How To Remove A Intake Manifold

Is your car experiencing rough idling, a loss of power, or decreased fuel economy? You might have a problem with your intake manifold. Replacing this vital component can seem daunting, but with the right knowledge and a bit of elbow grease, it's a task you can tackle yourself. In this guide, we'll walk you through the process of diagnosing intake manifold issues, safely removing the old one, and preparing for a replacement. Addressing intake manifold problems promptly is crucial for maintaining your engine's health and performance.

Symptoms of a Failing Intake Manifold

Identifying the signs of a faulty intake manifold is the first step towards resolving the issue. Here's a detailed breakdown of common symptoms:

Rough Idling: This is often one of the first indicators. The engine may vibrate excessively or feel unsteady when idling at a stop light or in park. The RPMs might fluctuate erratically.
Loss of Power: You might notice a significant decrease in acceleration, especially when trying to climb hills or merge onto a highway. The engine simply doesn't have the same "oomph" it used to.
Decreased Fuel Economy: A failing intake manifold can disrupt the air-fuel mixture, leading to a noticeable drop in your MPG. You'll find yourself filling up the tank more frequently.
Check Engine Light: This is a catch-all warning, but codes related to lean or rich air-fuel mixtures, misfires, or vacuum leaks are common when the intake manifold is the culprit. Use an OBD-II scanner to retrieve these codes for more specific diagnosis.
Hissing Sound: A vacuum leak within the intake manifold or its gaskets can create a distinct hissing sound, particularly noticeable when the engine is running. You might need to listen carefully, perhaps using a mechanic's stethoscope, to pinpoint the location of the leak.
Engine Misfires: If the air-fuel mixture is significantly off in one or more cylinders, you'll experience engine misfires. This feels like a momentary stumble or hesitation in the engine's performance. Repeated misfires can damage the catalytic converter.
Coolant Leaks: Some intake manifolds incorporate coolant passages. Cracks or gasket failures in these areas can lead to coolant leaks, often resulting in a sweet, syrupy smell and visible puddles under the engine.
Whistling Noise: In some cases, a cracked or warped intake manifold can create a whistling noise, especially under load. This sound is often higher pitched than the hissing associated with vacuum leaks.
Erratic Engine Performance: Overall, the engine may feel unpredictable. It might start hard, stall unexpectedly, or surge inconsistently during acceleration.

Root Cause: Why Intake Manifolds Fail

Understanding the underlying reasons behind intake manifold failures helps in preventing future issues. Here are the primary causes:

Gasket Failure: This is the most common culprit. Over time, the gaskets that seal the intake manifold to the cylinder head can deteriorate due to heat cycles, age, and exposure to chemicals. This leads to vacuum leaks, disrupting the air-fuel mixture and causing many of the symptoms described above.
Cracks and Warping: Intake manifolds are typically made of plastic or aluminum. Plastic manifolds are susceptible to cracking due to extreme temperature fluctuations and age. Aluminum manifolds can warp over time due to uneven heating and cooling.
Vacuum Leaks: Apart from gasket failure, vacuum leaks can also occur due to cracks in vacuum lines connected to the intake manifold or failures in vacuum-operated components attached to it.
Debris Buildup: In some engines, particularly those with direct injection, carbon buildup on the intake valves can restrict airflow and contribute to intake manifold issues. This isn't a direct manifold failure, but it affects its performance.
Coolant Leaks (Internal): If the intake manifold contains coolant passages, internal leaks can develop due to corrosion or cracking. This can lead to coolant mixing with air or fuel, causing significant engine damage.

Consequences of Ignoring a Failing Intake Manifold

Ignoring the symptoms of a failing intake manifold can lead to much more serious and expensive problems down the road. Here's what could happen:

Catalytic Converter Damage: Engine misfires caused by a bad intake manifold can dump unburnt fuel into the exhaust system, overloading and potentially destroying the catalytic converter. Catalytic converter replacement is a costly repair.
Engine Overheating: If coolant leaks are present, they can lead to engine overheating, which can warp the cylinder head or even cause catastrophic engine failure.
Poor Engine Performance: Continued operation with a bad intake manifold will result in progressively worse engine performance, making the car difficult to drive and potentially unsafe.
Increased Emissions: A malfunctioning intake manifold can cause the engine to run rich (too much fuel) or lean (not enough fuel), leading to increased emissions and failure to pass emissions tests.
Valve Damage: Severe vacuum leaks can cause lean conditions that lead to excessively hot combustion temperatures, potentially damaging the intake valves.

Recommended Fixes: Intake Manifold Removal and Replacement

The primary fix is to replace the intake manifold. Here's a general guide to removing it. Always consult your vehicle's repair manual for specific instructions and torque specifications. Safety is paramount, so disconnect the negative battery terminal before starting.

Preparation: Gather all necessary tools: socket set, wrenches, screwdrivers, pliers, torque wrench, OBD-II scanner, and a new intake manifold with gaskets. Have rags and drip pans handy.
Disconnect the Battery: This prevents accidental electrical shorts during the process.
Remove Air Intake Components: Disconnect and remove the air intake tube, air filter housing, and any related components blocking access to the intake manifold.
Disconnect Wiring and Vacuum Lines: Carefully disconnect all electrical connectors and vacuum lines attached to the intake manifold. Label each one clearly to ensure proper reassembly. Take photos for reference.
Disconnect Fuel Lines: Relieve fuel pressure first. Disconnect the fuel lines from the fuel rail, taking precautions to prevent fuel spillage. Have rags ready.
Disconnect Throttle Body: If the throttle body is attached to the intake manifold, disconnect it, including the throttle cable or electronic throttle control connector.
Remove Supporting Brackets: Identify and remove any brackets or supports that are holding the intake manifold in place.
Remove Intake Manifold Bolts/Nuts: Carefully loosen and remove the bolts or nuts that secure the intake manifold to the cylinder head. Work in a crisscross pattern to avoid warping the manifold.
Remove the Intake Manifold: Once all bolts are removed, gently wiggle the intake manifold free from the cylinder head. Be careful not to damage the cylinder head surface.
Clean the Mating Surfaces: Thoroughly clean the cylinder head and intake manifold mating surfaces using a gasket scraper and appropriate cleaning solvent. Ensure the surfaces are smooth and free of old gasket material.

Once the old intake manifold is removed, you're ready to install the new one. Follow the reverse order of the removal process, paying close attention to the following:

Install New Gaskets: Always use new gaskets when installing a new intake manifold.
Torque Specifications: Torque the intake manifold bolts to the manufacturer's specified torque in the correct sequence. This is crucial for proper sealing.
Reconnect Everything: Double-check that all electrical connectors, vacuum lines, and fuel lines are securely reconnected.
Check for Leaks: After installation, start the engine and check for any vacuum leaks or coolant leaks around the intake manifold.
Clear Diagnostic Codes: Use an OBD-II scanner to clear any diagnostic trouble codes related to the intake manifold.

Cost Estimates and Shop Advice

The cost of replacing an intake manifold can vary significantly depending on the vehicle's make and model, the type of intake manifold, and whether you do the work yourself or take it to a mechanic.

DIY: The cost of the intake manifold and gaskets can range from $200 to $800 or more. You'll also need to factor in the cost of tools if you don't already have them.
Professional Repair: Labor costs can add an additional $300 to $1000 or more, depending on the complexity of the job and the shop's hourly rate. Expect a total cost of $500 to $1800 or more.

Shop Advice: If you're not comfortable performing this repair yourself, it's best to take your vehicle to a trusted mechanic. Get multiple quotes and ask about the warranty on the parts and labor. A reputable shop will be able to diagnose the problem accurately and recommend the appropriate repair.

TSBs and Common Failure Mileage: Intake manifold issues are common enough that manufacturers often issue Technical Service Bulletins (TSBs) to address specific problems. Research TSBs for your vehicle's make and model to see if there are any known issues or recommended solutions. Many intake manifold failures occur around the 80,000 to 150,000-mile mark, but this can vary depending on driving conditions and maintenance history. Reviewing online forums and owner communities for your specific vehicle can also provide valuable insights into common problems and solutions. This collective data helps you understand the typical failure points and preventative measures you might consider.