A bent pushrod is a common issue in an overhead valve engine. It can cause a variety of problems. In this article, we will discuss the causes and symptoms of a bent pushrod and how to replace it. We’ll also look at the replacement cost and answer the most frequently asked questions about it.
Bent pushrods can cause several symptoms in an overhead valve engine, including poor engine performance, reduced fuel economy, rough idling, misfiring, increased emissions, and a failed compression test.
Table of Contents
What is a Push Rod?
The pushrod is an important part of the overhead valve engine operated by a camshaft. Push rods are used in overhead valve engines because they are simple and reliable. They are also relatively inexpensive to manufacture.
A pushrod is a metal rod that transfers motion from the camshaft to the valves. The pushrod is inserted into the engine block and runs through a series of guide plates that keep it aligned with the valves. At the end of the pushrod is a rocker arm. The push rod actuates the rocker arm, which in turn opens and closes the valves.
Without the pushrod, the internal combustion engines would not be able to function correctly. The pushrod helps to ensure that the valves open and close at the correct time, which is essential for the engine to run smoothly.
What are the Typical Dimensions of a Pushrod?
The push rods are made of steel or aluminum and are typically hollow. The diameter of the push rod is usually between 5/16 and 3/8 inches (8-10 mm). The length of the push rod depends on the engine design, but it is typically between 6 and 8 inches (15-20 cm).
Why is it Important to Adjust Clearance Between Pushrod and Rocker Arm?
The push rod ends are threaded, and they screw into the rocker arm and the camshaft. They are kept in place by adjustable nuts and valve springs that are screwed onto the threads at each end. The nuts can be tightened or loosened to adjust the clearance between the push rod and the rocker arm.
You must set the clearance correctly, or else the valves will not open and close properly. If the clearance is too small, the valves will not open far enough, and the engine will run poorly. If the clearance is too large, the valves will bounce off the rocker arms and make noise. The correct clearance is usually between 0.010 and 0.015 inches (0.25-0.38 mm).
What is the Function of a Push Rod Work in Overhead Valve Engine?
The purpose of the push rod is to transfer motion from the camshaft to the rocker arms. A rocker arm is an engine component that transfers the motion of the camshaft to the valves. It consists of a lever with a roller at the end that rides on the cam lobe and a pushrod that actuates the valve.
In a typical overhead valve engine, each cylinder will have two intake and two exhaust valves. The intake valves open to let fresh air/fuel mixture into the cylinders. The exhaust valves open to allow spent gases to escape.
In addition, there are two camshafts: one for the intake valves and one for the exhaust valves. Each camshaft is mounted above the cylinder head and has its own set of push rods. The intake and exhaust valves are opened and closed by the rocker arms, which are actuated by the push rods.
The rocker arms sit on top of the valves and are actuated by the camshaft. As the camshaft turns, it lifts the lobes on the intake and exhaust valves, pushing on the rocker arms. The rocker arms then press on the pushrods, which open the valves.
Bent Pushrod Symptoms
Many symptoms can indicate that a pushrod is bent. These include:
- Engine Misfires
- Rough Idling
- Ticking Noise
- Poor Performance and Acceleration
- Failed Compression Test
- Increased Emissions
Let us discuss these symptoms in a bit detail:
1. Engine Misfires:
An engine misfire is one of the most common symptoms of a bent pushrod. The misfire can be caused by a number of factors, but the most likely cause is that the pushrod is not opening the valve correctly. This can cause the air/fuel mixture to enter the cylinder at the wrong time, which will result in an engine misfire.
Other possible causes of an engine misfire include a faulty spark plug, ignition system, or fuel injector. However, if you have ruled out all of these other potential causes, then it is likely that the pushrod is to blame.
2. Rough Idling:
Another symptom of a bent pushrod is rough idling. This is because the pushrod is not opening and closing the valves correctly, which can cause the engine to run poorly. The engine may also stall or have difficulty starting if the pushrod is bent.
3. Ticking Noise:
A bent pushrod can also cause a ticking noise from the engine. Two things usually cause pushrod noise: the pushrod itself is damaged, or the rocker arms are worn out. If the pushrod itself is bent, it can cause the engine to run roughly and make a knocking sound.
Alternatively, if the rocker arms are worn out, they may not be able to properly actuate the valves, resulting in valvetrain noise. In either case, it is important to have a qualified mechanic check your engine to determine the root cause of the noise.
4. Poor Performance and Acceleration:
Another symptom of a bent pushrod is poor performance and acceleration. This is because the engine cannot breathe properly, which can lead to a loss of power. The engine may also hesitate or stall when you try to accelerate.
Bent pushrod causes poor performance and acceleration because it can not transfer the correct amount of force from the cam to the valve. This can lead to valves not opening or closing fully or at the right time. As a result, the air/fuel mixture may enter or exit the combustion chamber at the wrong time, affecting engine performance and power.
5. Failed Compression Test:
One of the most common causes of low engine compression is bent pushrods. When pushrods are bent, they can no longer properly transfer the force from the camshaft to the valves. This can result in the valves not opening all the way, which decreases the amount of air and fuel that can enter the combustion chamber. As a result, the engine’s compression ratio is lowered, and it may not be able to generate enough power to run properly.
If your engine is producing low compression on one or more cylinders, it’s possible that a bent pushrod is to blame. You can perform a compression test to check for this issue. If the readings are low on one side of the engine, it indicates that a bent pushrod is causing the problem.
6. Increased Emissions:
Bent pushrods can also cause increased emissions from the engine. This is because the air/fuel mixture is not burning correctly, leading to unburned fuel being expelled through the exhaust system. If you notice that your vehicle’s emissions are higher than normal, it’s possible that a bent pushrod is to blame.
Causes of a Bent Push Rod in an Internal Combustion Engine
There are several causes of a bent pushrod. The most common causes include:
1. Wear and Tear:
Wear and tear can cause the bending of pushrods in an engine system due to many factors. The most common cause is simply due to the metal parts rubbing against each other over time, which creates friction and heat. This can eventually lead to warping or even breakage of the metal.
In addition, repeated cycling of the engine (starting and stopping) can also put stress on the pushrods, which can lead to bending over time. Improper installation or engine maintenance (such as not changing the oil regularly) can also contribute to wear and tear that causes pushrod bending.
2. Loose Valve Guides:
Loose valve guides or broken valve spring are a few possible causes of bent pushrods in an overhead valve engine. When the valve guides are loose, they can allow the valves to move around more than they should. This can cause the valves to move erratically and disturb the motion of rocker arms.
Since rocker arms are directly attached to the pushrods, any anomaly in their motion whatsoever can bend the pushrods. Another important factor to consider is that pushrods are hollow metal tubes in length, so even a slight force across the longitudinal axis can cause them to bend.
3. Engine Overheating:
Overheating can cause the bending of pushrods in overhead valve engines by causing the metal to expand. This can lead to the pushrods becoming misaligned, which can cause engine knocking or misfiring. If left unchecked, this can eventually damage the engine.
To avoid this, it is important to keep your engine coolant level topped up and never allow the engine to overheat. If you think your engine is starting to overheat, pull over and shut it off as soon as possible.
4. Sticking Hydraulic Lifters:
Another possible cause of bent pushrods is sticking hydraulic lifters. Hydraulic lifters are used in some engines to actuate the valves. They work by using oil pressure to adjust the clearance between the valve and the rocker arm.
However, if they become stuck, they can apply too much force on the valves, which can cause the pushrods to bend. This can also lead to engine misfires and damaged valves.
5. Loose Rocker Arm:
As we know, in an overhead valve engine, the pushrods are responsible for transferring the motion of the camshaft to the valves. The rocker arms sit on top of the pushrods and act as a lever, opening and closing the valves.
If a rocker arm becomes loose, it can start to bounce up and down on the pushrod. This constant movement can eventually cause the pushrod to bend. Once the pushrod is bent, it can no longer properly transfer the camshaft’s motion to the valves, resulting in poor engine performance.
6. Accidental Damage:
Accidental damage is another possible cause of bent pushrods. This can happen if the engine is dropped or hit hard enough that it causes the pushrods to bend.
It can also happen if a foreign object (such as a piece of debris) falls into the engine and hits the pushrods. If you think your engine has been damaged, it’s best to take it to a mechanic for inspection.
7. Incorrect Installation:
Improper installation is one of the most common causes of bent pushrods. One way is by not properly torquing down the rocker arms. If the rocker arms are not properly torqued down, they can put excessive force on the pushrods, causing them to bend.
Another common cause is simply using too weak pushrods for the application. Pushrods made from weaker materials are more likely to bend under high loads and stresses, so it’s important to make sure that you’re using pushrods that are up to the task.
How to Prevent a Push Rod From Bending?
There are several ways to prevent a push rod from bending. These include:
1. Changing Engine Oil Regularly: This is one of the most important ways to prevent push rod bending. Oil helps to lubricate the engine and prevents metal-to-metal contact between the parts. Over time, this can cause the pushrod to bend.
2. Using Higher Quality Push Rods: Many different types of push rods are available today. Some are made from higher-quality materials less likely to bend or break under stress. Choosing a push rod that is right for your application is important.
3. Reducing Engine vibration: One of the leading causes of pushrod bending is engine vibration. There are several ways to reduce engine vibration, such as:
- Installing engine mounts
- Using balancing weights
- Adding damping material to the engine bay
4. Following the correct installation procedures: It is important to follow the correct installation procedures when installing push rods. If the push rods are not installed correctly, they can become bent or damaged.
5. Avoiding excessive stress on the pushrod: It is important to avoid putting too much stress on the pushrod. You can do this by avoiding hard starting and sudden stops and by not overloading the engine.
Bent Pushrod Replacement Cost
If you have a bent pushrod in your car, it will need to be replaced. The cost of this replacement will vary depending on the make and model of your car, as well as the severity of the damage. Replacing a bad pushrod is one of the most difficult maintenance tasks in an internal combustion engine. This is a very demanding replacement job since it involves opening and reassembling some of the most critical components of your car’s engine.
The average cost of a bent pushrod replacement is between $800 and $1,200. This repair can be even more expensive if the damage is severe and requires additional parts or repairs. A complete push rod replacement kit that includes associated components such as guide plates, rocker arms, pins, valve cover gasket, and seals can cost between $350 and $550. You may also need to purchase a new valve cover if the old one is damaged.
For a skilled mechanic, replacing a bent pushrod takes about six to eight hours. So, the cost of labor will be between $480 and $960. This is a difficult repair that should only be attempted by an experienced mechanic. It is also important to have the proper tools and equipment for the job. If you attempt to repair this yourself, it is important to follow all instructions carefully and take your time. Making a mistake could cause severe damage to your engine.
If one or more pushrods in an overhead valve engine become bent, it can cause several problems. First, bent pushrods can prevent the valves from opening and closing properly. This can lead to poor engine performance and may even cause the engine to stall. Additionally, bent pushrods can stress the rocker arms and other components, causing them to wear out prematurely.
If you suspect that your overhead valve engine has bent pushrods, it is important to have the problem diagnosed and repaired as soon as possible. Otherwise, you may find yourself facing serious engine problems down the road.
Frequently Asked Questions
Can you drive with a bent pushrod?
Yes, you can drive with a bent pushrod. However, it is not advised as it can cause engine damage. If you must drive with a bent pushrod, be sure to check your engine oil level frequently and avoid driving at high speeds.
Can you straighten a bent pushrod?
The short answer is yes, you can straighten a bent pushrod. But it is not recommended as it can cause further damage to the engine and potentially lead to more serious problems. If you attempt to straighten a bent pushrod, be sure to use caution and follow all instructions carefully. Doing so will help ensure that you do not cause further damage to your engine.
How long does it take to fix a bent pushrod?
The time it takes to fix a bent pushrod will vary depending on the severity of the damage. For a skilled mechanic, replacing a bent pushrod can take anywhere from six to eight hours. However, if the damage is severe, it may take longer.
What causes the pushrod to bend?
Many factors can cause the pushrod to bend. These include hard starts, sudden stops, engine overloading, and using the wrong oil. Additionally, bent pushrods can be caused by manufacturing defects.
What happens if you have a bent pushrod?
A bent pushrod can cause several problems with your vehicle’s engine, including decreased performance, increased fuel consumption, and damage to other engine components. In some cases, a bent pushrod can also lead to engine failure.
How do I know if my pushrod is bent?
There are a few signs that can indicate that your pushrod is bent. These include decreased engine performance, increased fuel consumption, engine knocking, and misfiring. Additionally, you may notice that your car is idling rough or that the engine is making strange noises.
What is the average lifespan of a push rod?
The average lifespan of a pushrod is about five to seven years or somewhere between 50,000 to 70,000 miles. However, this can vary depending on the make and model of your vehicle as well as how you use and maintain it.