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914World.com _ 914World Garage _ Is it Knocking or Not???

Posted by: Bruce Allert Jul 3 2005, 03:54 PM

I'd like to know what to look for when I take the 2.0 apart that was in Punkin. Since I've not gone into surgery of this kind I'm at a loss as to what I will see if it is a rod that was knocking.

When the engine was running a couple of us listened to it and proceeded to take a spark plug wire off one cylinder at a time to try to determine which one it was. We thought if the wire for the cylinder with the know was taken off it would cease to knock or quiet down which neither happened. Is this a way to find if it is a rod or which one it is???

.........b

Posted by: ! Jul 3 2005, 03:59 PM

Rod knocks or other noises can be from crank bearings, loose wrist pins, out of spec rods, or any combination....pulling a plug or injector will only tell you if a cylinder is firing or not....a dead cylinder will not change engine tone...a live one will when disabled by pulling the wire....

Posted by: Rand Jul 3 2005, 04:10 PM

Do you hear it most when accelerating or cruising? Rod knocks are easiest to hear when the engine is spinning freely, not under power... so while cruising, let of the gas slightly and see if you hear the knock come in and out while it's loafing there as you feather it.

Taking a plug wire off CAN help locate a rod knock because without the pressure on that piston the knock will raise it's head.

Posted by: ejm Jul 3 2005, 05:25 PM

Are you sure it's a rod that knocking? Have you dropped the strainer to look for bearing debris?

Any chance that something went down the intake..a stray screw, washer or whatever? Makes one hell of a racket getting pounded into the head and could be mistaken for a rod knock.

Posted by: Bruce Allert Jul 3 2005, 05:41 PM

QUOTE
Rand Posted on Jul 3 2005, 03:10 PM
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Do you hear it most when accelerating or cruising? Rod knocks are easiest to hear when the engine is spinning freely, not under power...

I first heard it while coasting/braking coming thru the timing gate then sitting & idling. Sounding almost like a lifter. It did get louder when I gave it some gas... that's when I shut it off

QUOTE
ejm Posted on Jul 3 2005, 04:25 PM
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Are you sure it's a rod that knocking? Have you dropped the strainer to look for bearing debris?

Any chance that something went down the intake..a stray screw, washer or whatever? Makes one hell of a racket getting pounded into the head and could be mistaken for a rod knock.

Hmmmmm... never thought of that I'll take off the strainer & if nothing there guess I'll remove the heads. Ain't got nut'n t'lose, eh?

thanks guys......... b

Posted by: TimT Jul 3 2005, 06:01 PM

this rod had to much knock

Attached image(s)

Posted by: TimT Jul 3 2005, 06:06 PM

anyhow, small end knock= tap tap tap

big end knock= thunk thunk thunk

big end know usually goes away as you raise revs, the rod floats on the increased oil pressure.

pulling the plug lead can help identify the offending cyinlder. Sometimes the knocking rod wil quiet down when no combustion pressure is driving that cylinder..

Oh and the bearing of the knocking rod will show copper or be hammered distorted somehow.

Posted by: Bruce Allert Jul 3 2005, 06:12 PM

Very interesting Tim. I just got thru with a high rev run (5k+) at AX & didn't hear anything while driving until I slowed to a crawl & 900rpm's.

Ve r r r r r y interesting!

........b

Posted by: Porsche Rescue Jul 3 2005, 06:18 PM

Bruce, drain the oil and then pull the sump plate and the "taco" plate. Look up in there with a flashlight. You "might" see the problem. Then pull both valve covers and look/feel each rocker arm. That also might tell you something. If a valve adjusting nut/screw came loose it could be the source of the clatter. After that, engine out and begin the tear down.

Posted by: Bruce Allert Jul 3 2005, 06:27 PM

Jim, engine is out already the first thing I did before pulling it was to check the rockers. They are still in adjustment as they were the day before AX meltdown. I'll get the tractor in the shop to hoist the engine up high enough to drian oil & pull the Taco & sump plates. Who knows, I might just get lucky then I'll have 3 Fat Tires

..........b

Posted by: redshift Jul 3 2005, 07:57 PM

G'luck Broose, hope it's something silly..

M