Engine Freeze Plugs (HELP) - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 11 (permalink) Old 12-28-2011, 01:03 AM Thread Starter
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Engine Freeze Plugs (HELP)

1989 7.3 idi Natural Aspirated (not a powerstroke) no turbo. New rebuild, shop replaced old freeze plugs when the block was cleaned, checked for cracks and honed. Freeze plug on right side over the engine mount blew out. Has anyone had luck with the expanding rubber plugs? The alternative appears to pull the engine again for a freeze plug repair.
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post #2 of 11 (permalink) Old 12-29-2011, 07:50 PM Thread Starter
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No responses on this.

This engine uses core plugs as opposed to freeze plugs. Core plugs are dome shaped wavers while freeze plugs are cup shaped.

Since one failed, I have no confidence in the rest of them and so I will remove the engine from the truck and replace all seven plugs on the engine.

(I didn't think the rubber plug was a good idea either!)
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post #3 of 11 (permalink) Old 12-31-2011, 04:15 AM
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Smart move if you have the time. When one fails the others should at least be watched close. On my lil VW the block heater used rubber o ring with a clamp that failed alot. Never liked it.
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post #4 of 11 (permalink) Old 01-01-2012, 02:01 PM Thread Starter
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I work alone and it takes me while to do big jobs because I tend to be very critical of my own work. I started on trucks and then worked on airplanes for a military career. Airplanes are all about clean and precise engine work. That has stayed with me especially when I work on my own stuff.

What I have learned: Core plugs are dome shaped wafers that fit snugly in the orifice intended. Once the plug is seated it must be dimpled in the center of the dome. The dimple causes the diameter of the plug to increase in size thereby creating a very tight fit. Literature that I found stated that a properly installed core plug may not act as a freeze plug and may not pop out in the event of a block freeze.

What I found when I pulled the engine: All seven of the core plugs were installed and virtually beat to a "reverse dome". This causes the plugs to fit loosely in the bore. Once the dome is dimpled beyond flat, it causes the plug to begin to retract in size. A dimple about the depth of half the height of the dome is good. More than that is not better! After installing the first plug, I sacrificed it by removing it. I found that the one I installed with a smaller dimple was much more dificult to remove than the plugs that were installed beyond "flat". I installed all new plugs in the engine and am ready to drop the engine back into the hull.

Last edited by courtem; 01-01-2012 at 02:04 PM. Reason: spelling
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post #5 of 11 (permalink) Old 01-09-2012, 12:14 AM Thread Starter
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I have a few hours on the engine since installing new core plugs. So far no signs of leaking. I'll start using it as daily driver until I have a couple hundred easy miles on the rebuild. Then I'll load it down and give her whirl!
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post #6 of 11 (permalink) Old 02-01-2012, 09:33 PM Thread Starter
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After 300 miles of break in: no signs of leaks from the engine. Runs strong, light diesel smoke on accelleration (normal), easy starting at 30 degrees f. Pulled about 8000 lb trailer, nothing came apart! ran at 50 to 60 mph for 20 miles with trailer and no probles with heat or power. I think I got it!
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post #7 of 11 (permalink) Old 02-02-2012, 06:39 PM
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Good to see it working for someone. Clean professional work is hard to find. Sounds like you will be your own best mechanic. I love driving my 85 even more than the 99PSD. Something about the sound and smoothness. The old truck cannot be broken. Other than hitching up a 15000 pound trailer to a truck that had been sitting for 4 years causing the tranny to blow nothing serious goes on the rig. Congrats on a job well done.
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post #8 of 11 (permalink) Old 02-05-2012, 03:04 PM
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You are correct, lots of shoddy workmanship out there. Core plugs are about the easiest thing to install, about all you need to worry about is clean surfaces, a small amount of sealant applied to the bore and prudence with placement. Obviously the machine shop could not get that simple task correct.

I was going to suggest performing this in-frame, but I think your results will be better having taken the engine out again.

'93 F-250 HD, 7.3L IDI, 5spd - FARM TRUCK
I Support: Trailer brakes an every axle over the towing vehicle's GVW; CDLs for RVers; Safety inspections for ALL vehicles and 6 axle trucks (97K GVW proposal).

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post #9 of 11 (permalink) Old 02-05-2012, 11:17 PM Thread Starter
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I am glad i took the engine back out. There is a total of seven plugs. Two on the right side, three on the left side, and two (one at the rear of each bank of cylinders) on the rear under the bell housing. All seven were over dimpled and were potential faillure points. The engine (which I rebuilt) is back in the truck and I am real pleased with the results. 12 mpg just like when it was new. C-6 three speed transmission, and a 410 rear end does not make a high mpg possible. I would have to either change the rear end ratio, or put in a high/low gear box to change the ratio. With higher gears, I would do better in the mpg area, but it would suffer when hauling a load. I think I will put up with the low miles to keep the towing capacity. It is a 1989 f-350 in pretty good shape. Unless I could find a used two speed gear box not too expensive, I am not inclined to start modifying the truck with big ticket items, it works well the way it is.
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post #10 of 11 (permalink) Old 02-06-2012, 03:55 AM
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YEOW! I'd be pretty p!ssed with 12 MPG as I am used to about 20 in our F-250. Granted it's a manual but still, we can pull anything that doesn't tear the GN ball out of the bed.

'93 F-250 HD, 7.3L IDI, 5spd - FARM TRUCK
I Support: Trailer brakes an every axle over the towing vehicle's GVW; CDLs for RVers; Safety inspections for ALL vehicles and 6 axle trucks (97K GVW proposal).

Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote - Benjamin Franklin

I vote for LIBERTY!
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