Is this the coolant plug on the 4.0?

[robfg67]

I have a 1990 MJ with the 4.0 motor.

 

Picture is taken from under the manifold on the left side of engine. I stuck the 8MM drain removal socket in it and it seems to fit perfectly.

 

I want to remove it so I can do a full coolant flush.

 

 

 

 

[Ωhm]

[robfg67]

Thanks for the picture.

 

I think that I'm in the right spot. Could there be another plug of the same size near it?

 

This is a difficult area to scan fully.

[cruiser54]

It's a 5/16" headed square drive.

An absolute b*@ch to remove. 

Even with the engine on a stand, I've had to resort to welding something to it in order to get it out.

I only did it on HO blocks when I was using them in a Renix application. For the CTS.

I would recommend leaving it there and remove the CTS instead if you feel it necessary to do a coolant flush. 

[robfg67]

8 hours ago, cruiser54 said:

It's a 5/16" headed square drive.

An absolute b*@ch to remove. 

Even with the engine on a stand, I've had to resort to welding something to it in order to get it out.

I only did it on HO blocks when I was using them in a Renix application. For the CTS.

I would recommend leaving it there and remove the CTS instead if you feel it necessary to do a coolant flush. 

I read somewhere that flushing through the coolant plug will get rid of crud that you can't reach by just any number of "typical" flushes.

 

Will going through the CTS instead get rid of the same crud?

[cruiser54]

yes