Rattle from engine

[austindavis1993]

Okay so i have a 93 mtx that has been making this rattle noise after 2500 rpm, im leaning toward throw out bearing because the noise becomes more apparent when i press my clutch pedal in. I was also thinking possibly being a worn out rod bearing, help please as this is my only form of transportation right now.

 

[Irish Pride]

A rattle noise could be several things. You will need to investigate a little further. It could be a rod bearing(lets hope not). Has your oil light been flickering at low rpms/idle?

It wont be the throw out bearing. Noisy throw out bearings typically get quiet when you press in the clutch. Set the parking brake and chock the wheels and let the car idle. Pop the hood and get under there and play with the throttle while listening to see if you can determine where the noise is coming from. Right or left side of engine? Upper or lower? Etc...

 

[austindavis1993]

There has not been an oil light, i will have to take a video and post it, could be crank cancer too, but it is odd that it acts up when pushing in my clutch, i dont hear anything at idle UNTIL i press my clutch in. But the sound acts up when i rev to 2500 without touching my clutch

 

[jelloslug]

Throw out bearing or timing chain tensioners are the main causes of odd noises under the hood.

 

[austindavis1993]

I hope its just my throwout bearing, i ordered rod bearings and am.going to install anyway just for preventative maintenance. But until then im gonna stick to being paranoid and shifting at 2k...lol

 

[austindavis1993]

http://www.youtube.com/watch?v=ITVtGmTh9Ms

here is a video i just took, listen closely

 

[Irish Pride]

Rod bearing is on its way out is what it sounds like to me. Can you determine if its coming from the top or bottom of the motor? If you keep driving it new bearings wont help. You'll be looking at a new motor.

 

[austindavis1993]

It seems to be coming from the trans area, im thinking im going to invest in a stethoscope so i can pinpoint exactly where its coming from

 

[Irish Pride]

Use a long screw driver. Works just the same.

 

[austindavis1993]

well i tried the stethoscope trick didnt hear anything unusual from the oil pan but hear some noises from the trans, which leads me to believe i have a rattling tob, but iam still going to replace rod bearings since i have them ordered.

 

[rubydist]

meanwhile, do NOT shift at 2000 rpms! the engine does not like to run less than 2000 rpms, and when you lug it you put more stress on the rod bearings, cause the oil pressure is not much at 1500 rpms so it is easier to break down the oil film.

 

[austindavis1993]

Yeah now that i know my rod bearings are okay ive been shifting at my regular 4000 rpms, but smh at noisy tob!

 

[Irish Pride]

I dont think that rattle is your TOB but i hope you get lucky.

 

[ShadetreeSHOguy]

Rod Bearing, Stop driving it. Change them.

If you do any kind of research on this forum you will find they are the achilles heel of these motors. If you have ANY doubt they haven been changed, change them.

But given the soudn that thing is making, it may be too late.

 

[austindavis1993]

Yeah but i didnt hear anything weird from my oil pan it sounded very smooth, then once i put my stethoscope on my trans thats when i hear the rattle magnified. Im really hoping its just the TOB, will do further investigation today

 

[austindavis1993]

Okay guys you were right it was a rod knock, my bearings were one step away from spinning, thanks for the help all!

 

[Irish Pride]

How did you finally confirm it?

If your crank is scored its ruined. Run your finger nail across it. If you can feel anything with your nail dont bother putting new bearings in it. What bearing(s) was it? #5?

 

[austindavis1993]

My crank journals were all pretty good, hand checked them all, and yes it was #5 how did you know?? #5 Bearings were really bad but my journal felt great.

 

[Off Road SHO]

If it was the #5 rod knocking and it's been doing it for a while, you should really do two measurements with a micrometer, 90 degrees apart on that rod to make sure the journal is not oval-ized. One test should be in the same plane as the direction of force applied by the piston on the power stroke, and the other should be 90 degrees out. Make sure the micrometer contact points aren't in the crank's oil hole when you measure. Measure in the center of the journal, not near the sides.

Tom