CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Weird sound coming from my engine

I have a 2002 Dodge Dakota with a 4.7L V8 Engine. The engine has 170,000 miles. I have a couple of noises in the motor that I can’t identify. It only happens when the engine is cold.When I first start the engine, I hear a little rattle followed by a single tapping noise. I engage the engine into drive. Then,I hear a high pitched noice if I hit the throttle hard while the engine is not warmed up yet. But, after the engine is warm, all of these noices go away and it runs perfect.I just can’t figure it out. The engine has a lot of power, uses or leaks no oil, and maintains very good oil pressure. If you have a idea of what this is,I would appreciate a reply.



Thanks,



Mike Kostial

Sounds like a classic lifter sticking.

The high pitched whine is something else, possibly a power steering pump. You can better isolate it by having someone stomp the gas while you have your head under the hood.

By the way, stomping the gas while the engine is still cold is really not a good idea. Parts actually change size and shape when they’re cold, and they’re designed to fit perfectly when they’re hot, not cold.

Excellent info. I thought it might be a lifter noise as well. I will check that out. Thanks again for the helpful information.

Mike, Don’t Overlook Checking Serpentine And / Or Accessory Drive Belts, Tensioners And Pulleys.

I had similar sounds and concerns on a Dodge car and properly tensioned the belts (the A/C belt was self-tensioning, but not the serpentine) and the cold start noises dissappeared. This was covered in a Chrysler bulletin for my model.

For less than 20 bucks you can buy an automotive stethoscope. Sears sells them. A little careful probing of a cold, idling engine could help you locate the source of the noise.

CSA

Thanks for great information.I will definitely pick up one of those stethoscopes and check the belts.

To CSA’s excellent advice, I want to add that you could be hearing the effects of dry bearings in the belt tensioner and/or belt pulley.

Recently, I had the first-ever repair on my '02 Outback, and it was the replacement of both of those items, due to dry bearings. It is rare, but it does happen occasionally, and the noise does tend to go away when the engine warms up a bit. However, it should not be ignored as you will lose the serpentine belt when one of those bearings suddenly seizes up.

Again, Be Careful. You Can Usually Touch The Stationary Nut In The Center Of A Pulley With The Probe.

I get better results if I apply a little pressure once I’ve made contact. Compare sounds and you may be able to tell a bad, extra loud sound from the others.

You can also touch stationary engine parts like rocker covers, engine block, or alternator housing, etcetera. Don’t touch moving belts or parts, of course as this could cause damage or injury. Be prepared for a shock to your ears if you accidently contact a moving pulley as the tool really amplifies sounds.

I looked. Sears sells it for 15 bucks and I’m sure there are other vendors as well.

Have fun. It drives the neighbors crazy. Do you have a white lab coat you can slip into for this examination?

CSA