Mine's a '91 and has or has had the same 3 problems.

After I recently had the leaky water pump replaced, mine started doing that exact same thing, temp would spike to way above where it should be, then suddenly drop to normal. They hadn't replaced the thermosat because it hadn't been overheating prior to the water pump change. But now that the system was sealed and operating at the correct pressure, the thermostat was apparently not up to it and was causing the problem. So I took it back and they replaced it for just the cost of the part. So, anyone out there who replaces a water pump should replace the thermostat, if it is old, while you are at it. It's cheap and easy to do while you are already in there with the coolant drained. (You said your thermo was new, though, and defective, I know.) I also just picked up a radiator cap to have on hand, as they are also cheap and easy.

I haven't been happy with my radio reception in the year I've had the truck either. But don't know when I'll have the time to delve into that.

I get a miss occasionally at idle even though all the tune-up parts are new. I occasionally add fuel injection cleaner to the tank and I think it may help. Eventually I hope to get a more thorough fuel injection cleaning at a shop.

In spite of the money I've spent on tires, shocks, a CV axle, the water pump, a corroded coolant pipe, exhaust pipe replacements, a complete tune-up, and other things in the last year, I do love my Blazer!

Anne
'91 S-10 Blazer
2 dr, 4X4, AT, 4.3L
150,400 mi.

 

Great advice Anne.
Anytime I replace a water pump I also replace the thermostat, both upper and lower radiator hoses, radiator cap, and back flush the entire system, including the heater core. The way I figure it, your there and those parts are just as old as the water pump.

 

That's exactly what I thought and I even hinted it to them while they were already replacing the water pump, serpentine belt, idler pulley, and upper and lower radiator hoses. They said something about how it's hard to test the thermostat because it is inside the thermostat housing. Even I know how easy it is to change a thermostat and how cheap they are..... so just replace it....... the old one had been in there for 80,000 miles, as far as I know! So maybe they were hoping they could replace it later down the road and charge the extra labor for it....or they didn't have one on hand and would have to make me wait longer while they ordered it. But as fate had it, it started sticking right away and they had to replace it labor free. I hope they learned their lesson. (I do like these guys and think they are generally competent...... everyone makes mistakes.)

Anne