350 vortec 5.7 lower intake leaking vacuum?? Help please

[squaredeal91]

Intake side. The nastiest here is 1,2,3,4.

 

[squaredeal91]

Head side

 

[RustyPile]

Way back in June 2000, I bought a '99 Suburban with that same 5.7.. At the time of purchase, it had less than 20K miles on it.. I also purchased an extended warranty.. within 6 months, it developed a water leak at the rear of the engine. Warranty replaced the lower intake gaskets and all was good for about a year, then the water leak returned.. Dealership replaced the gaskets again and then replaced gaskets 2 more times over a period of 3 years. During that time, I did some research as to why the gaskets wouldn't hold.. GM was using Dexcom (the orange stuff) coolant.. It was also being used by Chrysler in certain models, and also Mercedes Benz.. All were having gasket problems with their engines.

The extended warranty I had carried the vehicle to 60K miles. Around 58K miles the gaskets failed for the 4th - 5th (I lost count) time.. I replaced the gaskets myself, flushed the cooling system and put Prestone in the cooling system.. All the gaskets were the plastic type. I never had anymore problems with gasket failures.. I sold the truck in 2007 when the gas prices went through the ceiling...

 

[squaredeal91]

Way back in June 2000, I bought a '99 Suburban with that same 5.7.. At the time of purchase, it had less than 20K miles on it.. I also purchased an extended warranty.. within 6 months, it developed a water leak at the rear of the engine. Warranty replaced the lower intake gaskets and all was good for about a year, then the water leak returned.. Dealership replaced the gaskets again and then replaced gaskets 2 more times over a period of 3 years. During that time, I did some research as to why the gaskets wouldn't hold.. GM was using Dexcom (the orange stuff) coolant.. It was also being used by Chrysler in certain models, and also Mercedes Benz.. All were having gasket problems with their engines.

The extended warranty I had carried the vehicle to 60K miles. Around 58K miles the gaskets failed for the 4th - 5th (I lost count) time.. I replaced the gaskets myself, flushed the cooling system and put Prestone in the cooling system.. All the gaskets were the plastic type. I never had anymore problems with gasket failures.. I sold the truck in 2007 when the gas prices went through the ceiling...

Wow! I got a good laugh at the lost count part. I'm glad it was under warranty but wow. Good move on the coolant change. I did that 6 years ago I think. Do you recall if they replaced the bolts?

 

[SquareRoot]

Intake side. The nastiest here is 1,2,3,4.

 

[Bextreme04]

Wow! I got a good laugh at the lost count part. I'm glad it was under warranty but wow. Good move on the coolant change. I did that 6 years ago I think. Do you recall if they replaced the bolts?

The bolts are not torque to yield... not sure where you got that from. They do not need to be replaced and are not one time use. It looks like you put a ton of RTV on there under the gasket? Don't ever do that... it will more often than not cause a massive leak. The rubber O-rings in the gasket will seal well to a clean and flat metal surface with no additional RTV or sealant required.

 

[CalSgt]

Head side

It was the runner for #5 that had the suspected oil puddle right?

I'd bet your injectors for holes 5 & 7 are leaking down and washing those intake runners with raw fuel every time you shut the engine off, that's why they're so clean. That or the coolant port right there was pissing water down those two runners and washing everything up.

1,2,3, & 4 are always gonna be dirtier because they take the brunt of the heat and exhaust fumes from the EGR.

Last Vortec I had to do gaskets on we suspected may have had a bad head gasket too. When we pulled the heads cylinder #1 was sparkling clean from the intake runner sucking water out of the coolant port at the front of the intake manifold.

Is it me or did someone try porting the heads? or maybe ground them to match the profile of the last gasket set...
Also looks like there's RTV on the lower intake gaskets, IIRC GM doesn't call for silicone on the vortec intake gaskets except where they meet up with the lifter valley. I don't suspect that it hurts anything though.

 

[CalSgt]

The bolts are not torque to yield... not sure where you got that from. They do not need to be replaced and are not one time use. It looks like you put a ton of RTV on there under the gasket? Don't ever do that... it will more often than not cause a massive leak. The rubber O-rings in the gasket will seal well to a clean and flat metal surface with no additional RTV or sealant required.

I said they were one time use bolts, perhaps I was wrong.

ETA: I read it on the internet somewhere which means it must be true, right? LOL.

 

[squaredeal91]

The bolts are not torque to yield... not sure where you got that from. They do not need to be replaced and are not one time use. It looks like you put a ton of RTV on there under the gasket? Don't ever do that... it will more often than not cause a massive leak. The rubber O-rings in the gasket will seal well to a clean and flat metal surface with no additional RTV or sealant required.

Yeah I probably got carried away with it because I had to do them again after 6 months the first go around over 6 years ago.

 

[squaredeal91]

It was the runner for #5 that had the suspected oil puddle right?

I'd bet your injectors for holes 5 & 7 are leaking down and washing those intake runners with raw fuel every time you shut the engine off, that's why they're so clean. That or the coolant port right there was pissing water down those two runners and washing everything up.

1,2,3, & 4 are always gonna be dirtier because they take the brunt of the heat and exhaust fumes from the EGR.

Last Vortec I had to do gaskets on we suspected may have had a bad head gasket too. When we pulled the heads cylinder #1 was sparkling clean from the intake runner sucking water out of the coolant port at the front of the intake manifold.

Is it me or did someone try porting the heads? or maybe ground them to match the profile of the last gasket set...
Also looks like there's RTV on the lower intake gaskets, IIRC GM doesn't call for silicone on the vortec intake gaskets except where they meet up with the lifter valley. I don't suspect that it hurts anything though.

When I put this in over 6 years ago I matched heads and intake to match the gasket. Also the puddle was passenger side so its cylinder 6,8.

 

[CalSgt]

When I put this in over 6 years ago I matched heads and intake to match the gasket. Also the puddle was passenger side so its cylinder 6,8.

The intake runners cross sides in the manifold,

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[squaredeal91]

The intake runners cross sides in the manifold,

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Oh... lol so they do. Thank you

 

[squaredeal91]

@CalSgt No coolant leak that I can tell of and no loss of fluid. Also I got the new spider ordered. It won't be here soon enough lol

 

[CalSgt]

Oh... lol so they do. Thank you

All good Sir.

If you haven't already scrubbed and scraped everything clean, pay close attention to the gasket mating surfaces back there near 6&8. See if you can identify if water has made a path from that rear coolant passage to those intake runners.

It doesn't really do a whole lot of good but may help diagnose if that is why they are so clean. Especially since they are super dirty at their inlet inside the upper manifold.

 

[RanchWelder]

Clean the heck out of the EGR circuit all the way through the manifold, if possible.

I can confirm the bolts are not torque to yield. It is imperative to use the factory bolts with a stud tip, not threaded tip.
This stud bottoms in the holes to prevent crushing of the plastic.
However, when using the upgraded gasket, torque spec may prevent the stud from bottoming out.

This means cleaning any thread locker or sealant from the manifold bolt holes, has to be very clean/blown out.

** This is a good thing. When installing either the Fel-Pro thick paper or the metal gaskets, torque sequance may NOT bottom out the stud tips on the bolts.

Quoted from the 99' Dealership repair manual:

"Applying excessive amounts of sealant may prohibit the gasket from sealing properly"
"The lower lower intake manifold must be installed and the fasteners tightened while the adhesive is still wet to the touch."

1) Apply 4.0mm patch of adhesive GM Part P/N 12346141 at each end. (I was asked to select "The Right Stuff" by my machinist).
It shows a picture of the extreme outer lowest edge of the gasket. The very edge it touches the china wall.
1/4" wide by 4mm tall finger of sealant. |__|
Not much and not up the sidea of the edges.
It is inferred this is the back side of the gasket which goes onto the head, before alignment on the locating pins.
The front tabs get sealant later.

3) Apply 5mm bead to the front engine block.
4) Extend the bead 13mm (0.50") on to each lower intake manifold gasket.
So 1/2" up the rake, or onto the agle of the headmating surface. 5mm wide. Don't over do it, or globs of sealant will end up in your oil passages, filter and oil pump circuits.

The smallest chunk of sealant can clog a lifter and ruin everything.

Then it repeats the same instructions for the rear.

Resist the urge to add anything else. This is why the metal gaskets are highly recommended and the thick paper likely works as well.

8) Apply thread lock GM P/N 12345382 to the manifold bolts. Thread lock is not gasket sealant.

Here is where a lot of people screw up, especially with the plastic manifold.
Borrow the correct torque wrench or buy a new bar type in lb.

Torque sequence is as follows:

7-1-3-5
<---------- Front of manifold
8-4-2-6

9.1) First pass: 27 lb in
9.2) Second pass: 106 lb in
9.3) Final Pass: 11 lb ft (130 lb in)

The trick is finding a 3/8" Beam torque wrench. The 1/4" version only goes to 80 lb in. You run out of wrench for the final pass.
The GearWrench 3/8" will not read as fine on the first pass measurement, so take it easy.
The scale gets you on target for the second and third pass more accurately.
$59 on Amazon.

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Here's the Ares 70214 at $32.00 on AZ. It comes with a 3/8" to 1/4" adapter. :

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Paying attention to inch pound specs is really where the installation works without deforming the plenum or failing.

*** It is going to take "a day OR TWO" to harden the china wall seals.
If you try to start it and your timing is off more than 10 degrees, either way, you could suck the un-cured gasket sealer out and cause another leak.
Especially at the rear china wall, near the oil pressure sender port, where the china wall casting is thinner.
This is the exact area where the plastic gasket is known to leak and fail, at the coolant port.