Confirm my diagnosis?

[Speedwagon]

1992 3.0, misfire when cold that goes away after 10-60 seconds, often(but not always) smoke on startup when it's been sitting for awhile(at least a few hours), mysterious coolant leak that I can't find, and obviously goes through some oil because of the burn on startup. Occasionally, it sticks at a high idle as well, but not very often.

Checked the plugs(well, all but the hard to reach 2 on passenger side), and the #3 driver's side looked nasty. It had a reddish-brown crust along the rim of the threads, but the center looked fairly normal.

I'm leaning towards a bad head gasket at this point, around that cylinder. I just did the HG within the last year on this truck, so I dunno what happened here, but it seems to be bad.

Thoughts?

 

[bobbywalter]

maybe the head was also cracked minimally and is aging along on schedule.

 

[Speedwagon]

maybe the head was also cracked minimally and is aging along on schedule.

I don't believe I had it pressure tested, but I did take it to a shop and they did an once over on the heads when I did the gaskets. Had no reason to believe it would be cracked at the time.

 

[kawasakiman27]

sounds to be a good diagnosis to me. A once over on the heads isn't a smart idea considering you can't always see the cracks. I'd suggest turning the heads into a machine shop for full inspection and rebuild (or you could get a pair of reman ones for cheap like I did for $200). My truck had a mis on startup sometimes (when I let the truck sit for awhile) but I already knew the gasket was leaking. As for the oil burning on startup I'd have to suspect bad valve seals. Did the you replace the old seals when they did the head gasket? Oh, and one more thing, that reddish brown crust you talk about is part of the head gasket material I think because my 3.0 had that crap all throughout the cooling system when mine blew. That cylinder on the driver side rear is the number 6 cylinder and thats the same one that blew out on mine. I'll post a pic of the old gasket in a little bit, i just replaced them along with the heads last week. Hope this helps.

 

[Speedwagon]

sounds to be a good diagnosis to me. A once over on the heads isn't a smart idea considering you can't always see the cracks. I'd suggest turning the heads into a machine shop for full inspection and rebuild. My truck had a mis on startup sometimes (when I let the truck sit for awhile) but I already knew the gasket was leaking. As for the oil burning on startup I'd have to suspect bad valve seals. Did the shop replace the old seals when they did the head gasket?

They were supposed to replace the valve seals. I had the head gasket set, and left it at the shop for them to replace the seals. I did the actual work on the engine though. The truck started smoking on startup about a month after I had them do the work on the heads. Called them, and they told me the only thing they could do was to give me some new seals to do myself, or bring the head into them. I didn't really want to take the head off at the time, since I had just put it back on!

 

[kawasakiman27]

take them to a machine shop, you'll be way better off.

 

[kawasakiman27]

keep us posted on how things go.

 

[Rearanger]

Possible option for you:
http://www.cylinder-heads.com/

One other comment I'll add is that proper torque is very important. All head bolt threads should be cleaned, even chased with tap, and small amount of oil used on threads for re-install. Engine deck also needs to be cleaned with acetone and be perfectly clean of old HG, rust etc. Not that you didn't do that, but just a reminder.