LS 5.3 smoking

justjeepin86

justjeepin86

Well-Known Member
Joined
Jul 9, 2005
Location
Winston-Salem, NC
I have a friend with a 200k mile tahoe with a 5.3. Smokes a lot at startup then fades. I know typically this comes from the valve seals. He wanted to know if it was worth replacing them. Is that the likely culprit and will I run into much trouble doing this in the chassis? I have never touched an LS platform before.
 
If you think it's the valves, I'd find a low mileage set of heads and swap them out.

Could find a set of take-offs or even some at LKQ for cheap. It's probably easier and cheaper than changing all valves and seats.
 
Didn't say what year, but besides the possibility of leaky valve stem seals there are some PCV valve issues know to cause smoking on startup. Replacing the PCV with the newer style is the solution IIRC.

With 200k miles, you've got the possibility of either. PCV stuff gets sludged up, and the higher mileage blowby can tend to make things behave worse by shoving more oil into the manifold, etc.
 
Last edited:
Fabrik8 said:
Didn't say what year, but besides the possibility of leaky valve stem seals there are some PCV valve issues know to cause smoking on startup. Replacing the PCV with the newer style is the solution IIRC.

With 200k miles, you've got the possibility of either. PCV stuff gets sludged up, and the higher mileage blowby can tend to make things behave worse by shoving more oil into the manifold, etc.
Click to expand...
Hmm, that's a good place to start. Thanks
 
I think you can replace the valve stem seals with the engine in the chassis. Can't remember what's involved or needs removing. Need a spring compressor and one of those spark plug air hose adapters to provide pressure to keep the valves for dropping.
But I'd take a long, hard look at the PVC first, because it's easier and just as likely. Should be plenty of info around the 'nets about the PCV issue.
 
Check the casting number on the heads. If they are stamped 706, i'll tell you a sad story.
 
You guys are all wrong....






It's two stroke :D
 
There's a cheater's way to changing the valve seals without having to add compressed air to each cylinder as you change them, if a compressor is not available. Just bring each cylinder to TDC as you're working on it, and if the valve drops, it'll only go a little ways before contacting (softly) the piston, instead of falling all the way into the engine. The only difficulty lies in if you have a stubborn valve lock that doesn't want to turn loose...a rubber mallet is your friend. You can tap each valve spring retainer a couple times before putting the compressor on to loosen the locks...just don't whack them too hard. It would bring the suck to have to chase down your retainer, spring and locks, then go fish a valve up out of the cylinder. o_O

But this is a very easy job to do with the engine still in place, should you have the correct spring compressor on hand. Chances are you could get one of the cheap ones from the parts store that cranks down from the top and clamps the spring. Easy for stock springs, but a huge bitch for any sort of spring that has some ass behind them, i.e. solid roller, solid flat tappet, etc.

61mQuCW9BNL._SX355_.jpg




This is my preferred spring compressor...I love this one.
710-62370.jpg


I can change springs/seals with the heads installed, no need for compressed air, valve locks come off easily with a couple gentle taps with a rubber mallet, etc. etc.
 
They have bolt on LS spring compressors that are totally worth it.
 
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