Where are the soft plugs in the 4.3 1997 GMC Jimmy engine?

Answer 1

They are part of the engine block and apparently you have to hoist the engine up so you can move the axle out of the way to get to them The two types of plugs are alongside each other, both just above the pan rail on each side of the block. The drain plugs are screw in plugs which look very much like normal pipe plugs (which can in fact be substituted, they use pipe threads). They have either a hex head or a square head, I've seen both types. Usually they are either 1/4 or 3/8 pipe thread plugs, (which means they are 1/2" to 5/8" OD). They are for the purpose of draining coolant out of the block, and should be opened when ever you are trying to flush all the old gunk out of a car's cooling system. The core plugs, AKA soft plugs, AKA freeze plugs are in the same area, but are much larger, about 1 1/2" diameter, cup shaped, and press fit into holes in the block. There are 3 per side on Mopar blocks of this era. They have to be removed carefully, and there are at least two ways to do this. One way is by cutting them through the center with a very sharp cold chisel (be careful not to drive the plugs through the hole, they can drop down inside and be difficult to retrieve), and be careful not to smack the plug so hard that you damage a cylinder jacket, which is right behind some of them. When you have cut a large enough hole through the center, grab the remains with a good channel-lock or vise-grip and twist and turn the bugger until you work it out of the hole. They are tough, but once you've done one, you'll get the hang of it. The other way to do it is to drive one edge of the core plug into the block so as to get the plug to tilt out from the opposite edge, then grab that with your channel-locks and twist and pull it out. It helps to know how deep you can drive an edge in, and this is dependent on how close the cylinder bore is to the plug. You can sight down from the spark plug and see what is behind each one. If you do one that is between cylinders, you don't have to worry about hitting anything. If you do one that is right on a cylinder, you may hit the cylinder jacket before you can get it to go in far enough to tilt out the opposite edge. You'll just have to experiment with each one. Stay with it, you can do it! You install new ones by cleaning the holes carefully to scrape off all the old remains and rust, then put a skin coat of RTV sealant on the outer sealing surface of the new plug, and drive it into the block (NOT TOO FAR!) with a socket and breaker bar that fits well so you can tap on the end of the handle to drive it in squarely until it fits like the original. You'll find they are available in either brass or steel. I use brass for all but the center plug on each side (the brass is forever, the steel is to be a sacrificial anode and protect the block if you ever get lax on your anti-corrosion protection.) I put the steel one in the center position because it is the easiest to change.