Tmichaelson

wmf62

normally, there are also small pipe plugs on the lower sides of the block that can be taken out too. if so you can poke around in there with something flexible to loosen and flush anything laying down low in the block.

Bill

tbarb

The answer to your question is yes, remove the block drain plugs as mentioned above and plug the remaining openings so water will drain out through the block plugs. IMO, that will be more than sufficient to ensure everything is clean enough and it's about all you can really do, it will be fine.

MikeM

I doubt you'll get much of anything out by sticking a hose in the thermostat opening and trying to flush out of the water pump.

If it was me, I'd pour the cooling system full of white vinegar after I tied the top/bottom radiator outlets together. Let it sit awhile and then start the engine to agitate it and get it hot. Let it cool and repeat. Takes a couple of days to work. Drain the block out through the two bottom plugs above the pan rail and flush well with plenty of water. The holes in the bottom of the block will probably be plugged so you'll have to poke around to clear them.

Even better is oxalic acid (wood bleach) and washing powder. It used to be sold as cooling system flush. It works the same as vinegar only much quicker.

dmaxx3500

just run the garden hose thru the heater core and block openings till you get clean water

Vettegeezer

Be for-warned that these two pipe thread plugs can be extremely hard to remove. They are made of steel, 3/8" pipe thread, and, from memory, about 9/16" hex. Use a 6-point socket and 1/2" breaker bar. I had to use an additional 2-ft. of pipe on the handle to break mine loose! I had to get at mine from the top of the engine as there was no good way for getting at them from the bottom unless you have the car on a lift. Had to use so much torque that I thought I was going to strip the hex off of the plug!
Also, saw on TV recently that a company (I think it is Evapo-Rust), is making a coolant descaler that you pour into the engine, run it for a few minutes, and drain the system. I can't remember the exact name of the product, but check with your local parts store - they may be able to guide you to the right product.
Phil

Kerrmudgeon

The only true way to get rid of the corrosion of years in the block recesses is to PULL the motor, knock out the freeze plugs and poke around to get into the corners as much as you can, and maybe steam clean with a hi temp pressure washer in all those openings. Otherwise you're just whistling dixie.

And nix on the solvent/vinegar soak unless you want to dissolve or soften gasket material and perhaps get future problems with leaks.

plaidside

They are 1/4" pipe plugs and I replace with brass ones.
And I agree they can be a real pain to get out sometimes.
Joe

Frankie the Fink

What does the brass do for you Joe ? I would think its softer and would deform more easily.

BTW - somebody had replaced those plugs with radiator-style petcocks on my '61...

davekp78

Brass won't rust in like steel will. I agonized over the issue and went with stainless steel with anti-seize. Teflon tape would probably be OK, too.

benrep

I flush with distilled water. My shop would flush everything with distilled water (always remove the block drains), just to remove old coolant etc. When you fill if you know the total capacity fill 1/2 with antifreeze, and the rest with distilled water. It is cheap and really helps slow the crud from forming. There is a product for big rigs that Napa sells called Napa Kool. I t really helps keep the scale down. I think it is lye based so very little is needed, but I have never had a problem in any of my old rigs using it with good clean results. If you use it and flush once a year as described, it will clean your block and things will stay clean.

benrep

Getting the block drains out is an issue. I usually give them a "crack" with a small light hammer with more velocity than mass. Just tap them a couple of times. Then sometimes I apply a little heat, Map gas will work, get them pretty hot and smack them a couple more times. When they are out I always install drain valves. There are some nice ball valves that will thread right in, or even the radiator style butterfly valve will work. Then you can drain and flush easily.

Jim Rosenthal

There is a descaling solution that is sold by Detroit Diesel parts shops which is used for flushing those engines (two cycle DDs). It works very well, and also smells bad to say the least. You might look into that. I would favor pulling the freeze plugs as noted, but I would get the engine up to temp with a cleaner in the cooling system first and loosen as much as possible that way. Short of pulling the engine and soaking the block, which you don't want to do, using a cleaning solution and then draining it through the freeze plugs is the best answer.

davekp78

Is it possible to get new freeze plugs in with the engine in the car?

Jim Rosenthal

Well, we just did it in another car. But maybe it isn't possible with his car. We just did it in my GT40, but that is not the same engine. My mistake.

GTOguy

In your current situation, this is your best bet. I did the same thing, but used the old radiator and water pump to allow me to run the engine longer. The vinegar was left in for about 10 days to do its job (it's a mild acid). Be sure to neutralize the block after the vinegar with plenty of distilled water and washing soda, to cancel out the acidic effects of the vinegar once your new radiator is installed!

DUB

I would suggest using any of the different options of additives to clean the block and so on. I do not have one specifically that I recommend.

The reason is that when I go and install new parts much like what you are doing..I have already cleaned the system and got it as clean as it is going to get due to most of my customers do not want me to pull freeze plugs. Any remaining residual scale is so minute it is not going to effect the cooling system.

If your block drains are Allen head set screws....I use valve lapping compound when I insert the Allen wrench so the grit of the lapping compound helps fill in the looseness of the Allen wrench and also provides a bit more 'bite' so you do not round off the Allen wrench. Using the previously mentioned 'tricks' may be needed also.

And for whatever this is worth...I prefer using the socket head style hex head brass pipe plugs also. You do not have to tighten the living heck out of them to get them to seal. With or without Teflon tape on them I also like the steel ones like what the factory used in later years and ALWAYS use six point socket on them...regardless if they are steel or brass.

DUB

pop23235

Don't know the affect it would have on an assembled engine, but I've been using EvapoRust to clean the water jacket in heads and block. I use dumdum to plug the intake holes in the head and keep the face flat up. Fill it with Evaporust and after a day or so, pour it out. Looks like new cast iron. On the block with it on the engine stand, tilt till block head is up, flat, level, dumdum on the waterpump inlet, small pipe extension with cap on the side block drain. Fill it level full, wait a day or so, drain and flush. Rinse and repeat the other side.

The block and heads water jacket will be as clean as the day it was cast.

DUB

Interesting...something for me to consider.

DUB

Randy G.

It's pretty important to try to get the block drain plugs out. We had an old 350 in a C1 that was overheating so we went after it. We thought we finally had it cleaned enough to install a new radiator after flushing it several times several different ways including removing the water pump. Thankfully, we decided to get the car up in the air and get under it to get those plugs out. There was a lot of sediment and crap settled in the block that normal flushing didn't move. We used a pipe brush through the hole working it in and out to get the debris moving.