rattle from engine....ideas?

[Mirlyn]

Got a 1999 V6 Mustang coupe with 69k miles on it. Only addon is a MAC CAI. When on the gas I get a rattle. It is inconsistent (fades in and out in seconds) but the pattern/beat of the rattle is fairly steady. It stays whether I'm gently accellerating or even just holding a steady speed, but goes away when I release the gas. It also goes away if I put cruise control on (car shifts up when this happens). I'll have to count tomorrow to be sure, but I think its in 2nd and 3rd when it does it the worst (anywhere from 20mph to 45mph). I can't hear it that well inside the car, but with windows down and driving near a curb or fence, I can hear it quite well (bouncing off those). I don't feel the car buckle or jerk or anything when its doing it. My usual mechanic isn't sure, but thinks it might be the gears chattering against each other in the tranny. Anyone heard this before? I'm the second owner, and as far as I know, everything is original. I'm going to take it into a tranny shop Friday to have it checked, but the fluid looks and smells good. Hopefully it doesn't need a full rebuild.

He also suggested possible loose calipers, but lightly pressing the brake while on the gas doesn't quiet it, so I don't think thats it. I did a quick lookaround under the hood and under the car and didn't find anything loose. Exhaust/shields seem to be tight. I can't get it to replicate the sound when the car is parked (hence the gears consideration). I've been told the differential gears were noisy in this year, but there aren't any signs of leakage from the rear diff. There aren't any spots on the driveway either.

It began about two months ago by just doing it at a sharp rpm increase, for example, first to second while turning or from a stoplight. One thing I have noticed is for the most part (not all the time) it does it when the engine is hot. For the first few miles on a cold engine, I don't recall hearing it. When the weather cools down, its not as loud as it is when its warmer out and the car is hot. Today it warmed up (80s) and I had the windows down and really noticed it.

The car does have a tick from the passenger side of the engine when started cold. I think its a sticky lifter. After a mile or so, it goes away. Doesn't do it as bad right after an oil change, and gradually gets worse. Next change I'm going to try diluting it a little more (sub 1qt for marvel mystery oil). I have heard the tick could be an exhaust leak. I suppose the only way to find out is to pull the headers, as from what I can tell under the car the pipe looks solid from the cats back.
I don't know what else it could be...any suggestions?

Thanks!

 

[Inkara1]

Just so you know, earlier years of the 3.8 V6 tend to blow head gaskets starting right about at the number of miles you're at now. OK, I should say "tends to" is a massive understatement. Ford was supposed to have fixed the problem by '98 or so... but, well, ha.

Pay attention behind the car when you're driving it (or have someone else do so). Is there any white "smoke" coming out of the back? If so, does it do it more when you step on the gas, or more when you let off the gas? Have you noticed your oil level is inexplicably lower, or your coolant level? Have you ever smelled a hot raw gasoline smell around your car?

I'm not sure if a failing head gasket would be making the engine make noise... but I'm sure both Kruz and deanril have seen enough blown 3.8 head gaskets to tell you that it's an engine to avoid.

 

[Mirlyn]

I had thought about that. However, no smoke (white or black), haven't had to add coolant since July, and the last three oil changes looked normal and its holding its level between changes.

I've heard about the head gaskets, but heard it wasn't all that common. I heard it the problems were associated with the older 3.8, not this version.

 

[Spot]

where does the rattle noise seem to come from?
my old '98 stang needed to have the rear diff repaired (cant remember the exact problem, was a few years ago). it made a rattling/crunching noise when i was taking right turns, especially at lower speeds. never saw any fluids on the ground, just heard the ugly noise.
the noise got worse after driving around for awhile too.

 

[Mirlyn]

It sounds like its coming from up front, but it could be bouncing around on me too. It does it equally when I turn and when straight. If I didn't have a midterm in my class in 20 mins, I'd skip and take it in today.

I heard it today in 1st through 4th after driving around for 45 mins. Odd thing is, it'll stop as soon as I put cruise on, whether it shifts up or not. Almost like it has something to do with the amount of pressure on the pedal.

 

[Gato_Solo]

Valves?

 

[Spot]

maybe its just be dirty injectors or a problem in the fuel line like a clogged gas filter or something...
any hesitation when you hit the gas?

 

[Mirlyn]

maybe its just be dirty injectors or a problem in the fuel line like a clogged gas filter or something...
any hesitation when you hit the gas?

Nothing noticeable. There's always been a slight hesitation at the top of 3rd when I'm on it hard (highway merging) but it'll go away as soon as it throws over (its pretty much normal). I could track down and check the fuel filter. Ever done it before? Where's it at on the stangs? I'm used to my truck...everythings right there.

Think I should try some kind of additive/cleaner? Brand recommendations? I'd be extremely happy if it goes away with something as simple as a filter/injector.

 

[Gato_Solo]

Octan 104 works wonders on cleaning your filters and injectors. Just don't use more than one bottle per tank...I'm still thinking valves, though.

 

[Mirlyn]

Octan 104 works wonders on cleaning your filters and injectors. Just don't use more than one bottle per tank...I'm still thinking valves, though.

Dunno much detail about this kind of stuff...is there a way to check them myself, or what would that entail?

 

[Gato_Solo]

You'd have to pull the heads and check the seals. That's where the rattle would come from. Is it louder under acceleration?

 

[Mirlyn]

You'd have to pull the heads and check the seals. That's where the rattle would come from. Is it louder under acceleration?

Usually, yes. I can press it a little harder (and I mean lightly) sometimes to get it to sound louder. Sometimes though just a constant pressure makes them louder.

So taking the heads (valve covers, I assume) off would show me what I need to see? Hmmm...

Maybe try the filter/additive first, and then look into that.

 

[Gato_Solo]

Yes. Valve covers. Just make sure you change the gasket if/when you do it. Even if there's nothing wrong. Kruz could tell you quite a bit more if he still drops by here.

 

[Mirlyn]

Yes. Valve covers. Just make sure you change the gasket if/when you do it. Even if there's nothing wrong. Kruz could tell you quite a bit more if he still drops by here.

Yeah, I posted here hoping he too would see it. I'll pick up a shop manual and read more into it. Cool, thanks a lot guys!

 

[Kruz]

from your discription, it sounds like exhaust noise. possibly one of the cat's is broken internally and ratteling around.. take a rubber hammer and tap the exhaust system, listen for any rattles or jingleing at the cats or heatshields.. as far as the rear ends on those cars.. I have rebuilt about 6-7 mustang rearends. differential bearings give out as well as pinion bearings.. but this is a constant grinding / roaring sound that increases with vehicle speed and sounds like its comming from the back seat area..

 

[Inkara1]

I've heard about the head gaskets, but heard it wasn't all that common. I heard it the problems were associated with the older 3.8, not this version.

The problem was supposed to have been, but it takes 60,000-80,000 miles to crop up. The majority of '99 models are just now getting to that stage.

Here's a few gripes about '98 Windstars with blowing head gaskets:
http://www.consumeraffairs.com/automotive/ford_windstar_1998.html

 

[Mirlyn]

from your discription, it sounds like exhaust noise. possibly one of the cat's is broken internally and ratteling around.. take a rubber hammer and tap the exhaust system, listen for any rattles or jingleing at the cats or heatshields.. as far as the rear ends on those cars.. I have rebuilt about 6-7 mustang rearends. differential bearings give out as well as pinion bearings.. but this is a constant grinding / roaring sound that increases with vehicle speed and sounds like its comming from the back seat area..

Thanks Kruz....the shields were tight last I checked, but I didn't actually try to rattle the cats (or any of the exhaust system). I'll check it out first thing tomorrow morning. I'll try the fuel filter in the morning too. Picked up a Haynes manual on the way home and it doesn't look much different than what I did with the truck.

Its kind of a lower-pitched deep rattle, not the high-pitched chattering of thin metal. What are your thoughts on the valves, Kruz? Is there a good trick to playing with those?

 

[Inkara1]

Wouldn't you have to take the heads off the engine to do that? I don't mean the top covers with the "Ford" logo and the engine oil filler neck on them... I mean, the big, heavy things the covers screw onto, and the spark plugs also screw into.

 

[Mirlyn]

from your discription, it sounds like exhaust noise. possibly one of the cat's is broken internally and ratteling around.. take a rubber hammer and tap the exhaust system, listen for any rattles or jingleing at the cats or heatshields..

It does sound loose...but faintly. Like theres a little bit of sand in there. Could that amplify to something sounding deep?