Signs of a Bad Intake Manifold

The intake manifold is the part of a gasoline engine that distributes air (and sometimes fuel, depending on the type of engine you have) from outside the car to the individual cylinders, where the air and fuel are burned to produce power.

The intake manifold attaches to the engine’s cylinder head, with a gasket in between them to provide a tight seal. Depending on your engine’s design, the gasket may be there simply to seal out any stray air from getting into your intake manifold. But the gasket may also be there to seal the coolant (and sometimes oil) passages that run through your engine, to keep its temperature under control.

Symptoms of a bad intake manifold

There are numerous ways to tell that you might have a bad intake manifold:

• You notice leaking coolant on the ground: If you have a bad intake manifold, there can be coolant leaking from it, possibly as a result of a bad gasket. This leaking coolant will eventually work its way down the side of your engine, where it can be found underneath it. You can also open your hood and check around the intake manifold for signs of leaking coolant. While your hood is open, check your translucent coolant expansion tank to see what color your coolant is, and check whether the fluid that is leaking is the same color. This should confirm whether it is a coolant leak. If the level on the coolant expansion tank is low, top it up with fresh coolant and keep an eye on the level, to prevent it from getting too low. Call your mechanic and take your car in for repairs.

• Your engine idles roughly or stalls: This can be caused by a bad intake manifold that has an air leak. This lets too much air into the engine, producing erratic idling and even stalling at lower speeds. This can result in a very dangerous situation: you don’t want your car to stall in the middle of an intersection!

• Your engine performs poorly: A bad intake manifold can throw off your engine’s fuel-air mixture, causing some major engine performance issues as you drive it. These can include lack of power, rough acceleration, misfiring or backfiring.

• Your fuel economy gets much worse: In some cars, an air leak in your intake manifold will result in your engine computer trying to compensate for it by adding extra fuel. This causes your fuel economy to drop significantly.

• Your engine makes weird noises while idling: You can try listening to your engine to determine whether you may have a bad intake manifold. Open your hood and let the engine idle. In addition to a possibly rough, uneven idle speed, you may also hear whistling, sucking, gulping or hissing noises.

• Your check engine light comes on: Abnormal operating conditions and loss of performance can result from a bad intake manifold. This may cause your engine computer to trigger the check engine light on your dashboard.

• Your engine runs hot or overheats: If you experience a loss of coolant from a bad intake manifold, it can cause your engine’s temperature to rise, sometimes to dangerous levels. You may notice that your car’s temperature gauge is running higher than normal, or perhaps the temperature warning light on your dashboard has lit up. This can happen even if you have not seen any visible leakage from your car.

Should you drive a car with a bad intake manifold?

It's not a good idea to drive your car if it has a bad intake manifold, for these reasons:

• If you're losing coolant, your car could overheat
• If your car is stalling or not performing properly, you could get into an accident
• A minor intake manifold problem could turn into a major one, if you neglect it

Call a mechanic and get your car to the repair shop. Remember, a tow to your mechanic’s shop, at the first sign of trouble, will cost much less than repairing or replacing your entire engine.

How do you fix a bad intake manifold?

There are several types of intake manifolds, and they can be made of either metal or plastic. Some intake manifolds have coolant and oil passages running through them, some have only coolant passages, and some have no passages at all.

Depending on the exact symptoms your mechanic has to work with, the type of intake manifold, what it’s made of, and the extent of the damage, an appropriate fix can be made.

This can range anywhere from replacement of the intake manifold gasket, to repair of the intake manifold, to a complete replacement of the intake manifold itself. Other components of the engine that are connected to the intake manifold may also need to be removed to facilitate the repairs. Once repairs are made, everything is reassembled and tested for proper operation.

Can you fix a bad intake manifold yourself?

Unless you have plenty of experience working with automotive intake manifolds, you should leave this one to your mechanic. Dealing with a repair like this requires expert diagnostic skills, as well as the expertise to fix your car and return it to optimal running condition.