My buddy blew a head gasket on his 4runner ('95, 72k miles, 3.0) a few weeks back. We finally got around to replacing them this weekend - both gaskets, and anything else that was easy to get to. It was the #1 cylinder that went out, which I thought was strange, but whatever. We got it all buttoned up tonight, and it fired right up. But very quickly it started blowing white smoke out the exhaust. There's also a fair amount of steam wafting up from the back of the engine. I let it run for about 5 minutes until it got up to temp. No signs of overheating, and it ran real smooth. Just lots of burning coolant. No coolant coming out of the TB, and no leaks that I can see.

I'm sorta sick of this thing after about 16 hours of labor, so I just went home. Won't have access to the truck until Wednesday, but I'm trying to get some ideas of things to look for when I go back. First idea is that maybe this is still all residual stuff in the exhaust. Is 5 minutes enough for everything to burn off? Second idea is that coolant is leaking into the intake manifold somehow. But I traced all the lines and can't figure out where, and searching on here suggests that there really isn't anywhere it could be doing this. Third idea is that the new HGs are blown, and/or the heads are warped/cracked whatever. We didn't have the heads check out or anything, so it very well may be. Compression check time?

Any ideas are appreciated. The truck is about an hour away from me, so I want to have all my ducks in a row for the next time I make the trip out there. Thanks.

 

it took me an hour to get most of the water/coolant out of the exhuast idling and revving it time to time. but mine was severe, the noob last owner drove around with a blown headgasket, left tons of water in exhaust. drove around a bunch then the smoke was gone

 

If the truck was overheated my vote would be a warped or cracked head.

 

the cat will be full of of coolant. After i did my headgaskets (i put headers on at the same time) i drove to the exhaust shop open headers for them to put a new exhaust on.

i brought my old cat with me. I picked up a day later and got half way home (warmed up) and it started spewing white smoke out the back like in spy hunter. FREEKED me out! but by the time i got home it had tailed off to nothing.

 

Yea, it can take a while to burn out all of the residual coolant. Drive it around for a while (pay particular attention to the temp gauge), and see if it clears up before you tear it all apart again. The last one I replaced HGs on took a lot longer than 5 minutes for all of the resdual coolant to finally burn off.

 

OK, thanks for all the reassurances guys. I told my friend to start it up and just let it run -- after about 15 minutes all the smoke was gone and it's running like a champ. I'm gonna give it a once over tomorrow before I call it officially fixed, but it's looking good.

 

What do you think is going on there? If the steam started up right away, it probably isn't a coolant leak, and it might be steam leaking out of the exhaust somewhere, and the back of the engine is where it shows up.

But if the steam at the back of the engine only appeared once the engine was warm, you could have a leak there (in addition to whatever is giving you white smoke out the tailpipe). At the back of the engine is a fist-sized chunk of aluminum into which the various temperature sensors are mounted. You could have a leak where that chunk mounts to the intake manifold (or a dozen other places back there). But you should be able to find a wet spot on the back of the engine (not that you can see back there) once the engine cools down.

Do take things step by step, and try to investigate the simpler things (like cooking all the water out of the exhaust system) before you contemplate something tough (like removing the heads).

 

Yes, Zlathim is right. it took 15-20 minutes for mine to run clean. Also, because I didn't ask on this forum, after I did my 3.0 HG last fall, I started it and it blew white smoke like crazy. So after 2 minutes I shut it off and took the whole thing down again. Then put it back together, many more hours of needless work. A mechanic friend fortunately had been told of my plight and advised me that the exhaust system needed 15-20 minutes to burn clean, so I let it blow after the 2nd HG. Otherwise, I'd still be building, I guess.

 

OK, just to tie up this thread, I drove the car around a bit last night and everything seems to be in order. I'm guessing the steam coming from the back of the engine was just leftover coolant leaking through the exhaust donuts back there, or maybe stuff that dripped onto the exhaust while we were working. No leaks, no smoke, she's good to go. Thanks for helping prevent me from tearing it all down again folks