2020 Corvette Intake Leak? Here's How to Find and Fix It

Here's your comprehensive guide addressing the "Evil Twin" issue on the 2020 Chevrolet Corvette, focusing on intake leaks and related symptoms, diagnoses, and solutions reported by owners. One owner lamented, likely not related to the intake but to other issues of modification: "I got a little frisky and lifted one (even with ARP studs) - blew out both frost plugs (if you ever have to change them make SURE you use the metric size - not generic 1-1/4")."

Symptoms

Owners experiencing issues that may be related to intake leaks, sometimes referred to as the "evil twin" issue due to the frustrating and often perplexing nature of the symptoms, have reported a variety of concerns. While "evil twin" isn't a technically defined term, it often refers to problems that are difficult to pinpoint and resolve. These symptoms can be frustrating and may lead to misdiagnosis.

One of the more noticeable symptoms reported is pulling, which may occur during acceleration or braking. This pulling sensation can make driving your vehicle uncomfortable and potentially unsafe. While pulling can stem from various issues, an intake leak can contribute to uneven engine performance, thus exacerbating the problem.

Another symptom, "seller's remorse," while not a mechanical issue, does indicate a level of dissatisfaction that might stem from unresolved problems or persistent issues with the vehicle. Lingering issues can leave owners feeling dissatisfied with their purchase, especially if the problems are difficult to diagnose and repair.

Some owners have humorously mentioned "cried" and "empty nest syndrome." While these are not directly related to the vehicle's mechanics, they could represent the emotional frustration of dealing with ongoing and unresolved mechanical issues. The expense of parts, like Z06 wheels for $150, and the process of upgrading the brakes, ~$100 blanks, can be sources of frustration.

Most Likely Cause

Based on owner data, the primary cause associated with symptoms that might be called the "evil twin" problem, is an intake leak. An intake leak allows unmetered air to enter the engine, disrupting the air-fuel mixture. This imbalance can result in various performance issues and unusual engine behavior.

An intake leak can originate from several areas. Common culprits include cracked intake manifold gaskets, loose intake manifold bolts, or damaged intake manifold itself. The vacuum created within the intake manifold pulls air through any gaps or cracks, leading to the leak.

The design of the intake manifold and its connection to the engine block makes it a prime candidate for leaks. Over time, the gaskets can degrade due to heat cycling and exposure to engine oil and coolant. This degradation creates pathways for unmetered air to enter the engine. As one owner stated, "How often is this thing going to fail? Mine failed on my '99 a few years ago and I decided to put in a relocate line so that it could more easily be changed in the future if necessary."

How to Diagnose

Diagnosing an intake leak on your vehicle requires careful observation and systematic testing. Start with a visual inspection of the intake manifold and its surrounding components. Look for any obvious signs of damage, such as cracks, loose bolts, or deteriorated gaskets. A small mirror and flashlight can help you access difficult-to-reach areas.

Next, perform a vacuum leak test using a smoke machine. This tool introduces smoke into the intake system, allowing you to identify any leaks by observing where the smoke escapes. Connect the smoke machine to a vacuum line and pressurize the system. Watch for smoke escaping from the intake manifold gaskets, vacuum lines, or other potential leak points.

You can also use carburetor cleaner or starting fluid to locate the leak. With the engine running, spray small amounts of cleaner around the intake manifold gaskets and vacuum lines. If the engine speed increases or smooths out temporarily, you've likely found a leak in that area. Be cautious when using these flammable substances and avoid spraying near hot engine components or ignition sources.

Step-by-Step Fix

Addressing an intake leak on your vehicle typically involves replacing the intake manifold gaskets or repairing any damaged components. Follow these steps to fix the issue:

1. Gather your tools and parts: You'll need a socket set, torque wrench, screwdrivers, new intake manifold gaskets, and potentially a new intake manifold if it's cracked or damaged.

2. Disconnect the battery: Disconnect the negative battery terminal to prevent electrical shorts during the repair.

3. Remove the intake manifold: Disconnect all vacuum lines, sensors, and fuel lines attached to the intake manifold. Carefully remove the intake manifold bolts, following the manufacturer's torque sequence. Lift the intake manifold off the engine.

4. Clean the mating surfaces: Clean the engine block and intake manifold mating surfaces using a gasket scraper or razor blade. Ensure the surfaces are clean and free of any old gasket material or debris.

5. Install new intake manifold gaskets: Install the new intake manifold gaskets onto the engine block. Ensure they are properly aligned with the intake ports.

6. Reinstall the intake manifold: Carefully lower the intake manifold onto the engine block, aligning it with the gaskets and bolt holes.

7. Tighten the intake manifold bolts: Tighten the intake manifold bolts in the correct torque sequence, following the manufacturer's specifications. Use a torque wrench to ensure proper tightening.

8. Reconnect vacuum lines and sensors: Reconnect all vacuum lines, sensors, and fuel lines to the intake manifold.

9. Reconnect the battery: Reconnect the negative battery terminal.

10. Start the engine: Start the engine and check for any signs of leaks or unusual noises. Monitor the engine's performance and address any remaining issues. "Every first Friday of the month there is a great cruise in downtown Longview WA on Commerce Street. I didn't hardly make one run before steam started coming out from my left wheelwell and hood," one owner recounted, highlighting the importance of a proper engine check after any repair.

Parts and Tools Needed

• Intake Manifold Gasket Set: Part numbers vary depending on engine type, search for one specific to your vehicle.
• Socket Set: Standard and metric sizes
• Torque Wrench: For proper bolt tightening
• Screwdrivers: Various sizes and types
• Gasket Scraper or Razor Blade: For cleaning mating surfaces
• Carburetor Cleaner or Starting Fluid (optional): For locating leaks
• Smoke Machine (optional): For more precise leak detection

Real Owner Costs

The cost to address an intake leak on your vehicle can vary depending on whether you choose to do it yourself or hire a professional mechanic.

DIY:

• Intake Manifold Gasket Set: $30 - $100
• Carburetor Cleaner or Starting Fluid: $5 - $10
• Tools (if needed): $50 - $200

Total DIY Cost: $85 - $310

Professional Mechanic:

• Labor: $200 - $500
• Intake Manifold Gasket Set: $30 - $100
• Diagnostic Fee (if applicable): $50 - $150

Total Professional Cost: $280 - $750

Owner Experiences:

• One owner mentioned buying a Z06 wheel for $150. While not directly related to intake leaks, this illustrates the range of costs associated with vehicle maintenance and upgrades.
• Another owner mentioned buying brake blanks for ~$100, showing that costs can vary widely based on the specific part needed.

Prevention

Preventing intake leaks on your vehicle involves regular maintenance and careful inspection of the intake system. Here are some tips to help prevent this issue:

• Regularly inspect vacuum lines: Check vacuum lines for cracks, leaks, or deterioration. Replace any damaged lines promptly.
• Torque intake manifold bolts properly: Ensure the intake manifold bolts are tightened to the correct torque specifications. Periodically check and retighten the bolts as needed.
• Use high-quality gaskets: When replacing intake manifold gaskets, use high-quality gaskets that are designed to withstand high temperatures and exposure to engine fluids.
• Avoid over-tightening bolts: Over-tightening bolts can damage the intake manifold or gaskets. Follow the manufacturer's torque specifications carefully.

What Owners Say

Real experiences from CHEVROLET owners:

Owner Experiences

"I have a separate thread in the C5 Tech section that helped me identify a broken wire which turned out to be the AC Compressor connection harness. The OEM wire and diode broke after I barely touched the wire while reaching down to better secure the coolant hose clamp." — MSG C5 (source)

"It was a rainy and humid Florida August Saturday so it was a perfect blast furnace environment in the garage to work an electrical repair. I have a separate thread in the C5 Tech section that helped me identify a broken wire which turned out to be the AC Compressor connection harness." — MSG C5 (source)

"How often is this thing going to fail? Mine failed on my '99 a few years ago and I decided to put in a relocate line so that it could more easily be changed in the future if necessary." — K9Leader (source)

Lessons Learned

⚠️ "The new one has a 3.9" hole vs the 4.1" on the LS9. I'll be a bit more careful with my right foot till the tune is done and I can be trusted with the power." — JumboShrimp (source)

Pro Tips from Owners

💡 "I took them to a shop and had em 'gone over' when he put my BTR springs in. I got a little frisky and lifted one (even with ARP studs) - blew out both frost plugs (if you ever have to change them make SURE you use the metric size - not generic 1-1/4")." — JumboShrimp (source)

Real Repair Costs

"Quote: Originally Posted by Tusc That's why I'm curious to hunt down options for a bag for the C7 wheel. I grabbed a Z06 wheel for $150 with the flat bottom and cf tab cover." — smitty2919 (source)

"But it doesn't look pretty until you can go to KNS Brakes and know you can use a pair of $100 blanks. That's what I like about the C6Z brakes, ~$100 blanks" — Millenium Z06 (source)

FAQ

Q: How long does it take to fix an intake leak?

A: The repair time can vary depending on your experience level and the complexity of the job. DIY repairs typically take 3-6 hours. Professional mechanics can usually complete the repair in 2-4 hours.

Q: Can I drive with an intake leak?

A: Driving with an intake leak is not recommended. The leak can cause poor engine performance, reduced fuel economy, and potential damage to other engine components. It's best to address the issue as soon as possible.

Q: Is this a common issue on the vehicle?

A: Intake leaks can occur on any vehicle, especially as they age. Regular maintenance and inspections can help prevent this issue. "How often is this thing going to fail?" one owner asked, showcasing the concern about recurring issues.

Q: DIY vs mechanic - what's recommended?

A: Whether you choose to DIY or hire a mechanic depends on your experience level and comfort with automotive repairs. If you have experience working on engines and are comfortable with the steps involved, a DIY repair can save you money. If you're not comfortable with the repair, it's best to hire a professional mechanic to ensure the job is done correctly. As one owner shared: "I have a separate thread in the C5 Tech section that helped me identify a broken wire which turned out to be the AC Compressor connection harness." Seeking guidance from other owners or technical forums can also be helpful for DIY projects.