I want to check the antifreeze in my recently acquired 1982 300SD. The only radiator cap is on the overflow bottle. I do not believe the antifreeze in the overflow bottle is indicative of the antifreeze in the rest of the system. So, do I have to disconnect a hose to check the antifreeze?
And in the future, if I change out the antifreeze, how am I supposed to fill it up? Certainly not through the small hose on the overflow bottle?! So how then?
It looks like the top tank of the radiator is plastic. And I found no petcock at the bottom of the radiator to drain the antifreeze. Talk about a closed system! Could get messy draining it out of the lower hose and filling it through the upper hose.
There must be a better way?
Regards
Fred

Underneath the radiator on the left side you will find a plastic plug. Use a screwdriver to turn it unscrew it all the way. That is the drain.
Yes, that overflow tank is the way to fill the radiator. Seems to work ok. I would be inclined to drain the coolant and put in new rather than trust the age/ mix of what you find in there. Cheap way to avoid a potential problem.
Congratulations on you new aquisition.

Changing it out sounds like a good idea.
Are there block drains as well? Do you know the capacity of the coolant system? Are there some special requirements such as purging air out of a drained system?
Thanks
Fred

I don't recall this one needing an air purge. My 78 300D does for sure. On that one there is a bolt on the top of the thermostat housing. It needs to be opened to get the air out of the system. But I don't recall anything like that on the SD.
Capacity? Maybe someone has a book handy, but if memory serves is about 1.2 gls. Give or take.

Thanks Old Deis
Just got back from the parts store with a couple of gallons of antifreeze and Rotella T. Figure if I'm going down, may as well go all the way!

Fred

Fred
Owner's manual for my 84 300SD says cooling system capacity is 12.5 L or 13.2 US qt. Hope this helps

Owner's manual! Well duh, why didn't I look at it? Just like kid's toys - read the manual at last resort.
Thanks for the head's up.
Antifreeze draining now.

Waybomb,

You won't get all the old Antifeeeze out unless you remove the drain plug in the block. It is located on the side of the engine just in front of the starter.

You should run a cleaner/flush thru the system when you are draining the system. That will remove some of the dirt and rust and keep your new anti freeze cleaner.

P E H