Skip Navigation

Select Language

Technical Tips

How to Properly Use RTV

Clean and Dry

By now, you’re aware that the best way to install a Fel-Pro® gasket is clean and dry. Most engines built in the last 25 years use molded rubber gaskets to seal valve covers and oil pans. With these types of advanced gaskets, the overuse of RTV and other types of silicone sealers or other additives will prevent the gasket’s ability to form a reliable seal, causing leaks.

However, there are times that you may need to use RTV as a supplemental sealer while completing various gasket repair jobs. Read on to learn when and how to properly use RTV. Note – Be sure to always follow the manufacturer’s recommendations for proper use of RTV.

Note: Be sure to always follow the manufacturer’s recommendations for proper use of RTV.

When to Use RTV

Due to their shape and design, some molded rubber gaskets necessitate the use of RTV as a supplemental sealer.

  • Please note that RTV is not to be used on the entire gasket; the gasket should be installed clean and dry.
  • RTV should only be used on the corners of the gasket and/or stepped casting areas that have a gap. Using a small amount of RTV will fill in those areas to assure a leak-free assembly.
  • RTV is typically applied to the corner(s) or stepped areas on the engine so as not to smear the RTV during the installation of the component.

The Following Types of Gaskets May Need the Use of RTV in Certain Locations:

  • Where the side rail gaskets will meet the intake end seals (see images below)

We recommend a small dab where the side rail gasket meets the block before the intake end seals are installed


Once the intake end seals are installed, another small dab is recommended where the end seals meet the side rail gaskets

  • To form the complete intake end seals, some engines just use RTV as their end seals (see image below)
  • Where the timing cover meets the block and/or oil pan
  • Where the timing cover meets the oil pan
  • Where the RMB journal and timing cover journal meet the oil pan side rails (T-joint)
  • Stepped areas such as the front cover joint or RMB retainer to block joint (T-joint) (see image below)
  • Front 90-degree joint such as at the timing cover/oil pan joint
  • Rear 90-degree joint such as the RMB cap/oil pan joint (see image below)
  • Where front/rear cam journals form a 90° angle (see image below)
  • Stepped areas such as cylinder head to intake manifold joints (see image below)
  • Stepped areas where the front timing cover meets the cylinder head (see image below)
  • Stepped areas such as half-moon cam plugs


Tips for Using RTV with Gaskets

Proper application of RTV will result in a lasting seal; follow these tips for a successful gasket installation. Please remember that Fel-Pro gaskets are to be installed clean and dry, and that RTV is not designed to be used as a supplement sealer on gaskets. Uncured RTV can act as a lubricant and cause the gasket to slip out of place.

Use in the Right Situation

Only use RTV to seal corners and/or stepped joints where there are gaps – don’t apply to the entire gasket. Consult the repair manual for further directions on where and how much RTV should be applied. You can also check our FIT form (if applicable).

Be Careful

Applying RTV in the wrong areas can cause permanent damage, such as over compression and splitting, to the gasket. It may also cause the gasket to slide out of place. Rubber gaskets are designed to have a certain amount of compression applied to them. The addition of RTV or a sealer puts more compression on the gasket than what it was designed for.

Apply RTV Sparingly

Apply RTV only to the areas that need it – don’t put it on the entire gasket. Remember that when the casting/gasket is torqued into place, the RTV will flow into the joint and gasket. Some manufacturers will recommend the amount of RTV to be applied, and it’s good to remember that a little RTV goes a long way.

Take Your Time

The assembly should be installed within five minutes of the RTV application. Once the engine component is installed and torqued up, the RTV needs time to set up and dry – don’t rush the job. RTV typically needs 24 hours for a full cure.

Learn more about Fel-Pro quality gaskets that are specifically designed for the repair environment, find your car part, or find where to buy your auto part today.

The content contained in this article is for informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content.