Valve replacement

Valves are replaced when they are burnt, bent after a timing-belt failure, have stem wear or no longer seal at the face.

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Symptoms

Loss of compression in a cylinder, misfiring, loss of power.
A characteristic backfire into the intake or exhaust.

What's included

Symptoms are low compression in a cylinder, misfiring, power loss and a characteristic backfire through the intake or exhaust. We remove the cylinder head, inspect every valve and seat, and check guide wear. Each new valve is lapped to its seat and tested for sealing; without this, compression will not recover no matter how many parts are changed. We also assess the condition of stem seals and springs. After assembly, we check compression and confirm that the engine runs evenly in every mode.

Additional checks

Checking valve guides for wear
Inspecting every valve and its seat
Checking compression and even running in every mode after assembly

Why it matters

A new valve is always lapped to its seat: without this, compression won't come back no matter how many parts are replaced. The seals and springs are checked at the same time, to avoid taking the head apart again.

More details

Valves are replaced when burned, deformed after a timing belt failure, worn on the stem, or leaking at the seat face. The symptoms are a drop in cylinder compression, a rough idle (misfiring cylinder), loss of power, and a characteristic "backfire" into the intake or exhaust. We remove the head, inspect every valve and seat for defects, and check the guides for wear. A new valve is always lapped to its seat and checked for a proper seal — without this, compression won't be restored no matter how many parts are replaced. At the same time we assess the condition of the valve stem seals and springs. After assembly we check compression and make sure the engine runs smoothly in every mode.

Need a Technician Consultation?

Describe the vehicle and symptoms, and we will suggest which check to start with.