Left side oil leaks

[bmiszuk]

I've had a serious oil leak on the left (drivers) side for as long as I've owned my truck ('83 Suburban). I've replaced the oil cooler lines, oil sending unit (it was loose), and valve cover gaskets. The leak is visible on the back half of the engine, not towards the front. What else is back there that could be leaking? Can a head gasket leak oil? Sometimes I think it's from the intake gaskets but I've replaced them before. I'm now losing a quart every couple hundred miles and it's dripping off the left side of the engine. I figure I must be missing something big and obvious!

[john8662]

Valve covers are really difficult to seal properly. I wouldn't recommend gaskets for the valve covers, as these are normally cork, and won't retain torque.

For the valve covers I recommend RTV, and not just any RTV. The stuff you get in the toothpaste tube (squeeze) from most auto parts stores isn't up to the task here. Get "The Right Stuff" made by Permatex, comes in a cheeze whiz can. It's not cheap, but it does work well, and it's easy to apply.

Once your confident you've got the valve cover fixed, concentrate on the oil pan and related areas, they're hard to seal too, and I still recommend the right RTV here as well.

Check the Rear Main and front main seals on the engine.

As for the question about the head gasket's ability to leak oil, yes, this is possible, but not incredibly likely.

You may have to clean up things really well with some brake parts cleaner to kill all the fresh oil, then start looking again where it's coming from.

Another option is to buy a dye that you put in the oil that will help you determine exactly where the fresh oil is coming from.

In conclusion, leaks are just leaks, sometimes they're caused for other reasons, like the CDR Valve's inability to control crankcase pressure. Do some reasearch here on the forums in the form of using the search feature about CDR's and that will certainly shed some light on it's function and testing.

J

[bmiszuk]

Thanks John. When I resealed the valve covers I used a silicone sealer (not gaskets) and was pretty careful to get everything clean before that. I've never touched the oilpan and know it leaks some, but the serious leak is coming from up higher on the engine. I'll get a couple cans of brake cleaner and hose the engine down once the snow stops.

Good point about the CDR, I checked it a couple years ago but it wouldn't hurt to check it again. The vehicle has been sitting for 6+ months so who knows.

[bmiszuk]

Bad news. I crawled under the truck while it was running. It's dripping coolant and bubbling slightly from between the head and block right near the oil cooler lines.

At the very least, a bad head gasket. John, you said an oil leak from the head is unlikely. Exactly how unlikely? :)

I fear what I may find if I pull it apart. Strange thing is, except for huge oil consumption it runs well. The CDR and crankcase pressure checked out okay. Compression test I did a couple years ago looked okay.

[bmiszuk]

I've been reading old posts and found this from Robyn: "The head gaskets rarely leak oil. Have you checked the gasket on the oil pump drive"

Is the oil pump drive the same as the vacuum pump? The vac pump is one thing that I never considered.

[Robyn]

There is no pressurized oil that flows through the heads.
The only oil will be the drainback from the rockers.
This does flow down on each end of the heads at the front and back, but it flows back to the lifter chamber.
There is no oil along the bottom of the heads and block.
A really bad gasket could allow this to leak through But it is unusual.

Coolant and bubbles is not good though and is telling you its time to get it apart and fix it.

Keep us posted

Robyn

[john8662]

Is the oil pump drive the same as the vacuum pump? The vac pump is one thing that I never considered.

Short answer: Yes

More likely, the vacuum pump itself is leaking oil (from the pod side), if the leak is coming from that area that is...

As robyn said above, there is no pressurized gallery in the heads, but they can leak oil externally along the lifter galleries, and drain-back holes near the bottoms of the gasket.

I'd say from your description that it is probably your head gasket leaking the oil, probably on the bottom part where it drain back down into the block from the valvetrain.

At any rate, you've got an excuse to pull the head and investigate since you have an external coolant leak, again not so common, but more likely than the oil leak.

Also check the coolant blockoff plate on the back/top of head (or if yours has a glow controller there, cigar style).

[bmiszuk]

I'm gonna tear it down tonight while the weather is warm (working outside in the dirt). Can I leave the exhaust manifolds attached to the heads and deal with the (undoubtedly frozen) manifold bolts once the head is off the engine?

[john8662]

I'm gonna tear it down tonight while the weather is warm (working outside in the dirt). Can I leave the exhaust manifolds attached to the heads and deal with the (undoubtedly frozen) manifold bolts once the head is off the engine?

I believe so, I've always pulled the manifold bolts prior to head removal, but others I know leave the manifold on. Can't say specifically for your chassis, but I sure believe that there is enough room to do so.

J

[bmiszuk]

Looks like there's enough room to leave the manifold on, I'm going to try it.

I'm down to pulling the drivers side head but it's stuck. I've hit it with a small sledge and a block of wood but still stuck. What's the trick?

I have a tractor with loader, if that'd help.

[john8662]

There is a spot on the head's end where there is just gasket and a little space (on a corner). I just take a big flat screw driver in that area and carefully pry up till it starts to budge. When putting the screw driver in I make sure to put the driver in between the gasket and the head, not in between the gasket and the block. Once it starts to bugde (you can tell it's not seated any more) you can start pulling on that end with one hand and catch with the other (other end of the head).

[bmiszuk]

Thanks John. I got it off. I haven't cleaned it up yet but I notice the small cracks between the valves. Otherwise I didn't see anything obvious.

I have to remove the exhaust manifold from the head now but at least I can do that inside.

Besides cleaning the mating surfaces, should I do anything to the head or pistons or anything?

[john8662]

Just examine the old gasket really well so see where it could possibly leak, as you'll have it in hand to look at and know approximatly where it was leaking.

Clean up the head surface really well, as well as the block mating surface. This is extremely time consuming. I use a few heavy duty razors (kind that go in a scraper) keeping them square and abou ta 45 degree angle to the surface I'm scraping on. This gets all the small gasket material off the deck and head. You want it all back to bare metal.

You'll also need to tap the holes in the block to remove the old sealant from the holes. You need an M12 1.75 Bottoming tap.

If you can't find the leak, consider having the head checked out, manufluxed on that end, perhaps an external leak.

I'll still bet it's the gasket...