Recently purchased a 1999 v.6 3.8L from someone who was the only owner with 121,000 miles on it.

The previous owner maintained the car very well, a total freak when it came to maintenance, he was an older person therefore the car was never abused.

After purchasing it I changed the oil and oil filter, a few days later a weird " rattle " noise could be heard coming from somewhere in the middle of the engine.

Sounded as if it was the water pump, so I changed it, but that wasn't the problem, although the water ( original ) was starting to break down, so changing it was actually a good thing.

The car has never had any original parts replaced, all are still factory parts, except for the water pump of course.

The noise continues till this day!

When you start the car and keep the car in either park or neutral, the noise does not appear, when put in park and drive away the noise can be heard after reaching over 1000rpm's.

Sometimes the rattling noise disappears all together for a brief moment and comes back, it also tends to disappear when you speed up.

I took it to a friend who is a mechanic and Mustang freak, he looked for where the noise was coming from using a long steel bar placed on his ear, his conclusion is that it may be the timing chain, guide or tensioner.

I then took it to a shop of a gentlemen I know who has been a mechanic for over 35 years, his conclusion ( from just listening to the rattling ) was that it could be the Flexplate, he didnt seem to buy into the timing theory.

Both of them rev'ed the car up while in park using the throttle and no noises of any kind could be heard.

The car drives smooth, no shakes, no loss of power, no smoke, it's just that damn sound that's driving me crazy!

Any help will be greatly appreciated!

 

I have the exact same noise in my 01 3.8 been doing it for 1.5yrs, at first I thought it was an ehaust manifold. still cannot figure out what it is..

 

My engine is working in a good condition. I don't think there is any problem till now. Recently I have taken a Mustang and I am very happy. Till now the engine does not make any noise and I am happy about it. My friend has got 1999 Mustang and his engine is making a rattling noise.