One problem related to coolant leaking has been reported for the 1999 Chevrolet Tahoe. The most recently reported issues are listed below.
Continuously having to fill with coolant due to leak. No leak from hoses etc. The problem comes from a defect in heads that are produced by castech. Went on line to research this and found numerous numerous complaints about this and gm/Chevrolet will not fix. Extended warrenty companies will not fix because it is a defective part. Dealerships will not talk about it but if you talk to an mechanic at a dealership and describe the problem they are quick to tell you exactly what it is and that it is a defect. The coolant seaps through the poorly manufactured castech heads. Called some of the local mechanics and they are saying the same thing-defective part. Now like I said I have checked on line and hundreds or more people are having this problem and are having to have the heads replaced and engines at out of pocket. I did not see where a lot of people are complaining on this site because like me they did not know where to go. I found out from a lawyer who also had this problem to complain on this site. He just simply got rid of his Tahoe. One said they were stuck on the side of the interstate with young kids and no phone and no way of affording to getting home from out of town. Now that is bad.