When I first bought this pre-owned in 2013, it seemed to have no major issues for the miles it had. Minor things were a broken driver's seat lever (seems typical!), blown dashboard speaker, cracked vinyl dashboard, broken defrost vents. The ashtray with the cigarette lighter was hanging there and would not go back on. The A/C was not very cold and seemed to need charged. Most accessories were still in good working order, even for it being 15 years old. In more than a year I only put 4,000 miles on this, and they were city miles with only occasional off road driving. I've owned many Blazers and Jimmys, and these things seem to hit an invisible wall at about 150,000 miles. Once one thing starts to go bad, you can expect a string of things to go after that.
First thing to go wrong was the ABS light started coming on. First only in wet weather or if I drove off road. Then it just stayed on all the time. I took it to a garage and it needed front pads and rotors. These trucks eat up brakes like they are candy. They said it was fixed, but then the light still came on again. Plus it now makes a shuddering sound when braking sometimes. I fear it is the calipers.
The service engine soon light starting coming on not long after the ABS light did. Again it was intermittent at first, but now is steady. I had the codes read by an auto parts store, and they said that light is not the important one to worry about. Check engine light is worse?! I'm not sure I believe that. Seems like a bad sensor somewhere causing me to only get about 15 MPG, even on the highway.
I had a thermostat go bad, causing the water pump to fail and spew coolant through the engine. They flushed the system, and while working on it the garage noted that the head gasket would need replaced eventually. Every time you take this truck to the shop for one thing, you find out it needs even more.
It was making a knocking noise and creaking in the front suspension, so I took it in to have it lubricated and they told me a 1998 Blazer has no lube points! Isn't that convenient! So all the parts have to be replaced when they make noise. As many others have said, these trucks are impossible to keep aligned for long. You will constantly be buying some new parts for the suspension. And since it does not stay lined up, you go through many tires. Don't buy new tires because you will be wasting your money.
Next thing to go wrong was the alternator. Another common thing on Blazers, ever since the 80s. The 4.3 engine apparently puts a lot of stress on alternators. I got lucky and found one at a junkyard for $25.00. There is no shortage of Blazers and parts in a junkyard. I wonder why?!
Once cold weather arrived again, the next thing to go wrong has been that dreaded fuel gauge sensor in the gas tank. It has caused me to run out of gas in the middle of the highway several times. This is very dangerous and shame on Chevy for never doing a recall on this. The problem seems to be widespread. I have not fixed it because you have to get a whole fuel pump and it is expensive.
Lastly, a problem that has come up this year in 2015 is the transmission has been slipping in weather under 32 degrees. For some time, I had noticed hesitation while backing up, but now the transmission issues are more widespread. It does not want to shift from 2nd to 3rd. At 40mph the engine's RPM redlines and it does not shift. Just the day before in warmer weather it did not do this. This is possibly the final straw for me and I may just get rid of the vehicle.
To be as fair as possible, I am putting the positive comments here. The 1998 Blazer has some positives, but they are outweighed by all the mechanical issues. The seats very comfortable. I like that the rear ones fold down to haul things. The 4-door version is very spacious. There are many compartments and pockets in it to store things. The thermometer and compass is a nice touch. At least in mine they work. The 4WD works great. The Blazer is like a tank in 4WD and very hard to get stuck in snow or mud. In an engine that is working properly, these trucks have enough power to do most anything. I like the rear wiper and defroster. Factory CD stereo is good, but the speakers are junk!
The bad outweighs the good in my opinion. As others have said, you better have a lot of money for the gas and the repairs. I used to be a diehard GM guy, but I have owned so many of these things I am starting to think they all have the same problems. Maybe GM has done better with Blazers since this one, but I would not recommend buying the 1998 version!