ToolManTimTaylor

My neighbor's cousin stopped by and I heard the truck make a really bad rap (Ball Peen against an anvil sound) at idle. <br><br>Back when I had My 6.5 it made a similar noise (2000 mdl year) and come to find out the inspection lookin like plate had a harmonic vibration but was very light in sound. <br><br>This truck was RAPPIN BIG TIME kind of non rythmicly. I discounted a bad rod because of that but now I winder if I was wrong. He has had great luck, runs great and man It was certainly an awesome truck (Contractors Body) clean and upkept. He fears a pushrod me I was left ??? how.<br><br>Anyone wanna take a stab at what this coulda been?<br>I still say not a rod and keep in mind this truck is showing no oil pressure loss.

tmiller24

Might be a broken piston skirt. If it's the culprit, it will have a double knock sound, caused by the piston changing direction, from up to down or vise-versa. That would be my guess as they are very prone to breaking in the cold temps.<br> Tony

Dieselbuilder

You never said how it idles,Could be a bad injector leaking down when running making it knock. Had the same thing happen with my old 6.9 ford

ToolManTimTaylor

It Idled smooth. This is a weird one.<br><br>Yeah I can see a skirt issue, However I also have heard about the Glow plug issues in the past coming loose. Can this happen on a 1999?<br><br>

Hummin Cummins

Standard fare.<br><br>Those chevy 6.5's are noisy.<br><br>Mine had the knock you mention. Take it out and run it until it gets nice and warm and the noise should quiet down (not exactly go away).<br><br>Couple things to remember about chevys.<br><br>1) if the engine is cold it could be knocking due to a weak glow plug. The chevy has 8 of them which allows you to start the engine even when you have a faulty glow plug and that is the good thing (a completely bad glow plug= rough idle)<br><br>2) the chevy has little metal shields on the bottom of the cyclinder head which pronounces this cold start &quot;not quite a fully warm engine&quot; knock.<br><br>3) the noise is typically louder on the passenger side of the engine than the drivers side. Why..I think the turbo location and manifold upweep has something to do with the harmonics.<br><br>4) the injectors are right on top of the engine...actually exposed, so if one of these just happens to be noisy it could be the culprit...<br><br>5) the injection pump is also extremely noisy and is mounted right on top of the engine...this being said any noise will travel through the metal injection lines and wreak havoic on the ears.<br><br>bottom line...chevy 6.5 is noisy.<br><br>One of the better tests I can tell you to do is simple. Check the oil, then start the engine cold. If everything idles fine and it dont smoke (but should make a lot of noise) the glow plugs are good. Then take it out and RUN IT! When it is warm...full throttle the engine and leave it self shift (or shift around 3000rpm if manual) Do a couple of these and note if there is any exhaust smoke present and the color. Now after a couple of 1/4 mile runs pull over with the engine running and remove the oil cap (watch your fingers and knuckes in the fan blades) and see if there is oil smoke coming out of the filler neck...if there is the rings are bad and leave it for someone else.<br><br>If there is heavy knock and the truck is skipping after it is &quot;good and warm&quot; it could need any of a multitude of repairs...lift pump, injection pump, bad wiring connectors to the injection pump, water in fuel, leaky injector, scaling of the metal fuel lines and so on. At that point if you really want the truck take it to a GM diesel mechanic who &quot;knows what he is doing&quot;....that was one of the biggest problems I had when I owned my 6.5 chevy. I had to travel to the nearest large city to get the thing worked on. The 96-99 GM 6.5 does have silent extended warranties on the injection pump, but takes about a week to get them fixed until all the paperwork and crap is taken care of.<br><br>Hope it helps.

BigBlue

My dad's 6.5 is extremely quiet. Never noticed any knock except for the cold startup knock that most diesels get.

Hummin Cummins

Could be air in the injection lines as well...they dont necessarily cause a &quot;miss&quot; as air is lighter than fuel but do cause a knock.<br><br>It took me 3 dealerships till they figured that out one time.<br><br>