2005 Tahoe PCV Hose Routing

[Alberta Tahoe]

The Tahoe (2005 LM7) is giving that telltale sign of a plugged PCV system with a large cloud of blue smoke on startup. It's also leaking oil which is a condition that's getting worse.
Research points to the above condition.
I'm not necessarily asking for the repair procedure as I'm just going to pull the valve covers, starting with the drivers side and give everything in the PCV train a thorough cleaning.
That brings me to my question.
What exactly is the PCV hose routing? I ask because the web is full of conflicting information and much of that is tied to these engines being installed in vehicles other than what they were originally and the hose routing is modified to remedy the problem that plagues them. That would be in addition to the new and improved valve cover that GM specs in a TSB.
I've got:
PCV valve/fixed orifice hose from the L.S. valve cover to the intake plenum.
A hose to to the throttle body from the R.S. valve cover.
Is there a 3rd hose? Our hot rod LS3 has a hose from the valley pan to the intake tube but no such thing exists on this stock LM& (5.3)
There is more a curiosity adventure more than anything but this inquiring mind wants to know.
Thanks in advance.

 

[OR VietVet]

The Tahoe (2005 LM7) is giving that telltale sign of a plugged PCV system with a large cloud of blue smoke on startup. It's also leaking oil which is a condition that's getting worse.
Research points to the above condition.
I'm not necessarily asking for the repair procedure as I'm just going to pull the valve covers, starting with the drivers side and give everything in the PCV train a thorough cleaning.
That brings me to my question.
What exactly is the PCV hose routing? I ask because the web is full of conflicting information and much of that is tied to these engines being installed in vehicles other than what they were originally and the hose routing is modified to remedy the problem that plagues them. That would be in addition to the new and improved valve cover that GM specs in a TSB.
I've got:
PCV valve/fixed orifice hose from the L.S. valve cover to the intake plenum.
A hose to to the throttle body from the R.S. valve cover.
Is there a 3rd hose? Our hot rod LS3 has a hose from the valley pan to the intake tube but no such thing exists on this stock LM& (5.3)
There is more a curiosity adventure more than anything but this inquiring mind wants to know.
Thanks in advance.

You will never get the PCV system cleaned out on the D/S valve cover. You will clean it some but it will not last. When I see the clogged LS pcv systems signs, the smoke and the oil leaks, I am putting on a new valve cover, at least the D/S but always do both. Then fix the oil leaks.

 

[Fless]

If it's severely plugged you should be able to feel the crankcase pressure by removing the oil fill tube cap. I agree with @OR VietVet if it's that bad just do the new (& updated) DS valve cover.

 

[Scottydoggs]

my moneys on your valve seals are wasted. cant see the pcv being clogged cause smoke on start up.

 

[Alberta Tahoe]

You will never get the PCV system cleaned out on the D/S valve cover. You will clean it some but it will not last. When I see the clogged LS pcv systems signs, the smoke and the oil leaks, I am putting on a new valve cover, at least the D/S but always do both. Then fix the oil leaks.

Fair comment and I have no illusions as to what I'm contemplating will solve the problem. It's more along the lines will it alleviate the problem and then I have a direction on where to go. A cause and effect sort of thing.
It used to be, before any of these buggies existed (this generation of LM7 that is) that oil smoke on starting pointed to valve guides and oil smoke under full load indicated piston rings.
That said, is the PCV on these engines limited to the two lines? D.S. cover to intake and P.S. cover to throttle body or is there something more?
I'd like to address them all in the simplest way possible and then go from there.

 

[LsHart]

Updated valve covers

 

[Alberta Tahoe]

Other posts have popped up since I answered the first.
Especially the oil smoke on start up. Seems the clogged PCV will result in oil pooling in the intake plenum. Then it's ingested when next started.
To the poster that mentioned valve guides...yes sir. That was my initial thought. Then this whole PCV issue came to light.
Thus, my approach to picking the low hanging fruit, so to speak.

 

[TJ Baker]

If you get the valve covers off and they are full of gunk, do check for the Castech 706 head cracking issue. (If you have the 706 heads of course)

 

[OR VietVet]

If you get the valve covers off and they are full of gunk, do check for the Castech 706 head cracking issue. (If you have the 706 heads of course)

Very good call and warning.

 

[Alberta Tahoe]

Yes. 706 heads.
Interestingly that may be the problem with one of the other Tahoe's in the "fleet".
The 03 has two weak cylinders. 5 and 7 with one at about 70 psi cranking pressure and the other around 130. Doesn't appear to be a head gasket and the suspicion is a couple of burnt valves.
Not that it matters as that truck is due to be parted out and the carcass hauled off to the recycler.

 

[Alberta Tahoe]

Now, back to the thread title.
Is there a valley pan hose in these engines? Which would be a 3rd hose. I don't see it.
FTR, the crate engine LS3 we have does have one.

 

[mikez71]

I don't see a third hose in diagrams. Does the crate ls3 have a connection to both valve covers as well?

PCV Valve Hose: Service and Repair — 2005 Chevrolet Tahoe 4WD V8-5.3L VIN T Service Manual | Operation CHARM

Detailed repair manual for the 2005 Chevrolet Tahoe 4WD V8-5.3L VIN T.

charm.li

I wonder if that engine with low compression on 5&7, could have a gasket leak between cylinders? Not sure if that could cause burnt valves, since there is a fairly large difference in compression still..

 

[Alberta Tahoe]

I'll have to check the LS3.
It's been hot rodded and is in a 69 C10 so the original layout is just a memory. There may be something in the picture history though.
As for the head gasket, that was an initial thought although, as stated, the difference in compression kind of points otherwise.
If I can manage it (but doubtful) I'd like to pull that engine and do a refresh/rebuild. Then I'll know. It would make for a handy spare or easily sold.

 

[Fless]

Now, back to the thread title.
Is there a valley pan hose in these engines? Which would be a 3rd hose. I don't see it.
FTR, the crate engine LS3 we have does have one.

No. Just knock sensor pits.

 

[Alberta Tahoe]

No. Just knock sensor pits.

View attachment 486873

I figured as much.
Thanks for verifying.
If the weather in this part of the world settles down, I'll be digging into this on the weekend.

 

[RET423]

Stock routing is drivers side to intake plenum on top of the plenum, passenger side from throttle body to valve cover

My opinion on your smoke is standing oil accumulated in the intake plenum due to the vacuum pulling on the PCV valve exceeding the valves ability to deflect the oil mist in the blowby efficiently; a common issue on LM7 engines

The fix is to remove the upper plenum & poor the standing oil out it, then reinstall the plenum. Replace the valve cover if your PCV valve is not replaceable and install a sealed catch can inline between the PCV valve and the upper plenum vacuum port

At first the catch can will trap lots of oil so check it & dump it often.

Over time the cylinders will begin to burn off the oil coking that happened before the catch can and your oil control rings will begin to do a better job at regulating cylinder lubrication as your compression rings will begin to seal better which will reduce the blowby some

The amount the catch can traps will reduce over time as the blowby decreases so it won't require dumping as often.

Do not buy a catch can with a vent/filter to atmosphere, you want to retain the "Closed PCV System" that came on the LM7, a sealed catch is nothing but a much larger & more effective PCV valve, these engines need more volume in the PCV valve than the stock valves can handle; especially at higher mileage when the blowby is increasing the oil content in the crankcase vapor/blowby

Good luck!

 

[Alberta Tahoe]

The catch can seems to be popular approach. Before the high mileage (and well abused) hot rod engine in my Camaro was rebuilt, I incorporated one in an effort to keep the oil out of the intake as the blowby was excessive. It did it's job.
As for the Tahoe, I may possibly try that as well.
As for pulling the plenum, that's something I'd like to avoid. At one time, prior to getting educated on this whole LM7 PCV mess, I'd contemplated addressing what I thought might be valve stem seals. That too is a lot of work.
The PCV fix appeared easier.

To this point, all I've done is ensure that the hoses weren't plugged and that the orifice in the D.S. valve cover wasn't either (no proper valve). I unloaded a small amount of brake cleaner into it and then changed the oil.
The amount of smoke produced at start up seems substantially less although not gone altogether. I know the next step is to remove and inspect the inside of the cover. Maybe get the replacement although they seem to be unreasonably expensive. At least my preliminary shopping indicates that.

Interestingly, even before my "fix", it wouldn't smoke every time. Maybe 3 out of 5 starts which I found odd. Driving conditions were generally the same each time. That being a highway commute and then sitting overnight before another commute.