Indispensable for Car Repairs: The Mechanic’s Tensioner

Indispensable for Car Repairs: The Mechanic’s Tensioner


Tension gauge: different types

Role and legitimacy of the tension gauge

Price of a tension gauge

Intervention on a belt without a tension gauge

An improperly tensioned belt can have catastrophic consequences for the engine, which is why the use of a tension gauge by automotive technicians is absolutely necessary. What is the role of this tool highly valued by mechanics? The answer follows in the lines below!

Tension Gauge: Different Types

Mechanical Tension Gauge

This is the universal tension gauge that is now practically abandoned by manufacturers due to its lack of precision. It consists of a fixed claw and a mobile claw calibrated by a spring, into which the belt is inserted; the alignment of two indices allows the tension to be adjusted.

SEEM Unit Tension Gauge

This is a mechanical tension gauge with a digital display that provides tension in SEEM units (= South East Electro Mechanic: it is a unit of measurement that includes the parameters of belt flexion, its thickness, and tension force in newtons). This tension gauge comes with a table of different tension values by brand and engine (the SEEM unit value is also provided by the vehicle’s technical review).

Frequency Tension Gauge

Based on the principle that tension implies a specific frequency of vibrations (in Hertz), this type of device is equipped with an optical sensor placed in front of the belt, which analyzes this frequency after the operator activates belt vibrations manually. This gauge also comes with a manual table of frequency values.

Role and Legitimacy of the Tension Gauge

Indispensable for Car Repairs - The Mechanic's Tensioner

Modern automotive engines are equipped with devices driven by belts that must have an ideal tension:

The alternator, power steering pump, air conditioning compressor, and in some cases, the water pump through the same and only accessory belt.

The timing belt: for the engine crankshaft; the camshaft(s); high-pressure pump for diesels; often the water pump.

This ideal tension is adjusted by the tension gauge, under the risk of causing significant malfunctions of engine parts. For instance:

  • A loose accessory belt may “flap” and slip, emitting a loud noise and quickly self-destruct.
  • A loose timing belt, on the other hand, risks shifting, desynchronizing the engine, and causing its destruction.
  • An excessively tight accessory belt exerts force on the bearings of the components and quickly leads to their destruction.
  • An excessively tight timing belt, with engine expansion when hot, will quickly break and lead to its destruction (it then emits a characteristic whistling).

Even for experienced mechanics, the use of the tension gauge will be necessary as the adjustment of belt tension requires precision.

Price of a Tension Gauge

While the mechanical tension gauge is within everyone’s reach, starting at $45 on e-commerce websites, electronic SEEM tension gauges with an average price of $400, and frequency measurement gauges at $600, available at professional automotive tool dealers, are much less affordable for individuals.

Intervention on a Belt Without a Tension Gauge

In some specific cases, there is no need to use a tension gauge:

  • Manual Method: This empirical method can only be applied to certain types of older generation engines with simple design. It involves twisting the belt and checking that it rotates a maximum of 1/4 turn, requiring a certain sensitivity acquired after several years of practice.
  • Automatic Adjustment: Some engines are equipped with automatic tensioners for accessory and timing belts, which do not require the use of a tension gauge.

Note: There are now accessory belts without a tensioner, but their installation on pulleys requires specific tools.

The tension gauge proves to be an indispensable tool for automotive technicians in ensuring the proper tension of belts in modern engines. While various types of tension gauges are available, their accurate usage is crucial to prevent potential engine malfunctions and damages. Despite the higher cost of advanced electronic gauges, their precision justifies their value for professionals. For individuals, manual techniques or engines with automatic tensioners offer alternatives. Overall, the tension gauge remains a key ally in maintaining the optimal performance and longevity of automotive engines.

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