I've got a new smoking at startup problem. If the truck sits for about 40 minutes or more, I get tons of smoke from the exhaust and it idles rough, and I get more smoke the longer it sits. It's been doing this for about a week now. I pulled all of the plugs and they all look normal. It's a very light white smoke; it doesn't have the bluish tint and smell of burning oil. When the truck sits overnight, I get the smoke for up to three minutes while driving and it creates a huge cloud behind me.

I've been wondering if it's coolant. It's hard to say because I've developed a decent coolant leak at the timing cover that I've got to fix in a couple of weekends. I lose a quart of coolant about every 300-500 miles, but I'm pretty sure that this is due to the timing cover leak.

The smoke doesn't particularly have a sweet smell to it; it's hard to describe though. It smells kind of like burning WD40.

Any thoughts? In May, I pulled the upper and lower intakes and the right head (because an intake bolt broke off). I did not get the head milled before I put it back on since I wasn't pulling the other head as well. My first inclination was either a head gasket leak to a coolant passage or a bad lower intake gasket, but it runs fine after it stops smoking, and I can't find any strange fouling on a particular plug. The motor has about 75k miles on it.

 

well with it being a white smoke i would guess that it is a coolant leak into a cyl or two what baffles me is that it stops second guess would be the lifter seals are seaping its hard to tell with out being there

 

Are you certain your leak at the timing cover isn't allowing coolant into the crankcase or that the leak isn't actually at the coolant cross over passage at the front of the lower intake. If your leak is there...the failed or failing intake gasket could be letting coolant in through the normal intake runners. It may quit because heat expansion seals the leak into the air passages after the engine warms up.

 

That was one of my thoughts, but from the looks of it, the external leak that I'm seeing is definitely coming from the timing cover. But that sure doesn't rule out the intake leak. I may just pull and reseal the intake when I'm taking things apart in a few weeks.

 

After driving it for a another week, I pulled the plugs after letting it sit overnight. There wasn't any fouling, but the #6 plug was definitely wet. I tasted it (yummy) and it was clearly coolant. I did a compress test and found about 125 psi on all of the cylinders except #6, which was slightly lower at about 110-115 psi. I guess I'll do it right this time--pull BOTH heads, get them milled, and go ahead and replace the stem seals while they're convenient. O yeah, and that timing cover too...

 

Just as a follow-up to this, we finally got the Bronco back on the road this morning.

Pulling the heads revealed a blown head gasket to the water jacket on #6, cracks in the combustion chambers in #s 5 and 6, and blown out exhaust valve seats on #s 5 and 6. The machine shop fixed everything up pretty nicely.

We also discovered the source of the exhaust leak that I was never able to find, but could isolate with a rubber hose to underneath the plenum between injectors 2 and 3. The lower intake gasket on that side had a larger-than-normal hole cut for the exhaust passage from the head to the intake; in fact, the hole was so large that it extended above the top of the intake, resulting in a nice exhaust-burned color to the clearcoat that I had put on the intake after I had it tanked back in May.

I spent a lot of time tracking down that exhaust leak--I replaced the gaskets on both exhaust manifolds, replaced the crossover pipe (which is difficult with the plenum still on), and spent many hours examing and re-examining all of the exhaust plumbing. Only to find out that it was an internal passage which was being vented to underneath the plenum due to a defective gasket. Weird. At least it's quiet and on the road now.