to start i have a 96 4 door 4.3l 4x4. and discovered a non oem coolant pump in the engine. was proper flange mounts but had different heater core hose set up on top. the pulley flange
was tack welded and everything let go. with a little more tylenol was able to retrive the proper coolant pump and resolved that issue.so then we have a leak on the block?? potential overheating of engine. not really able to see up and around the exaust and firewall, but can visually see some coolant dripping downthe bell housing and across crankcase halves. any feedback greatly appreciated. thank you

 

before ruling that its a blown head or intake make sure you check all heater hoses especally if there is one going into the block/intake man. i almost tore apart my intake and head before i looked harder and found that the heater hose connector on my intake was leaking causing the same drip you have. for a while i was fearing a blown intake or head but there where no tell tell signs like gray oil or coolant in the radator. there had been a time when all the problem was a blown fuse but was found after a full recharge system replace$$$$
like some have said b4 check the cheap b4 doing the pricey
good luck

 

my "guess" is the freeze plugs on the rear of the engine. they like to rust and start leaking.....but it could be the lower intake either leaking out the back or leaking in the front and running to the back.....

 

The original poster has not been around since he posted this almost one year ago. FWIW, there are no freeze plugs on the rear of the 4.3 engine.

 

you might wanna look again there are 2 freeze plugs in behind the flywheel......

 

i actually had the same problem and after pressure testing my cooling system, a friend and i discovered that it was coming from the lower intake manifold gasket. so i would check that because they are common

 

I cannot find any verifiable picture or drawing from GM or any other source to label freeze plugs at the back of these engine blocks. I know some have claimed there are 2 at the back, but all I can find that resemble freeze plugs back there are a plug for the balance shaft and one for the cam. I have also heard that the older 4.3's had 2 at the back, but that later years did not. If you can provide a photo or drawing from from a good sourceidentifying freeze plugs back there, we all would appreciate it.

 

There are two plugs, I will give you that, but they are not open to the water jackets. They cover the back of the cam and balance shaft bores.

*EDIT* - Just to add to this, here is the picture of a marine engine (same exact block casting as the 96+ trucks) with an aluminum pan (98+). As you can see in the image below, the 96+ blocks do not have any freeze plugs in the rear of the engine. As stated by rriddle3 and myself, the only plugs in the rear of the block are for the cam and balance shaft bores.


Image pulled from eBay auction <Click

 

I stand corrected they only had rear freeze plugs up until 1995