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07-23-2009, 11:51 AM #1
Help! Strange Noise From Engine...Need to help brother move this weekend!
I have a dilemma....my engine/tranny (TBI 350.th400) is making a wierd noise, but the problem is it only happens under load so it almost impossible for me to crawl around the truck to try and pin-point the where the noise is coming from!
The only way I can duplicate the noise without the truck moving is to put her in gear, stand on the brakes and give the engine a little gas to simulate a load...and I don't really want to be crawling under the truck with someone else doing that!
Here is my best description. When I'm pulling away from a stop sign, going up a hill or even just up my driveway...doesn't need much load....I get a rapid light metalic "ticking" noise....that increases/decreases with rpm and only happens under load.
It sounds almost exactly like my metal cooling fan is tapping the edge of my fan shroud, but I took the fan off last night and sound still happened. I've never heard engine knock or pinging before or detonation but this noise almost sounds to "light" to be something that bad....but??
I'm starting to think transmission now...like maybe the torque converter? What else in the transmission would make a loud ticking noise under load?
I had my fiance' get in the driver's seat so I could at least walk around the engine bay....I couldn't tell where it was coming from!! It is so frustrating...
Please help, I have a rare chance to really show off my truck this weekend and help my brother move..but now I'm worried about my truck
07-23-2009, 02:27 PM #2
Sounds more like a rod knocking to me. You sometimes can't hear them at idle.
07-23-2009, 02:49 PM #3
Thanks for you vote Evil...that would make me very sad...as this engine has less than 1000k miles on on it...and becuase I don't drive the truck much..the 1-year warranty on the rebuild is expired. :(
What is rod knocking exactly? Does that mean the rod is loose and is knocking against wrist pin in the piston or what?
Rod knocking vs. engine knock vs pinging vs detonation....are they one in the same?
07-23-2009, 04:51 PM #4
- Join Date
- Jun 2006
- River Ridge Louisiana-4 miles W of New Orleans-didn't flood-water stopped 800 yards away.
To me pinging/knocking sounds like pebbles rattling in a tin can-a bit like you describe.It happens under load, and is usually more common in hot weather. It probably is something else, but it is worth a try to use 93 octane.
The under load might indicate pinging.
Try some 93 octane and see if it is less Fill up with 92 with a nearly empty tank , so you actually get 93 octane.
If the pinging is gone or nearly gone, it is pinging/knocking.
A build up of carbon can cause hot spots-preignition- or even increase the compression enough to cause detonation.
07-23-2009, 05:10 PM #5
Pebbles in a tin can? That sounds too random to be what I'm hearing.
My noise sounds exactly like sticking a pencil into a house-hold box fan. A very sharp and precise tick-tick-tick-tick-tick...louder than a lifter, but a very sharp tick sound that increases/decreases with rpm but only under acceleration or load.
An exhaust leak? Maybe?
To add to the mystery, I hooked up a trailer with a bunch of yard waste the other day and had no problem all the way to the dump and back, didn't make the noise. Seems to happen most right after I start the truck when she's cold, but have had it happen once even after she's warm...
I'm definitly going to do the high-octane thing to rule out detonation/pinging etc. The noise sounds very mechanical...like something metal rubbing aginst something else that is rotating.
Last edited by Big6ft6; 07-23-2009 at 05:16 PM.
07-23-2009, 05:53 PM #6
Now that you de3scribe it that way... No I wouldn't suspect a rod. "Rod Knocking" is the pushrod for the piston. What usually happens are that the bearing between the piston rod and the crankshaft get spun or burn up, causing the rod to wiggle waggle around on the crankshaft, throwing it into the cylinder block.
I wouldn't waste the money on high octane fuel at this point.
If in a year's time you only drove it 1000 miles, I would say it is probably related somewhere in the valvetrain, especially when you say it now happens most when you start it cold. Try running a little Marvel Mystery oil thru it, then immediately change the oil. You probably have a lifter or somethign that didn't get lubricated properly on the rebuild and the problem has been exasperated by the truck sitting for most of a year.
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