I have a 2003 suburban Z71 with 5.3L. I have to add about a gallon of coolant every two months or so. The mechanic did a pressure test on it and found no leaks. I have never seen any coolant leaks butit still goes through coolant. Somebody told me to check the oil and see if it is leaking in there. Ichanged the oiland can't find any trace of coolant in the oil. Can anyone tell me where it might be going and what is wrong?

I all of a sudden have a knocking noise coming from the engine. It sounds like a lifter. It only does it for about 30 seconds a then quits. It started about a week ago. The first couple of days it made the knocking noise for about five minutes of driving and then went away. The knocking noise would get louder with more RPM's. Not sure if these two are related but just thought that i would see if anybody could give me some insite on what is wrong.

 

If it were me......And I'm not the brightest bulb in the room.....I'd check my spark plugs for water contamination. Just on the off chance it is a small leak into one of the chambers, it would burn off so you wouldn't see a leak, but it would leave the brownish-white residue on the spark plugs.

Just a guess

 

Thanks for the info. I will check the plugs. Any more info from somebody else would be great.