Core plug

PabloPicasso

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A core plug ( also I believe called freeze or Welch plugs) on my engine is weeping and needs replacing. Should a gasket type sealant be used when putting in a replacement?
 

rotrax

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AFAIK, two types of core plug used. One, slightly dished, tapered edge, placed into hole and the whacked in the centre to expand the edge into the matching machined taper in the block.

Little chance of ANY sealant working for long with this type.

The more modern sort with a right angle edge about 20% of the diameter. Sealant will work here.

With both types, scrupulous cleanliness when preparing the hole is paramount.

Although a core plug might be pushed out should the engine freeze and perhaps limit damage to the water jacket, they are only there as a requirement of the casting process during making the block/head.

It allows the sand core to be removed after casting, hence the name " Core plug. "

"Freeze plug", totally irelevent.
 

PabloPicasso

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AFAIK, two types of core plug used. One, slightly dished, tapered edge, placed into hole and the whacked in the centre to expand the edge into the matching machined taper in the block.

Little chance of ANY sealant working for long with this type.

The more modern sort with a right angle edge about 20% of the diameter. Sealant will work here.

With both types, scrupulous cleanliness when preparing the hole is paramount.

Although a core plug might be pushed out should the engine freeze and perhaps limit damage to the water jacket, they are only there as a requirement of the casting process during making the block/head.

It allows the sand core to be removed after casting, hence the name " Core plug. "

"Freeze plug", totally irelevent.

It's the slightly dished type. I will take your advice on being especially particular about cleaning.
 

VicS

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Is that an epoxy mix, not a sealant as such

From the Loctite technical data sheet

LOCTITE® 540™ is a thixotropic anaerobic sealant designed
for sealing core plugs and many other high strength sealing
applications where non-migration is desired. This product is
easily applied with LOCTITE® applicators and prevents rusting
in the threaded engagement area. Applications include sealing
and securing cylindrical metal assemblies, e.g. engine block
cup and core plugs, water pump seals, and hub and shaft
assemblies. The thixotropic nature of LOCTITE® 540™
reduces the migration of liquid product after application to the
substrate.​
 

PabloPicasso

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As it is awkward to get at, would sealing over the weeping rim with liquid metal be a good option? Assuming it can be dry and clean of course.
 

rotrax

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As it is awkward to get at, would sealing over the weeping rim with liquid metal be a good option? Assuming it can be dry and clean of course.

As you have the slightly dished tapered edge type, no sealer is normaly used. The pressure caused when thumping it in the centre would no doubt displace any sealer applied.

Buy two, clean as perfectly as possible, fit core plug and using a reasonable diameter drift-say half inch ish-whack it firmly in the exact centre quite hard.

Fill and test. If leaking, try sealer using the spare plug. Remove by drilling and sticking a phillips screwdriver in the hole and levering. Personaly, never had to use it with this type of core plug.

It sounds like access will be your biggest problem.

In the period when Ethylene Glycol anti freeze was unobtainable, Methanol based ones were used. This caused early internal corrosion of core plugs, so, if you were in the motor trade and on the tools, you invariably fixed plenty a couple of years later.

As I did.............................
 

Daydream believer

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From the Loctite technical data sheet
LOCTITE® 540™ is a thixotropic anaerobic sealant designed
for sealing core plugs and many other high strength sealing
applications where non-migration is desired. This product is
easily applied with LOCTITE® applicators and prevents rusting
in the threaded engagement area. Applications include sealing
and securing cylindrical metal assemblies, e.g. engine block
cup and core plugs, water pump seals, and hub and shaft
assemblies. The thixotropic nature of LOCTITE® 540™
reduces the migration of liquid product after application to the
substrate.​

That data sheet seems to conflict with itself slightly.
I the first part it starts talking about sealing threaded connections - which one can understand
Then it mentions core plugs which are not threaded. The ones I have seen ( & I admit that my experience from years ago is limited to the dished & tapered type) The surfaces are totally different. & the applications must be different.
That makes me question the data sheet. There is no natural space for the sealant to do its job, as there is with a thread on the tops of the threads.( these often have only 70% engagement, hence 30% voids for the sealant to work) With a core plug it is 2 flat surfaces together and no natural void.

As far as the OP is concerned I would get a piece of wood & try holding it square to the core plug & hitting the other end with a heavy hammer with one good wack. That may just be enough to tighten the plug & stop the weep- assuming it is the domed type. But we all know the definition of assumption:ambivalence:
 
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burgundyben

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It allows the sand core to be removed after casting, hence the name " Core plug. "

"Freeze plug", totally irelevent.

That's all correct, but its not why they are there. The cores have to be suspended in the right place in the sand, they cant just hover in the cavity in the sand, so they have to contact the outside face of the casting. Leaves a hole behind, which is used to clear out the core debris, then plugged.
 
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