What Is The Idler Pulley Torque Spec To Tighten It Properly?

Do you want to know more about the idler pulley torque spec? You don’t know how much is the correct torque spec for tightening the part in your engine? 

Actually, you are not the one who is seeking a thoughtful answer for this common query.

I have consulted some experienced experts in the field and want to share some useful information about the topic to help you unclog this interest.

This way, you can better accompany your automobile in the coming days.

What are you waiting for? Join with me now to get the answer.

What Is Idler Pulley?

idler pulley torque spec

An idler pulley is a prevalent component that is encountered in most automobiles. Its key feature is to guide the motor drive belt and offer tension.

These parts appear on different components of the motor, such as the water pump, alternator, power steering pump, etc.

In a nutshell, the idler is a complementary pulley that helps the whole system operate smoothly.

There are some cues of wear and tear on idler pulleys, which you should pay attention to keep your engine healthy.

Visual signs: The part is getting worn out with time. This wear lessens tension which might result in belt slippage.

More specifically, it can lead to damaged or cracked bearings and pulleys. These issues sometimes make my engine stall and leave me with torn belts.

Auditory signs: Squealing sound from the motor belt might be a clear indicator.

Once the part is worn-out, the engine belt would squeal (especially on cold startups) when it scrapes the outer zone of the idler pulley. It will get worse and worse over time.

By and large, all idler pulleys are vital to the engine function, and changing or fixing them isn’t a simple task.

What Is The Idler Pulley Torque Spec?

chevy 5.3 belt tensioner torque specs

Interestingly, there are no cut-and-dried answers for this, but the idler pulley torque spec varies with car models. It could be 17 ft-lbs, 21 ft-lbs, 30 ft-lbs, or even 50 ft-lbs, etc.

I will dive deeper into the torque spec of my Chevy and Subaru.

Chevy 5.3 Belt Tensioner Torque Specs

When it comes to the specs of the Chevy 5.3 (in this case, Chevy Silverado 1500 5.3), I really want to share with you some key features related to the engine before mentioning torque specs.

In general, this automobile belongs to the family of 4DR trucks. It has launched on the market with a 3-year warranty, estimating around 36,000 miles.

It offers 383 ft-lbs @ 4100 rpm in terms of torque and 355 HP @ 5600 rpm regarding horsepower.

Its engine is a gasoline V8 5.3L with eight cylinders having OHV Valve (Overhead valve) Configuration.

The idler pulley and belt tensioner torque spec of Chevy 5.3 is both 37 ft-lbs.

It utilizes 2 head bolts (different from head studs) with different sizes named M11 and M8. The first one is bigger than the other.

When installing a cylinder head, the M11 is tightened with 22 ft-lbs with an additional 90° turn and then a 70° turn. For M8, applying a force of 22 ft-lbs is enough to tighten it down.

When installing crankshaft caps, you should put 10 ft-lbs of torque at first, then increase to 15 ft-lbs the second time. The third time you should give an extra 80° turn for every inner bolt.

For outer studs, you need a torque of around 15 ft-lbs and give an additional 53° turn. For side bolts, the power you need to put on is 18 ft-lbs.

When installing an oil pump, I use a force of 18 ft-lbs to torque down this pump assembly. The pump cover should be tightened down to 8 ft-lbs.

Subaru Bolt Torque Specs

I’ve synthesized some key specs and shown them in the below bolt torque values table. 

Bolt SizeNumber of TorquesTorque specs
Center Strut Hat Mounting TorqueM10141 ft-lb
Front Upper Strut Hat NutsM8314.5 lb-ft
Lower Strut Mount at KnuckleM142129 lb-ft
Back Lower Strut MountsM142162 lb-ft
Back Strut Hats NutsM8314.5 lb-ft
Forward Support arm Bolts M14430 lb-ft
Rear Key Subframe boltsM144106.9 lb-ft
Back Lower Strut MountingM12159 lb-ft
Back Upper Strut Hat Mounting NutsM10222 lb-ft

Besides, the belt tensioner and idler pulley torque specs of Subaru will differ among models. For example, that torque spec for my Subaru EJ25 is 29 ft-lbs.

Why Is It Vital To Set The Correct Idler Pulley Torque? 

n54 pulley torque specs

There are various designs of idler pulleys discovered in engines. Wrong torque might trigger different troubles depending on the pattern.

  • Some idler pulleys are fixed in cast aluminum. Excessively tightening might strip the specific bolt threads, leading to a pricey repair.
  • A timing belt pulley that is screwed excessively will vibrate, which might trigger the belt to slip off easily.
  • A too-tight belt pulley won’t move freely. This could result in premature wear and tear on the belt. Squeaking noise will be a clear symptom you can find out easily on this worn-out part.

As mentioned, different engines have different idler pulley torque specs. In some motors, it is 33 ft-lbs of torque. In others, it is 50 ft-lbs. It might be 17 ft-lbs in other engines.

Therefore, it is hard to get a uniform torque spec for all engines. That is why it is key to know the correct torque specs before screwing the belt idlers.

Keep in mind that you should not miss your vehicle handbook. Most automakers will unveil the right specs in this instruction. The timing belt pulley might be named the belt idler pulley there. 

This is also my answer to the common question: Can you over tighten an idler pulley

Final Thoughts 

Once you have kept your patience with me until these bottom words, I bet you reached a thoughtful answer to your curiosity earlier about idler pulley torque spec.

Finding the right belt tensioner or idler pulley torque spec is indeed necessary to avoid unnecessary trouble for your vehicle.

This is an important part of helping your entire engine to run smoothly. Don’t forget to pay more consideration to frequently checking it.

Thank you, and see you soon.

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