Gasket Removal, Replacement Tips

Gasket Q&A: Removal tips and more

Question: When replacing a gaskets on an engine, do I just scrape or peel off the old gaskets, or do I have to do something else?

Answer: Removing gaskets used to be a fairly simple procedure. Most engines used to have cast iron blocks and heads, with iron manifolds and stamped steel covers. Iron castings could withstand a lot of abuse, so if the old gaskets were stuck in place, you could scrape them loose or grind off the residue. You didn’t have to worry too much about damaging the sealing surface.

Question: On late-model engines, what procedures have changed?

Answer: Today’s engines are different. Most are either “bi-metal” engines with aluminum cylinder heads on cast iron blocks or all-aluminum. Stamped steel valve, oil pan and timing covers are still used, but so are cast aluminum, magnesium and plastic covers. Plastic intake manifolds also are common. These softer materials can’t take the abuse their cast iron ancestors could, so gasket removal requires more finesse rather than brute force.

Use care to avoid scratching, gouging or damaging these parts when gaskets are removed. A small scratch or gouge may not seem like a big deal, but it doesn’t take much of a surface imperfection to create a leak path on many of these engines.

At the same time, gaskets have also changed. Many engines today have soft-faced composition head gaskets with a solid or perforated steel core surrounded by graphite or a non-asbestos material. Some have a slippery “non-stick” coating that improves cold sealing and also makes the gasket fairly easy to remove, but others have a sticky silicone coating that adheres to metal surfaces and is difficult to remove. Many late-model engines also use multi-layered steel (MLS) head gaskets. These gaskets are made of three to five layers of steel and have a very thin rubber coating on the outside to improve cold sealing. The rubber tends to stick to the surface and can be difficult to remove.

MLS head gaskets also require a very smooth, almost polished surface finish to seal properly, which means you have to be extremely careful not to scratch or gouge the surface when replacing a head gasket on one of these engines.

Most cork/rubber valve cover, oil pan and timing cover gaskets have been replaced with molded silicone rubber gaskets (which come off easily but should not be reused), and some covers have no gaskets at all. They are sealed with RTV silicone, which has to be scraped off and replaced with fresh sealer or a gasket when the parts are reassembled.

Gasket RemovalQuestion: Can an engine have a bad head gasket but not leak coolant into the crankcase?

Answer: Yes. If the leak is between cylinders, the gasket may not leak any coolant into the crankcase or cylinders, but it will leak compression between the adjacent cylinders. This will usually cause a steady misfire and a significant loss of power. A compression test or a power balance test can be used to confirm the problem.

This type of head gasket failure may be the result of overheating, detonation or improper torquing of the cylinder head bolts. Any of these may crack or crush the steel armor that surrounds the combustion chamber.

If a head gasket is leaking coolant, the loss of coolant will eventually allow the engine to overheat, which may cause further damage to the head gasket and possibly the cylinder head, too. An internal coolant leak can be confirmed by pressure testing the cooling system to see if it holds pressure.

Question: What about adding a sealant to the coolant system?

Answer: Adding sealer to the cooling system may seal a few head gasket coolant leaks, but such a product is no help whatsoever if the head gasket has a compression leak between cylinders. Replacing the head gasket is the required fix.

Question: How do I remove difficult gasket residue?

Answer: Many intake manifolds are sealed with gaskets that have raised or printed silicone beads on a metal or plastic carrier. Others have no gaskets at all and just use sealer.

One of the safest ways to remove old gaskets is to spray them with aerosol gasket remover. Give the chemical time to work (usually about 20 minutes), then carefully scrape away the gasket residue with a scraper tool (not a screwdriver) or razor blade.

The trick to properly using a gasket scraper is to scrape at an angle that is almost parallel to the surface. By keeping the angle small, the tip of the scraper will slip under the gasket and shear it away from the surface without digging in. If you try to use it like a chisel, you’ll probably end up gouging the surface and damaging the part.

Using an abrasive pad in a drill to whiz off gasket residue on aluminum or plastic parts is risky because the abrasive pad may remove material that leaves a depression that may cause the replacement gasket to leak.

You May Also Like

Beyond the Warranty

What does it take to keep a car going for 120,000, 180,000 or 250,000 miles? The key is maintenance and inspection. 

Step up maintenance to go farther

What happens after the bumper-to-bumper warranty and powertrain warranty wear out? If you look at any factory-recommended service intervals, after 100,000 miles they cease to exist.

What does it take to keep a car going for 120,000, 180,000 or 250,000 miles? The key is maintenance and inspection. 

Misfire Codes P0300, P0301-P0312 and P0313+P0314

The only way to clear the code is to use a crankshaft position relearn with a scan tool.

What Caused The Turbo To Fail?

Up to 50% of turbocharger failures are due to oiling problems.

Valve Lifter Technology

Hydraulic lifters are precision-fit assemblies.

Supercharger Pros And Cons

Customers generally look to superchargers for the instant throttle response, not fuel economy.

Other Posts

Plastic Timing Chain Guides

Timing chain guides are designed to wear, but the guides are designed to last the engine’s life.

It’s Got Spark!

Why can’t you trust some spark tests?

Honda Electronic Throttle Body Service Tips

Using care and following OEM procedures will help you to avoid unnecessary parts replacement and comebacks.

Belts and Pulley Alignment

A misalignment of the plane of the belt can occur when a pulley is not parallel to the other pulleys on the belt drive system.