Although often termed "freeze plug" and they can help avoid block damage if the coolant freezes, I've heard a more proper name is "core plug" and their purpose was a place to shake out the sand from between the cylinders after the block is cast. You often find other things inside the block, like corroded steel wires which were used to keep the sand cores for the cylinders from shifting. I had a small coolant leak from the center of a core plug in a rebuilt 1969 Dodge slant-six engine. It was coming from a dab of apparent epoxy in the center of the plug. I wondered if the shop had drilled a hole to install the plug or vent air. I shook a tube of Aluma-Seal in the radiator and it quickly plugged the leak and it never recurred. A few times that powder sealant has worked for me. Might have worked on your core leak, and much less risk than the silicate block sealants.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

X 1,000 for 'Aluma-Seal' ~ it cannot clog anything like Bar's leaks and others will .

The big three in the U.S.A. all use it in new production .

What did you time the IP to ? .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I installed freeze plugs in a boat motor using a socket and extension. The extension managed to fit between the starter and the block. The socket fit the plug well. I just lined everything up, stood on my head, twisted, cussed and tapped. It went in easily once everything was figured out. Tap easy and make sure it's straight.

It was at that time I learned that boat motors use sacrificial zinc to avoid eroding motor parts.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Thanks for the alums seal tip. I may toss some in the trunk.

I timed using my Sealy piezo pickup and timing light to 19 deg BTDC at 1000rpm. At idle it’s 15 deg BTDC.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

Sounds good to me .

I bought one of those (I think) but have not yet had the nerve to try it out...

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

When first I hired in to the C.O.L.A. I was a Truck Mechanic and at that time we had a fleet of mostly 1970 ~ 1973 vehicles, light duty tended to be Chevies, plus 3 yard gasoline powered Dodge D300 dump trucks etc., etc...

We had dozens of 1973 Chevy 1/2 & 3/4 ton pickups, almost all were 350CID V8 powered and the driver's side freeze plug right behind the motor mount tended to let go for some odd reason .

I'd jack up the engine and jamb a bit of wood between the oil pan and cross member, remove the motor mount and both side brackets then use a long 3/8" drive extension and socket to knock the new plugs in .

The old plugs were a breeze to remove : bang 'em really hard edgewise, they'd turn 180 degrees and I could easily pry them out of the block with a pinch bar .

For some reason the old timers thought this was a really bad job and so dumped them on me .

Those were *REALLY* good trucks, at the time my shop truck was a battered (but unbowed) 1946 Chevy 3100 series 1/2 ton pickup I built out of two junkers and lots of junkyard & swap meet parts so I had little concept of how nice a modern truck could be even is a base stripper with nothing extra .

Now I understand why the Mechanics would jump to buy them at the salvage auctions for maybe $500 with 60,000 miles or so .

Quite a few of them (all were TH350 slushbox equipped) had flat cams, we'd slip in a new one faster than I can imagine now, the GM master parts book must have had 15 different cams to choose from so we picked one at random and WOW ~ suddenly these old beaters would chirp the tires going into second gear of you stood on it .

It turned out we'd stumbled across some pre smog (1967) 3/4 ton motor home C-Class chassis cam .

The driver's all loved us whenever we'd get permission to replace a flat cam but as long as the truck could make 40 MPH most supervisors didn't care .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Yeah I’ve posted about the piezo pickup. It is a touchy measurement. Too much pressure on the tube clamp you get no signal, too little,no signal. It’s made out of very brittle ceramic crystal so it’s important not to over tighten it otherwise it’ll crack.

My technique is I put it on the timing light and slowly tighten the clamp till I get a steady flash on my timing light. Even then it is jittery and it requires some guesstimating as the timing mark flits around. What I’m saying is it isn’t perfect.

The 15 deg and 19 deg BTDC figures have been bandied around here in the electronic timing threads so I used those. One day I’ll get a drip tube and try to time it the real way.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

I'd think the signal jumping around stops when the engine is off idle ? .

The entire point of dynamic timing is to increase accuracy .

In my old gassers I typically set the full advance ignition timing but I don't want to fry any pistons in my Mercs .

A drip tube is easy to make.... just cut an old injector line off at an angle .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Second installment. So I decided since my freeze plug behind the IP was leaking I'd better change the others. So I took off my turbo, exhaust and intake manifolds. Routine stuff. Just followed the stickies given by Pelican.

Turbo Out.


Manifolds out.


Not sure if this is leaking but I have found coolant around this location in the past and not really known where it came from. Some rusty spots and corrosion around the back of alternator suggesting I had an intermittent leak in the area. Maybe it was this?



The two back ones arent so bad.



All new.


Tips: use lots of penetrating oil and be patient. Let it soak in a day. My wife got me a new 3/8" Milwaukee M18 impact driver for Christmas. Big thumbs up for this tool. This made removing the exhaust bolts easier on my old arms. I view them kind of like reading glasses. It really makes breaking free exhaust nuts and removing them fast and easy on my tired body. I like how it doesn't need maintenance like my old air tools that always seem to need a rebuild kit whenever I am reaching for them.



Here are the old plugs. The bottoms are corroded up like the other side that was leaking. Pretty beat up inside. Lots of little pits that will eventually become pinhole leaks. So chalk this one up to preventative maintenance.

There is one more plug behind the tranny. I think if that one leaks I'll just use sealant and move on with life. Come to think of it I should put a tube of Alumaseal in the trunk along with my gallon of water just in case.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles