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On newer cars, trucks, and SUVs, the electronic ignition system supplies and controls the operation of the ignition system by depending on a series of sensors and advanced mathematical calculations. Not too long ago, the distributor took a more mechanical approach to ignition timing by measuring the rotation of the camshaft and supplying power to individual spark plugs at a predetermined time segment. Inserted directly into the engine through the intake manifold, the distributor relies on either a series of seals or a single O-ring to keep oil inside the crank case, and to also reduce the likelihood of debris falling into the engine block.
Vehicles made before 2010 use a distributor as a primary part of the ignition system in the vehicle. Its purpose is to route electrical voltage from the ignition coil to the spark plug. The spark plug then ignites the fuel and air mixture in the combustion chamber to allow your engine to run smoothly. The distributor O-ring is a critical component that needs to be in tip-top-shape in order to keep engine oil contained inside the engine and also to keep the distributor properly aligned for smooth operation of the combustion engine.
Over a period of time, the O-ring tends to wear out for multiple reasons including:
- Exposure to the elements inside the engine
- Excessive heat and electricity
- Build-up of grime and debris
If the distributor O-ring starts leaking, oil and grime will build-up on the outside of the intake and on the exterior of the distributor. One way to prevent this from occurring is to have the vehicle serviced and "tuned-up" every 20,000 miles. During most professional tune-ups, the mechanic will inspect the distributor housing and determine if the O-ring is leaking or showing signs of premature wear. If the O-ring needs to be replaced, a mechanic can complete this process very easily, especially if components have been removed ahead of time.
Like any other mechanical part designed to wear out over time, the distributor O-ring will exhibit a few common warning signs and side-effects if it's damaged or leaking. Some of the most common warning signs include the following:
The engine runs rough: When the distributor O-ring is loose, pinched or damaged, it may cause the distributor to fit loose inside it's housing. If it moves to the left or right, it will adjust the ignition timing, either advancing or retarding the timing of each cylinder firing pattern. This tends to impact the way the engine runs; especially at idle. You'll typically notice the engine will run very rough, misfire or even cause a backfiring situation if the O-ring has been damaged.
Loss of power in the engine: Changing the timing can also impact the performance of the engine. If timing is advanced, the cylinder will fire before it should for optimum efficiency. If the timing has been reduced or "retarded," the cylinder fires after it should. This will negatively impact performance and power of the engine, cause stumbling or in some cases, a pinging sound to occur.
Leaking oil at the base of the distributor: Like any O-ring or gasket failure, a damaged distributor O-ring will cause oil to seep from the base of the distributor. When this occurs, dirt and grime will build up near the base and can cause the distributor to become damaged; or lead to debris entering the engine case.
If you're vehicle does not have an electronic ignition system and still has a distributor and ignition coil set up, it's recommended to change the distributor O-ring every 100,000 miles. Occasionally, this component can fail or wear out sooner than that 100,000 mile threshold. For purposes of this article, we'll focus on the best recommended methods for replacing the distributor O-ring. The process for removing the distributor is unique and different for all vehicles, but the procedures for replacing the O-ring is generally similar on all vehicles.
Part 1 of 2: Causes of broken distributor O-rings
There are several reasons why a distributor O-ring becomes damaged in the first place. The most common reason revolves around age and extensive use. If a vehicle is driven daily and put under extreme driving conditions, the distributor O-ring can wear out sooner than a car that is an around time grocery getter.
In some situations, increased engine pressure, caused by a damaged vacuum line may cause the O-ring of the distributor to push out of alignment. Although this is extremely rare, it's important to understand why the O-ring is damaged; so that the cause of the problem can also be resolved at the same time you are replacing the component.
- Warning: The procedures for removing a distributor are always unique to the vehicle where it is used. It's is always recommended to fully review the manufacturers service manual before attempting to complete this job. As we've indicated above, the instructions below are GENERAL STEPS for replacing the O-ring located on the distributor. If you do not feel comfortable completing this job, always defer to an ASE certified mechanic.
Part 2 of 2: Preparing the vehicle for replacing the distributor O-ring
According to most service manuals, the job of removing the distributor, installing a new O-ring and reinstalling the distributor can take two to four hours to complete. The most time consuming part of this job will be removing ancillary components that restrict access to the distributor.
It's also vital to take time to mark the location of the distributor, the distributor cap, spark plug wires and the rotor on the bottom of the distributor before it's removed; and during the removal process. Failure to properly mark and reinstall the distributor exactly as it was removed can result in serious engine damage.
To complete this job, you won't have to raise the vehicle on a hydraulic lift or on jack stands. The distributor is typically located on the top of the engine or on the side of the engine. In most cases, the only part you'll have to remove to gain access to it is the engine cover or the air filter housing. This job is categorized as "medium" for DIY mechanics on the difficulty scale. The most critical part of installing a new O-ring is making sure to properly mark and align the distributor and distributor components for proper ignition timing.
In general, the materials you'll need to remove and replace the distributor and the O-ring; after removing ancillary components will include the following:
- Clean shop rags
- Hooked O-ring removal tool
- Screwdriver(s) flat and Phillips head
- Socket set and ratchet
- Replacement O-ring (recommended by manufacturer and not from a generic kit)
After collecting all these materials and reviewing the instructions set forth in your service manual, you should be ready to complete this job.
Part 2 of 2: Replacing the distributor O-ring
According to most manufacturers, this job should be completed within a few hours; especially if you've collected all the materials and have a replacement O-ring from the manufacturer. A huge mistake that many DIY mechanics make is using a stock O-ring from an O-ring kit. The O-ring for a distributor is unique and if the wrong type of O-ring is installed, it can cause serious damage to the inside of the motor, the distributor rotor and the ignition system.
Step 1: Remove battery cables. You'll be working on the ignition system and as such, should remove the battery cables from the terminals before removing any other components. Remove the positive and negative terminals and place them away from the battery before proceeding.
Step 2: Remove engine cover and air filter housing. On most domestic and imports, you'll want to remove the engine cover and air filter housing in order to have free access to remove the distributor. Refer to your service manual for exact instructions on how to remove these components. A good tip is to replace your air filter while you're working on the distributor, which you can do at this time.
Step 2: Mark the distributor components. Before removing any parts on the distributor cap or the distributor itself, you want to take some time to mark the location of each components. This is vital for consistency and to reduce the potential of misfire when you reinstall the distributor and distributor accompanying parts. In general, you'll want to mark the following individual components:
The spark plug wires: Using a marker or tape, mark the location of each spark plug wire as you are removing them. A good tip is to start at the 12 o'clock position on the distributor cap, and mark them in order in a clockwise motion. This will ensure that when you reinstall the spark plug wires on the distributor they will be in order.
Mark the distributor cap on the distributor: Although you don't need to remove the distributor cap in most cases to replace the O-ring, this is a good practice to get used to completing. Mark both the cap and distributor as the image shows. You'll use this same method for marking the placement of the distributor on the engine as well.
Mark the distributor on the engine: As indicated above, you want to mark the location of the distributor as it aligns on the engine or manifold. This will help you realign it during installation.
Step 4: Remove spark plug wires: After you've marked all items on the distributor and where it's supposed to align on the engine or manifold, remove the spark plug wires from the distributor cap.
Step 5: Remove distributor. Once the plug wires have been removed, you'll be ready to remove the distributor. Typically the distributor is held in place by two or three bolts. Locate these bolts and remove them with a socket, extension and ratchet. Remove them one at a time.
After all the bolts have been removed, carefully begin to pull the distributor from its housing. When you're doing this, makes sure to note the position of the distributor drive gear. When you're removing the O-ring, this gear is going to move. You want to make sure to place this gear in the exact location as it was when you remove the distributor when you install it again.
Step 6: Remove old O-ring and Install new O-ring. The best way to remove the O-ring is to use a hooked O-ring removal tool. Hook the end of the tool around the O-ring and carefully pry off the bottom of the distributor. In many cases, the O-ring will break during the removal (which is OK if this happens).
To install the new O-ring, you'll want to place the O-ring in the slot and work the O-ring into position with your fingers. Sometimes using a little bit of oil on the O-ring will help you complete this step.
Step 7: Reinstall distributor. After the new distributor O-ring has been installed, you'll be ready to reinstall the distributor. Before completing this step, make sure to complete the following:
- Reset the distributor gear in the same location as it was when you removed the distributor
- Align the distributor with the marks on the distributor and the engine
- Place the distributor straight until you feel the distributor gear "click" into position. You might have to gently massage the distributor until that gear connects to the cam housing.
After the distributor is flush against the engine, install the bolts that secure the distributor to the motor. In some cases, you might have to install a clip or bracket; as such always refer to your service manual for exact instructions.
Step 8: Replace spark plug wires. Making sure you place them exactly as they were removed, reinstall the spark plug wires to complete the assembly and installation of the distributor.
Step 9: Verify the distributor is aligned on the marks on the engine. After the plug wires have been installed, and before you reassemble other engine covers and air filters you removed, double check the alignment of the distributor. If it's not aligned correctly, it can damage the engine when you attempt to restart the engine.
Step 10: Replace engine cover and air filter housing.
Step 11: Reconnect battery cables. When you have finished this task, the replacement job of the distributor O-ring has been completed. If you've reviewed the steps in this article and are not confident completing this project or need an extra set of professional hands to help fix the problem, contact YourMechanic and one of our local ASE certified mechanics will be happy to assist you replace the distributor O-ring.
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