I'm new here gang, so hey! I gotta throw this one out there for some help. My daily driver '04 GMC cracked one of it's junk 706's at 135K. Tore it down to the short block had the junker repaired, both pressure tested and back together. Lasted another 50K started blowing clouds of white smoke on start up. Figured I either cracked the other head or same one again. Pulled the whole engine. Tore it down, thoroughly cleaned, honed, new rings, new rod and main brgs, oil pump, timing set, lifters and a set of reman 862's. 600 miles still randomly blows clouds of white smoke. I drive about 25-30 miles to work and then it's shut off for a full 24 hours. when I leave the next morning is when it seems to be the worst. I mean it billows a fog of white smoke and it chugs like it's hitting on about 5 cylinders. I tore it back apart thinking they might have given me some bunk heads but machine shop says they're straight and pressure tested fine. I don't get it. Any ideas? I'm ready to yank it back out and tear it down again to have the block magnafluxed, bored, new cam bearings and have the decks checked and surfaced. Other than that and having the heads torn down and reworked by someone locally, I'm at a complete loss. Help? Anyone?

 

Could be fueling issue. Any engine codes? An ECT failure defaults to -32*F & the PCM will dump gobs of fuel. Could be many things related to PCM codes if they exist. Also, PCV &/or EGR if not valve seals.

 

White smoke is usually coolant. You did use new head gaskets and bolts each time you tore it down?

 

I was thinking Valve seals too, surely new head gaskets were used so count that out. What is the oi level? What about the coolant level? What does it smell like? Burnt oil or sweet tea spilt on a hot stove?

Chad

 

No Codes. No EGR. It's coolant, but why? Oil level is good. I'll get a wisp of blue smoke here and there but I expect that from new rings. Yes on the new head gaskets, both times and new bolts. Let me throw this possibility out there. What about the deck surfaces on the block? I've been reading about RA #'s and that a minimum of 60RA is required with 40-50 preferred or cold sealability will be affected. Anybody run into this yet?

 

losing a very minimal amount of coolant so far but it is disappearing.

 

Please don't be offended by any of these questions, but I'll ask just in case. You sound like you know what you're doing.

You copper coat the head gaskets? Highly recommended

Clean out the bolt holes thoroughly? I missed this step, and stuff wouldn't seal up

Your replacement 862 heads have the notch by cylinders 3 and 6? If they do, and you used cometic gaskets they won't seal no matter how much you work them.

Is it worth trying a coolant additive as a last ditch effort to avoid tearing it all down?

 

No offense taken. I didn't copper coat the gaskets because everything I've read says don't. Bolt holes thoroughly cleaned. Brake clean, compressed air, ran old bolts all the way in, more brake clean and more compressed air. Notch? Can you be more specific? No Cometic. FelPro. Not a fan of coolant additives or "stop leaks" of any kind. Turned wrenches professionally for about 15 years before exiting for the Fire Dept. I'm not happy about having to tear it back down but, I want to be almost certain that when I do it's going to be the last time I need to and that I will resolve my problem. This has to be my dependable daily driver for another 5 years.

 

I attached a thumbnail of the notch. The older ls heads had them. 853's, some 241's, and some 862's. I don't think the 706 had it, which is why I thought of it. If your head gasket is for the original heads, this could be the issue. I spent hours researching head gaskets specifically for this issue. Sometimes it's so bad water just pours out the head gasket after torquing properly.

Totally understand not wanting to tear it down. Again. I personally like the copper coat, but I'm paranoid about gaskets. I've read about some who have filled the notch in with weld and then decked the head a few thousandths to get rid of it.

Just thought of one thing that might be worth checking as well. There is a coolant line that runs through the throttle on firebirds and camaros. If there is one in your truck, you can bypass it. Maybe it's leaking very slowly into your intake? Be easier to check than the heads.

 

Pretty sure my 862's weren't notched like that. My truck has a coolant line that runs across the front and just under the throttle. I don't believe there's any way that it could actually leak into it. I will look though. Have you had any issues using the copper coat? I'm really starting to wonder if I maybe got the decks of the block off a bit too much when I cleaned them up and that's why it's not sealing. I drove it around on Weds. Just short trips. Got a couple of very small wisps of blue smoke. I expect that from an engine with new rings. It never fogged white smoke. Went out yesterday to go to work. Again, very slight wisp of blue smoke. Drove, 27 miles to the Fire Station and parked it. It sat for a full 24 hours. Walked out this morning got in fired it up and it ran rough and chugged out white smoke. Something about trips over 20 miles and then being parked for extended periods. The heating and cooling cycles seem to allow leakage. The way it runs while it's doing this seems like it's doing good to be hitting on 5 cylinders. I may be wasting my time but, I'm going to pressure test the cooling system and maybe run a compression test or leakdown.

 

Sound like after it sits water is leaking into the cylinders. Hopefully you don't hydrolock your motor.

 

It's not a significant amount of coolant that is disappearing. I marked my coolant tank. Over a period of 650 miles now the level has dropped maybe 1/2". I changed my oil yesterday for the 1st time since it's been back together. Magnetic plug had a nice ball of crap on it and the oil was a pretty metallic color. Again, nothing unexpected. No sign of antifreeze mixing with oil either. I got my oil pressure back too. 35-40 at idle and 45-60 under acceleration. Solid 45 at highway speed. Pretty sure the filter was packed and causing the oil pressure to be low. I'm getting more and more convinced that I have a cold sealability problem and that the block decks are my cause. This engine has never been froze in the winter and has never over-heated. I've never (knock on wood) had a temperature related issue. I'm getting a head stud kit, tearing it down and having the decks surfaced, the block hot tanked and some new cam bearings installed. I may also have the heads surfaced just to be on the safe side. If it doesn't seal up after that then it becomes a core for a new crate.

 

I agree it sounds like lack of cold seal. I have very good results with copper coat. I put two coats on both sides of the gaskets. Don't spray the heads or block. That's where I think it causes people trouble. It melts in and fills in the minor blemishes in the metal. You can machine the heads but the block is a different matter. That's where I think it'll help.

The had stud kit is a good idea, because you can torque it more. Make sure to lube the nuts so that you get accurate torque readings. As an aside, even if just doing heads, I only go 100 miles on that first oil change, because that first filter gets plugged fast

 

Not sure if this was covered, but what do the plugs look like? Hopefully (upon diagnosing of course) you are providing enough coolant in the cylinders to isolate which cylinders are possibly being introduced to coolant. Another question, do you have access to a coolant system pressure tester? We use one here at Porsche man and it works wonders on finding ridiculously small leaks. About $130 for a good one (Mac Tools, Matco, Snapon, ect.)

 

Could the block be cracked and leaking coolant into the cylinders? If the engine has been rebuilt and different heads were used, IMO it points to something else. If it's missing that bad you should have some misfire codes.

Have you pressurized the coolant system and let it set over night to see if holds pressure?

The next thing I would do is a combustion leak test. It shows if there are any combustion gases in the coolant system.

 

I agree with LilJay, another simple test you can perform is put dye in the cooling system,
let it run for a while and see if you have dye in the oil. You can get a dye kit from autozone for about $15.

 

Darth, using copper coat on head gaskets, what's the most mileage you've put on an engine using that method? Only asking to try and get a gauge on the longevity aspect of using it. Anybody else here coating their head gaskets? I haven't pressure tested the cooling system yet. That's coming soon. Checked all my plugs. With only 750 miles on a fresh set, it's hard to get a good read. The #1 plug was the one that looked the worst at 400 miles. The rest of them looked the same. I'm surprised it hasn't set a misfire code too. I don't have any reason to suspect the block being cracked. It's never been frozen in the winter and never over-heated in the summer.

 

167,000. Granted, it wasn't an LS motor. I did a rebuild on a truck that had 361K on it, and I swapped the motor out for a bigger motor at 528K.

 

Nice. I did some more reading. I know the 862's with the cutouts in the center won't seal with MLS gaskets. BUT I read somewhere else that the coolant passages won't seal using MLS gaskets with early LS1 casting numbers 5339, 8806 and 9862 and that composite gaskets are the only guaranteed way to get them to seal with the only real draw back to using composite gaskets is cleaning up when and if you ever have to pull the heads again. Guess what I'm going to do to avoid another costly trip to the machine shop? Composite gaskets, copper coat and a stud kit. Thursday is the day for tear down and replacement. I'll get back to you on the success/failure of the project soon. Thanks for all the input everybody. Greatly appreciated.

 

Kudos to you for doing your homework and not just taking the first opinion that came along