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Steve, Auto Service Technician
Category: Car
Satisfied Customers: 5494
Experience:  25+ yrs experience as a professional working technician; ASE L1 master technician
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What damage can leaking intake manifold do if not repaired?

Customer Question

what What damage can a leaking intake manifold do if not repaired immediately? The lower intake manifold is leaking coolant internally and externally on a 1999 Buick Century with 90,000 miles. The car performs fine. I have been replacing coolant every month or so. Can I continue to do so without expensive repair?

Submitted: 11 years ago.
Category: Car
Expert:  Steve replied 11 years ago.


The external coolant leak is not as much of a concern as the internal one. The external leak will merely result in the coolant level dropping slowly; this is compensated for by keeping an eye on the coolant level and adding some as needed.

the The internal coolant leak is a different story though. When an intake manifold is leaking coolant internally, the coolant is leaking into the engine oil pan and mixing with the oil. This has 2 effects: the antifreeze and oil mixture does not lubricate sufficiently to prevent engine damage to critical moving parts that depend on an oil film to keep them separated, and the antifreeze chemically attacks some of the metals used in engine bearings. Operating an engine with an internal coolant leak will destroy it from lack of lubrication very quickly. If you have been running the engine with an internal coolant leak, it has already sustained some level of internal damage and has had it'sits life expectancy shortened; the leak was probably going on long before you noticed any symptoms. Now that the leak is large enough to have to add coolant, the best thing to do is to park the car and not run it untilluntil the leak has been repaired.

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What does an intake manifold do?

Intake manifold (inlet manifold) is a part found within the engine that provides an air/fuel mixture to the cylinders. This part can be made up of rubber, paper, metal or occasionally all three. The primary purpose of an intake manifold is to equally supply the air/fuel (or just air) mixture to each cylinder head. Supplying this mixture is important because it affects the performance and effectiveness of the engine. Also, an intake manifold may help hold the throttle body, carburetor, fuel injectors, and other parts of the engine.

Symptoms of a failing or bad intake manifold

Common signs include leaking coolant, the engine overheating or misfiring, or less acceleration or power.

  • Misfire: less acceleration, fuel economy or power. Typically, the most common problem with an intake manifold is performance problems with the engine. When a vehicle has high miles, the manifold starts to wear out and often leak. When the manifold starts to wear out, the intake manifold gaskets cannot maintain the engines vacuum and pressure, causing performance issues. When a vacuum leak occurs, this can affect the engine’s fuel/air mixture and cause more issues with stalling, misfire, less power and acceleration, and a lower fuel efficiency.
  • Leaking coolant: when an intake manifold is failing, coolant will often begin to leak. Manifold gaskets help seal the coolant, but when the gasket becomes worn out, coolant will leak. A coolant leak can cause a noticeable smell, drips or puddles under the car, or steam. When a vehicle is leaking coolant, this should be taken care of as soon as possible to help avoid costly repairs.
  • Overheating: a common symptom of a bad/faulty intake manifold is the engine overheating. When the coolant levels drop too low the engine cannot cool down. The engine can still overheat without a visible sign of a leak.