Internal head gasket failure and it's signs... - GMC Terrain Forum
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post #1 of 24 (permalink) Old 12-30-2017, 08:31 PM Thread Starter
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Internal head gasket failure and it's signs...

Hi all,

I have experienced what nearly everyone who has ever had a GM vehicle with a 3400 engine may have experienced at least once, a head gasket failure, but, not the common type, and it was certainly slow developing. I hope in telling a little bit about the signs, that most can catch it early if they are experiencing the same issues as I was.

I've learned that there are actually 4 types of head gasket failures:

1. External leakage where you actually have coolant leaking out of your engine (This is the one that everybody expects).

2. Internal where coolant leaks into the oil (usually easy to figure out).

3. Internal where coolant leaks directly into cylinders and directly out the exhaust. (The most silent and slow occurring one that no one expects).

4. Any combination of the above.

The type I had was the 3rd one and it apparently had been present since I bought the car. Since I bought my second Nox, I had noticed that even after everything else was corrected, the engine still had varying RPMs and it kept setting off the 02 sensor at what seemed at random.

When I would connect Tech2Win, there was always an extremely slight misfire on cylinders 1 and 4, however, if you pulled the spark plugs, they looked clean. Also, just before the 02 sensor would go off, there would be a slight bump in the engine. I now believe this was coolant being passed through one of the cylinders directly into the first 02 Sensor. If you pull the sensor and clean it, their might be white water deposits left on it. This is a sign of gasket failure.

This went on for 7 months, until recently, the car had no heat, and, eventually the engine would try to overheat.

Now, take note, there was no mixing of oil that was occurring, and, any coolant passing through was passed directly to the exhaust manifold.

When the leak got bigger, because pistons can act like an air compressor, they pushed air into the coolant system and were displacing the coolant causing the engine to overheat...... Just before this started to occur, there would be some puddling of coolant (it will look like condensation) at both before and after the muffler.

Also, note that if this kind of failure is happening, there will be almost no loss of power or any other signs until the vehicle goes into "limp home" mode.

I advise that if you are experiencing any of the prior tell-tale signs such as extremely slight rough idle/misfire and/or if the 02 sensor with "Catalyst Efficiency Bank 1 Low" code, even after replacing all the parts, have a compression check done immediately.

There will be no mixing of coolant with oil or any other signs usually with this type of failure and their might be coolant dried to the first 02 sensor or the spark plug(s) of the cylinders involved.

Now, just to let you know, you can save yourself on the road if a failure happens a couple of ways. One is to, every few miles, release air from the coolant system by very slowly unscrewing the bleed screw and relieving it while the engine is running. This may take several stops for your return home, but, it will get you home... just use your heater as an indicator and watch the temp gauge. Just make sure to pick up plenty of water along your way.

Another method is to find a Wal-Mart Supercenter along your route, and, prepare to spend a little money. Get the Bars Leaks Block Head Gasket Fix that is usually $26, at least 1-2 bottles of 50/50 Dex-cool approved coolant, and, at least 2 large bottles of water. While you're in the Wal-Mart parking lot, follow the instructions on the Bars Leaks bottle closely, except, after you've allowed the engine to cool on the last step, start the engine and relieve the air in the coolant system via the bleed screw. This may take up to 5 minutes before you see coolant. Add coolant and water as necessary to get home.

After either method, consider gasket replacement immediately. Take note that a blown head gasket in the case of the 3400 DOES NOT MEAN the death of your engine, and, can be rather easy and in-expensive to replace especially if you order them from eBay with everything, including the bolts.... There is a YouTube video on the entire replacement from start to finish.

It's not a bad tear down at all really, and, it gives you a chance to clean everything. Here's the video:

I hope this helps some on this silent but deadly issue....

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Last edited by Starflare5; 12-31-2017 at 05:30 PM. Reason: Adding more info.
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post #2 of 24 (permalink) Old 01-16-2018, 10:17 AM
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I have started to see some coolant leak on left side of engine bay from the intake and head gasket, the head that is closer to cabin, the head thats in front of car isnt leaking. will start to buy all my parts and program a head intake gasket change. I just changed a month ago the water pump and 1 year ago the tstat. I know its something simple but since I have detected it I can prepare for it. Its a 11 year old Nox, it is only 96,000 kms on the odometer
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post #3 of 24 (permalink) Old 01-17-2018, 09:18 AM
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Nice write up. The 3400 is a good engine that doesn't get the love it deserves. Even a dealer will do the head gasket job for under $1K, and yet I know people that act like it's the death of the entire car.

2017 Equinox 3.6L Premier AWD
2011 Silverado 1500 LT, 5.3L 4X4
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post #4 of 24 (permalink) Old 02-13-2018, 07:03 PM
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Let me also add the symptoms I had with my blown head gasket(just recently jan 201 as my symptoms can be even more devastating because of the lack of evidence. (hope this can help someone)

2006 LT AWD with 105k miles and I had a bluetooth ODB device connected to my phone monitoring coolant temperature

These all appeared in this order over time (about a month)
1. Started hearing air running thru the heater core(behind the speedometer) upon acceleration (not gurgling but tiny bubble sounds like a sizzle)
2. Heat started to become erratic.(Heat would come out of the vents in bursts of cool and then fire hot and repeat)
3. Vehicle started to overheat DESPITE the pressurized reservoir having fluid in it. (No visible leaks in the engine compartment or on the ground)
4. Started consuming about a gallon of coolant per hour of driving (again with no sign of where it was going)
5. Radiator hoses would be rock hard yet warm not hot when the engine is operating
6. pulling the upper radiator hose off the engine pipe would find an almost bone dry interior pipe (again the reservoir was always full)

I took it in and the shop performed a compression test and two of the cylinders failed compression tests. The head gasket had failed in a way that the compression of each engine stroke was forcing air into the coolant system and displacing the coolant in the engine and forcing it into the reservoir and out the relief valve. The car was literally dumping the coolant.

Due to the cars age/condition and the fact that its next owner was going to be the junk yard I decided to try a leak sealer. I bought a $50 bottle of Barr's BLOWN HEAD GASKET REPAIR (there are 3 types and i got the one for the most severe leak) after doing some research on youtube of others that had my symptoms. I followed the directions EXACTLY as on the bottle and within an hour the engine stopped dumping coolant, heat returned to a constant hot, and the car no longer overheated.

It's been 3 weeks and I monitor my coolant temp at all times thru the ODB and is consistent at 194 degrees when driving.

Obviously this fix is a old car/financially strapped driver fix and over time i dont know how this fix will hold but I am pleased as it saved this car from the junkyard for the time being.
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post #5 of 24 (permalink) Old 07-15-2018, 09:55 PM
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Have same 2006 chevy equinox 3.4l junk. Had same head gasket problem like everyone else here. Bubbling reservoir and coolant evaporating out of the exhaust... I wouldn't bother with the quick fix stuff it won't last. Replacing the head gaskets on this car was relatively easy. I am not a mechanic but i was able to do it. The dealer wanted to charge me $ really comes down to time. I had another car so i was able to lollygag a bit. Pulled both head blocks and cleaned them carefully as best I could with acetone. Bought Felpro gasket kit.. replaced both gaskets (both the old gaskets were just cruddy/failure everywhere)...two rocker bolts snapped during the put back so i had to deal with that but that was about it. I replaced the spark plugs and wires since i had it apart already. This job was fairly easy if you take your time. There are videos out on the web you can follow. Just remember to follow all torque procedures...44lbs and 90degrees on the head bolts. Out of pocket.. $175 for the head kit, $35 for head bolts, $7 for a fuel disconnect tool, $30 for spark plug wires, another $30 for some nice Bosch spark plugs, $7 for some acetone and that's about it...Surprised...The car cranked the first time i turned the overheating visible leaks(don't for get to use the black silicone in the valleys). Anyway i don't think these gaskets are designed to last for this car(like a lot of other parts). Its not surprising after going through this, reading gasket failures at 65k and 75k miles... The gaskets are likely to fail again i think...
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post #6 of 24 (permalink) Old 08-13-2018, 04:41 PM
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Watching the video he missed an import thing to look for.

The combustion pressure was pressurizing the block and stopping fluid. If he would have taken off the radiator cap and looked he would have found bubbles and the same odor.

The radiator cap would have released at about 7psi, and the overflow tank would have also bubbled with exhaust gas.

So he got the right diagnosis but missed the easiest way to confirm it.
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post #7 of 24 (permalink) Old 08-26-2018, 12:12 PM
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i got my 06 on the 4th of july with bad headgaskets. head job is easy. been driving it for 2 weeks. it is fairly quiet. oh and a bad center support bearing. and tires with 80% tread which have a whine/rumble at 40mph and up. dont feel like spending more for new tires than i paid for nox. maybe some rube on CL will buy them and i can get another set for not much more money. i had a real nice set of 18" chrome rims (5x115) i sold last year for peanuts. but i was not planning on getting a nox. i have had 3 saturn vues and this one just popped up.

Last edited by cavell; 08-26-2018 at 12:18 PM.
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post #8 of 24 (permalink) Old 06-05-2019, 12:13 PM
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I have just joined the club of Head gasket blow, my leaking coolant from ouside head in the heads that are towards the cabin, will do the job myself with lots of planning and will work slow but very precise on the job, mine is 2007 LT with 77500 miles on it, think its a low miles for the year but well its ok. Bought a beater for the wife, its 1998 Grand Cherokee Laredo 5.2 4x4 with 88,000 miles in pretty decent condition, its my SUV muscle car toy.
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post #9 of 24 (permalink) Old 08-18-2019, 01:54 AM
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doing head gasket as of this week, having trouble getting tstat bypass pipe, theres this stud on the head that fix the pipe and cant get the intake off, any tips
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post #10 of 24 (permalink) Old 08-20-2019, 06:33 PM
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well half way there, can only work on weekends for now, bought a MAHLE complete engine gasket kit, replacing all the gaskets I see leaking. Takes time and some parts are a pain to get out because of some of them are dificult to loosen up
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