C5/C6/C7 Engine Cleaning

Whether prepping your Corvette to roll across the auction block or display at a show, cleaning the engine adds value. A spotless engine shows just how important and well maintained is your Corvette. Filthy engines are more apt to retain heat and make it difficult to detect small leaks. Dirt and dust cause pulleys and belts to squeak from undue wear. Worst of all, it just looks bad.

Since the 1997 and newer engines use one ignition coil per cylinder, they can be cleaned without worry of water damage. Ignition distributors can be troublesome during engine cleaning, even with early cars, and very troublesome with the 90-96 LT series engines.

This is very important: the engine must be at ambient temperature with no heat buildup. Don’t start the engine for any length of time! Park the car overnight where the engine cleaning will take place. If the engine is even slightly warm, electronic components can condense moisture internally when cold water hits the surface.

All electrical components and connectors are weatherproof so direct water will not cause corrosion or damage. There is no need for a high pressure washer or steam cleaner in most cases. Steam cleaning is not a good idea because it will cause condensation. Pressure washers can force water into places it shouldn’t be, making it difficult to remove. Water should only be directed at the engine block or cylinder heads.

Annual cleaning makes the procedure simple. A garden hose has enough pressure to safely remove any dirt, dust, and debris. While you are cleaning the engine and compartment, the radiator should be checked for debris. Radiator debris can be flushed out with the garden hose.

Keep things cool to avoid plastic part damage. Washing in the direct sunlight can discolor plastic covers if the cleaner dries on the pieces. Keep a water hose handy to rinse the exterior if any cleaning product gets on the paint.

If the underside of the hood is dirty, wash it first then rinse the exterior well. Apply cleaner to the engine and entire compartment. Wait approximately ten minutes before rinsing. Keep all areas wet with cleaner until rinsing is started.

We use Greased Lightning cleaner everywhere under the hood. Greased Lightning lifts the dirt and dust to limit hand rubbing or brushing. There aren’t any coated components that will discolor so citric acid cleaners will work without causing damage.

We remove the engine covers and clean under them. Once everything is rinsed, compressed air should be used to blow off the water. Corrosion may begin if water is left under the engine covers.

Once the engine bay is cleaned you’ll be proud to show it off at any show or cruise night. It makes a good impression on a potential buyer to see an engine that has been maintained properly.

Remove air filter intake duct and cover throttle body opening with duct tape, for a thorough cleaning of the engine front. Check air filter element or service a high performance washable element. Remove air cleaner housing or cover opening to prevent water intrusion.

Removing the radiator cover is simple and allows better access to radiator and A/C condenser. Cover is affixed with two 10 millimeter hex head bolts on each side. Once removed, cover lifts straight up. You may be surprised by the debris built up on the radiator and condenser.

Remove plastic engine covers before applying cleaner. Spray entire engine with cleaner, including inner fenders and radiator area. If the sun is beating down on the engine it is easier and safer to clean in sections. Apply cleaner as many times as necessary; however, if the engine is wet, the cleaner won’t be as effective.

As you can see, we have no fear. Give the engine as much water as required to remove cleaner and dirt.

Use compressed air to blow water from the engine and compartment. Be sure to blow all the water out of the alternator before starting. A landscape blower will do a good job if compressed air is not available but it’s difficult to direct into close areas.

Once cleaning has been completed, apply spray silicone lubricant on plug wires. Spray silicone on a clean cloth and then wipe the wires. Silicone helps repel water and does a good job of cleaning plug wires.

Finish by applying high temperature grease at the hood latches. Spray the hood hinges with lubricant. Super Lube multi-purpose synthetic spray lubricant sprays as a liquid but leaves a film of lubricant as it dries. LPS #1 is a similar product that works equally well.

Story and photos courtesy Chris Petris

20 thoughts to “C5/C6/C7 Engine Cleaning”

  1. When I start my C5 and let it run it makes a squeaky sound and when I turn on the AC the sound stops until I accelerate. Sometimes the sound will stop after I’ve driven the car awhile. I’m not sure if it’s the pulley (AC) or what. Can you give me some advise as to what you think it could be? Thank you.

    1. First step I would do is open the hood and try identifying where the noise is coming from. If unable to identify then I would recommend taking the car to a certified Corvette technician.

  2. I am a Minnesota resident and getting ready to store my C6 till April. Recommendations appreciated. Does it need to be placed in a heated garage like I have kept both of my C5 and C6 in the past with a battery tender?

  3. MAAAAAAN, I wish I had read all this before having the engine in my ’98 C5 pressure washed! Now the wipers operate whenever they want to and I get a strange whining noise under the dash that is intermittent and sound like a sound between a baby crying and a geiger counter. The damage is done and I will NEVER AGAIN allow water under my hood. Any way to stop these obscene noises?

    1. I had the same problem with the windshield wipers on my 99. It seems they (engineers) put the motor in a ‘bowl’ and it has a small drain hole in bottom, a leaf or an acorn will stop it up and then the motor starts doing things on it own. I had the mechanic put multiple holes on the ‘bowl’ about the size of a nickel so it could drain better.

  4. Great advice all around. Low pressure and hand washing followed by the silicone treatment is pretty foolproof. There are a lot of small openings that can accumulate water and cleaners. The space by the radiator is quite the debris trap and a crevice tool on a vacuum is just about the right fit when used carefully. My 04 Roadster gets this treatment spring and fall. The engine covers can be tricky on the driver’s side especially. A little silicone on that braided hose can help the cover slip off.

  5. I spray everything under the Hood with STP tire foam. Let it set for bout 15 minutes the mist excess off. Then take dry micro rag and wipe down then air dry with leaf blower then one final wipe down. It’s cheap and the STP foam cuts dirt film build up and leaves all black parts nice and semi glossed. It also is a non greasy formula that will not make belts slip. The leaf blower is equivalent to a 500 mph wind tunnel but unlike an air hose and forced air from a compressor does not force air in unwanted areas. Sounds like almost too simple but you’ve got to try it. Used to work at a bike shop as a weekend hobby and detailed a lot of motorcycles and ATVs this way no scratches and took about a half can for a bike and whole can for ATV. Note: cover windshield to prevent overspray and will not hurt painted surfaces.

  6. I have a C5 and a El Camino with a LS1 and basically use the same procedure as 1-7 with great success. On the C5 I cured overheating problem using step 2, the area between the radiator and condenser collected a lot of trash, problem solved.

  7. I wipe my engine and other accessible areas under the hood with a damp cloth when I wash the car and it looks great. What is all the fuss about?

    1. They just pop off but be careful when removing the driver’s side. You have the braided fuel line that passes through the FRC and it requires you to flex the cover opening around the line.

  8. I have never been a fan of turning a high pressure hose under the hood of a car or truck with all of the electrical boxes, solenoids and in some cases even part of the energy management systems are under the hood. But in the case of the electronically managed systems with the coil packs I would not want to pressure wash any of this type vehicle.

  9. I’ve been told not to wash motor because of getting water to the knock sensors. I took my car to dealer for pinging on hard acceleration, the first thing they asked me if I had pressure washed my engine. I haven’t and hate a dirty engine compartment, wish someone could clear the big question up.

    1. I wouldn’t recommend pressure washing. Low water pressure and hand drying after is the key. If you’re still not comfortable with that, trying using a rag and engine degreaser.

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