Diagnosing Noises in Your Car
Other Engine Compartment Noises
The engine itself is not the only thing that can cause a noise under your hood. There are also accessories driven by the engine that can make noise, such as the AC compressor, the power steering pump, the alternator, the water pump, or any other belt-driven device. These can be difficult to track down, because the noise often travels through the drive belt; in fact, it could be the drive belt itself that’s making the noise.
To find a noise like this, you can do a couple of quick tests. Say you suspect that the AC compressor is making the noise. With the engine running, turn the AC on and off. If the noise goes away when you turn the AC off, then you know it likely has something to do with the AC compressor or something in the AC system.
With the power steering pump, try turning the steering wheel from lock to lock. If the noise gets louder or changes when you do this, it could mean a problem with the power steering.
As for the alternator, water pump, auto tensioner, or other belt-driven accessories, you need to put your ears on it. There are a couple of different ways I do this. The first is with an automotive stethoscope. You can often find these at your local auto parts store, and they aren’t that expensive.
These can be used to find all kinds of noises, not just the ones in your engine compartment. Another method that also works is to use a long screwdriver, the longer the better. You place the tip of the screwdriver against the part you suspect is making the noise, then place your ear on the screwdriver handle. This amplifies the noise and makes it easier to hear.
The purpose of both of these tools is the same: pinpointing the noise. With a little detective work, you can often find the source of a noise. Once you find the source, you can begin to address it. Here’s a video about drive belts that offers more information on finding noises in the engine-driven accessories.
One other method is to remove the drive belts one at a time, and run the engine after you remove each belt. Of course, this only works if you have multiple drive belts. This method can help you pin down a problem accessory or belt. Don’t worry; the engine can run for short periods of time without these accessories just fine. Just don’t do it too long; run the engine just long enough to determine whether or not you’ve found the noise.
If you have a timing cover over your water pump and timing belt tensioners, this can make finding these noises more difficult. In cases like this, I sometimes remove part or all of the timing cover and run the engine. This can help you pinpoint the source of the noise. This might be more trouble than it’s worth, depending on the situation. If the timing cover is difficult to remove, you might just stick with an educated guess and prepare yourself to replace the timing belt, water pump, and its tensioners to address the noise.
One last thing while we’re on the subject of drive belts and engine noises. I have sometimes seen the harmonic balancer or crank pulley break and cause a noise. These often have a layer of rubber between the inner and outer part of the pulley. Sometimes this rubber breaks or deteriorates, and as a result causes all kinds of noises.
If you hear a noise on the front of the engine, it’s a good idea to check for this problem. It’s usually much easier to do after you remove the drive belts.
Automatic Transmission Noises
Automatic transmission noises can be minor or serious; it really depends on where it’s coming from. Automatic transmission noises are often very different than engine noises. They’re usually constant, either a whine or growl during transmission operation. Sometimes you get the occasional tick or thump as well. It’s hard to describe, but transmission noises sound very different than engine noises to me.
One thing to pay attention to is when the noise occurs. Does it happen with the engine at idle? When shifting gears? When going from drive to reverse? When cruising at a certain speed? Any information you can gather will help you nail down the source of your transmission noise.
Some automatic transmission noises can be cured with a simple transmission fluid change. If you have a transmission noise, it’s worth considering this possibility. A word of caution on changing automatic transmission fluid: It is true that if you haven’t changed your automatic transmission fluid in some time, shortly after you change the fluid, the transmission can fail. The reason for this is that the new fluid will flow differently than the old fluid. Old automatic transmission fluid is thicker and full of contaminants. This will actually help seal an older, worn-out transmission. If you remove that old, thick fluid and put new, thinner fluid in, it might leak past the seals that were intact and sealing before you changed the fluid. So if you decide to change your automatic transmission fluid, proceed with caution. However, if you’ve kept up on your maintenance, you should have no trouble changing your transmission fluid.
Thumping Noise When Changing Gears
If you get a clunk or bump when you change gears or go from drive to reverse, check the engine and transmission mounts. These sounds are often a classic symptom of this condition. You’re in luck if this is the case. Replacing engine and transmission mounts is a heck of a lot cheaper than replacing or rebuilding a transmission.
Buzzing or Whining Noises, Automatic Transmissions
A whine or buzzing noise during transmission operation is a bit more serious. A bearing or other issue inside the transmission could be causing this type of noise. If that’s the case, I would recommend you take it to a specialist to be diagnosed. I say this because automatic transmission diagnosis often involves special tools and years of experience to be done properly. If you’re intent on just swapping out your failed transmission with either a rebuild or salvage replacement, then go for it. Replacing automatic transmissions is not nearly as difficult as rebuilding or repairing them. Rebuilding automatic transmissions is best left to those experienced people with the proper tools. Trust me on this.
In summary, automatic transmission noises limit your options. If you find that you have an automatic transmission noise, I would suggest taking it somewhere to be properly diagnosed. As I said, you need specialized equipment to diagnose them properly. These are tools that are not often loaned out at your local auto parts store. I’ll get into automatic transmission diagnosis more in the Transmissions article.
Manual Transmission Noises (General)
You can split manual transmission noises into two categories: clutch noises and transmission noises. It’s important to separate these noises, as they really involve two different systems. Let’s start with clutch noises.
Clutch Noises
Noises when using or engaging the clutch often mean that there is a problem with the clutch or its linkages. If you depress the clutch and hear a noise, it’s likely it has something to do with the clutch itself and not the transmission.
One more thing to note on clutch noises: It’s important to figure out if the noise is coming from the clutch pedal area or the transmission. If you hear a noise coming from the clutch pedal, try sticking your head up under the dash to see if you can pinpoint where it’s coming from. Noises often come from the clutch pedal return springs or sometimes the clutch linkage itself. I’ve even seen clutch pedal mounts break and cause noises and issues when activating the clutch.
As for noises at the transmission, look to the clutch linkage itself. Some clutch linkage is adjustable and you might be able to fix the problem with a simple adjustment. Here’s the procedure for adjusting a cable-operated clutch on a Honda. It’s a similar process for other makes.
Sometimes the linkage gets rusted or bent. If that’s the case, try a little lubrication to see if that cures the noise or changes it enough to confirm your suspicions. If you have a high-performance clutch, expect problems with the clutch linkage or hydraulics. High-performance clutches have a much higher clamping force, and as a result they put a lot more strain on your clutch linkage. If you have a high-performance clutch and you’re hearing noises, be sure to check the clutch and its linkage.
Manual Transmission Noises
I can help you break a couple of things down here; as for the repair, it’s really up to your tools and skill set. If you have a transmission noise when you let the clutch pedal out with the engine running, this is often the input shaft bearing. If you have a grinding noise when shifting into a particular gear, it’s likely you have a synchronizer problem. If you have a grinding noise when shifting into every gear, check your clutch and clutch adjustment. If there are other grinding or whining noises during transmission operation, you might consider changing the transmission fluid and rechecking for the noise. You’d be amazed at how well this can work sometimes.
It is very important that you use the correct fluid when changing manual transmission fluid. Unlike automatic transmission fluid, which is pretty much universal, manual transmissions are anything but. I’ve seen everything from gear oil to automatic transmission fluid in manual transmissions. It just depends on how it’s designed. You must consult the service manual to find out which transmission fluid is best for your vehicle. In the case of Hondas, it’s Honda MTF. You can also use GM Syncromesh fluid. I’ve had great success curing manual transmission issues in some Honda transmissions with Syncromesh fluid. I do not recommend using regular motor oil in a Honda transmission.
In summary, try to find out if the noise is coming from the transmission or the clutch. If you have a clutch noise inside the bell housing, don’t waste your time. Get a new clutch, pressure plate, throw out bearing, and pilot bearing before you pull the transmission out. You’re going to have it out anyway; you might as well be ready to replace the parts should you need to. As with automatic transmissions, if you hear a clunk or thump as you change gears, check the engine and transmission mounts. Loose or broken engine mounts can cause this type of noise. For more in-depth information on manual transmissions, see the Transmissions article.
