Common Problems with the Northstar Engine
Common problems with the Northstar Engine usually relate to dealing with stripped head bolts. For example, if you own a Cadillac STS engine Deville 97 with a 32 valve 4.6L Northstar Engine with a blown engine, chances are good that by simply doing a pressure test and a spark plug test, you will discover that the head gasket has blown. After identifying what bank it is on, you have to work on getting it replaced. Simply fixing the gasket itself is not a realistic option because of the cracks. Unfortunately, repair, which is a replacement job, is neither cheap nor easy. It is nearly impossible to do it on your own with a simple set of hand tools, nor can you get your local mechanic to do it unless he or she has plenty of experience with this particular problem.
In retrospect, the problem of stripped head bolts emerged after 1996 and gradually disappeared after 1999. Although most automotive experts contend that by 2000 the problem was behind GM, some critics argue that it took GM another 10 years to fully resolve the problem.
What happened in 1997, 1998, and 1999 models is due to poor decision making on the part of GM. The run of GM problems with Northstar Engines began when they moved away from a green silica based coolant and moved to another coolant called Dex cool. This coolant simply could not do the job. The Northstar Engine problems are similar to the problems associated with the Quad 4. In both cases, the head bolts had a fine thread that easily stripped once the engine reached a certain level of inability to effectively dissipate heat. What stripped the head bolts was the chemical reaction between the steel bolts and the aluminum block. Basically, aluminum was too soft. Thus, it is not really due to defective bolts or to defective blocks, but the reaction of one to the other, specifically the reaction between steel bolts with aluminum blocks. Unless the coolant was perfectly maintained, the threads dissolved when the heat became too intense, resulting in the engine blowing up. Once GM reduced the block hardening process that they had previously used, the block and the bolts began to go to wrack and ruin, a chemical reaction similar to applying a flame to a block of cheese. Usually, this problem became typical when the Northstar Engine was closing in on the 100,000 mark. At this point, the Northstar Engine could not stay cool enough to prevent the threads from dissolving.
Resolving the problem was not simple. The entire engine had to be pulled, then drilled, then retapped, and then finally have timeserts installed. This not only took about 40 hours or more, but it cost car owners from $3,000 to $5,000. Moreover, unless the work was expertly done, results were often less than satisfactory. Considering that the models from 1997 to 1999 have a value of $6,000, the repairs came close to the cost of the entire car itself.
A better solution to fixing the Northstar Engine or buying a new engine is to get a used engine where the bolts have been beefed up. Once the bolts have been replaced with head studs, the Northstar Engine begins to work like a charm.
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So instead of hunting down an expert on Northstar Engine and instead of buying a new engine with the same defective bolt-gasket chemistry, it is much cheaper and less time consuming to get a used engine with reinforced bolts.