Head Gasket Leaking?

[dmtaurus]

I changed spark plugs 3 weeks ago in my 06 TB, 91000 miles. Plugs looked good and I torqued the new plugs to spec. Last Monday it started to miss and run rough. After warm up the missing tended to go away, but the service engine light came on. I pulled plug #1 to start an inspection and found that #1 plug was wet and stark white on the porcelain, there was moisture in the spark plug well, and the top of the piston was wet. I figured it was a leaking head gasket. I pulled the oil stick and thankfully the oil looked normal; no milky color; bottom end bearings probably saved. I think I caught it early.
I took it to the Chevy dealer for his diagnosis. He said that #1 plug had over 4700 misses recorded and that other cylinders had random misfires. He drove it extensively and he cannot get it to miss or run rough. He said that the 4.2 in the 06 year had little track record of headgasket problems. He also said that there is no way that coolant can leak into cylinder #1 because of the water passage design. I am not so sure about that one. So he is tending to not think it has started to leak though he is not ruling it out. Yet, he knows something is wrong and he doesn't want to return it to me till he knows what the problem is.
Anyone familiar with the block and head design on this engine, or the same experience on this engine? If so, please comment.

 

[Mooseman]

My guess would be the ignition coil seals are letting water into the plug wells and causing the misfire. Another thing, did you use ACDelco plugs (41-103)? This engine is VERY picky on plugs and only likes ACDelco. Could also just be a bad coil. Pull the #1 coil and swap it with #2 and see if the miss follows it. Make sure you wipe all the moisture out of the plug wells and use a bit of dielectric grease on the inside of the plug boots and seals.

The piston may be wet/clean because of the misfires and the gas washing it out. If you still suspect a leaking head gasket, do a compression test on the whole engine. If there is a leak, it will show there. There would have been other signs such as exhaust smelling of coolant.

 

[triz]

Plug one IIRC is the one up front. Most likely a very simple fix. I was having misfires after changing the plugs and it was because of the plastic trim right up front that was not allowing the coil pack to seat. With a panel trim tool I popped the trim piece off enough to allow the coil pack to seat properly. After that was done. Vroom no more misfire. Took us about 30 minutes to figure that one out.

 

[dmtaurus]

My guess would be the ignition coil seals are letting water into the plug wells and causing the misfire. Another thing, did you use ACDelco plugs (41-103)? This engine is VERY picky on plugs and only likes ACDelco. Could also just be a bad coil. Pull the #1 coil and swap it with #2 and see if the miss follows it. Make sure you wipe all the moisture out of the plug wells and use a bit of dielectric grease on the inside of the plug boots and seals.

The piston may be wet/clean because of the misfires and the gas washing it out. If you still suspect a leaking head gasket, do a compression test on the whole engine. If there is a leak, it will show there. There would have been other signs such as exhaust smelling of coolant.

Good questions. Here are the answers:
1. I used the 41-103 plugs because, like my Taurus, these engines like the factory plugs. And the now on-going Delco rebate on the plugs doesn't hurt either.
2. I was hoping against hope on the COP seal leaking. But when I pulled the plug I could smell the coolant, and unfortunately not gasoline. The moisture felt like coolant, and what did evaporate took a while to do so and left the slight, greasy feel, of coolant; it didn't feel or behave like water. Also, we haven't had any driving rains, or much rain at all, since I did the spark plug change, and I haven't washed the engine, so that, to me, ruled out water getting up in there.
3. The dealer did do a switch around of #1 and #2 coils to see if that would cause a misfire; it didn't.
4. In my conversation with the dealer, I wanted to ask if he did a compression test or cooling system pressure test, but I didn't. I'll ask him about them next time if he did, and if so, what were the results.

The one thing the dealer said that seems not correct is, "there is no way that the cylinder could get coolant in it because of the coolant passage design." I find that, frankly, hard to believe since each cylinder is going to have to have passages around the sleeve to keep them cool. Yet, I haven't seen the block and head mating surfaces for myself so I guess I can't say it with 100% certainty.

 

[dmtaurus]

Plug one IIRC is the one up front. Most likely a very simple fix. I was having misfires after changing the plugs and it was because of the plastic trim right up front that was not allowing the coil pack to seat. With a panel trim tool I popped the trim piece off enough to allow the coil pack to seat properly. After that was done. Vroom no more misfire. Took us about 30 minutes to figure that one out.

And that's a good point.
Yet I did use my Streamlite to light up the area and look closely to make sure that the COP was sealed all the way around; it was. And the boot wasn't cracked or torn. I was really hoping that was the culprit but I didn't see evidence of it.

 

[Mooseman]

Water can get into the wells from rain water dripping from the cowl. #4 coil has a higher failure rate because of this.

With these engines, anything is possible. It may have a low possibility of a coolant leak into the combustion chamber, it's not impossible. BTW, here's a very long thread of someone who did replace the head which ultimately ended in failure (caused by the machine shop's incompetence):
http://gmtnation.com/f24/4-2l-i6-head-removal-engine-restoration-4425/

We also can't discount the possibility that it's an issue with the block itself. A leak between the sleeve and the block at the top comes to mind.

 

[dmtaurus]

Wow! That was a story fit for a book!

As an aside, I called a radio show today out of Detroit, WJR, and talked to a couple of car guys about this. They said to check for a leaking injector. They reasoned that the injector could be washing the plug white. But they didn't have a comment for the wetness in the spark plug well. They did say that this engine doesn't have a history of cylinder gasket leaks. Not sure what to think.

 

[Wooluf1952]

I can see coolant getting into the cylinder from a bad head gasket, but unless the head is cracked, I don't know how it would get into the plug well.

 

[Mooseman]

Here's an idea. Send an oil sample to Blackstone and get it analyzed. If there is a coolant leak of any kind or a leaking injector, it will be in the oil. Coolant has to wind up in the oil if it's getting in the combustion chamber, it has to get past the rings and into the oil, even if it's a minute amount. Same for a leaking injector. In fact, I remember when an engine gets severely flooded that the oil has to be changed because it had so much fuel in it. A slight amount could be from the misfire. A higher amount would be from a leaking injector.

 

[xtitan1]

Don't they have those test tube kits for your coolant that changes color if your coolant has combustion gases in it (indicating head gasket leak)? I they're like $30 and do it yourself at home.


Google "Scotty Kilmer checking for head gasket leak" for the YouTube video

 

[NJTB]

Generally, if coolant leaks into a cylinder, there will be TONS of white smoke out the exhaust. If it leaks into the oil, you get the 'chocolate milkshake' on the dipstick.

 

[Mooseman]

Another test I just remembered is a leakdown test. If there is a leak into the coolant, it will show up with bubbles coming out the radiator filler neck.

 

[dmtaurus]

These are all very goods suggestions. I will probably be talking to the service manager tomorrow to see if they have determined the cause of failure. I think the cylinder leakdown test and the cooling system pressurization test would be the first tests to perform to verify major items. I guess what kind of concerns me is if the dealer is somewhat uncertain if he wants the job. Given the earlier mentioned thread about what the Marine went through with broken bolts in the block, a dealer may prefer to avoid this kind of job.
Is it a fact that the bolts break off in the block on these engines virtually every time the head is removed? If so I would think that GM ech support would have created a procedure to get broken bolts out without removing the block, say with using Easy-Outs.

 

[Mooseman]

I would imagine that dealers have the best of the best tools so they should be able to get broken bolts out fairly easily. The other guy was doing it in his garage probably with basic tools. As soon as the bolts broke, he knew he was over his head and the machine shop was able to get them out for him after he took the engine out. He did OK after that except that the machine shop botched the head rebuild and he gave up the truck. So sad because he was so gung-ho, doing videos, live broadcasts, texting while he was working on it. He made sure he had the right info and did it right. I think the whole forum was more upset than he was.

The dealer should give you an estimate and shouldn't deviate from it unless there is something much more serious, like a problem with the block or the head is shot.

 

[dmtaurus]

Well, I finally got the Trailblazer back. To summarize, the dealer kept it for a total of 6 days with 4 of those in trying to diagnose the misfire condition. When I talked with him on day 4 he said he could not detect a problem with it after spending 6 hours of diagnostic time and 60 miles of driving over those 4 days. He said on 4 mornings he started the engine from a cold condition and did not see any white smoke from the exhaust, as thought it could have a blown head gasket. He pulled all the spark plugs, switched cylinders 1 and 2 coil positions, and retested for a misfire condition; he could not find any problem. He said the coolant level did not drop. He did not do a coolant pressure test nor did he do a cylinder leak test. His reasoning was that he just didn't see a need because he said that each time he started and warmed the engine it "purred like a kitten". He said to take it and drive it, and if it started missing again to bring it in as soon as I could. For all his diagnostic work he charged me $0. That alone tells me that he is a dealer that looks to satisfy the customer.

For the last 2 days he had it I asked him to replace the fuel level sensor under the GM/NHTSA agreement and to replace the driver door BCM under the GM recall. He quoted me $150 +tax for the fuel sensor as my part of the replacement cost and, of course, $0 for the BCM replacement. When I got the bill it was $137, including the tax. Again, this dealer strikes me as honest and as one that looks for the root cause of a problem.

I've driven it the last few days and it does not miss. Time will tell.

And a round of thanks to everyone who read this saga and for the replies.

 

[Mooseman]

Quick, somebody call the National Enquirer. A dealer that didn't charge for diagnostics and charged LESS than quoted! Must be aliens! A dealer like that is worth it's weight in gold and is definitely worth your business.

Hopefully the problem has cleared itself up.

 

[dmtaurus]

I agree with you 100%. A dealer that is fair and honest is hard to find, no matter what the brand.

So far she's running good.

 

[mrrsm]

Two other places to examine: (1) If you don't have "Chocolate Milk" for Motor Oil evident after repeated sampling with your Oil Dipstick and... (2) You don't see Droplets of Oil floating around in on the surface of your Radiator Fluid when you open the radiator cap when the engine is cold ... then your Head Gasket has probably not failed.

The "Waist Foam" casting method used to make the I-6 Aluminum Engine Block allowed the GM Engineers to design Press-In Steel Cylinder Sleeves that are only 1.5 MM thick and since all liquids are essentially incompressible...if you had a crack in the cylinder... the presence of liquid suddenly arrived within the cylinder while the rotating assembly was in motion... that would almost guarantee a bent connecting rod at higher RPMS and of course, the engine would self-destruct.

 

[Mooseman]

Uh, this is like a 2 year old dead thread and said it was fixed by the dealer.

You into "necroposting"?

 

[mrrsm]

Sorry... I got my wires crossed... i though itt popped up somehow as something recent. I have just got to get to bed and get some rest before I become "Necrotic".