GM 3500/3900 Intake Mainfold Gasket Info

[The Critic]

The two latest GM six cylinder engines are the 3.5L and 3.9L V6. There are multiple versions of these engines used in a variety of applications, but in this post, I will be focusing on the issue of plastic intake manifold gaskets.

All GM 3.9L V6 engines contain an aluminum intake manifold gasket. On the GM 3.5L V6 however, not all versions use the aluminum intake manifold gasket.

There are two main versions of the GM 3.5L V6. There is the GM 3.5L V6 (LX9), which is used in the Malibu, Malibu Maxx, G6, and the minivans, while there is also another GM 3.5L V6 (LZ4) which is currently used in the Impala and Monte Carlo.

The GM 3.5L V6 (LX9) still uses the plastic intake manifold gasket. However, this engine will be slowly phased out in favor of the LZ series engines. For those of you who have the GM 3.5L V6 (LX9), please do not automatically assume that an intake manifold gasket leak is inevitable, as it isn’t true.

All GM 3.9L V6 engines, and the GM 3.5L (LZ4/LZE) engines all contain the aluminum intake manifold gaskets. The GM 3.5L V6 (LZE) is used is an E85 capable version that is used in fleet Malibu vehicles.

Lastly, all GM 3.9L V6 engines and the LZ4/LZE versions of the 3.5L V6 contain a physical water cross over casting on the front of the cylinder heads to allow for a total separation between the coolant and engine oil to provide maximum protection against coolant intrusion into the crankcase.

Corrected Engine Code

[ May 17, 2006, 11:11 PM: Message edited by: Bio-T ]

 

[T-Keith]

Good info. I think the LX9 is the non-VVT engine correct? From what I've heard the Malibu, G6 and others get VVT for 2007, so the non-VVT 3.5 is already on it's way out.

 

[The Critic]

Correct.

The GM 3500 (LZ4) engine will bring VVT, full E85 compatibility, and increased horsepower/torque over the current 3500 (LX9) engines. The GM 3900 V6 (LZ8) will also bring Displacement on Demand Technology for 2007.

 

[jsharp]

quote:

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Originally posted by The Critic:


Lastly, all GM 3.9L V6 engines and the LZ4/LZE versions of the 3.5L V6 contain a physical water cross over casting on the front of the cylinder heads to allow for a total separation between the coolant and engine oil to provide maximum protection against coolant intrusion into the crankcase.

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What a modern miracle from GM engineering. Flathead Fords had this in 1932...

 

[unDummy]

"physical water cross over casting"

C'mon guys. It was a vote between 'using motor oil as the coolant' or a 'coolant cross over'.

I know many mechanics that will be sad when they read this!
Boat/RV payments will still need to be made.

 

[therealdeal770]

yeah i just got an 06 impala with the 3.5L engine.its the one with varable valve timing.seems like a great engine so far.glad to hear they fixed the issues with the intake gasket.

 

[mshu7]

More info on the current/future lineup of the GM pushrod V6's:

http://media.gm.com/servlet/Gateway...monthlyreleasedetail.do?domain=74&docid=25971

It appears that they are really trying to make up for all the intake manifold gasket leaks in the older V6's (which I applaud):

quote:

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Multilayer steel (MLS) head gaskets – These premium gaskets offer great durability over conventional graphite gaskets and were validated to 150,000 miles.

A “U”-shaped coolant flow system is used in the 3.9L engine. With it, coolant follows a specific path: It enters the engine at the front of the block and is carried to the back, before flowing into the rear of the cylinder head. As the coolant enters the rear of the cylinder head it flows forward, completing a U-shaped path that delivers more uniform cooling than the previous engine.

The water pump is mounted approximately 4 inches lower in the coolant’s path, which helps ensure steady flow if the system loses a small quantity of coolant. The new cooling system design also incorporates a coolant crossover at the front of the engine and requires no coolant to enter the intake manifold.

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[The Critic]

quote:

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Multilayer steel (MLS) head gaskets – These premium gaskets offer great durability over conventional graphite gaskets and were validated to 150,000 miles.

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I've personally never seen a well-maintained engine experience a head gasket failure prior to 150,000 miles. With that said, I wonder how many miles the "graphite" gaskets were validated to.

 

[lght1]

GM did have a run of black plastic framed LIM gaskets last year, and to date, they seem to be doing well as do the plastic FelPro ones for the 3800.

But the alu framed ones is what I would look for either in a repair or new engine.