Pros, doing a compression test is a well-known and accepted test method. Most mechanics will have a compression tester in their toolbox and are used to using it. There are several styles of testers. Both the screw in type as well as a hand-held type that makes for a very quick test. As the tester is just held against the spark plug hole while the test is performed. Lastly, the test can be performed anywhere as it does not require a source of compressed air.

CV axle bearingreplacement

The Transmision fluid looks normal. It is a bit dark but it has 25k miles on it. There are no signs of metal particles.

If the brake pads have plenty of meat left on them and the rotor isn’t scored and if the wheel spins nice and quiet, then I would lean towards the CV joint. It shouldn’t be loose at all.

Axleshaftbearingnoise

With a leak down test, I know straight away if there is an issue or not. And if there is an issue I know exactly where to go to fix the problem. Even though the set-up time is a little longer, I know that I will have meaningful results that can be acted upon. So, if you are trying to decide on what test to use, my advice is to go with the leak down test.

A leak down test works by putting air pressure into the cylinder and the gauge measures the amount of pressure drop or leakage in the cylinder. First, you must remove the spark plug, then set the cylinder that you wish to test to TDC compression, (Top Dead Center of the compression stroke).  Then install the leak down test adaptor and connect to the gauge. The leak down tester is connected to the shop air supply and will put air pressure into the cylinder to test it. Once one cylinder has been tested the gauge is moved to the next cylinder. Repeat the test until all cylinders have been measured.

Did you check the condion of the transmision fluid to see if it was burnt or discolored? If the bearing has been going bad for 5k miles there may be metal contaminants in the fluid.

DON’T!!! listen to the advice you were given. This sounds like a wheel bearing. A failed CV joint is going to make a clicking noise when turning. If you do not hear a clicking noise on turns then it is not a CV joint. If it is a humming or whining noise it is most likely a wheel bearing.

CV axle bearingnoise

If the noise is from the right, then that seems more like a wheel bearing as the trans is on the driver side (left). You can try driving by a high curb on either side with the windows open to hear the reflected noise to try to confirm the source. You can do this with a bridge too.

To use a leak down test or compression test, which one is going to give you the best indication of what’s going on in the engine? Both a leak down test and compression test are ways to get a picture of the condition of the combustion chamber of your engine. However, one test is far better than the other

Thank you, I have been looking for details about this subject matter for ages and yours is the best I’ve discovered so far.

If you stopped reading right now, a novice might choose a compression tester. You can’t use a leak-down tester without an air compressor or nitrogen tank. Someone just getting into engine work might not have either of those in the shop, which could mean a considerable extra investment. To use a compression tester, you remove the spark plugs, insert the hose of the tester into one spark plug hole, and crank the engine over. After about 4 to 8 revolutions, you read the pressure on the gauge. Repeat the test for each cylinder of the engine.

Hi Robert, yes not having a compressor really limits the range of testing you can do. And if you dont have that compressor then a compression test is better than no test at all.

During the early stage of failure, a bearing can be quiet with no load as when you turn the wheel with the car on a jack, yet become noisy with the car’s weight on the bearing.

A compression test is exactly as it sounds, it measures the amount of pressure that an engine can generate while cranking. The way that this test works is that all the spark plugs are removed from the engine. Then install a compression gauge in place of one of the spark plugs. Then crank the engine over using the starter. The compression gauge will record the amount of pressure generated by the engine, usually in PSI. Once one cylinder has been measured the gauge is moved to the next cylinder. Repeat the procedure on all cylinders.

hi, i want to find out if your problem has been fixed, I’m experiencing the same problem like you does. what was the solution?

Front DriveAxleInner ShaftBearing

Since the original post was 15 years ago, it is not likely you will hear back. You would be better off starting a new thread and Describing your specific issue.

This is great when checking a used engine or an unknown replacement engine. The leak down test is always conclusive. The source of the combustion leak is always known by the end of the test. If an intake valve is leaking air pressure can be felt coming through the intake system. If an exhaust valve is leaking then air will be felt or heard coming out the tailpipe. When the rings are leaking then air will come out of the oil filler cap. As a side note, there will always be some air pressure coming out of the crankcase as piston rings will never have a 100% seal.

Here is how to check. Drive straight ahead until you hear the noise. Try some right turns and left turns. If the noise gets louder when turning, it’s a wheel bearing.

CVjoint and wheelbearingreplacement cost

I have had two CV joint failures so far and in both instances, the steering wheel vibrated occasionally. In only one instance, the CV joint made clicking noises when backing while turning. The damage to the CV joint that vibrated more often and worse when it did and also clicked was far worse than the other.

For me, the leak down test far outweighs the time savings of performing a compression test. A compression test is subjective to cranking speed and temperature. So its results just don’t give a good enough picture of the combustion chamber condition to make an informed decision. If a true low reading is given, usually anything less than 100 PSI. There is still more work to find the actual source of the leak. For example rings, or valves.

Tucker, I understand your point. However, the other side of the coin is spending needless money on a misdiagnosed engine fault. If the battery is low or the person cranking the engine forgets to open the gas pedal and they get a low compression reading. Then they proceed to tear the engine down to fix the supposed low compression, only to find nothing is wrong. Now it would have been cheaper and more effective to spend $100 dollars on a small compressor than spend hours chasing a fault that doesn’t exist. Thanks for reading

Excellent items from you, man. I have to keep in mind your stuff previous to and you are simply extremely magnificent. I really like what you’ve got here, certainly like what you’re stating and the best way in which you say it. You are making it enjoyable and you continue to care to keep it wise. I can’t wait to read much more from you. This is actually a wonderful web site.

Cons, the leak-down tester needs compressed air to work. Depending on the size of the compressor being used it may not be as accurate as when the test is being performed in a shop. The test takes longer to perform. Because the engine needs to be set at TDC compression for each cylinder it just takes more time. Sometimes it can be hard to correctly locate TDC on all cylinders. If the cylinder is not right at TDC it will rotate when air pressure is applied to the cylinder. This means resetting the cylinder back to TDC and starting the test again.

When a true low compression reading is given the gauge needs to be removed and then oil added to the cylinder and the test redone. This is an attempt to locate the source of the low compression. A high compression reading after adding oil to the cylinder indicates worn piston rings. This is also known as a “Wet Compression Test”.

Cons, a compression test if done improperly will give you a false result indicating a low compression. If the vehicle battery or starter motor is defective resulting in a low cranking speed then the compression test will be false and most likely show low compression. If the throttle is not held in the wide-open position then the test will show a false low reading.

Subscribe to our email list and get regular notifications of new videos and blog articles on how to repair your own car.

Axle bearingvs wheelbearing

CV axle Bearingsymptoms

If it is the CV axle I am leaning towards repairing that myself in my driveway. If it is a bearing in the Tranny it has to go to the shop for repair.

Two failed CV joints for me caused more vibration on the first than the second but both occasionally vibrated at speed. The joint that vibrated more had more damage when inspected.

As we know, the leak down test and compression test both are ways to get a picture of the engine condition. I would like to have both kits in my garage/workshop. If anyone hasn’t purchased an air compressor yet, the compression test is the ideal one. But the leak down test is the best.

I jacked up the front end of the car and found the outer cv joint is tight. The inner joint seems loose but it seems like the play is in the differential out put shaft. Considering the noise it sure seems like the bering in the transmission. Does anyone know how much this may cost to repair at a shop???Thanks

You said you replaced the transmission VS. replacing only the bad bearing in the tranny. Was this more cost effective because of labor involved or was there another factor?

Axleshaftbearingreplacement

what kind of car? I had the same noise and it turned out the trans bearings were going bad. Honda (accord) replaced the trans and the noise went away. I tried to rotate tires, spare tire, etc. but the noise was at 30MPH and higher until high speeds when road noise overpowered the bearing noise. That’s what was wrong with my car. Not saying you have the same problem but just food for thought.

Pros, when using a leak down test the engine does not need to be cranked over using the starter motor. This means the test can be done without relying on other systems than can produce a false reading. Because it doesn’t require a starter to crank the engine, an engine can also be tested while out of the car.

A leak-down tester may represent a larger initial investment, and a leak-down test takes more time to perform, but it can give you a more accurate and detailed picture of the engine’s overall health.

One way to differentiate a differential carrier bearing problem from a wheel bearing problem is to unload the transmission while rolling at a speed where the noise is most noticed. Lift the throttle pedal or shift the transmission to neutral. If the noise changes significantly, then the problem could be in the differential bearings although it is unlikely with your transmission design. If the noise remains, reengage the transmission and do a couple of lane changes (observe safety). If the noise gets worse making a lane change to the left it probably is the right wheel bearing. Diagnosing wheel bearings can be deceptive when the weight is off the tires and not spinning fast IMHO.

I have a noise as I drive coming from the front right section of the car. No vibration and the car tracks fine. The noise reminds me of a bad wheel bearing or a tire problem. The faster you go the more noticable it gets. I rotated the tires and the noise did not move. The wheel in question spins fine, seems tight and there is no signs of over heating of the brake. The CV joint half shaft does seem a bit loose. But as I recall, a failing CV joints makes clicking sounds on corners. This does not happen. Everything else in that area seems tight and ok. Any comments or ideas?