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Rule #1: always look at what the FSM says.
Guess I'll goop em up too
I've got one of those plugs in the front passenger side expansion plug port behind the motor mount. After flushing my engine thoroughly this past weekend, it started leaking. (surprise surprise!) So, having already spent a weekend replacing the water pump and radiator, I wasn't inclined to get back down under the motor to remove and replace both expansion plug and motor insulator. I bought a $4.5 bottle of Bar Leaks rabbit turdz, poured them into my pristine, clean green coolant solution, and the leak stopped.
That Dorman expandable copper plug has served for over 3 yrs now, and was shellacked into place to insure its hold. IDK if the shellac cracked or what, but that was the first sign of leaking I've had from it. When workspace lacks, those copper plugs do a good job.
I use Indianhead Shellac for my goop, and ALWAYS use brass or copper plugs. The latter I resort to only when I lack space to cleanly drive the brass plugs in. I've never been so blessed as to be able to pull an engine for the purpose of replacing expansion plugs, though be sure: I'll damned sure do that when I pull the engine!
Revisiting this thread as I have a follow-up question. I wanted to clean out the coolant jackets of the engine block and I've read that most of the debris would accumulate at the back of the engine so I've removed the center and rear core plugs on both sides. Trying to scrape it clean as best I can cause the aforementioned "crud" is certainly there. Are the inside surfaces supposed to be somewhat smooth? What the hell is this stuff I'm getting out of it? It's really gritty but also pretty hard. Is it okay to try and break it off with a screwdriver or is that too risky?
Having recently experienced this EXACT phenomenon in extremis, please consider a few humble suggestions to relieve your own plight;
If convenient, use the rearmost or center expansion ports, and open at least one, if not both. I assume your engine still rests in the compartment, and you don't care to pull it. You might want to remove the starter for the driver side port, as that would be the best way to get to the debris there. I've done so in the past, w Mathilda, but didn't have to o Gertrude, as the driuver side jacket, remarkably, was relatively CLEAN of any discernable objects, using fingers, lasers, drain snakes all as sensory guides.
Anyway, MANY crystals DISSOLVE only when water solutions have been heated to boiling or hotter temperatures, then precipitate as the solution cools. Organo-metallic compounds such as calcium-ferro-X, where X can be any organic compound from simple carbonate to oxalates, silicates, phosphates, borates to large alchohol tails from old coolants and other additives. If some fool ever filled that jacket from a garden hose, as commonly occurred before about 1990, when bottled drinking water had not yet become the national norm, then the chances that you have ferrous calcium salts clogging your system approach 100%.
Like turbinado sugar or heroin, most of these crystals only dissolve in water with heat. Thus Thermocure becomes a USEFUL flushing agent. As I recently learned, this kind of agent, run for some hours if your engine will do it without severe over-heating, can do MUCH to force these salts into solution and KEEP THEM IN SOLUTION until you drain the cooling system.
BUT, your cooling jacket is SEVERELY clogged you say? Time for the drain snakes then! Supplement these with long handled, large flat blade screwdrivers or other chisel like implements, use some lights to help you see, small mirrors for the same, and start MINING that crap OUT! I also would get some long LOOOOONNNNNNGGGG stiff bottle brushes, and as you open longer channels in the crud, use these to sweep the debris DOWN AND OUT OF YOUR PRECIOUS MOTOR!
Also, get some 1 5/8"rubber bungs (expansion plugs) at least one for each side of the block. Remove those steel factory plugs for this job, mine out all you can for your first session, then use the rubber bungs to close the ports for the interim. You CAN re-use these too, if careful. Get an air compressor and shop vacuum, and use each of these alternately to remove the debris after your mining operations. A good shop vac can even remove most of the coolant via the lower engine hose to the radiator, especially after removing the thermostat.
OK, let me now organize these thoughts for you into a formal Procedure:
1. Drain the cooling system. Radiator first, then each of the 3/8" threaded plugs on the sides of the block. This should get around 2-3 gallons of coolant out, which you can dispose of. You might need to use a punch to break through deposits over the plug ports. After removing the screw in plugs, if no coolant flows, get the punch, carefully knock through the crystals, and allow the coolant to drain. You might have to do this several times, just as you might need to drain the block several times. Hopefully, after the second time, there shouldn't be enough debris left to plug these small ports. REMOVE THE THERMOSTAT! It blocks flow and you need ALL THE FLOW YOU CAN GET FOR THE NEXT WEEK OR SO!
2. Select one of the "freeze plugs" preferably the rear most, but the center has advantages like ease of access. Use your judgement here. Punch it out carefully, as you will need to seal the cooling system here later. Inspect the debris, use your "mining tools" with care, break up and remove all crystalline deposits within reach. While debris tends to accumulate toward the rear, it CAN pile up anywhere, especially if odd circumstances come to bear on the system. That's one reason to use the center port. Use compressed air, then vacuum cleaner, then compressed air and vacuum again, then close the port with the rubber bung.
3. First flushing: If afflicted with the hard sorts of crystals afore-described, Use the Thermocure or other non-polar, catalytic flushing agent. I'm a zealous, recent Thermocure convert, as the stuff helped save my 383 block. Bear with me please. Run the Thermocure for 6 hours driving if you can, then flush the system using a tee and radiator spout type system. You can use tap water with the Thermocure, or distilled water, depending on your budget and preference. It did fine with tap-crap for me.
4. Second mining: Open the rubber bung port(s), inspect, mine, blow and suck out all solid debris as before. I pray no more then 2 of these sessions will be needed in your case. I WILL be TRULY HORRIFIED to learn there is a WORSE CASE than the rat excrement encrusted, calcium ferro-carbonate plugged to the cylinder head coolant port level engine I just now am able to fill with Zerex case. God-willing, after this session, there will be no discernable solid debris left in the cooling jacket. If this is the case, replace the expansion plug with a brass or even steel one, as per preference. I use brass plugs and seal them with a bit of Indianhead shellac around the edges. The stuff sets slowly, permitting you to still open the plug if within a few days, without great effort, but once it sets, it sets VERY HARD! For both water based and gasoline based solutions, I've never found a better sealant within certain limits.
5. Second Thermocure Enema: Again, use Thermocure as per instructions. THIS time, it should get out the LAST of the solid impediments in your block! The water solution should look black with dissolved crystals as it first appears. Again use the hose, Tee, spout flush and run it until you can drink from the spout. That's how I know the cooling system is CLEAN.
6. Drain all tap water, refill with good coolant, drive and enjoy a C body Mopar! With my full blessings too.
I use Indianhead shellac to goop my freeze plugs. I composed a little procedure regarding severely clogged engines for you. Good luck!
Thanks a million Gerald! I've closely followed your threads about Gertrude and those were EXACTLY the reason for me to look into my engine. Real good you were able to save that 383! Couple clarifications on my part:
1. You are correct to assume the engine is still in the car and it's staying there since although I'm WILLING I'm certainly not ABLE to pull the engine.
2. Currently the FOUR rear plugs have been removed, leaving only the two plugs blocked by the engine mounts. Passenger side threaded plug is out but driver side is real stuck and afraid I'll shear it off.
3. Mining is in full effect! Have cleared plenty of debris already and the immediate areas feel okay but my fingertips can still feel it between cylinders 5 and 7 so I'll get out the drain snake and coat hangers.
You said to use compressed air and shop vac to clear out the crystals but would some decent water pressure work also?
What is a radiator spout type system?
Regarding flushing, any comments on using vinegar? Seen it mentioned a lot online.
Thank you @Gerald Morris for your wisdom!! Helped me a lot to clean out the coolant jackets. Just in time for the cold and not perfect but they're a whole lot cleaner than they we're!
I like that these plugs say "USA" on them. And yes, I did try my best to align them this way.
FYI...... They are NOT freeze plugs. That would lend one to think they are designed to pop out under pressure of ice.... They are not!
The correct term is "core plugs" The holes they fill are the result of the casting process.
I've seen a lot of different names for these things online but judging how difficult the old ones were to remove and the new ones to put in, I'll agree that they are not supposed to pop out