What Causes The Sawing Sound When An Excavator Is Digging?

What causes the sawing sound when an excavator is digging?

Causes and Troubleshooting Sequence for Harsh, Sawing-like Noises During Excavator Operation

Noise Characteristics: Resembles the sound of a saw or harsh friction; prominent under load/stress, while faint or absent during idling. The noise triggers immediately upon digging or applying force. Categorized into two main types: external mechanical friction and internal hydraulic whining.

I. Most Common: External Metal-on-Metal Friction (A genuine friction sound, closely resembling sawing wood)

1. Dry friction at the excavator bucket pins and bucket ears (Highest probability)

Symptoms: A "creaking/sawing" sound occurs during bucket retraction or digging under load; the noise intensifies when rotating the bucket; pins appear blackened, hot, and lack grease.

Causes: Clogged grease nipples or failure to grease over a long period; dry friction between the pin and bushing creates a sawing noise from metal-on-metal grinding.

Remedy: Clean grease nipples and apply high-temperature lithium-based grease; replace bushings or pins if wear is severe.

2. Dry friction at the boom/stick pins and linkage

Friction occurs during lifting or retracting the stick under load; the sound originates from the mid-section of the boom assembly; also caused by a lack of grease.

3. Hard friction between the bucket base plate/side teeth and rock

Occurs when digging hard soil or rock; the bucket's steel plate scrapes against the rock, producing a continuous rasping or sawing sound; no noise during unloaded swinging.

Remedy: Check bucket teeth for looseness, deformation, or upturned edges; grind down any protruding steel plate sections.

4. Track and Undercarriage Friction (Noise occurring during simultaneous travel and excavation)

Carrier rollers or track rollers are seized due to lack of lubrication, causing the track chain to scrape against the guard plate;

Improper track tension causes the chain to rub against the guard during travel, resulting in a continuous, harsh scraping sound.

5. Interference/Friction between Hoses/Lines and the Boom Structure

Hydraulic hoses rub against steel plates due to prolonged vibration; movement of the boom creates a continuous "sawing-like" friction sound—close inspection reveals wear marks on the hose outer casing.

II. High-pitched, piercing hydraulic system noise (resembling the sound of sawing wood) with no signs of significant metal wear

Issues with hydraulic fluid, the pump, or the filter element can cause high-pitched, grating noise that intensifies during heavy digging operations:

1. Insufficient hydraulic oil / Air intake

Low oil levels in the tank cause the hydraulic pump to draw in air; this results in a high-pitched, rasping, saw-like screeching sound under digging loads, accompanied by jerky movements.

Solution: Top up with OEM hydraulic oil; check the intake line seals and filter element for air leaks.

2. Clogged return or suction filter elements

Restricted oil flow and high pump suction resistance cause a continuous, piercing noise during high-speed digging, accompanied by sluggish movements and engine lugging (stalling under load).

3. Main pump wear / Valve plate scoring

Internal metal wear causes high-pitched, saw-like noise whenever a load is applied; the noise is quieter when the machine is cold but intensifies as it warms up, accompanied by rising oil temperatures and a loss of power.

4. Relief valve screeching due to frequent pressure release

When digging hard soil and the bucket stalls against the ground, the main relief valve repeatedly opens, producing a sharp, screeching sound resembling a saw cutting wood; the engine lugs, and movements become jerky or stutter.

III. Abnormal noise from the engine drive system (varying with engine speed)

1. Fan belt slippage or damaged tensioner bearing: High-load operations (such as excavating) cause the belt to emit a high-pitched squeal resembling the sound of a saw;

2. Lack of lubrication or wear in the engine idler pulley or alternator bearings;

3. Aging of the rubber coupling block connecting the hydraulic pump, or metal-on-metal friction.

Quick and simple self-check steps

1. Listen to the source of the sound:

● Sound from the front of the bucket → Pin lacks grease;

● Sound from the boom in the middle of the machine → Boom pin / hydraulic line interference;

● High-pitched whining and sluggish operation → Air in the hydraulic system / clogged filter element;

● Noise occurs only when traveling while digging → Undercarriage/tracks;

● Noise varies with engine speed → Belts, engine bearings.

2. Simple operational test:

No-load movement (without digging/scooping soil): No noise = Friction from external forces (pins/bushings, or bucket scraping against rocks);

3. Persistent harsh noise during no-load movement = Issues with the hydraulic pump, filter element, or air intake.

4. Basic excavator maintenance:

Grease all pins and bushings → Check hydraulic oil level and replace hydraulic filter → Inspect oil lines for rubbing against the chassis.