Intake Manifold Leaks>>>WHY?


#1

What the heck is it about INTAKE MANIFOLDS and why do they tend to start leaking no matter how little?? Just had my Wife’s 97 Chevy Monte Carlo repaired, leaking a small amount of oil, but only has 60,400 ORIGINAL miles & well maintained. Had to have this done years ago with an 87 Chevy Camaro, that was fortunately still under an extended warranty at that time. And a good 77 yr. old retiree friend of mine, also a Chevy man, has a well maintained, LIKE NEW, late 80s Pickup, whose V8 intake manifold also had to be repaired. What is it about that area that stresses it out? Or is this unique to this one manufacturer?? If so, my next NEW and last new car (I’m 66) will not be a Chevy, although I have been a Chevy person for 40>50 yrs.


#2

It’s because GM decided to make the intake manifold gaskets using a plastic frame with a thin silicone seal bead on both sides of the plastic frame.

Because the lower intake manifold is made of cast aluminum and the heads made of cast steel, these two materials expand and contract at different rates. Over time this difference causes the silicone beads to become dis-attached from the plastic frame and a leak develops.

You can see the silicone beads on the plastic frames here

https://www.rockauto.com/catalog/moreinfo.php?pk=447245&cc=1056462&jnid=534&jpid=1.

Tester


#3

NOT a Chevy only issue, but the state of the industry as a whole.
The meterials being used for the sake of weight reduction often don’t stand the test of time and heat like the good ol’ cast iron manifolds of yore sitting on paper gaskets.
Plastic and aluminunum manifolds sitting on rubber bead gaskets just aren’t like the old days.
and YET, not all of those fail at any such rate as to be called a product wide defect at all. Jut one or two here and there.
So , why one fails and the next hundred don’t ?


#4

GM is the only manufacturer that I know of that uses silicone/plastic composite intake manifold gaskets.

Tester


#5
The meterials being used for the sake of weight rediction often don't stand the test of time and heat like the good ol' cast iron manifolds of yore sitting on paper gaskets.

I think it is more of a cost reduction than weight.


#6

It’s a demanding environment. On the 20 year old examples, those were certainly earlier designs than what you see typically today. At some point, the mileage isn’t as determining a factor as time. 20 years is a long time for some of the materials used in the sealing process to last without experiencing some significant degradation. In low mileage situations can sometimes be more demanding because people let them sit longer with acidic conditions eating away at the parts because they aren’t using them enough to burn off the contaminants or changing the fluids enough for the severe service environment.

Newer issues can be due to growing pains with new design/materials.

Then there are latent design issues that are left to exist for years in production.

But in short, the reason you see this interface fail more often then some others is that it is a challenging task and takes a lot of care to design it right. Even then, it’s a tough world out there :wink:


#7

@Tester

“GM is the only manufacturer that I know of that uses silicone/plastic composite intake manifold gaskets.”

You can add Ford to that list :neutral:


#8

I’ve never seen it.

Can you provide an image?

Tester


#9

Well here’s a picture of a Ford 3.8 liter family intake gasket set.

And the venerable 4.6 and 5.4 family of engine also use these.

Must be a million of these engines out there.


#10

Then only difference I see is FORD is using aluminum heads along with an aluminum intake manifold.

This could be why there’s no problem with the FORD intake manifold gaskets.

Tester


#11

The oil filter adapter gasket on some Ford engines is plastic composite with silicone rubber inserts. The one on my Lincolns look like this.
Sometimes prone to external oil or coolant leaks or sometimes coolant and oil mixing; all depending.

http://contentinfo.autozone.com/znetcs/product-info/en/US/fpr/70415/image/3/


#12

To Twin Turbo>>>@Time??? Sure I can understand that, but we also have a 94 Chevy S10, with a 4 banger that hasn’t had THAT issue, a HEAD GASKET repair when it was in the 40K miles range, but so far knock on wood, no intake manifold issue. And since the head gasket repair in 2008, just normal maintenance, oil/filters, new tires, etc. and runs like a Swiss Watch.


#13

TwinTurbo is correct about time being a factor. Through luck of the draw some cars make it their entire lives without an issue and some do not.

Rubber anywhere degrades over time; be it engine gaskets, tires, accessory belts, master cylinders, brake lines, A/C seals, you name it.


#14

The intake manifold gasket on your S10 can’t leak oil, the manifold doesn’t seal a camshaft valley.


#15

@Nevada_545 is dead on target

Comparing v engine intake manifolds to inline intake manifolds is comparing apples and oranges


#16

Well, if the OP is determined to to never own a Chevy again because of a gasket design then they’re going to be on foot a lot because there’s not a car or truck made that doesn’t have some design which could be construed to be faulty and lead to disgruntlement.


#17

Thanks for all your comments so far. Good answers :-). P.S. Re: My S10>>Goes to show you how much I know about engines>>LOL. Drums I know, cars, NOT>>LOL.


#18
NOT a Chevy only issue, but the state of the industry as a whole.

I don’t think so. GM (all V6 and some V8’s for a range of about 12 years leaked)…Some Ford and Chrysler’s had the problem also.


#19

Does anyone, for sure, know of any car manufacturers, domestic or foreign, that does NOT put them together in this CRAPPY way??? Why not use a REAL gasket kit, like they use upon repairing one at a repair shop??? These manufacturers are MORONS IMO :slight_smile:


#20
Why not use a REAL gasket kit, like they use upon repairing one at a repair shop????

Do you have data that shows the repair is better than the original?