Did you know that the extra length of the timing chain could cause problems? We have seen a large number of used engines with timing chain tensioner (TCT) issues.
Let’s go through the various bad timing chain tensioner symptoms. This way, you can know what’s wrong with your vehicle and avoid expensive repairs.
What Is a Timing Chain Tensioner?
The camshaft is the brain that provides mechanical logic to control the opening as well as the closing of the valves. Small changes in the cam grind can make or break engine performance. The rotation of the camshaft and crankshaft is synchronized by a timing chain.
The chain tensioner, on the other hand, ensures the timing chain has the necessary and correct tension. The tensioner usually surrounds the camshaft and crankshaft sprockets. It applies full control to prevent slack and rattling. It also does a great job of protecting water pumps and alternators from failing. Usually, the tensioner is found in the cylinder block.
Types of Timing Chain Tensioner
There are two popular types of timing chain tensioners: the hydraulic timing chain tensioner and the mechanical timing chain tensioner. Let’s differentiate the two.
Hydraulic Timing Chain Tensioner
This tensioner uses a hydraulic mechanism to do its job. It is held in place by a pair of bolts. It provides a free rebound with a superior damping effect.
A hydraulic tensioner is made of a tensioner pulley in combination with a hydraulic actuator. The piston rod movement is transferred to the tensioner pulley through a separate or integrated lever. The hydraulic actuator normally functions as a suspension strut to control the dynamic chain forces.
Mechanical Timing Chain Tensioner
This type of timing chain tensioner is made to replace the stock chain tensioner. Mechanical types offer a more constant as well as positive tension. So, the chance of the valves hitting the pistons is reduced where clearance is tight. It is also held in place by two bolts.
Bad Timing Chain Tensioner Symptoms
The following are the most common bad timing chain tensioner symptoms to look out for.
Loose Chain or Excessive Slack
One of the most common symptoms of a bad tensioner is a loose chain or excessive slack. Your timing chain will have a slack, which shouldn’t be there. Slack of any kind may cause your vehicle to stall now and then.
This is so because the camshaft will not be able to turn in the motor and your vehicle won’t be able to power up the engine. The timing between the pistons and valves will be out of sync. Whenever a gear is skipped, the timing will be out of calibration, causing misfires. If it is a preexisting problem, then your engine may fail to start because the combustion is compromised.
An excessively loose timing chain due to a bad timing chain tensioner usually produces a knocking sound when the chain hits the guides or cover. The produced noise is metal to metal contact, which can be intermittent or constant. If the problem isn’t dealt with, it may lead to metal contamination of the motor oil as the chain wears into the cover.
Bleeding of Oil Pressure
Hydraulic timing chain tensioners are normally fitted with a ratchet or manual device to set preload. The device helps maintain minimum chain tension when there’s no oil pressure, such as when the engine starts.
A problem may arise with a hydraulic tensioner due to variations in oil pressure. Timing-related noises may be caused by a timing chain tensioner bleeding oil pressure during a prolonged soak time. Damage of timing components is typically caused by low oil pressure.
You could experience broken chain rails from timing chain slap that’s caused by low oil pressure failing to keep the tensioner extended correctly. Noises that are produced at hot idle are normally caused by low oil pressure.
Stretched Timing Chain
Wear in chain components normally leads to a stretched timing chain. Poor maintenance is usually the main cause of wear. When the rollers and links are not properly oiled, they will rub against each other.
Elongation or stretching occurs when the chain moves across the crankshafts and the cam. A stretched chain will not allow the tensioner to do its job. If the elongated chain is not replaced, the vehicle will suffer poor running conditions.
This could also lead to camshaft or crankshaft sensor correlation fault codes. Excessive stretching will compromise compression and lead to significant power loss.
When the chain is highly stretched, the camshaft may lag behind the engine’s crankshaft. This normally leads to retarded camshaft timing, which could cause lower performance as well as poor fuel economy.
A loose or stretched timing chain can cause backfiring and your vehicle is likely to lose power abruptly. Once the chain is stretched, you may start to hear noises when the chain hits the timing cover. Not to mention that a loose timing chain could turn on the check engine light.
Noises Coming From Timing System
Excessive engine noises from the timing chain area are usually caused by a bad tensioner.
Some of the noises caused by a bad timing chain tensioner are rattling, slapping, knocking, and clacking. A weak hydraulic or bad spring-loaded tensioner will make the timing chain have excess slack. The timing chain will slap against the timing guides or cover.
Timing chain noise is normally common on startup. A bad timing chain tensioner may cause the timing chain to jerk when you start the engine. The jerking usually increases the wear of the timing guides and chain. If timing chain wear is not too much, the noise may decrease with an increase in oil pressure.
Low Power and No Start
When the timing chain tensioner goes bad it can make the chain jump some teeth, which will cause the timing to be off. This will directly interfere with engine performance. The condition may also trigger the check engine light for valve timing codes.
Problems occurring from a bad tensioner vary, depending on how many teeth the chain jumps. Retarded camshaft timing normally results from a chain that jumps time, reducing engine power as well as efficiency. A timing chain that jumps one or two teeth may lead to reduced engine performance, hard-starting, increased emissions, reduced fuel economy, and a possible camshaft position code.
If a timing chain skips more than two teeth, then you should expect a no-start followed by an irregular cranking sound.
Incorrect camshaft timing due to a bad tensioner can lead to engine damage. The amount of damage inflicted depends on the engine type as well as operating rpm when the timing chain jumps teeth or breaks.
Damaged Cylinder Head
You can also look for damage to your cylinder head and timing chain. The noise that you hear when your vehicle’s timing chain goes bad is actually the timing chain colliding with the cylinder head.
If you pop up the valve cover, you should be able to see gouges in the cylinder head where the timing chain travels on the exhaust side of your engine. If you take a closer look at the outside of the timing chain, you will observe gouges on the chain links.
What Causes Timing Chain Tensioner Problems?
The following can cause a timing chain tensioner to fail.
Over and Under Tension
Over tensioning is likely to put the timing chain under too much stress. The excess tension will not only increase friction but also heat within the timing chain components.
The rollers may have a hard time rolling over the pins. The rollers may end up seizing on the pins, snapping on the timing chain. A very tight timing chain can cause the chain to rub against the timing guides as you accelerate and you can stall very easily. We recommend tightening the timing chain tensioner until you get rid of the rattling noise.
Under tensioning, on the other hand, will introduce slack into the chain, which can lead to premature fatigue and slapping. A loose timing chain can cause misfires.
Loss of oil for lubrication will cause the engine to seize and stop suddenly. Another cause of engine seizures is overheating. The sudden stop of the engine can force the timing chain tensioner to fail and the chain to break.
Use of Incorrect Engine Oil
The most important attribute of engine oil is viscosity. The term viscosity simply refers to the relative thickness of a liquid. Thick slow-flowing motor oil has a high viscosity and thin free-flowing motor oil has a low viscosity.
Motor oil that is too thin will not function properly and oil that is too thick may not be able to circulate through all engine parts. Your vehicle’s engine parts, including the timing chain tensioner, need motor oil that will flow efficiently regardless of the temperature. Multi-viscosity motor oil can satisfy the viscosity requirements of both cold and hot temperatures.
The variable valve timing (VVT) system and the hydraulic timing chain tensioner are dependent on the type and grade of motor oil. Incorrect engine oil may result in low oil pressure, which may cause the chain tensioner and VVT to malfunction.
The chain tensioner, in particular, will not be able to get rid of chain slack. The cam will not be advanced normally, leading to engine timing offset. Engine performance will be affected, emissions will increase, fuel economy deteriorate, and the Check Engine light will display.
Use of Unclean Motor Oil
The key to high performing timing chain tensioner and the timing system is the use of clean and high-quality oil. Premature timing component failures are usually associated with impure oil. If the oil you use is dirty, the gunk and dirt will get trapped between pins and chain links. This may cause the tensioner to fail and the timing chain system to malfunction.
Related: How to Dispose of Old Gas
How to Check Timing Chain Tensioner?
Here are a few steps you can follow to diagnose bad timing chain tensioner symptoms:
Step 1: Check for Slack
As the timing chain wears out it will slowly lengthen and then introduce slack to the chain. Normally, this would not be a problem because a timing chain tensioner is spring-loaded or is using oil pressure.
This unique design will automatically adjust when slack is introduced. But there is a design flaw in the stock timing chain tensioner, which can prevent it from maintaining tension on the stretched-out timing chain. The lack of tension causes the chain to rattle around in the engine and make timing chain tensioner noise.
Step 2: Listen for Timing Chain Tensioner Noise
So, how do you know if your timing chain tensioner has failed? Listen for a rattling noise that usually occurs shortly after starting your vehicle when it is already warm.
When the problem worsens you will also hear the rattling when your vehicle is idling while warm. When the situation becomes severe, you will hear the bad timing chain tensioner noise at all RPMs when the vehicle is warm. The noise is usually a loud and fast metal-on-metal tapping.
Step 3: Check Oil Pressure
You can know your timing chain tensioner is bad by checking oil pressure. You are likely to find a mysterious leak in the oil pan, which is normally caused by an excessive timing chain slap.
Shut down the engine, open the cover, and try to push against the chain tensioner (make sure you wear mechanic gloves). You will know the tensioner is bad if it has no oil pressure because you will get no resistance when pushing. This is usually the case if the internal components fail inside the tensioner.
If the tensioner is good, you shouldn’t be able to push it even half an inch and there should be no oil coming out the escape hole.
Step 4: Check the Condition of the Sprockets
While you are diagnosing the condition of the tensioner, it is also recommended to inspect the sprocket teeth for wear. If you have been driving with a stretched chain for a while, chances are that the elongated chain might have stretched or broken some sprocket teeth. So, when you decide to replace the chain, you must also replace the crankshaft sprocket, camshaft sprocket, and tensioner.
How to Replace Timing Chain Tensioner
We have looked at the timing chain tensioner and other timing system components. If you follow all the aforementioned steps and find significant flaws like low oil pressure, then you will have to replace the tensioner with a new one. Try replacing the stock tensioner with a model that is loaded against a ratchet to prevent any issues.
The tools you need for this service include a 10 mm socket, a 12 mm wrench, a 17 mm and 19 mm offset wrench, a 17 mm and 19 mm wrench, mechanic gloves, and safety glasses.
Step 1: Drain the Oil
The first thing you need to do is drain the oil out of the oil pan. You just need a 17 mm socket to open the drain port. Make sure you reinstall the drain plug once all the oil is out.
Step 2: Locate the Timing Chain Tensioner
This could be the simplest or hardest part, depending on your vehicle’s make and model. You may have to remove a few parts to get access to the tensioner like the air intake.
Step 3: Remove the Timing Chain Tensioner
Before removing the timing chain tensioner we recommend you place some paper towels below the TCT and above the oil filter. When removing the TCT, some oil will leak out. The paper towels will help prevent any oily mess.
When you look at the exterior of the timing chain tensioner, you will notice that it has four bolts. You’ve got two silver bolts that hold the inspection cover in place and two brass bolts that secure the TCT to the cylinder head. Use a 10 mm socket to remove the two brass bolts.
Try to pull the TCT out. Sometimes it may get stuck and refuse to come out. You pry it out from the inside of the cylinder head. Once removed, make sure the piston is pointing upwards to avoid spilling out the internal components of the TCT.
Step 4: Install the New Timing Chain Tensioner
Before installing a new timing chain tensioner, make sure you compare it to the old one to verify that they are the same. You have to pre-lube the new tensioner before installation. It is extremely important you use the manufacturer’s recommended oil type. A TCT with a ratchet system will need to be set before installation. Then gently insert the tensioner into position, place the bolts, and tighten.
Before starting your vehicle, you have to turn the crank in the opposite direction of rotation to release the timing chain tension spray to put pressure on the timing chain. Not doing this may lead to serious problems.
The Bottom Line
A timing chain tensioner is one of the most important parts of your engine’s timing system. It eliminates slack from your timing chain. If it goes bad or fails, the slack can be too much, leading to timing chain noises, misfires, no start, and poor fuel economy among other things. So, it is important to know how to identify symptoms of a bad timing chain tensioner.