How do I flush the radiator and block on this old dog?

[MBro204]

Hey everybody first time on Mack forum, I'm working for a farmer and hes got a couple old Mack's that I'm working on and I cant get any info about these old trucks and I was wondering if maybe someone on here could help me out? I dont even know where the block drain is on this truck or the proper way to even flush it to be honest. I found a drain on  the bottom elbow of the main big pipe coming out the bottom of the rad and beside that is a little brass valve; does that valve have anything to do with draining the block? Or do I just drain that plug and it's that easy? The truck is a 1975 Mack RL600L. Any help will do thanks!

Edited May 2, 2019 by MBro204
Forgot to add info

[alex g]

That little brass valve will drain your antifreeze. There probably isn't a drain on block. As far as flushing it out I have used dish soap and water. Run it for a while then drain it and repeat til your water starts getting clearer.

[JoeH]

Usually they also have one on the passenger side of the block near the back, near the air compressor.

[Freightrain]

^^This.  The radiator drain will only get the radiator for the most part since the water pump is so high up in the front.  To get the block, look for the drains.  For sure passenger side, I think there is one on the drivers side also?  Maybe, have to check.