Diagnosing a Failing Timing Chain: Step By Step Guide

Engine timing would not be complete without timing chains. The intake valve is opened first in a typical four-stroke engine during the first “stroke.” Air and fuel enter the cylinder through an open intake valve when the piston pushes downward.

The piston returns to the starting position, compressing the mixture of air and fuel, and closing the intake valve. After that, the spark plugs ignite, causing combustion and repositioning the piston so that the exhaust valve can open and release the engine’s air supply.

Exhaust valve opening and closing must be timed precisely for engines to work properly. Intake valve opening and closing must be timed precisely. The timing chain is in charge of coordinating the opening and closing of the valves.

Timing chains are a type of equipment that requires regular upkeep. This causes various performance issues and can even cause catastrophic engine damage as they wear down and stretch over time. We’ll examine timing chain operation in depth, as well as how to tell if your timing chain is failing.

What is a timing chain?

An engine’s intake and exhaust valves are opened and closed by a timing chain. A set of gears on the front of the engine block connects the timing chain to the camshaft and crankshaft.

When the engine is turning, the camshaft turns only once every two times the crankshaft does. Small lobes, referred to as cams, on the camshaft open valves by pushing against them.

A timing chain system includes components like this one: the chain, sprockets, tensioners, and guides.

Additional timing chain components

To keep it in working order, the timing chain must be lubricated with engine oil. To protect it from road dirt and debris, the timing chain is enclosed in a timing chain cover that is bolted to the engine block. The cover also lubricates the timing chain with engine oil.

As well as the timing chain, there are timing chain guides on the sprockets to help keep the timing chain in place.

A tensioner is the final component of a timing chain. By using a timing chain tensioner, you can be certain there is no slack in the chain. In order to keep the chain tight, most tensioners use oil pressure instead of springs.

Why do timing chains fail?

Timing chain stretch is the most common cause of timing chain failure. There is a lot of heat generated because the timing chain is so close to the engine block. The metal chain gradually stretches as a result of the heat it has been exposed to. It can “jump teeth” or even fall off the sprockets when the chain gets too long and starts stretching.

Why do timing chains fail

Low oil levels can also cause timing chain stretch. A poorly lubricated metal chain will generate heat and friction because of the gears’ metal surfaces. It is possible that the chain will be starved of lubrication and stretch as a result of low oil levels.

Timing chain tensioner failure

Low oil levels or oil pressure leaks can cause hydraulically actuated tensioners to malfunction. Oil pressure is used by the tensioners to maintain the chain’s tension. The tensioner lacks the pressure it needs to keep the slack from getting into the line when oil levels are low.

Timing chain guide failure

Another common failure point is the timing chain guide. Because the guides are usually made of plastic, heat, engine vibration, and other factors can break them over time.

When the guides break, the chain can go off course and either jump teeth or come to a halt.

Timing chains vs. timing belts

In their most basic form, timing chains are simply metal chains that turn on gears or sprockets when applied to an application. As previously stated, timing belts are rubber-coated and do not engage with sprockets in any way. In addition, timing chain covers protect chains from damage, whereas engine bays typically leave belts exposed.

Timing chains vs timing belts

Belts last longer than timing chains, but timing chains have more failure points. Timing chain covers, tensioners, and guides, among other things, can develop leaks or break. There are fewer supporting parts to fail in a timing belt, but timing belts stretch with use and tend to last less time.

Failing Timing Chain Symptoms

  • Cylinder misfires
  • Metal shavings in engine oil
  • Knocking or rattling noises from engine
  • Rough idling
  • Engine no start

The valves open and close at the wrong times when the timing chain is stretched, jumps teeth, or fails completely. Chain jumps will result in poor performance, misfires, and other problems such as rough idling.

Even though the valves are controlled by the chain, they can fly into the pistons if the chain jumps a lot or completely falls off. As a result, severe internal engine damage can result if this occurs.

How long do timing chains last?

How long do timing chains last

Although most timing chains these days are made to last the lifetime of the engine, timing chains frequently fail after 100,000 miles.

Before they completely fail, timing chains usually exhibit some symptoms. It is common to experience misfires and poor idling as a warning sign that your timing chain is beginning to fail, but it hasn’t failed completely.

Two of the most common causes of timing chain failure are low oil levels and excessive engine heat. Due to the additional heat and stress caused by both of these scenarios the timing chain may stretch.

Preventing timing chain failure

  • Check for leaks in your timing chain cover on a regular basis.
  • Be cautious not to let the engine oil level fall too low
  • Do not allow the engine to become overheated; if this occurs, do not attempt to continue driving.

Can I drive on a bad timing chain?

The timing chain, as previously stated, stretches with use. You can drive with an old timing chain, but it’s best to replace it as soon as you notice any signs of wear and tear or other indications of failure.

The longer you drive on a bad chain, the more teeth it will jump or break. This can cause catastrophic damage to your engine’s internals.

Timing chain replacement costs

The majority of timing chain components cost between $100 and $200. The factor with the greatest degree of fluctuation is labor cost. The average cost of labor is between $250 and $1,000, but it can be much higher in some cases.

When the timing chain on an Audi 4.2 V8 needs to be replaced, the engine must be completely disassembled. As a result, this will be a $5k+ job replacement.

That’s an extreme example, but the point is that replacement costs are primarily determined by how difficult it is to replace something versus how much it costs.

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