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Dorman expansion plug was pretty hard to install.

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  • Engine: Dorman expansion plug was pretty hard to install.

    A couple of weeks ago I was headed out to a local SDC meeting. It was a cool afternoon and I was looking forward to a “fun” drive. After the 500 mile round trip to Branson and back I was gaining confidence in the ’55 President State Sedan. I decided I did not need to glance at the temperature and oil pressure gages every minute or so.

    About ½ mile from home I heard what sounded like something fell out of the car but I did not see anything in the road behind me so I blew it off and kept on driving. I saw what looked like oil smoke coming out the exhaust and knew that I had not seen that before and became a little concerned. A couple more miles down the road I looked at the temperature gage and the needle was at the top of the normal range.

    That got my attention and I did a u-turn and headed back home. By the time I got the three miles back home the needle had pegged on the hot side and when I shut off the engine steam was rolling out from under the hood. The first freeze plug of my lifetime had popped out. I did a search of the forum and there were some outstanding threads on the subject.

    The Dorman 1 1/2 inch expansion plug had been recommended. I ordered one up and got under the car to fix it. The freeze plug was the front one on the left side of the 259 V8. Of course it could not have been one of the rear two which were pretty easy to get to with the starter dropped. I loosened the crossover pipe and turned the wheels which allowed me to at least reach the hole with a 7/8 combination wrench.

    A couple of the earlier posters to the freeze plug threads had mentioned the hex nut on the Dorman plug was pretty shallow. That proved to be the case. I did not have any metric wrenches that large but the 7/8 fit pretty well. I tried to hold the plug with the 7/8 wrench while tightening the small hex to expand the plug. There was no way I could keep the wrench from slipping off and therefore the plug turned in the hole and never did get very tight. It just fell out.

    After studying the situation and a little prayer, I felt the problem was a combination of shallow hex and the 7/8 wrench. The wrench had a beveled area before it actually got to the teeth or whatever the 12 points are called. Te beveled area was allowing the teeth to barely get a hold on the hex nut. I had an older, cheaper 7/8 wrench which I ground down the beveled area on. It was able to get a better bite.

    Some Permatex 2 was placed around the edge of the plug and this time I was able to hold it pretty good while tightening the smaller acorn hex. I was putting some pretty good pressure on the ½ socket and I think got it pretty tight in the hole (I hope). I drove the car a few miles this evening and at least it did not pop out.

    I am now a little gun shy about driving the car. Maybe a few more trips will get me a little more relaxed. The problem I see is that all six freeze plugs were installed the same way. If one has popped out there is a possibility another one could also. I sure wish now I had read StudeRich’s suggestion to flatten the concave disks which I am sure would have maximized the compression between the plug and the block. I used a socket and hit it pretty hard with a 4 lb. sledge which created a depression in the plug but evidently not enough. At least next time I will be able to understand what is taking place a lot faster. I pulled the plugs and did a compression check on the left cylinders and there is no indication of a blown head gasket. The engine runs nicely so hopefully nothing was damaged.

    Charlie D.

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  • #2
    Grinding the wrench was smart solution.
    Jim Bradley
    Lake Monticello, VA
    '78 Avanti II


    • #3
      One more interesting story to fit into your saga of getting that car on the road. Glad it wasn't more serious.
      "In the heart of Arkansas."
      Searcy, Arkansas
      1952 Commander 2 door. Really fine 259.
      1952 2R pickup


      • #4
        About 1960 I was driving a 53 Commander at night and heard a"thunk" sound and soon saw the heat gauge rising. I pulled into a SERVICE STATION and the night attendant/mechanic put the car on the hoist and replaced a freeze plug. We filled the radiator and I was on my way in less than 1/2 hour. Those were the days. Never had another one fail on that car.
        Don Wilson, Centralia, WA

        40 Champion 4 door*
        50 Champion 2 door*
        53 Commander K Auto*
        53 Commander K overdrive*
        55 President Speedster
        62 GT 4Speed*
        63 Avanti R1*
        64 Champ 1/2 ton

        * Formerly owned


        • #5
          You could use the "S" in a set of "letter" stamps to smack the center of the plug.
          In the alternative, about a 3/8 inch round punch or drift.


          • #6
            I sold those Dorman copper/Brass expansion plugs for years, about fifty years. And often wondered how that shallow hex would ever work. And after Dorman was sold to the Motormite folks, quality dropped as they were being manufactured overseas. I would try to steer folks to the standard cup style or the rubber type.
            Trouble with the rubber type was folks tended to over tighten them causing a tear in the rubber which would lead to a failure.
            sigpic1957 Packard Clipper Country Sedan

            "There's nothing stronger than the heart of a volunteer"
            Lt. Col. Jimmy Doolittle
            "I have a great memory for forgetting things" Number 1 son, Lee Chan


            • #7
              Welcome to my world! I fought this on 3 separate occasions, every time I thought I had it fixed another one would pop out. I don't worry about it now. Carry a rubber one in the trunk for insurance and when you get time pull the engine out, take it to your machine shop and tell them you want stainless steel plugs threaded into all six holes. I did. Then you can quit worrying about it. Speaking from experience here, they wont pop out when you want them to. It's always the most inopportune time. In my opinion, once these engines get some corrosion in the core plug hole its all over with they will never stay in and you will never be able to trust it again.


              • #8
                I put the rubber Dorman plugs in my '64 Commander after the original plugs started to leak. They worked well for many months but one started to leak. I bought the steel plugs and had a mechanic install them.
                55 President Deluxe
                64 Commander
                66 Cruiser

                37 Oldsmobile F37 4 Door


                • #9
                  Changed all the plugs on my Avanti with brass ones......20 years later still bone dry!
                  Originally posted by 2moredoors View Post
                  I put the rubber Dorman plugs in my '64 Commander after the original plugs started to leak. They worked well for many months but one started to leak. I bought the steel plugs and had a mechanic install them.