Instructions for replacing valve stem seals – Mercedes

Replacing valve stem seals: small part, big difference

At Stolk Car Parts, we regularly see engines start consuming oil after many years due to, among other things, worn valve stem seals. These small rubbers have an important task: they regulate the oil supply to the valve stem and prevent excessive oil from leaking past the valve guide into the combustion chamber.

As hard as a Lego brick

Valve stem seals are made of rubber. As they age, they can become hard and brittle. We sometimes joke: “As hard as a Lego brick.” The rubber then no longer seals properly, allowing oil to leak past the valve stem.

This can lead to increased oil consumption, blue smoke from the exhaust, and fouling of the combustion chamber. If driven with this condition for too long, it can also affect the engine and, for example, the catalytic converter. It is therefore important to replace worn valve stem seals in time.

How do we replace valve stem seals?

The exact procedure varies per engine. Therefore, we always follow the manufacturer's specifications and regulations. For some engines, the valve stem seals can be replaced without removing the cylinder head. For other engines, it is advisable to do so in combination with other work, such as replacing valve guides or during a cylinder head overhaul.

A commonly used procedure for a mounted cylinder head is as follows:

1. Remove valve covers

Before we begin, we carefully clean the area. This prevents dirt from getting into the engine.

2. Dismantle the valve actuation

Depending on the engine, the valve lifters, rocker arms, and possibly the camshafts are removed. Parts are neatly sorted so that they can be returned to their original positions.

3. Place the cylinder in the correct position

The piston of the cylinder we are working on is positioned according to the prescribed procedure. When working with compressed air, it is important that the motor is properly blocked and that the correct position is maintained. This prevents the motor from rotating unexpectedly or a valve from falling into the cylinder.

4. Hold valves in place

In our garage, we use a suitable compressed air adapter to apply compressed air to the cylinder. This keeps the valves pressed against the valve seats. The correct pressure and procedure depend on the engine and the tools used.

5. Remove valve springs

The valve springs are compressed using special tools. Next, we remove the valve shims and the retainer above the valve spring. The valve shims are small parts, so it is important that they do not fall into the engine.

We use a small magnet for this. A little grease on the tip of a screwdriver can also help hold a valve stem in place during some work.

6. Remove old valve stem seals

The old rubber seals are carefully removed. We use suitable tools for this so that the valve stem and valve guide are not damaged.

7. Install new valve stem seals

When installing the new rubber seals, we use a mounting sleeve. We slide this sleeve over the valve stem so that the new rubber is not damaged by the sharp edges of the grooves for the valve stem seals.

A little bit of motor oil helps with careful assembly. Then we remove the sleeve and check if the rubber seal is properly in place.

8. Reassemble everything

Next, the valve springs, retainers, and valve stems are reassembled. Then, where necessary, the camshafts, rocker arms, and other parts are reinstalled.

For engines with adjustable valve clearance, it must be checked according to the regulations after the work and, if necessary, readjusted.

A small part, but important work

Replacing valve stem seals may seem like a minor repair, but it requires precision. Proper installation, cleaning the work area, and carefully reinstalling all parts are important to prevent problems.

After the work is completed, we briefly warm up the engine and then change the engine oil to remove any debris. Naturally, we follow the manufacturer's instructions.

Valve stem seals for Mercedes

Valve stem seals are available for various Mercedes engines. We supply parts for the M116, M117, M119, and other classic Mercedes engines, among others.

View our valve stem seals in the webshop.

Also for the right mounting sleeves for valve stem seals you can come to us.

Do you have questions about replacing valve stem seals or the right parts for your Mercedes? Please feel free to contact us. We are happy to assist you.

Stolk Car Parts – specialist in Mercedes parts.

Important

This installation advice has been compiled with the greatest possible care and is intended solely as a general technical guideline. The official workshop manual and the manufacturer's specifications for the relevant vehicle and engine type are always the guiding principles.

Always check the correct assembly procedure, adjustments, and tightening torques for the specific motor before commencing work. We accept no liability for damage resulting from incorrect assembly, improper use, or the application of incorrect or incomplete technical information from this assembly advice.