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Addressing 6.2L Oil leak(s)

B.barket

B.barket

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Jul 20, 2016
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S-West Ontario Canada
Hey guys.. My 84' 6.2L Diesel Jimmy is bone stock.. Its in good shape and runs beautifully.. The engine has been well cared for but there is some inevitable oil leakage that I would like to address.. This is my first diesel so please forgive this very elementary question.. Where are the most likely sources of oil leakage on a 6.2L Diesel?.. I'm an average wrench turner at best, but I certainly don't mind getting after things like this on my own.. I bought this truck to tinker with and get my hands greasy anyway, so what better way to blacken my hands than chasing oil leaks I suppose.. I'm not loosing a significant amt of oil.. But its obvious that its been leaking for years, as there is enough gunk spread around the motor from top to bottom that I can't definitively say where exactly all of the leaks are coming from.. The more info the better from you guys who don't mind taking the time would be fantastic.. Pictures and any tips or tricks for doing the work is appreciated.. Like the easiest way to remove parts for access? - what needs to be removed and what doesn't to get at a seal or gasket? - Must have tools? -Gasket application best practices? etc.. I'm sure any other 6.2 owners who stumble across this thread will appreciate it too.. So thanks in advance for any info.. And since I haven't yet posted a pic of my truck on the forum since joining.. Here's one!..

 
Nice truck!! 6.2L's are like Harleys...if they ain't leaking they're empty!
 
I had a leaky 6.2 and I changed my cdr valve and boom no leaky. I'd wash the nasty thing first then run it. See what's fresh oil.
 
I've posted about my 6.2 being a leaker,from several places,I've nicknamed it "The Valdez"..--one oil leak is the rotted oil pan I haven't been able to replace myself that I keep patching up,and it has another elusive and potentially dangerous leak coming from the area of the rear drivers side head--cant tell if its the valve cover or not for sure,it almost looks like it oozes out of the head gasket area ,and the oil drips right on the exhaust manifold and pipe..

It's not a "gusher",it varies between losing a quart in only 50 miles,to as much as 200-300 miles..sometimes it seems to stop leaking on its own,then the next time I look,everything is covered in oil again..

I have washed the area off with oven and brake cleaner in hopes of pinpointing where it originates,to no avail..it is not the oil sending unit,that is bone dry,so is the valley under the intake manifold,which I hear is a common place for oil that leaks out around the injector pump and collects there--then gets blown back or gravitates to the rear of the engine due to the slight angle it sits on the mounts (lower in the rear)..and makes it appear its coming from somewhere "back there"...another spot is the vacuum pump where it goes into the block..mine is dry there too..

Since the "leak" isn't steady and sometimes almost stops,I suspect my CDR valve could be to blame,maybe its letting crankcase pressure build up ?....but 70 bucks for a new one is not in my budget,for a part that may not do a dam thing to help it...

It is more likely the 15W-40 oil is now much thicker being winter and cold,and takes longer to thin out enough to leak, from wherever the oil comes from..

The "right" way to fix my leaks would be to yank the engine right out,replace the oil pan,valve cover gaskets,and "might as well" replace the right side rotted exhaust manifold thats ready to crumble,and do both head gaskets,remove the glow plug that wont come out while the heads are off,and it would probably need a valve job too,---where does it end ?.

I'm not really that fond of the 6.2 and after all that work & expense. it would probably toss a rod or something a week later..that's if I didn't find cracks in the main bearing webs first,which would negate doing any "repairs" to it..

My first inclination if I had to pull the engine to fix all that,would to leave the diesel out and replace it with a gas engine,if the truck was worth doing all that work-(and I could find a carbed V8 for it for under 500 bucks that isn't junk).....and its not really worth it,its rusted and getting long in the tooth everywhere..most everyone else would have scrapped my truck long ago..

I just keep it running best I can and full of oil,and hope it doesn't scatter on me far from home..pretty soon it'll likely be downgraded to "yard truck" status and only used to plow my driveway..unless I hit the lottery and can afford to buy all the sheet metal,and pay someone else to "restore" it..
 
diesel4me said:
I've posted about my 6.2 being a leaker,from several places,I've nicknamed it "The Valdez"..--one oil leak is the rotted oil pan I haven't been able to replace myself that I keep patching up,and it has another elusive and potentially dangerous leak coming from the area of the rear drivers side head--cant tell if its the valve cover or not for sure,it almost looks like it oozes out of the head gasket area ,and the oil drips right on the exhaust manifold and pipe..

It's not a "gusher",it varies between losing a quart in only 50 miles,to as much as 200-300 miles..sometimes it seems to stop leaking on its own,then the next time I look,everything is covered in oil again..

I have washed the area off with oven and brake cleaner in hopes of pinpointing where it originates,to no avail..it is not the oil sending unit,that is bone dry,so is the valley under the intake manifold,which I hear is a common place for oil that leaks out around the injector pump and collects there--then gets blown back or gravitates to the rear of the engine due to the slight angle it sits on the mounts (lower in the rear)..and makes it appear its coming from somewhere "back there"...another spot is the vacuum pump where it goes into the block..mine is dry there too..

Since the "leak" isn't steady and sometimes almost stops,I suspect my CDR valve could be to blame,maybe its letting crankcase pressure build up ?....but 70 bucks for a new one is not in my budget,for a part that may not do a dam thing to help it...

It is more likely the 15W-40 oil is now much thicker being winter and cold,and takes longer to thin out enough to leak, from wherever the oil comes from..

The "right" way to fix my leaks would be to yank the engine right out,replace the oil pan,valve cover gaskets,and "might as well" replace the right side rotted exhaust manifold thats ready to crumble,and do both head gaskets,remove the glow plug that wont come out while the heads are off,and it would probably need a valve job too,---where does it end ?.

I'm not really that fond of the 6.2 and after all that work & expense. it would probably toss a rod or something a week later..that's if I didn't find cracks in the main bearing webs first,which would negate doing any "repairs" to it..

My first inclination if I had to pull the engine to fix all that,would to leave the diesel out and replace it with a gas engine,if the truck was worth doing all that work-(and I could find a carbed V8 for it for under 500 bucks that isn't junk).....and its not really worth it,its rusted and getting long in the tooth everywhere..most everyone else would have scrapped my truck long ago..

I just keep it running best I can and full of oil,and hope it doesn't scatter on me far from home..pretty soon it'll likely be downgraded to "yard truck" status and only used to plow my driveway..unless I hit the lottery and can afford to buy all the sheet metal,and pay someone else to "restore" it..
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^^ Thanks diesel4me.. Good write up on what you've done and might do.. That's the kind of info I'm looking for and that I think other 6.2 owners will enjoy reading about.. Advice on what to do and stories like yours discussing what has been tried are great.. I've considered giving the engine a full shampoo to see if that helps to pin point leak points but I'm just not sure about how sensitive these engines are to being washed.. Mine runs well and I'd hate to screw it up by washing it.. does anyone have thoughts on shampooing a 6.2?.. Any stories good or bad about scrubbing down one of these motors?..
 
Washing it off cold wont hurt anything,I would avoid spraying cold water on a injection pump that was at operating temperature though..

Remember high pressure from a pressure washer can actually penetrate seals and any voids in a gasket (or perhaps make some!)--so go easy if you use high pressure...I used dollar store oven cleaner and it works well,then used brake cleaner to spray off the oil that drooled down while I was lying under the truck trying to pinpoint the source,but didn't have much success--my sight up close sucks,even with reading glasses on..

In my trucks case,a clean truck is a RUSTY ,rotted out truck!--the places where the leaking motor oil and an ATF drip from the T-case has blown back and collected on the frame & underbody are like new,while everything else where its dry, is rusty and rotten...

I think your better off leaving it oily,especially in a salt belt state.....also the bolts I've had to remove that were coated with oil came right out easily,while others that were not had heads whittled down enough so sockets wont grab them,and often bust off instead of unscrewing when I'd use a bolt out extractor to try and loosen them..
 
I'm up in Canada so there's no shortage of snow, salt and all of the other nasty weather issues that soooo many square bodies have fallen victim to.. It took me a long time to find a middle of the road clean unit because the majority of them up here have been destroyed by our winters.. By middle of the road I mean a reasonably clean stock truck that wasn't either a $30k trailer queen, a rotted mess needing full restoration, or lifted and heavily modified.. The good news on that front is that my rig is a fare weather vehicle only and will never see snow again.. At least as long as I own it.. I'm gonna take a swing at shampooing and then I think I'm gonna start with the valve covers.. I have been suspicious that the passenger side cover is one on the main culprits of the leak.. After a little tour around the internet I've seen discussions indicating that the valve covers aren't necessarily easy to remove but not hard either if you take your time and are careful when moving the fuel lines to get he covers off.. It's also been noted that the intake doesn't need to be removed to get at them.. Any thoughts on the method of removing the valve covers?.. Is RTV the ideal product for sealing them up when reinstalling?..
 
I've resisted attempting to remove the valve covers on my pickup's 6.2 because the injector lines will likely twist off and break instead of unscrewing..they are rusty--but not to the point they would start pissing fuel (I hope !) yet..just assume add oil and leave them be,than create a big headache during the worst weather when I need the truck most to plow with..

So,I'm not much help as far as "how to" --I have read the intake doesn't have to come off too,but it looks to me it would be a lot easier to take the injector lines off the pump if the intake was not in the way..the injector lines have clamps that are held down by the intake bolts so some of them would have to come off anyways,and when I tried to loosen one of those bolts,the clamp wanted to turn with it,and threatened to kink the steel line..
I'm just going to run it until one rusts thru and starts spraying--if the rest of the truck doesn't have a major issue before then..

I read RTV is used factory with no gaskets,but you can buy gaskets aftermarket if you desire..the "Right Stuff" RTV by Permatex seems to be the choice of most mechanics,its not cheap though,and others may work just as well,but I'd want to use whatever will prevent you from ever having to do the job over again,seeing its such a suck pill to do the valve covers on a 6.2..(at least in comparison to an old school small block,that can be done in less than a half hour easily)..
 
Removing the intake is only helpful if you want to remove the lines. When I redid mine I disconnected the injectors and gently bent the lines upward until I could slip the cover out from underneath. Install gasket, torque bolts, and then gently return lines to original orientation. @diesel4me has a good point though, breaking a line is a real possibility, and something that I did on a different engine that I worked on. Check for rustiness before you try your hand at bending them. If you have to replace one, make sure that it is exactly the same length as the old ones, or the engine timing will be off.

When you disconnect line(s), you will then have air that must be bled out of the injection system. If you do just one bank at a time, this isn't a huge deal (start it on the 4 undisturbed cylinders and let it run until the other 4 bleed themselves out). If you have air in all 8 lines, or if you replaced a line entirely (so it's full of air) there is a bleeding procedure that involves cranking for a while before fuel finally reaches the injectors and it starts. Much more headache than just changing a valve cover, it can be a real headache when the lines break.
 
campfire said:
Removing the intake is only helpful if you want to remove the lines. When I redid mine I disconnected the injectors and gently bent the lines upward until I could slip the cover out from underneath. Install gasket, torque bolts, and then gently return lines to original orientation. @diesel4me has a good point though, breaking a line is a real possibility, and something that I did on a different engine that I worked on. Check for rustiness before you try your hand at bending them. If you have to replace one, make sure that it is exactly the same length as the old ones, or the engine timing will be off.

When you disconnect line(s), you will then have air that must be bled out of the injection system. If you do just one bank at a time, this isn't a huge deal (start it on the 4 undisturbed cylinders and let it run until the other 4 bleed themselves out). If you have air in all 8 lines, or if you replaced a line entirely (so it's full of air) there is a bleeding procedure that involves cranking for a while before fuel finally reaches the injectors and it starts. Much more headache than just changing a valve cover, it can be a real headache when the lines break.
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Great info campfire!.. Another question if you don't mind.. While I'm in there.. I also have a bad a/c compressor and need to remove it to replace it with a new one that I was given when I bought the truck.. I may as well do all of this at the same time.. If you or anyone else knows the process for removing the a/c lines from the compressor and the compressor itself.. Is there much to it?.. Do I need to drain the coolant from the a/c system first or anything?.. Or is it best just have a professional change out the compressor for me?..
 
Removing lines is pretty straight forward. So is replacing the compressor. Charging the system afterwards is a little bit of an art form, but easy enough that Autozone/NAPA/etc all sell kits to do it at home. Yes, the pro usually does a better job in most things, but that doesn't mean that hiring things out is always the best call. YMMV.
 
I have read the injector lines also have a glass like inner lining that can fracture if you bend them,and let the debris get into the injector...another reason I'd rather not disturb mine!..:eek:..
 
diesel4me said:
I have read the injector lines also have a glass like inner lining that can fracture if you bend them,and let the debris get into the injector...

Dear lord.. Really?!.. Geeezzz!.. I just want to replace a simple valve cover gasket.. Why must there always be problems?!.. haha!
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You know, I was told that many years ago the same thing about a Ford 6.9. I was suspicious, but had no real reason to question the statement at the time. However, I've never heard it since, and now suspect it was either just a complete hoax (old wives tale) or simple misunderstanding at the time. And specifically I've never heard that about GM diesels, and myself have bent the lines a little with no ill effects (just don't kink), so I think you are safe, at least on that point.
 
BadDog said:
You know, I was told that many years ago the same thing about a Ford 6.9. I was suspicious, but had no real reason to question the statement at the time. However, I've never heard it since, and now suspect it was either just a complete hoax (old wives tale) or simple misunderstanding at the time. And specifically I've never heard that about GM diesels, and myself have bent the lines a little with no ill effects (just don't kink), so I think you are safe, at least on that point.
Click to expand...

This is my observation for my one truck. But it's hard to generalize from just that once.
 
B.barket said:
Dear lord.. Really?!.. Geeezzz!.. I just want to replace a simple valve cover gasket.. Why must there always be problems?!.. haha!
Click to expand...

Yep. This is one of the downsides to this IDI design. My other leaky engine is getting a simple Lucas Oil treatment because I haven't yet felt like doing it again. :rolleyes:
 
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