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Chronic freeze plug failure
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1960desotoman
Posted 2021-03-31 12:34 PM (#610554)
Subject: Chronic freeze plug failure



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Location: Estes Park, CO.

I have a 1960 DeSoto Fireflite with a stock 361. I have been driving this car regularly for about a year and have had no issues with the cooling system other than a bad heater valve. In the past month or two I have blown three freeze plugs. The first time I though it was a one time problem, put a rubber expanding plug in it, and moved on. The second time I was slightly concerned but thought it might be related to air in the cooling system so I thuroughly flushed it and burped it to remove any air pockets. The third time I finally decided something is not right. It is currently parked at a friend's shop where I am planning on replacing all of the freeze plugs, regardless of their appearent condition. There is no rust or sign of erosion or leakage on or around any of the original freeze plugs. Has anyone else experienced chronic freeze plug failure like this? What was the cause? And finally, will the more common cup shaped freeze plugs fit in the block without modification? (the original freeze plugs are the disk type)

 

P.S. all three times it was the factory installed plugs, not the rubber plugs, that failed. I have heard from a few car guys I know that the rubber plugs can last quite a while, though not ideal.

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Powerflite
Posted 2021-03-31 1:02 PM (#610556 - in reply to #610554)
Subject: Re: Chronic freeze plug failure



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It could be that the hole has worn out due to rust or maybe it was made a little larger than normal. I recommend that you use a T-bar type of plug on it. Hot Heads sells a set of them for the early hemi. I'm not sure if they are the same size or not, but you can check with him, or give me a dimension and I will compare it to mine. The T-bar plug will not come out no matter what happens and seals using an o-ring to seal so it can compensate for larger holes. But I recommend that you always use RTV or other sealer with it as well because the surfaces aren't perfect.
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1960desotoman
Posted 2021-03-31 1:59 PM (#610557 - in reply to #610554)
Subject: Re: Chronic freeze plug failure



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Location: Estes Park, CO.
Excellent, I'll look into that.
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Dave L.
Posted 2021-03-31 3:36 PM (#610561 - in reply to #610557)
Subject: Re: Chronic freeze plug failure



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Disc-type core plugs, or cup-type?
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normsclassicradio
Posted 2021-03-31 4:54 PM (#610566 - in reply to #610554)
Subject: RE: Chronic freeze plug failure



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The 361 in my 64 880 uses cup plugs. Due to sediment in the lower block, they all rusted out. I thoroughly flushed the block while they were out. I used brass one as replacements. I ended up doing the same with the plugs in the heads, but had to use steel plugs, couldn't find brass ones in that size.

Edited by normsclassicradio 2021-03-31 5:01 PM




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Stroller
Posted 2021-04-16 11:00 AM (#611128 - in reply to #610554)
Subject: Re: Chronic freeze plug failure


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You could coat the plugs with permatex and it will be a bear to get them back out. I use brass plugs in everything. Did you by chance with a plug out and radiator drained stick a garden hose in a hole and see if you could blast out any sludge? My idiot brother once used JB weld on some plugs because of rot the holes got too big.
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Powerflite
Posted 2021-04-16 11:02 AM (#611129 - in reply to #610554)
Subject: Re: Chronic freeze plug failure



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JB weld would work. If you want to remove them, just heat with a torch
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22mafeja
Posted 2021-04-17 1:13 AM (#611162 - in reply to #610554)
Subject: RE: Chronic freeze plug failure


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I thought the disc type freeze plug was used on all 361 58-64...apparently not.
For me it has happened a couple of times that disc type plugs has popped out but never cup type.
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mikes2nd
Posted 2021-04-17 9:59 AM (#611171 - in reply to #610554)
Subject: Re: Chronic freeze plug failure


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i used the screw in type from hot heads for my 392. You must use permatex sealant with any of them.

I would check your pressure... sounds like your getting to high.



Edited by mikes2nd 2021-04-17 10:07 AM
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