96 Yukon Knocking Bad

[grandprixfamily]

I did search, lol, so dont jump my bones too bad, im sure this has been gone over before. i did find some info, just lookin for more thoughts.

 

my 96 Yukon with a 99 burb motor (same stuff, but anyway) has developed a pretty serious knock.

 

i havnt been able to look too much into it. but id like to hear your thoughts.

 

cold, it will do it nearly every time, and it takes a good 5 minutes at least to simmer down and fade away. it can occasionally tick a bit at a stop, traffic light, etc, when warm.

 

this started after about a 20 hour roundtrip roadtrip helping a neighbor move, 13 there, 6 back, pulling a loaded uhaul trailer there and empty back.

 

its progressively been getting louder, before when i first heard it it was a real light tick, now it almost sounds like a rod knock. its definately the drivers side, and more toward the front of the engine, likely the first 2 cylinders.

 

this worries me because i got the truck, and the old motor spun a rod on cylinder 1. i replaced everything, the motor, all the stuff attached to the motor came with the new one, and i even used the new motors oil cooler lines. just before the trip i also put the 2.25 inch core radiator in. it was a small amount overdue on its oil change.

 

i am running 10w40 right now. and i did read that i should go 5w30. i went a bit thicker being that its a truck, i beat on it, etc. i did an oil change today, and no change in its behavior. cut the old filter open, and it was pretty dirty, but i didnt see anything that struck me as obviously wrong.

 

the magnet on the plug had a good amount of metal film on it, however it could have been from the old radiator cooler, as im sure it was fairly dirty from the previous engine.

 

im running a pf52 ac delco duraguard filter, before i was running a supertech 3980, same filter, even made at the same factory, just different labels.

 

oil pressure drops to 20-24ish at warm idle, cold idle is above 40. cruise is about 50 cold, 40 warm.

[grandprixfamily]

ok, so a quick update. being that i was posting this, thought id do a test.

 

went out, started it up, truck is reading below the lowest line on coolant temp, its 36 degrees outside right now, and the truck hasnt been driven in over 4 hours.

 

popped the hood and started it up.

 

nothing, almost dead silent. a VERY slight tapping that i could barely make out from the valve cover area. i let it run about 5 minutes, blipped the throttle a couple times, and no change.

 

so im not AS worried as i was. but im still cautious. cant afford another motor.

[gmtech4]

any warranty ?

 

 

it may be piston slap

[grandprixfamily]

no, no warranty, it was a private party deal. good guy, but i wouldnt expect to get any money back. he bought the motor to convert a jeep over, and never did the project. so he just sold all the stuff.

[gmtech4]

is the motor new or used?

[grandprixfamily]

motor was used from a 99 suburban, had just over 50K when pulled.

 

i am currently in the process of doing the water pump and LIM gaskets. ive had a small coolant smell for a little while, thought it was just the radiator (had the common drivers side tank crack, replaced with a proliance 2.25 inch thick unit) but i used my system pressure tester and the WP started spewing, along with small amounts of seepage from the lower manifold area.

 

all is apart now. sucks, i just did an oil change, and now im going to have to do another one.

 

it hasnt been knocking anymore. i did notice however a large amount of sludge in the lifter valley. thick nastyness. cleaning it out as best i can now.

[Mike G]

Could be that you were just getting a little oil starvation do to drain back blockage. A bad knock does not go away, it gets replaced. Since the occurence changes, I would clean everything up real nice while you are in there, maybe run a little cleaner in the oil and go 5-30 on the oil change and see what happens.

--Mike

[grandprixfamily]

all seems fine now.

 

i did the LIM and UIM gaskets, and a new water pump. changed the oil AGAIN, put it all back together, and it purrs like a brand new truck now.

 

i am still running 10-40 oil, but ill prob change that on the next oil change.

 

i can faintly hear some valvetrain tick, but nothing like before. im maybe thinking a lifter collapsed? it was pretty loud, and had me thinking more of a bottom end noise, but i dont see any decrease in oil pressure, and the noise has not come back at all.

 

so ill just drive it, and hope all is well.

[Nytemare]

all seems fine now.

 

i did the LIM and UIM gaskets, and a new water pump. changed the oil AGAIN, put it all back together, and it purrs like a brand new truck now.

 

i am still running 10-40 oil, but ill prob change that on the next oil change.

 

i can faintly hear some valvetrain tick, but nothing like before. im maybe thinking a lifter collapsed? it was pretty loud, and had me thinking more of a bottom end noise, but i dont see any decrease in oil pressure, and the noise has not come back at all.

 

so ill just drive it, and hope all is well.

Try some GM Engine Oil Supplement on your next oil change...or a quart of Rislone...(you can also buy concentrated Pint size cans) I have had luck with both to quiet or stop valve train ticking.

[grandprixfamily]

ahh, GM EOS, yea, i had to use that once to quiet some lifters on one of my grand prix's. my GT coupe has 325,000 miles on it. put some in one oil change at around 225K and it quieted up, been fine ever since.

 

ill grab some and put it in.

 

the ticking is real slight, nothing to bother me, just me being anal about stuff.

[Nytemare]

ahh, GM EOS, yea, i had to use that once to quiet some lifters on one of my grand prix's. my GT coupe has 325,000 miles on it. put some in one oil change at around 225K and it quieted up, been fine ever since.

 

ill grab some and put it in.

 

the ticking is real slight, nothing to bother me, just me being anal about stuff.

Could be injector tick too...or exhaust related. A bottle of EOS on an engine that has been sitting isn't a bad Idea anyway.