How to Stop Engine Valve Seals From Leaking

Written by tyler ellington
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How to Stop Engine Valve Seals From Leaking
Engines with older seals are more likely to leak. (New car petrol engines image by Christopher Dodge from

A leaking valve seal can contribute to damage or failure in your engine. The most common leak is oil and it will be dark brown or yellow in colour. If your oil level is low, you should check the valve cover and oil pan gaskets to see if there is a leaking seal. The valve seal leak can worsen over time, so it is important to stop it at the first sign of problems.

Skill level:

Things you need

  • Oil stop-leak additive
  • High mileage motor oil
  • New seal

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  1. 1

    Add an oil stop-leak additive to your engine for a temporary fix. Add it in the oil filler tube, just as you would motor oil. An oil stop-leak additive is designed to give valve seals extended life by causing them to swell. The swelling of the seal may temporarily stop a leak.

  2. 2

    Use a high mileage motor oil. These oils have seal conditioners in them to stop or reduce leaks. The oil is designed to keep the valve seals soft and pliable in an effort to reduce corrosion that is caused by ageing.

  3. 3

    Replace the leaking seal. Remove the cover over the seal. Scrape away any build-up that has occurred on the area where the new gasket will go. Put gasket sealer on both sides of the new gasket if it is made of cork. If it is made of rubber, you will not need to apply the sealer. Position the new gasket into place in the spot where the old one was. Put the cover back on the new gasket and tighten the bolts.

Tips and warnings

  • High mileage motor oil is for cars with over 75,000 miles.
  • An oil stop-leak additive will not stop a major leak or repair a broken gasket or seal.

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