Jeep Diagnostics: Vehicle Noise

Ticking or tapping sound from the engine:

This typically occurs when the vehicle is cold, at start up. Once warm, the noise usually subsides or goes away. This indicates a valve tappet going bad. It can go on for months or even longer. It means eventually you'll need to replace the tappets (and keep an eye on your valves). You can get to most tappets by removing the valve cover.

Many Jeep vehicles (mostly those with the 4.0 engines) have tappet sounds that owners just live with (or add a little extra oil to reduce the noise). You won't hurt the engine running it with this sound. If it's an older engine and you're getting more and more tappet sound, I'd suggest keeping an eye on your compression (to know if the valves are going bad).

Once the noise seems to not go away as quickly, I suggest you get it to the shop or pull the valve cover and make the necessary repairs.. Keep plenty of oil in the engine, and consider using supplements like oil additives (Lucas, STP, etc.). These thickeners will help the valve parts continue working smoothly until you can get them fixed. Change your oil often - every three months or 3000 miles.

Ticking or hissing or clicking sound when warm and running at high speeds:

This typically indicates an exhaust leak. You can drive for years with an exhaust leak that isn't too serious. It's mainly annoying. Eventually you'll need to track it down and repair it. When you first hear this, look for loose or missing head and exhaust bolts. This can be an easy fix in this case.

Also look for holes in the muffler/exhaust system. Pipe and muffler repair kits are readily available to cheaply fix this problem. If you notice significant drops in power, get it fixed.

Sometimes a hissing sound can be attributed to a loose or disconnected vacuum line. You may also hear hissing sounds if wind is getting through the fire wall into the vehicle. This usually means a rubber fire wall grommet has given up the ghost. Easy fix. Just find it and replace the grommet.

Clunking sound coming from rear end or underneath the rig:

This usually means a U joint going out. GET IT FIXED. Crawl underneath and wiggle the U joints on the drive shaft. If they move and clunk, it means you need new ones. It's not that expensive. Replace the whole U joint: both if there's any doubt. If it does not appear to be the U joints, because they are tight and secure, then keep reading.

Crawl underneath and check all drive line components for anything that seems loose or worn. Check linkages too (t-case, tranny). Look for missing parts (bolts).

If it's a clutch problem (like throw out bearings), it's hard to pin point, but make sure you have clutch fluid first. Check the clutch pedal and connections carefully. Do a complete road test (in and out of gear, slow, fast, up, down, whatever you can do to completely isolate the problem).

Examine all lube type fittings for leaks or old, built-up grease. This may tell you of a problem. Old grease build ups sometimes indicates a part (bearing or whatever) that is wearing out and causing problems (or soon will).

Check your shock mounts for worn or broken parts. Wiggle everything. The rule of thumb is to TOUCH IT. That's why cleaning your rig can really help you maintain it better. When your cleaning something, you're usually touching it. When you touch it, you find things that don't feel right.

Rattling or clunking sound coming from the engine compartment:

Use your pipe to ear trick, or use a mechanics stethoscope to pinpoint the problem area. Sometimes something simple like an idler pulley bearing or a power steering pump can make the engine sound like it's falling apart. But the main step is to identify where it's coming from.

A good point to remember is that if you're in the driver's seat, and think you know where the noise is coming from, you're probably wrong. Noises travel through the hollow chassis and frames of vehicles, often masking the true source of the noise - that's what you use special tools and lay your hands ON things - just to be sure.

NOTE: If you're going to work on your own rig, buy the Factory Service Manuals (FSM) from the manufacturer. They're expensive but worth it - they give you all the info you need to do anything you want. Further, get yourself a mechanics stethoscope or a long skinny pipe that you can hold up to your ear. Finding the exact spot of an unusual noise really makes fixing it easier. Please use common sense and be safe while using these items near moving parts.
A big thanks to Del at for sharing this info with us.