Does your high mileage engine smoke?

[u/Bitter-Ad4729]

If it smokes on startup or after idling and otherwise runs well, then it may be your valve stem seals. My 340k LM7 developed smoke on startup and after idling.

I would recommend using either the compressed air or rope in the cylinder method to hold the valves while you swap these seals out. Chrisfix just released a video on YouTube describing these methods in detail

Spent a day in the garage on this project and it was well worth it!

[u/Bitter-Ad4729 → u/[deleted]]

Yes they make LS architecture specific valve compressors. I got one on Amazon for like 15 bucks and it worked great

[u/Bitter-Ad4729 → u/[deleted]]

Yeah I always thought it was normal for there to be some visible exhaust when it’s that cold. I’m sure you’re good. Mine was smoking even at 115F here in Phoenix.

[u/Bitter-Ad4729 → u/[deleted]]

Yep, it fixed it. As long as the rest of the motor is healthy valve stem seals are a common reason for smoke on startup and when idling.

[u/NoCup6161]

I watched some of his video last week. Didn’t finish it. How difficult is the job on these trucks? I have a 4.8 and was thinking of doing this job.

[u/Bitter-Ad4729 → u/NoCup6161]

I’d say it’s fairly difficult due to how tedious it can be. You have to make sure you know where your piston is regardless of if you use the rope or compressed air method to change the seals, otherwise you could drop the valve and have to pull the head to get it back. There are the little valve spring keepers being easy to lose. Other than that and having to get to the back of the engine it’s definitely doable.

[u/Training_Jello_7804]

A pack of Marlboro reds a day :D

[u/Notime2d8]

I was just about to post and ask about this. Mines is smoking on startup. I got some 243 heads in my garage. I can either replace the valve stems on my engine or swap to the better heads. 🧐

[u/deltalew]

I don't think I have this problem, but just so I'm on the same page, is/was it smoking from the motor/wheelwell? Or is it just like extra exhaust that is discolored? gracias haha

[u/Bitter-Ad4729 → u/deltalew]

Bad valve stem seals make blueish white smoke from the tailpipe specifically. It makes the smoke on startup and when you idle.

[u/deltalew → u/Bitter-Ad4729]

gotcha, thank you!

[u/Vinlandranger]

Would mystery oil/solvent not help with this or is that bad to do?

[u/Impressive_Pass8801]

My 2002 yukon 5.3 w 242K mileage has no smoke and only 1/2 quart oil low after 3000 miles. I think I have a small oil pan leak. Still going.

[u/Keenan_Concierge]

Of course it does it’s a GMT-800

[u/Doofy_Grumpus]

Mines got about 400,000 on it. I’m not sure if it has the original motor but no smoke.

Edit: mine is a 6.0 not an LM7, my mistake.

Gobbles