Topic: new motor knocks too

[huntingbuck101]

little over  a week ago I replaced my motor with 163000 on it due to a knocking sound at idle. It was in my opinion not the lifters but something deeper like a rod bearing. I found a motor which I was told had only 5000 miles on it for $600 so I did the swap. I drove the jeep home and on the way I stopped at the place I bought it from and both me and the guy that sold it to me listened to how nice and quiet it was. that was with 13 miles since the swap by the time I got home 12 miles later it sounded like the old motor but about 1/2 as loud. :brick:I would say it just the normal sound of a 2.5 but why was it quiet for the first 13 miles? also some times on the new motor the sound seems to go away. some days by the time I get to work it's quiet others not.I now have over 300 miles on it.
I can't help to wonder how much longer till the new motor sounds as loud as the old one.
I hear a lot about how great of a motor the 2.5 is so do I just have that bad of luck?
the other day a  jeep pulled up to me in my truck at the light the other day so I rolled my window down an it was making the same stinking sound and just as loud as my old motor.

[Jeffy]

Have you tried a stethoscope or use a dowel or screwdriver to listen to the engine?

[huntingbuck101]

I hear what you are saying. I too have wondered if it could be in the transmission but why would it be quieter with the new motor and at first nonexistent after the swap? I have put a stethoscope on every part that  I can think of and really cant hear it coming from any part but you take the scope off and you hear it.
I also had about 6 other people with automotive background listen with the scope with no luck ether. the weird part is on the old motor it never went away, on the new one it does and it's the exact same sound.
it make me think it's maybe a piston clearance issue. it seems to sometimes go away when I run it a Little harder like the piston expanded from the heat taking up some of the slop and maybe the old motor was so worn that even with it expanding it wasn't enough. this is just my theory I know some one will tell me I'm on crack but I've had two Chevy's that have rattled like a diesel until they warmed up.
also will wrist pin noise sound like a Knock at idle?

[might4banger]

Did you reuse your exaust manifold? Could be an exhaust leak... Check all lower mounts as well. If the spade type (near the transfer case) is not inserted  - could be that the movement from the exhaust system broke the seal at or near the manifold. This is just a guess - BTW. One more thing to check off the list.

[aw12345]

Piston slap and wristpin knock can occur at idle some engines can get old with it. Try pulling one sparkplug wire of at a time at idle to try and isolate it to a specific cylinder. if its post injected you can pulla injector wire plug of at the time. Also check for crackshaft end play/ trust clearance by prying the crank forwards and backwards. should have almost no clearance and this can cause a knock at idleand while running and will come and go. If its this and its an automatic the torque convertor is balooning and you need to replace that also.

Art

[huntingbuck101]

I did the plug pull with no luck. I will check the crank of both of my motors tomorrow If it's the crank what would it take to fix it and what could happen if nothing was done.

[aw12345]

If it is the crank and it's not to bad you can just change the main bearings. It has one that has a flange on both sides. This is called the trust bearing as long as the crank is not dished/worn to bad where these flanges ride you can just replace the bearings other wise it needs the crank also. If you do nothing it gets louder and eventually something will fail since it starts wearing the engine block throws the rods out of alignment and so forth but that takes quite awhile. Is this Jeep an automatic? if it is and it has excesive end play on the crank it will need the torque converter replaced. Since that could very well be the reason that both engines started knocking because of end play

Art

[huntingbuck101]

my jeep is a manual

[aw12345]

still could be the cause or if you swapped crankshaft dampners it could cause a knock to that comes and goes some noises you will never find though. We had one little Ford v6 at work that had a knock in the engine and we pretty much tore that thing apart never found the noise and its still ruunning 2 years later. If the oil pressure and compression is good run it

Art