Headphones make this tool more useful in a noisy shop.
Photo credit: JS Products Inc (Steelman)
This stethoscope operates on a 9-volt battery.
Photo credit: S&G Tool Aid Corp
Some video scopes have a removable/remove screen.
Photo credit: NTE Electronics Inc
The simplest video scopes sell quickly.
Photo credit: Autel
This stethoscope includes a tube for pinpointing ambient sounds.
Photo credit: VO Scope/Visual Optics
This scope has a high-rez screen and video output connection.
Photo credit: Snap-on
This scope has the camera lens on the side of the probe.
Photo credit: Sound Environmental Products
A smaller probe gets into tighter spaces but usually requires a little more finesse.
Photo credit: Matco Tools
A remote screen can be handy.
Photo credit: OTC
Photo credit: Matco Tools
Some scopes have removeable/rechargable batteries.
Photo credit: ACDelco
A pressure gauge kit with storage case
Photo credit: Matco Tools
Oil pressure gauge kit wtih a complete adapter set
Photo credit: Lang Tools
Direct Hit: 295581
Vehicle Application: 2004 Nissan Maxima, 3.5L engine
Customer Concern: Timing chain rattling noise.
Average Reported Mileage: 96427
- Check oil level and condition. Change the oil and see if the noise goes away.
- With the engine idling, energize the intake valve timing control solenoids by grounding the Red wire for the bank 1 and the Yellow wire for the bank 2 and see if the noise goes away. This indicates faulty intake camshaft sprockets.
- If the noise does not go away, check the timing chain tensioners per the Nissan TSB NTB07-042d.
- Oil pressure test gauge
- Stethoscope (mechanical and electronic)
- Video inspection scope
Noise coming from inside an engine means something is broken or worn. Engine wear is controlled by supplying oil pressure to the bearings and valve train components. On this engine, oil pressure also operates the timing chain tensioners. Measuring the wear on any of these parts requires at least partial disassembly of the engine. However, with a few special tools and just a little bit of diagnostic time, it’s possible to learn more about the noise described here before committing to hours of engine surgery.
Oil condition and pressure testing
It’s not really possible to determine the condition of the oil just by pulling the dipstick, especially in this situation. It’s faster and ultimately less expensive to just change the oil and eliminate that as a possible cause. Don’t forget to catch the oil in an open pan and look for the tell-tale swirls of metal or other contaminants. If there’s nothing obvious, or even if there is, the next step is to check oil pressure.
An oil pressure gauge on the instrument panel is generally not accurate enough or doesn’t have enough resolution for diagnostic purposes. Better to measure oil pressure directly with an external mechanical gauge. Remove the oil pressure sensor or sending unit, and install a gauge or adapter directly into the same hole. Many domestic models use SAE straight thread or pipe thread for the oil pressure sending unit, while imports generally use ISO metric thread or a banjo bolt fitting.
There are test kits available with adapters for all the different threads and sizes, and a quick-connect fitting for the gauge. Some have fittings that allow the gauge to be used for checking transmission pressures too. Some are also suitable for use with fuel systems, but they should not be used that way unless instructed to do so. If the kit includes an extension hose, the gauge can be temporarily taped to the windshield to check engine oil pressure or transmission fluid pressure while driving the vehicle.
What's that sound?
This engine has variable intake camshaft timing, operated by oil pressure and controlled with a solenoid valve on each camshaft. In Step 2, the control valves are driven fully open, and if the intake cam sprockets are faulty, the noise should go away. However, this engine has three timing chains: a long main timing chain and a short one on each cylinder head. Each has its own tensioner, and the water pump is also driven by the main timing chain. With so many items that could cause timing chain noise, you’ll need a way to isolate each component to pinpoint the source. An electronic stethoscope is the answer.
Most techs are familiar with using a long screwdriver or socket extension as a stethoscope, but an electronic listening device is far more precise and effective, especially in a noisy shop environment. An electronic stethoscope has an extremely sensitive microphone that tightly focuses the ‘listening area,’ and the headphones block out ambient noise so you only hear what the mic picks up. The amplifier has a volume control, and some also have an adjustable noise filter.
There are two basic types of electronic stethoscope. One type has a flexible wand that must be in direct contact with the subject, just like a mechanical stethoscope. It’s ideal for pinpointing a bad bearing or a dead injector, or in this case a slack timing chain. Some have a light at the tip of the wand, providing an easier point of reference in dark, tight spaces.
Another type of device has the microphone mounted in a hollow tube, so it can detect sounds several feet away but remain tightly focused on just one square inch of space. This type often comes with a separate sound emitter that makes a ‘chirping’ noise. When placed inside a closed vehicle, the listening device can be used to find leaks around doors and windows. By fitting a solid wand onto the tube, this device becomes a regular contact stethoscope.
A picture may be worth a thousand words, but a picture taken inside an engine could be worth thousands of dollars. On this engine the main timing chain tensioner and water pump sprocket are behind removable covers, perfect for looking inside with a video inspection scope.
Unlike the optical borescope, a video scope uses an electronic camera to create an image on a video screen. Over the past few years the price of the most basic video scope has come down quite a bit. Scopes with more features cost more, but some of those features can be well worth the cost.
Depending on the tool’s features, the video image can be adjusted for lighting conditions, rotated, reversed, zoomed, stored on a memory card as still shots or video, and/or uploaded to a computer with a large viewing screen. This makes it easy to obtain useable color images that eliminate a lot of guessing. You can even email those images to customers when calling for repair authorization.
Among the many different features available, there are a variety of screen sizes and camera head sizes. Those with a larger camera head (typically about 10mm) usually produce a superior image, but those with a smaller head (5.5mm) can reach into tighter spaces. At least one has interchangeable camera heads of different sizes. Some scopes have a removable wireless viewing screen, with a wireless range of up to 30 feet.
The camera wands range in length from 12 to 80 inches or more, and some are watertight. Many have adjustable lighting and/or different colored lights at the camera end, and some have an ultraviolet light to illuminate leak detection dyes. One model has the camera lens on the side of the wand, not the tip.
There are video scopes that connect directly to a computer through a USB port and send their picture directly to the computer screen, but most are stand-alone units with rechargeable battery packs. Battery life has been an issue with some models, but newer models seem to have solved that problem.
When diagnosing engine noises, don’t forget basic techniques like running it with the drive belts removed, dropping the transmission into Drive and checking for broken accessory mounts. Once convinced the noise is internal, electronic instruments that record sounds and sights not only lead to a more accurate diagnosis, the recordings will also document your diagnosis. That fact alone can provide a handsome return on your investment in these state-of-the-art tools.