working on it for the Sheriff's Office had pasted the pan and everything else together with enough RTV to do five 6.2 engines. It was still puddling when I bought it. They had been using it for a jail service truck and everyplace it sat around the jail, there was puddle marks. It was not the pan or seal at all, it was not oil, it was dirty diesel fuel. The lift pump was seeping, the fan was blowing the droplets back on the pan rail and they were running to the back of the block and dripping off the back of the pan. It sure looked like a rear seal was leaking. I got lucky and was parked on a steep upslope, trying to figure out how to mount a winch and saw it drip. It took a few minutes to figure out where it was coming from. Glen

 

[68impalass]

One more thing to check. See if your IP throttle is dripping diesel and running down the back of the block and out the hole in the inspection cover.

 

[Rich Johnson]

What is an IP throttle?

I drove it today went about 15 miles and no leak. Then about 8 miles, and it left a 4 inch puddle. Then about 15 miles back to radio shack, no leak.
Seems strange.

Im driving at about 60mph with 285 tires. I have a hard time not hitting 65 becuase the truck wants to go that fast or more, if Im not constantly keeping my foot off the gass I find Im doing nearly 70.

 

[68impalass]

I meant the injection pump throttle shaft seal. After these engines sit for a long time the shaft seal (o-ring) stops sealing, the diesel fuel leaks and goes down the engine valley to a hole in the back of the block. It then drains down the back of the block and out the hole in the inspection cover. Just a possibility to look at.