Intake Manifold: 5 Symptoms Of Bad Intake Manifold Gaskets

What is Intake Manifold?

The intake manifold, also known known as the inlet manifold, distributes air to the engine’s cylinders, and on many cars it also holds the fuel injectors. On older cars without fuel injection or with throttle body injection, the manifold takes in the fuel-air mixture from the carburetor/throttle body, to the cylinder heads.

The manifold lets air into the combustion chamber on the intake stroke, and this air is then mixed with fuel from the injector, after which the combustion cycle continues.

The air reaches the manifold through the air cleaner assembly, which contains the car’s air filter.

The air filter stops dust and other foreign bodies from entering and damaging the engine, so it’s vital that you regularly change it.

Inlet manifolds are usually made from aluminum or cast iron, although some cars use plastic manifolds.

It isn’t unknown for an intake manifold to split and develop a leak. If you lift the bonnet and listen to the engine when idling you’ll be able to hear a whistling or hissing noise, and the engine itself may idle roughly or stall when idling.

If the split is small it can normally be repaired, but replacement is usually advised.

It’s easy to replace an intake manifold on a modern car, because parts are readily available. However, this may not be the case for older models.

Sometimes replacement inlet manifolds simply don’t exist and you’ll have to either carry out an extensive repair on the old one or find a specialist who can make one for you. However, this will be expensive.

Problems with inlet manifolds are relatively rare, but some diesel car models’ manifolds incorporate what are known as swirl flaps, fitted before the intake ports.

They are designed to improve airflow at lower engine speeds but the flaps can become fouled by the exhaust gas-recirculation process, and either stick or hear off altogether and be ingested into one or more engine cylinders, causing catastrophic engine damage.

How Does an Intake Manifold Work?

Air travels through the intake and the throttle body into the plenum of the intake manifold. The plenum then equally disperses the air to each of the runners.

During the intake stroke, the piston moves down and creates low pressure within the cylinder. This sucks the air from the runner (an area of high pressure) into the cylinder.

When the intake valve closes, it creates pressure waves that send the air back up the runner. It then bounces off the plenum and comes back into the cylinder when the intake valve opens again.

This process happens over and over again for each of the cylinders until you shut off your engine.

Why Do Intake Manifolds Fail?

Intake manifolds fail because of the high levels of constantly changing heat and pressure they are subjected to daily.

The strain they are put under inevitably leads to cracks developing – it is up to the driver to diagnose the problem and deal with it at the earliest opportunity.

5 Symptoms Of Bad Or Failing Intake Manifold Gaskets

The intake manifold gaskets are some of the most important gaskets found on an engine. Gaskets are the seals placed between engine components before they are assembled in order to provide a reliable seal. They can be made of paper, rubber, metal, and sometimes a combination of the three.

The intake manifold gaskets are responsible for sealing the intake manifold against the cylinder head(s). Apart from sealing engine vacuum, certain designs will also seal engine coolant.

When the intake manifold gaskets have an issue, they can cause drivability problems and even engine overheating. Usually, a faulty intake manifold gasket will produce a few symptoms that can alert the driver of a potential issue.

#1. Coolant leaks.

Another symptom of a faulty intake manifold gasket is coolant leaks. Some intake manifold gaskets also seal engine coolant, and if the gasket wears out it may lead to a coolant leak.

This may produce a distinct coolant smell, along with steam, and drips or puddles of coolant underneath the vehicle. Coolant leaks should be addressed as soon as possible, in order to prevent them from becoming a greater issue.

#2. Engine Overheating.

Engine overheating is another symptom of a possible issue with the intake manifold gaskets. A coolant leak will eventually lead to engine overheating when the coolant level drops too low, however, there are instances where overheating can occur without any visible leaks.

If the intake manifold gaskets leak coolant into the intake manifolds the engine may overheat as a result, without any visible external leaks.

Any coolant leaks should be addressed as soon as possible to prevent the possibility of serious engine damage occurring due to a bad intake manifold gasket.

#3. Engine Stalling.

When the engine stops turning or is turning too slowly, then stalling will occur. This can happen when a faulty intake manifold gasket causes a vacuum leak, which messes up the ratio of air to fuel.

Then you could be driving and all of a sudden experience a stalled engine. Of course, there could be many other reasons for a stalling engine, but a bad intake manifold gasket is surely one of them. Go see a mechanic to have them verify if it is this gasket or not.

A mechanic will be able to perform a smoke test to rule out vacuum leaks. A smoke test injects smoke into the intake system. If there is a leak in the system, smoke will come out from an area it’s not supposed to.

#4. Bad Fuel Economy.

Since a faulty intake manifold gasket causes a disruption in the air to fuel ratio, then your engine is going to consume more fuel than normal.

This means you will be spending more money on gas for doing the same amount of driving that you normally do. As a result, your fuel economy will decrease greatly.

#5. Loss of Acceleration.

Aside from an engine stalling, you may notice a simple loss of acceleration after you step on the gas pedal. You may get a little bit of power at first, but then the acceleration will stop and start again as you keep your foot on the pedal.

You obviously shouldn’t continue to drive your vehicle when it is in this condition since it’s dangerous to do so. If you are experiencing two or more of the other symptoms, then you definitely need to have your intake manifold gasket replaced promptly.

How Much Does It Cost to Fix? Can’t I Do It Myself?

Unless you’re an experienced home mechanic with the proper tools and a safe place to work, it’s probably best to leave manifold work to the pros.

The steps to remove, replace, and safely reconnect everything can be difficult to understand without experience, and the consequences of messing something up can be serious.

Having said that, it’s important to note that paying someone to fix an intake manifold won’t be cheap.

On average, you can pay between $400 and $600 for intake manifold repairs. Labor is the major expense here, ranging from $340 to 420. The parts, on the other hand, only cost about $80-$165.

Can You Drive with a Bad Intake Manifold Gasket?

While it is indeed often possible to drive with a bad intake manifold gasket, you should not drive too far. Issues like this don’t go away on their own, and they also don’t tend to get better with time.

Leaking additional unmetered air into the combustion chamber has the potential to make the car run lean, which means the engine is likely to run hotter. Knock or pre-detonation is also more likely. Too much knock under load can actually destroy a perfectly good engine.

An overheating engine is likely to cause additional damage to the engine, including a warped or cracked head or a cracked block. This damage would cost far more to repair than a simple intake manifold gasket replacement normally would.

FAQs.