Changing coolant

[JerryinTx]

Today I drained the radiator and then opened the stopcock on the engine block and nothing came out.  Checked the capacity on a 218 and it's supposed to take 15 quarts.  I added 2 gallons of coolant and expected it to take 7 quarts of water after that.  It only took about 5 quarts. I'm wondering what is the discrepancy due to and why didn't I get any coolant out of the block?

[Happy 46R]

From my experience you could have a couple of problems. There could be some debris behind the stop cock that prevented the block from draining. It could be any size really as long as it blocks the discharge hole. It could also be that there is a larger quantity of scale and buildup in the block that is making up the difference in volume. If that is the case I would expect a temperature issue during operation. My first test would be to slide a small piece of wire into the open end of the stop cock and see if I could auger the blockage from in from of the valve. After that there would be some other choices including frost plugs, thermostat housings and maybe even a reverse flush system. There are several good articles about this in this forum under different headings and they all offer good options for flushing and cleaning the block. Hope it works for you.  Dave

[Los_Control]

Could be a few issues, first remove the petcock from the block make sure it functions as should.

 

If the block still does not drain, it is the lowest point of the block.

When the engine blocks are cast in sand, it is common to have some sand left over in the block .... then 70 years of crud ... it all settles in this area plugging the petcock drain hole.

 

If this is the case, you probably want to pull the soft plug near the petcock & a upper top soft plug. You can run water into the top, use a long piece of wire from the bottom to loosen all the crap and flush it out.

 

You will be surprised how much crap can settle in that area reducing your coolant capacity & coolant efficiency.

 

I read about this issue years ago on this site, it is kinda common. I cleaned mine out and was amazed how much crap I fished out of the block.

I did have my water pump removed and put water through the distribution tube to flush., I pulled all soft plugs .... they needed replaced anyways.

 

Up to you how involved you want to get .... very least you need to pull the bottom soft plug to fish wire all around the side of the block to loosen the crud.

[JerryinTx]

Thanks for the replies!  Both make perfect sense.  The engine had a complete overhaul 20 years ago, including new core plugs, so I assume the system was clean then. But I guess a lot can happen in 20 years.  It does not run hot - never over 160 unless sitting at an idle for a long time, then maybe 170-80.  

 

Since its full of fresh coolant I think I will leave well enough alone for the time being.  Thanks again for the explanations.