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What is an Intake Manifold Gasket?

Intake manifold gaskets prevent air or air-gas mixtures from leaking out from the gap between the manifold and cylinder heads.
Intake manifold gaskets fit under a manifold between it and the cylinder heads and engine block.
Article Details
  • Originally Written By: Eric Tallberg
  • Revised By: C. Mitchell
  • Edited By: Jay Garcia
  • Last Modified Date: 14 October 2014
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    2003-2014
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An intake manifold gasket is a flexible, fitted part of a car engine that helps prevent air from leaking out during fuel combustion and helps regulate chamber temperature. Most cars use a type of engine known as “fuel combustion,” which basically means that they get their main energy from a series of mini-explosions powered by gasoline. These explosions need oxygen, though, and in most cases that oxygen is drawn in from the outside environment with the intake manifold. The gasket fits between that intake pipe and the cylinder heads in the engine, and its main purpose is to reduce the chance of air leaking out, which can hurt the car’s efficiency. People who have weak or faulty gaskets may notice their engines sputtering out or stalling more frequently. Replacing this part is usually pretty easy, but does require some mechanical expertise.

Basic Function

This automotive part is a critical yet comparatively delicate piece of equipment. Its main job is to keep heat generated through the engine block from creeping back into the air intake manifold. Fuel ignites best with cooler air, which is denser and generally contains more oxygen. The thickness of the gasket is usually driven by the strength and power of the engine. Heavy duty models are ordinarily used in turbocharged engines, but the piece has been modified to work well for heat management in almost all scenarios.

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In most cases the gasket is also really important when it comes to keeping air in. Leaks decrease the amount of available oxygen, which can impact overall car performance ans well as engine strength.

Where It’s Found

Car engines are somewhat complex from a sheer parts standpoint, though comparatively speaking the gasket is fairly simple. In most vehicles it is a series of small caps or shields that sit just on top of the main cylinder openings. Most have a ring-like look to them, and are often made of either metal or hard plastic. They can usually be unscrewed fairly easily to allow access to the interior chambers, as well as to diagnose problems or look for cracks.

How it Works

The intake manifold operates as a sort of plenum, drawing and funneling air and fuel from the carburetor to the cylinders or, in fuel injected engines, just air to the injection ports. A measured amount of air is sucked from the manifold into the vacuum and from there it’s injected, along with fuel, into the cylinders to be ignited. The air drawn into the cylinders will suddenly hit the shut door of the intake valve and will rush back upon itself causing a wave of high pressure in the manifold runners. The intake manifold gasket is there to keep everything contained. It must be able to withstand this constant change in air pressure and temperature.

Common Problems

Even though this part is small, its operation is often critical to proper car functioning. A leaking intake manifold gasket typically contributes to poor fuel economy, higher emissions, and poor engine performance, and can also cause stalls and sputtering. The typical automobile engine runs on a stringently controlled air-fuel ratio. The intake manifold gasket, in conjunction with such mechanisms as the intake valve and the fuel injector computer, maintains that ultimate ratio. Should any of these components begin to fail, the vehicle’s gas mileage decreases, its gaseous emissions increase, and eventually the engine stops running altogether.

The proper distribution of air into the cylinders is obviously very important to the efficient operation of the engine. All gasket material has to be pliable and must be installed using a special gasket cement or sealant to ensure that it remains firmly and correctly in place.

People who know a lot about cars and who have some expertise in engine construction are often able to diagnose and fix gasket problems on their own, and the actual work itself isn’t usually very difficult. Knowing the right techniques and placement is where things get trickier. Most experts recommend that car owners get a professional opinion from a trained mechanic before they start fixing things themselves unless they’re really sure they know the ins and outs of what they’re doing. Gasket problems are usually pretty quick for professionals to fix and aren’t usually expensive.

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Discuss this Article

anon969699
Post 14

If your check engine light comes on and it stalls, it does sound like the gasket. It's losing combustion. Get it checked out and repaired. You don't want your pistons to fry.

anon235546
Post 13

I'm really glad I found this forum. I have been having a major issue with my truck (1998 F-150) running hot on me. To be exact, if I don't warm up my truck for at least 15-20 minutes, the truck will run hot. I have changed the thermostat, had my radiator flushed, and checked to make sure my head gaskets were fine. I was finally told by a mechanic that had no idea of these problems that I needed a new intake manifold gasket. This was the first time I had heard of such.

Just a question to anyone who has or is enduring problems such as mine: does your vehicle get to operating running temperature (as seen my gauge), then drop down under the "C" for a while, then shoots up to "H"?

anon208442
Post 11

Fuel doesn't ignite better with cool air. That's rubbish. The reason why you want cool air is because it is more dense than hot air, so you can fit more air molecules into the cylinder. This means you can burn more fuel, and so you can get a more powerful combustion. If you put hot air in the engine, the mixture will be lean, the engine will overheat and self-ignition will occur.

anon150042
Post 7

the article mentions a special gasket cement/sealant. Any recommendations?

anon128492
Post 6

@EarlyForest: I had the exact same problem with my five year old, paid off but still under warranty car. Was idling hard at one light, then smooth at the next, check engine light came on and stayed on. Engine stalled out a couple of times and I'd had enough. Dealership said it was intake manifold gasket and got everything done for free since warranty was still in effect. Good luck! --Kat

anon122883
Post 5

@Early Forrest: These are the exact symptoms I have been having for a long while now with my car - 1995 Olds Ciera Wagon w/3100 V6 FI - and I was told by one friend over the phone (because I called him telling him its been dying so many times in a row) and he said it was probably camshaft sensor. But he said to bring it over to be sure.

Apparently it had cooled down enough to go so it made it there but with the check engine light on. I got there and first thing when he opened he could tell by smell the coolant was leaking. He says "You have an intake manifold gasket going."

He calls two other friends to have them come over to check to make sure, both of whom are mechanics of good reputation, and they each independently confirmed it was that gasket. Especially the friend who had recently done that exact gasket replacement about six months or so prior on his own 2000 Chevy Malibu with the same engine. Then he proceeded to tell me he dropped the big aluminum piece onto concrete and had to get a new one for $250! (But it was his help's fault.)

So now it's in the shop being replaced and I'm going to see how well it lasts this time. Yes, this is the second time this has happened in 15000 miles. I'm not hot-rodding this wagon by any means, and I'm not doing anything terrible to it, but it was also independently confirmed by all three friends that if this was fixed once the right way, it would not be doing it again with only 125k miles! Anyone know what happened here? --Zach

anon121345
Post 4

@anon115290: You're probably fine with your thermostat. Thermostats just control the *minimum* operating temperature. When your engine reaches about 190 degrees it opens up and lets the coolant flow, at least, that's what they recently taught us in my automotive class.

So in short, it's not your thermostat causing your engine to heat up, it's another problem.

That being said, thermostats are usually pretty cheap so you might want to replace it for good measure.

anon115290
Post 3

my van overheated the other day so I took it in thinking that it was the thermostat. They just called back and said it was because there was a leak in my intake gasket. Does that really cause the overheating or should they replace the thermostat as well?

gregg1956
Post 2

@earlyforest -- That does sound like it could be your gaskets, though I would have a mechanic check it out just to be sure.

You could fix it yourself, but if your car is still under warranty, I'd just get the dealer or a mechanic to repair it -- save yourself the headache.

Hope that helps.

EarlyForest
Post 1

How do I know if I have a problem with an intake manifold gasket?

I've been driving my car for about five years, and recently it's started to have trouble idling, the check engine light comes one erratically, and it stalls out sometimes.

Does anybody know if this could be caused by a bad intake manifold gasket, or something else?

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