Big Block Freeze Plug Question

[MTPockets]

All of my Mopar experience has been with slant six's and I have a few V8 questions. My newly acquired 1974 D200 with a 400 in it had no coolant when I bought it and last weekend I intended to remedy that. I started pouring coolant into the radiator and heard the sound of coolant pouring right back onto the driveway. A quick inspection revealed that the middle freeze plug (frost plug, core plug, etc.) on the passenger side of the block was missing. I ran to the parts store and bought an expandable rubber plug, popped it in there and resumed filling the radiator. Again, there was that sound of coolant pouring onto my driveway. I saw that the middle freeze plug on the driver's side of the block was also missing. Another trip to the parts store and another rubber plug installed. Third time is a charm, right? As I poured coolant into the radiator I once again had a coolant leak. This time it seemed to be coming from the side of the head (towards the front of the engine) behind the exhaust manifold. I couldn't see it very well but it's either another freeze plug or a BIG head gasket leak. I know the right way to fix this is to pull the engine and replace them all with steel or brass plugs. However, I am assuming that a previous owner let water freeze in the cooling system and that's why the freeze plugs are missing. I sure would hate to pull the engine, replace all of the plugs and reinstall the engine only to find out I have a cracked head or block.

I have a few questions:

1. Do the heads have freeze plugs in them and if so, where are they?

2. Are there any freeze plugs in the back of the block that can only be accessed by separating the engine from the transmission?

3. What are the chances of me being able to replace all of the freeze plugs without pulling the engine?

In case you haven't noticed, I really don't want to pull the engine, replace all of the freeze plugs and reinstall the engine only to find the block has frozen and is ruined. Suggestions and advice is appreciated!

Thanks,
Scott

 

[HALIFAXHOPS]

Yes sounds like it froze. Try to replace the ones you see bad and run it, usually the side and heads pop out first, there are two I believe in the back but have never seen them come out. Hope this helps.

 

[Darter6]

Yes it has freeze plugs in the front and rear of the heads also at the back of the block.You will have to pull the transmission or the engine. Now if it did freeze you may have a cracked head or block.Seldom do the plugs actually save the components from cracking.

 

[Cranky]

No freeze plugs in the back of the block (thank God for big blocks! Small blocks do have them on the rear of the block) but the later model heads do have them on the ends and two on the sides under the exhaust manifolds. Early heads do not have them on the ends. If you plan on keeping the engine, replace them with brass. Most core plugs these days are from China and I do not trust them and using brass is always better than steel.

 

[moparwacko]

Just buy a kit, brass from NAPA, ADVANCE, or wherever. 1 5/8 for block , 1 1/4 for the heads, and 1 " I believe for the end ones on the heads. You'll have to jack the motor for the ones behind the mounts, remove the exhaust manifolds for the 2 on side of heads, the rear one on head is near impossible without removing head, front one easy. there are none (coolant) in the rear, just a cam one.
Agree that I would try to get the thing running as leak free as possible and check for oil contamination before sinking more $$ .

 

[GTXperience]

Tough situation because apparently, there was a freezing that affected many (if not all of the plugs to one degree or another). Pulling a motor and/or trans is a PITA but so is attempting piecemeal repairs only to find out that there are still leaks in the hardest of locations to get to or that it is coming from a cracked cast iron component. If it's a head gasket (check oil for contamination), that's a head pull scenario. But back to the plugs. If you don't want to pull the motor and/or trans, you can go after each leak as they occur and see if you get lucky with just replacing the more accessed plugs. If you can get it to seal somewhat, I would pressure test it along the way. This could be a long tedious frustrating project but hopefully the plugs that were affected are the easier ones to get to. Also, I'm not a big fan of a poopload of expansion plugs. They were meant to be temporary fixes. As mentioned, brass is preferred but I always install one steel in the center side of the block (easy to get to) as a sacrificial piece just in case there is an issue and also for inspecting. GL with the project.

 

[dieseldazzle]

I don't see you getting to all of the expansion plugs on a later model motor without pulling the engine. There are 1 inch plugs in the heads. These are nearly impossible to get to and you have to strip the manifolds off anyway, remove the motor motor mount pad etc so might as well pull the engine.

I recently did this in a survivor 69 roadrunner

 

[Darter6]

oops, Got to get glasses,, I was thinking small block rear freeze plugs.

 

[mmissile]

Keep filling, watching/listening[watch for water and oil mixing], and replacing. My hemi kicked the same 2 outta the sides, when it froze. I was fortunate, and it only hurt a head gasket.

 

[ckessel]

You can use 1 5/8 if thats all that can be sourced but the correct size is 1 41/64 which is a tad bigger and a tighter fit. 1 5/8 is what is commonly found in freeze plug kits as its a chevy size too. Dorman and others make the 41/64, it may just take a little more work to find depending on what you have for resources.

 

[moparsteve636]

When you replace the block fps I suggest putting 3M trim adhesive on the edge! I've had the plugs pop out for no reason! Just a little extra insurance!

 

[mopar 3 B]

It does run? Compression check been done? Disconnect radiator and heater hoses cap and pressure check the cooling system after replacing freeze plugs if the first 2 steps prove ok. If it will not hold air it will not hold water.

 

[mopar 3 B]

Does it run? Compression check been done? If the cylinders do not hold pressure replacing freeze plugs and adding coolant is a waste of time.

 

[MTPockets]

Does it run? Compression check been done? If the cylinders do not hold pressure replacing freeze plugs and adding coolant is a waste of time.

It does run. Quite well, in fact. But without any coolant in it, I have not run it very long. It's currently -11 degrees here in Northern Indiana, so I pulled the battery and am going to let it sit until Spring. As soon as the weather breaks I'll check the compression. Thanks for the help everyone!

 

[WileERobby]

Is it leaking from the water jacket of the exhaust bolt ? Did you seal the bolts ?

 

[MTPockets]

Is it leaking from the water jacket of the exhaust bolt ? Did you seal the bolts ?

I didn't seal any bolts, as the vehicle is new to me. It was difficult to see exactly where the leak was coming from because I was using a mirror. But it looked like it was coming from behind the exhaust manifold. I assumed it was another freeze plug because two freeze plugs were pushed out already.

 

[dieseldazzle]

It's these guys zoom in on the front of the head, driver side. The rear ones were leaking.

I had to tamper with this survivor roadrunner to do them. Sucked

 

[WileERobby]

Well, check the exhaust bolts, they have to be sealed as they enter water jackets.