Camshaft

What is an engine camshaft?

An engine camshaft is a mechanical component in truck and bus engines that determines when the valves open and close. Its cam lobes convert rotary motion into a linear push on the valve train, and it sits at the center of the timing system, setting the sequence in which intake air enters the cylinder and exhaust gases leave it. In the workshop, this part is also known as the cam shaft or simply the cam. The surfaces that wear first are the cam lobes that contact the valve followers and the shaft body that rides in the bearings. When the cam faces lose material, valve lift drops, causing power loss, uneven idle and valve noise.

How does an engine camshaft work and what does it include?

Rotation from the crankshaft is passed to the camshaft through the timing gear, chain or belt, and the shaft drives the valve train according to this rotation. The following parts work together in the camshaft assembly.

Camshaft: The main shaft carrying a cam lobe for each cylinder and transferring the rotation.
Cam lobes: Curved surfaces on the shaft that push the valve lifters, setting the timing and duration of valve opening.
Timing gear, chain or belt: Transfers rotation from the crankshaft to the camshaft at the correct ratio and prevents timing from slipping.
Bearings and bushings: Surfaces that let the shaft turn smoothly on an oil film inside the block.
Cover, plugs and seals: Elements that close the shaft ends and the cover area against oil leaks.
Position sensor and mounting hardware: Parts that report the shaft angular position to the engine control unit and keep it fixed in place.

Engine camshaft types

Complete camshaft: Cam lobes, bearings and gear come together; preferred when wear appears on several cams or on the shaft itself.
Cam lobe set: Used to replace only the cams and related sections when the shaft is still sound.
Surface-treated camshaft: Cam faces are hardened against wear and are preferred in engines expected to carry high loads over long service life.
OE-equivalent quality camshaft: Standard type matching the engine model, a direct equivalent of the removed part.

How to choose the right engine camshaft?

The right choice should be made by reviewing the marks on the removed part, the engine type and the cam layout together. Even within the same model series, Mercedes-Benz, MAN, Scania, Volvo and DAF can use different layouts, so choosing by model name alone is an error. The cam order, gear marks and bearing surface of the old part should be compared with the new one, and the engine type and system layout should be recorded before removal.

Criteria	What to check	Why it matters
Engine type	Cylinder layout and valve design	Cam layout varies by type, and the wrong part disturbs timing
Old part reference	Cam and gear marks on the removed shaft	Rotation direction and cam order must match the old part
Cam lobe surface	Scratches, pitting and wear marks	Surface loss reduces valve lift and shifts the timing
Bearing and shaft surface	Scoring in the bearing, ovalization on the shaft	A worn bearing makes the camshaft vibrate
Gears and drive elements	Condition of gears, chain or belt	A loose drive connection can shift the timing
Sensor and position mount	Condition of the mark and sensor connection	Wrong position data leads to faulty engine control unit operation

Installation and maintenance points

Timing marks: Marks on the crankshaft and camshaft gears must be aligned before fitting.
Lubrication: Bearing surfaces and cam lobes should be coated with engine oil before fitting; never install them dry.
Bearing caps: Caps must be tightened in the manufacturer's sequence and torque, as a loose connection causes leaks and vibration.
Gasket and seal: The cover gasket and shaft seal should be renewed, and the old gasket must not be reused.
Chain or belt tension: Drive element tension should be checked, as a loose chain shifts the timing.
Oil change: Oil and filter should be changed regularly, since dirty oil speeds up wear on bearings and cam surfaces.

Common faults and solutions

Valve noise and ticking: Cam lobe wear or incorrect valve clearance; the camshaft is checked and a worn cam or shaft is replaced with a new one.
Power loss: Timing drift or reduced cam height; the timing marks are checked, the drive element is retensioned or the camshaft is renewed.
Uneven idle: Bearing scoring or vibration; the bearing surface is inspected and the worn bushing and bearing are replaced.
Oil leak: Worn cover gasket or shaft seal; the gasket and seal are renewed and the surfaces are cleaned.
Warning lamp: Position sensor fault or timing mismatch; the sensor connection and gear alignment are checked.

Frequently Asked Questions

When should an engine camshaft be replaced?

Replacement should be considered when clear wear shows on the cam lobes, valve noise increases, power drops or timing drifts. Before deciding, the bearings and drive elements should also be inspected.

Is a cam shaft the same as a camshaft?

Yes, both names are used in the workshop for the same component. The engine type and the cam layout of the removed shaft should be the reference for choosing the right part.

Is valve adjustment needed after camshaft replacement?

Valve clearance may need to be checked after replacement. Adjustment varies by engine type, so the manufacturer's instructions must be followed.

Can a camshaft from a different engine be fitted?

If the cam profile and gear layout do not match, timing will be disturbed and serious engine damage can occur. Before fitting, the marks on the removed part and the engine type must be verified together.

Which other parts should be renewed when replacing the camshaft?

The cover gasket, shaft seal, bearing bushings and the chain or belt are recommended parts to renew in the same job. Leaving old parts in place can quickly carry wear over to the new camshaft.