Strange Engine noise out of no where

-
S

Shane

Well-Known Member
Joined
Feb 3, 2008
Messages
351
Reaction score
1
Location
Ontario, Canada
Hey all,

As of yesterday afternoon, I start up my 340, and it has this horrible sounding raddle coming from the motor. I shut it off, check the oil it has no metal shavings and no coolant I can see.

I check the coolant, no signs of oil.

So I start it up again, and rev it up to 1500 rpm. Nice and quite, runs perfect. Oil pressure is right where it should be...

anything under 1500rpm and a horrible rattling sounds.. I should mention I drove home with no issues...just kept the choke on so it never went under 1500rpm when I came to a stop sign..

Any suggetions on what you guys may think it is, or where to start looking?

I have a valley pan tray installed under the intake. I think I am going to check that first, I am thinking if the spring strap that held it came loose it could be rubbing on the pushrods. The engine shakes alot at idle, and smooths out with more RPM's, so thats my line of thinking right now..

Anyways,

thanks for any ideas...

Shane
 
Not a whole lot of info here, but listen from underneath, and if you are really lucky a converter bolt may be a little loose. When trouble shooting I always try to start with the cheap and easy basics, as opposed to the panic and throw parts at it.
 
Sorry, what other info do I need?

The car is a 4 speed. could be loose fly wheel?

I agree with not going with the panic... I want to check any and all possiblitlies and see from there..
 
Not sure if the flywheel could be loose. I was just guessing that you had an automatic.
My Dart makes a raddle noise also at idle, but it is the exhaust pipe hitting the floor board 'cause it needs a tune-up.
 
thats what i was thinking a torque converter bolts gone loose because that sounds EXACTLY like a rod knock.
 
Rod knock is what I am scared of, but at and above 1400-1500rpm it runs fine... I drove it home with no worries..

The motor was newly rebuilt when I got it 2 years ago..I have only put around 7000 miles on it..And I havent really driven it hard...yet..
 
You need to identify more closely where the noise is coming from. If it is coming from the bottom I would really worry. I use a stethoscope to try to isolate noises. You can hear things going bad with one way before you can see or hear without one. Check the accessories and anything you can think of. Maybe it's just a loose air cleaner.
 
Rattling noise,top or bottom?It could be a losse bolt or exhaust hitting somewhere.Can you post a video of the sound?
 
I am going to try to take a video of the sound tomorrow afternoon. I am off tomorrow afternoon and going to try to pin point where the sound is coming from. I did manage to borrow a stethoscope from a friend today.. So I will use it to check around also...

btw, the car has headers...it seems to be a top end noise from my initial listening yesterday..
 
I would check all the pulleys, the fan, things like that. Far better to figure it all out before something goes thru the radiator, or out the side or bottom or whatever. The word stranded comes to mind. I see you have a stethoscope, I was going to suggest a wood dowel, they work fairly well also. I have one question that may help. You made it sound like you parked the car and it was fine, then you started it in the afternoon and it was making noise. Can you think of anything, even the most minor thing, that you may have done to the car. This would include adjust a hanger, check the oil, fill the radiator or washer reservoirs, tighten a belt, the list could go on forever. Maybe you leaned on the cowl and it's hitting the fan. Or you left a bottle top under there, or even a wrench on top of the engine that's rattling around. Start with anything you may have messed with in the last few days. I hope this is not a case of the dreaded I let someone use my car!
 
I cant say forsure what it is when its rattling, but the car was warm and was at 45psi when I kept the rpms at 1500rpm... I will double check the pressure when its rattling when i start it up tomorrow..

Magnumdart, its a good question, but i hadnt done anything...My little sister wanted to go for a ride in it, so I started it up, drvoe the 40 mins to our family cottage. I started cutting the grass, had to move the car to cut under it while the lawnmower was still running in the backgorund... I thought I heard something out of place but jsut ignored it..

Started it up to go home a couple hours later and rattles at any rpm under 1500... Before that I have driven it about 700 miles this season on fresh oil with no issues...
 
OK. I'll think about it a little more, but the easy options are runniing out, and it's begginning to look less than good. BBL, I got to go in the basement and attend to a beam that some moron engineer sized wrong. (That would be me.)
 
Have you taken the valve covers off yet to have a look if you might have a loose rocker. Happened on one of my other cars right after a fresh oil change and a 20km test drive. Parked it in the evening everything was fine and in the morning on start-up i have a collapsed lifter. Just make sure none of the rockers/pushrods have excessive play in it.
 
It sounds logical that something worked its way loose since it happened on the way to the cottage. Hopefully it will be a cheap easy fix what ever it is.
 
67cuda360 said:
Have you taken the valve covers off yet to have a look if you might have a loose rocker. Happened on one of my other cars right after a fresh oil change and a 20km test drive. Parked it in the evening everything was fine and in the morning on start-up i have a collapsed lifter. Just make sure none of the rockers/pushrods have excessive play in it.
Click to expand...

That would also explain it running rough, a loose flywheel would knock but motor would run smooth.

Time to pop the valve covers off, I seen the rocker shaft bolts snap off in the past and allow the rocker shaft to lift. I now use studs to hold the shafts down.
 
Thanks for the ideas guys... I am making a list so i dont miss anything stupid when I start looking..

The thing I dont understand is why it only rattles at low rpms... something stupid must be loose...
 
dodge freak, so the loose flywheel would knock around, but would it smooth out at high rpms?

The engine seems to be running fine... just terrible rattling noises at lower rpms..
 
I have a bad rattle as well that turned out to be my choke linkage. Still drives me crazy but at least I know what it is now.
 
Shane said:
The engine shakes alot at idle, and smooths out with more RPM's, so thats my line of thinking right now..

Anyways,

thanks for any ideas...

Shane
Click to expand...


But its running fine?

Well will not hurt to check the flywheel. All you can do is check everything out until you find what is loose.
 
You must log in or register to reply here.
-

Back
Top