Last night after getting a few runs in with some friends, my car started smoking white smoke very lightly. So I immediately thought right away that I blew my head gasket. After slowly coasting it back to the parking lot, I heard a light knocking coming from the bay. I pulled over, shut the car off. I then proceeded opening the radiator, no pressure at all, but the fluid was in sight when i looked into the radiator. Car had good oil pressure (40psi) and temp gauge was still below 210 (160-180).

After adding more coolant I started the car again, and this time the knock got a little louder. I limped it back to a buddies house (continued to lightly smoke white on the way back).

The knock seems like it isn't consistent, it sounds like it quiets down above 1500 rpms at any throttle but the most throttle I probably gave it at above 1500 rpms is 10-20%. When its below 1500 rpms, if I give it the right amount of gas which is less than 10% throttle the knock quiets down where I can barely hear it. At idle you can hear it knock quietly. To me it doesn't sound like a rod knock, I've heard rod knocks many times and rod knocks are usually loud as hell while this is more quiet.

No idea where to start so I first pulled the plugs, cylinder 5 & 7 had coolant on the plugs. Plugs were still wet. I then did a compression test and all cylinders were 150psi, except cylinder 5. Which had 190psi... (Could it be a false reading from there being coolant in the cylinder?)

I opened the throttle body and there was coolant in the throttle body, PCV valve, and intake. (I did the bypass mod years ago, so the coolant is not coming from the throttle body). Pulled the dipstick to check for coolant in the oil pan and no coolant was found. No oil was found in the radiator either. But there was coolant found under the oil cap, and inside the valve covers, it turned to a milky substance of course.

Pulled the intake off to check if I could visually see anything, but nothing was to be found.

I'm all out of ideas, anybody ever come across something like this???

 

I've seen fluids end up in strange places with blown headgaskets...I'd check there

 

The coolant in the valve covers was most likely pulled in through the PCV from the intake.

It's time to pull the driver-side head.

 

i think you may have just had a hard lesson on the
comprssion limits of liquid..hate to say it, but id be willing
to bet a headgasket let go, and bent a rod

 

^^^^
I'm with this guy.

 

Ok I will pull the head this weekend when I get the chance, anything else I should look for?

How do I know if a rod is bent? Any way to check without pulling the motor?

 

Anything else I should check for besides blown hg?

 

I was thinking the same thing but I didn't want to believe it. I guess that could explain why the compression is soo high in cylinder number 5... I guess the rod was bent enough where the piston comes up alittle higher than normal? Is it possible that the coolant is causing the compression to be high if the rod isn't bent?

 

Sometimes you can get a knock sound from a blown head gasket and not have any lower engine damage. This can happen when the gasket is blown between two cylinders and pressure from one cylinder shoots into the adjacent cylinder over-pressuring it. Hopefully that is all it is.

When you have the head off, inspect the circumference on top of all the pistons looking for any possible visible damage to the rings or lands. Also, you can put a dial gauge on all of them at top dead center and see if any are down in the hole more than the other.

 

The coolant could give a false compression ratio. Having a bent rod would make the piston not travel as far in the bore. When you pull the head, rotate the motor over and see if all the piston on the drivers side come equal to the deck of the block. If 5 doesn't, I would pull the motor and replace the rod. A bent rod would cause the knocking.
Sorry for bad news.

 

Beat me to it...I'm always a day late and a dollar short...lol

 

since you know for sure there is water in the oil, i would just refresh the whole engine anyway. better safe than sorry.

but first, pull the heads off, clean the deck and pistons with a plastic wheel. check to make sure all the pistons stick up .005 from the deck surface.

 

Ok so a healthy motor without any bent rods should have pistons that stick out .005 of an inch above the deck?

 

That is the way LS motors are set up.

 

...unless you have a bearing that's messed up badly enough to give a false reading. In that case you would have a VERY bad engine knock.

 

Well the knock isn't that bad to me, it sounds more like a tick to me but my brother thinks its a knock because we can't tell if its coming from the head or block. But my brother thinks its too loud to be a tick and I think it's kinda quiet compared to all the rod knocks I have heard

 

+1

Water/Antifreeze in the oil will cause premature bearing failure if not sooner than later. Water and oil do not mix. I would cut my losses and tear it apart. Replace thrust bearings, rod and journal bearings, bore/hone clean up, new rings and ARP bolts all around with new gaskets. I would also have the block dye penetrated.

 

This is the best option here...maybe not the cheapest, but might aswell do it right the first time

 

Yea, so from what I'm gathering from every one so far is that the headgasket blew, coolant got into the combustion chamber and the piston tried to compress the fluid and ended up bending a rod? You guys think my 241 heads are still good and not cracked?

I'm currently pretty sure my rod is bent because of the high compression in one cylinder... And I've also been debating about replacing the ls1 with a 6.0 iron block, any input in the iron block idea?

 

When my head gasket blew, i had no choice but to drive 50 more miles on the motor, because a tow cost more than a new engine in san diego. So i ended up with a hole in a piston, warped heads, cracked block and blue bearings. After all that, there was still NO noise from the bottom end. The only noise was from a dead lifter. They don't like water. So I'm thinking you may have a dead lifter. If you had a bent rod, you would have less compression in that cylinder, not more.

As far as iron blocks go, I'm happy with mine. I bought my LQ4 as a complete engine, but i wish i had just bought a shortblock and installed the LS3 top end from the beginning. A complete LS3/L76/L99 top end cost less than a FAST intake alone and makes a lot more power than a FAST with stock 243's or 317's.