Chevy K1500 gray smoke.

[navigator]

I know this should more appropriately go on GMTN but I'd rather talk to you guys about it. As many of you know, I recently purchases a spare truck, 1994 GMC Sierra 4x4 with the 5.7V8.
I got a really good deal on it but the guy told me he thought it might need valve seals eventually. He said when you first start it up of a morning it would puff a little white smoke but nothing else.

When I test drove it, the truck was cold, hadn't been cranked in several hrs and didn't smoke at all. I've been driving it as much as possible the past few days to check things out.

I've noticed when you first crank it if it has been sitting overnight it does have a little bit of white smoke . If you sit idling at a stop light it has a decent amount as you pull off. I don't notice it smoking at all while driving even if you romp on it pretty good, it runs good.

I knew it was loud when I got it, but they removed the cat and mufflers. I somehow didn't notice it when I crawled under it to check for leaks etc.

So no cat, no mufflers and it never gets over about 150 degrees.
Oil looks good, coolant looks good, levels are stable.
I'm getting ready to put new exhaust in it and a new Tstat.
Does anyone think the smoke is due to the engine never getting fully warmed up?
I'm thinking that possibly part of it could be it is never warming up and running rich but just wanted to get some ideas from the experts here. It also wouldn't surprise me if it was beginning to show it's age at 208k.

Also on exhaust, I was planning to just do a single exhaust but am debating true duals. I don't figure I would ever need the performance added but I really don't like the connecting pipe running right under the tranny and it would help it breathe.

Any thoughts or on duals? Would it be much of a gain for a hauler? I called one place nearby and the single exhaust will run <$400 and the duals about double that.

[v7guy]

white smoke says seeping head gasket to me, it's white cause of steam. Pulling the plugs will give you a better indication.
blue/grey smoke is usually excess oil
black is usually excess fuel


with that said i pulled the plugs on the ole GTO and she was pouring white smoke. The plugs looked pretty decently tan. I didn't realize that it was definitely a head gasket until it started blowing coolant out the spark plug hole onto my hand.

[navigator]

maybe it is gray, it does seem to have some smell as well.
Not long after I got it, I changed the oil and used synthetic 10W30.
I'm not sure if it is smoking a little worse after the oil change or not. I didn't drive it a whole lot before changing it and mostly noticed it in town the other day at stop lights.
I'm going to fix the exhaust and Tstat and drive it.

[jonbo2002]

if it smells kinda sweet, then its coolant. A buddy of mine said it smells like honey nut cheerios lol which actually seemed true.

[SmokeyMcBlazer]

could be that its running lean.

[DirtyBacon04]

So it only smokes for a little bit during a cold-start? If thats the case, I wouldn't worry too much about it. Seems fairly normal (for an old engine) to me. I assume, it being a 94, that it's got a carb? Check your plugs. Thats usually how I check my air/fuel mixture. A white burn on the plug means you're getting too much air and you're going to burn your pistons. Dark black/charred/wet obviously means too much fuel. If you've got oil on the plug, it's your rings. DISCLAIMER: My knowledge of carbs is based off of 4 stroke dirtbikes. Theory of operation is the same, so it should, in theory, translate well.

[navigator]

thanks guys, I took a closer look and it is more grey with a bluish tint at times. I think it is oil.
I've changed the oil and the front axle oil. Rear end, xfer case and Tstat is next then plugs, wires hoses and belts.

New exhaust went in this morning.

[dvanbramer88]

I assume, it being a 94, that it's got a carb?

It is a TBI system.

[navigator]

I assume, it being a 94, that it's got a carb?

It is a TBI system.

yup, it is TBI. I'll have to say though it was weird to look under the hood and see the doughnut shaped air filter.
I think the last truck I had with one of those was my 85 and 86 nissan pickups.
Our 94 ranger had the square box type filter

[Bcchevy]

Sounds like valve guide seals in the heads. How many miles?


Sent From The Unit

[navigator]

yes, I think that is the conclusion. It has about 209k miles.

Initially when I changed the oil (to synthetic) it seemed to smoke worse.
Now that I have run it with the synthetic a few days it seems to smoke less.
There was no cat/muffler on the truck when I first got it, could the new cat be "filtering" out some of the smoke or could the synthetic oil be cleaning deposits and reviving the seals? Maybe it is just my imagination. I can't imagine it getting any better. I'll keep checking on it but it seems to be getting better.