Dolores

Hi all - according to the FSM, in order to completely drain the cooling system you have to remove the “Cylinder Block Plugs”. Are these freeze plugs or screw-in type? The FSM shows what looks like three freeze plugs per side. Getting the car up on ramps next weekend to check.

Thanks
Andy

Run to Rund

They are 1/4 NPT plugs with hex heads, just above the oil pan rail.

joe_padavano

Since you have a full size, the two front plugs will be hidden behind the motor mounts. The other two are just aft of the motor mounts. You'll likely need to drop the starter to reach the one on the driver's side.

Fun71

Do you really need to completely drain the cooling system? Just asking since I never did that in 30+ years of wrenching on my car, other than pulling the engine and stripping the block for a rebuild.

jaunty75

Neither have I, and I've changed radiator fluid on more cars so many times over the last few decades that I couldn't possibly count them all.

Unless someone is doing something more than change the coolant, I can't see that it's necessary, especially given what is required to get at the freeze plugs, and that's assuming you can loosen them even if you do get at them.

When I change the coolant, I flush the system until it runs clear, using distilled water. When I refill with new coolant, I put it in undiluted, figuring it will be diluted by the water left in the system plus whatever I add to bring the system to the full point after all of the coolant is added. After all, 16 quarts (for example) is 16 quarts. If that's the capacity of my system, and I add 8 quarts of pure coolant plus enough water to bring the system full, by simple mathematics, I should have added 8 quarts of water to fill the system, and I should have a 50/50 dilution. I can always check it with a hygrometer and adjust if necessary, but I've never had to.

This is why I don't like to buy the pre-diluted coolant. The only way it stays 50/50 is if you know the system is fully drained before adding, and that will not be true if you don't resort to freeze plug removal, which I don't want to do.

joe_padavano

Why does anyone buy the 5050??? Pre-diluted coolant is simply a tax on people who are bad at math.

Let's see, I can buy two gallons of 50-50 Prestone at $16 each ($32 total for those bad at math), or I can buy one gallon of regular Preston at $18 and add one gallon of water for free to get two gallons of 50-50 for, uh,... $18.

Yeah, yeah, I get that there are people who only use distilled water in their coolant. Fine. A gallon of distilled water is what, $3, max? Still a better deal.

jaunty75

The other thing I don't like about the pre-diluted stuff is the simple fact that you're paying for water, as you essentially point out.

Around here, distilled water is about $1.50 a gallon and less per gallon if bought in larger containers.

Fun71

50/50 is great for achieving a 66ºF reduction in freezing point (down to -34ºF), while giving only 15ºF increase in boiling point above that of plain water. So if you don't live in the frozen tundra of the north, you can get by with a lot less than 50/50. 33% will protect down to 0ºF, which is sufficient for most parts of the country, and still give plenty of corrosion protection.

steverw

Went to the dollar store, bought distilled for $1.00 per gal.
I actually just did drain from 1/4 NPT plugs, after draining and filling with 9% vinegar,running it to temp, letting it sit over night, then draining and flushing until clear all the way down to the block plugs. I was amazed at how much rust it flushed out of the block and radiator. I then installed antifreeze and distilled water. The engine is running about 167 degrees by laser on the thermostat housing, after driving for miles. It only makes sense that crud builds up in these 50 year old motors and takes up valuable coolant space around the base of the cylinders. In another post i mentioned of almost 1 pound of crud, looks like dirt in a bag, that i scraped out of the water jackets after having the block vatted and machined. Hey every little bit of cleaning and opening up the water jackets helps. I have read dozens of post on here of people and their cars running hot. I have know of people knocking old freeze plugs into the block rather than pulling them out. Anything obstructing flow or taking up coolang space in the water jackets will likely eventually lead to cooling problems.

OLDSter Ralph

The vinegar thing is interesting and cheap too. Thanks for tip.
Ralph

Ozzie

This is an excellent testimony about utilizing the block drains to help remove the crud which accumulates in the lower portion of the engine's water jackets. No other flushing with the engine in the car will get the job done. Replacing the plugs with valves will significantly improve the flushing procedure. However, sometime plug removal can be a real "bear" of a task after 50 years.