I bought a '97 Blazer 4x4 4.3L back in April (about 150k currently). It always had a strange warm start. It would crank about twice as long than a cold start. Also, it would be missing about 1/2-2/3 Cup of coolant about every 6 weeks. This was described to me as being a possible manifold gasket leak.

Well, the gf came home (6-8min drive) the other day and it was smoking. I took a look immediately and noticed coolant coming from the top of the engine. It's leakin on the passenger side, just behind the alternator. Further inspection of the head bolts seems to confirm this. There's still small pools of coolant on top of the engine, behind the alternator. The head bolts and what I can see of the mounting surface are clean. Bear in mind I haven't run it since she parked it here.

I've read that the manifold gaskets are a more common problem and am inclined to think that's what needs replacing. Any advice or comments? Thanks!

 

Intake gaskets are a common issue. I would get a compression test kit from local parts store, they are often part of the tool rental system. Test the cyclinders for compression. Are the plugs bad in any of the cyclinders? Is the oil milky?
Head gaskets are normally not an issue on these rides...but it is a machine.
Good luck. If you do the intake...get the felpro gaskets with a 't' in the number...they are the better set. Its not a terrible job...it took me 12 hours or so to do mine.

 

I haven't checked the compression or started it since it happened. I checked the oil at time of incident and did notice there was coolant in the oil..and opened the radiator to confirm the opposite. It was hard to tell if there was oil in the radiator, but it looked like it's never been flushed.

I checked the plugs and they've been changed, but I have no idea how long ago.

 

The only way to tell is to get a cooling system pressure tester. I had a similar problem about 6 monthes ago. The school I go to has cooling system pressure tester and found the leak at the back of the engine where the intake manifold is. An intake manifold gasket fixed it, I didn't have an internal leak so I didn't see water in the motor oil.

Usually cooling system pressure will help find an external leak, but generally not an internal leak. A good test to try is take the radiator cap off (when the engine is cold) and start the engine. A head gasket leak will cause the coolant in the radiator to bubble, as if it is boiling, a head gasket will cause this. A manifold leak usually won't. It's not difficult fix either way, but you need the proper tools for pulling apart an engine.