843 no coolant draining from engine block

[Auggie]

I tried to drain the coolant yesterday on my 843 and nothing came out of the engine block. The radiator is full and I had the cap opened when draining. Is there something I'm missing?
The drain plug that I found was on the lower right side of the engine block. It had an aftermarket knob/cap on it that was really tight and when I removed that nothing came out. Thanks for the help

 

[Auggie]

Update - If I blow air into the coolant drain plug on the engine block and I hear air coming out of the engine breather hose that comes off the head cover, does that mean I have a cracked head? Cause that's what's happening.
But still why would the radiator be full of coolant and the engine empty?

 

[Wayne440]

Are you sure that you are not blowing air into the crankcase?

 

[Auggie]

I was wondering that but I don't know where else the coolant drain plug would be. The drain plug cap wasn't standard, but it's in the right place. Here's a couple photos of no cap and cap, on the right side of the engine

 

[Wayne440]

I claim no expertise, but to me that "cap" looks a lot like a pressure sender with part of it broken off. The engine may not have a coolant drain, many do not.

 

[Auggie]

Oh that's very interesting! It's the isuzu 4JB1 engine. It seemed to match the location in the manual, but I hope you're right! I'm looking around online - if anyone else can weigh in that'd be helpful. Thanks

 

[Auggie]

I took a slightly different perspective and I think you're right wayne. Thanks! I'll try and drain it this afternoon. I think it's the one up and to the left of what I thought was the plug... doh

 

[Wayne440]

That location is more likely, notice it is close to a "freeze plug", so probably has coolant behind it.