[Saloon-lovers] Dorman rubber plug size - A good spare to keep on hand

Saloons
1

As a temporary fix and frowned on by several veteran
contributors I offer up the part number and size for a spare
freeze plug in case you get into a bind in the middle of no
where. The Dorman part number is 02603 and it is 1 1/2 to 1
5/8 inch which equals 38 to 41 mm in diameter. The packing
is usually in the self help fix it area of your local parts
store in a yellow and blue package. The goes much further
into the engine block than than factory steel or commonly
used copper expansion plugs. It will actually begin to turn
once it is tight in the block. It must be installed dry to
get a good fit and expand into the crevices of the block
hole. I also changed my t-stat cap to 7 psi and I am running
normal temps after about 20 miles of testing. Water level in
the radiator is stable and the plug is not leaking at all. I
have a spare on hand just in case which will go into the
tool box in the boot.

I think with a 1/2 inch and 7/16 inch spanner on hand for
the headers and downpipes I might be able to change a blown
plug in the field after a reasonable cool down of the engine.
Gerard
Loveland, CO
3.8 MK2 MOD 1966–
The Jag Man
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2

In reply to a message from The Jag Man sent Sat 6 Jun 2015:

I might be able to change a blown
plug in the field after a reasonable cool down of the engine.
Gerard

OH SURE–LOL–
DAIMLER : V8 SALOONS SAFELY FAST AND BUILT TO LAST
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3

In reply to a message from GNB sent Sun 7 Jun 2015:

Oh, I’ll need a few pints with that repair job no doubt !!–
The original message included these comments:

OH SURE–LOL

–
The Jag Man
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4

In reply to a message from The Jag Man sent Sun 7 Jun 2015:

Experience has taught me that you can do almost anything roadside
if you are sober and stubborn enough. Fix first, pints later, and
you’ll be ok.

Andrew–
The original message included these comments:

Oh, I’ll need a few pints with that repair job no doubt !!

–
1968 3.8S
Zurich, Switzerland
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5

In reply to a message from JagWaugh sent Sun 7 Jun 2015:

In 46 continuous years of owning and driving Jaguars , I have
never had a core plug blow out.

Jaguar to my limited knowledge seemed to be successful in
places like Le Mans without using alternatives.

The makers, Hubbard Spring, an American company, advise
against using barrel plated core plugs as the barrel plating
can nick the edge, causing a point which will nor seal by
expansion. Which seems to be the symptom recorded here.

It should be reiterated that these are not ''Freeze plugs .
Calling them freeze plugs is like calling the ‘‘brake pedal’’
the ‘‘steering wheel’’.
They are nothing to do with freezing protection .–
Ed Nantes SS
Melbourne, Australia
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6

In reply to a message from Ed Nantes sent Mon 8 Jun 2015:

I’ve never had one blow out. I’ve had and seen quite a few that
weep, but not so bad that some coolant additive didn’t stop it
until it was time for an engine out R&R.

Andrew

btw, the ‘‘Freeze plug’’ is the term that was used in the US and
Canada iirc. You are right… it is a core plug, used to locate the
(sand) core in the cope(?) while assembling the mold.–
The original message included these comments:

In 46 continuous years of owning and driving Jaguars , I have
never had a core plug blow out.
It should be reiterated that these are not ''Freeze plugs .
Calling them freeze plugs is like calling the ‘‘brake pedal’’
the ‘‘steering wheel’’.
They are nothing to do with freezing protection .

–
1968 3.8S
Zurich, Switzerland
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7

In reply to a message from JagWaugh sent Mon 8 Jun 2015:

Do these ‘‘plugs’’ not pop out in cases of extreme cold thus
saving the block from cracking during the contraction of the
cast iron??

Next time one of the other plugs starts weeping, I will add
an additive and hopefully save myself a lot of work :))

Gerard
so far so good riding on a rubber plug.–
The original message included these comments:

I’ve never had one blow out. I’ve had and seen quite a few that
weep, but not so bad that some coolant additive didn’t stop it
until it was time for an engine out R&R.

They are nothing to do with freezing protection .

–
The Jag Man
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8

In reply to a message from The Jag Man sent Mon 8 Jun 2015:

Gerard,

I've never seen one actually come out without my

deliberately causing it to do so, with a tool. They may
well come out if the car is stored without sufficient
antifreeze in a particularily cold climate - I have
heard/read of it, but never seen it myself, and I grew up
in Toronto, where the winters are definitely cold enough.
I’ve always made sure that the cars I deal with have enough
antifreeze.

Even if the plugs DO Pop out during winter, that does

not mean that that is why the designer put them there. I
submit that they are core plugs, rather than a safety
device. If you look at really early engines (pre 1930s
say), the castings are pretty thick, certainly thick enough
to withstand the force of the coolant freezing. On early
engines the core holes are often threaded plugs, which are
more expensive to produce and fit than the disc type.

Think of it this way... if freezing really were the

reason the core plugs are there, why don’t you ever see a
frost ‘‘fuse’’ device on a Radiator? Brass is significantly
weaker than CI, rads are made of very thin brass, and brass
work hardens very rapidly.

If a freeze plug does come out, summer or winter, I

would submit that what has happened is that it has been
corroding for an extended period (insufficient antifreeze)
and the RUST is where the leak is, as opposed to ice having
moved it. If the engine goes through a few such cycles the
corrosion may well be advanced enough that ice or coolant
pressure could push them out, but this only because they
have already failed. In Summer, if the core plugs are
healthy, even if your rad cap is faulty I would expect that
a hose would burst, or a leak would develop at the rad LONG
before a (healthy) plug will move.

Andrew–
The original message included these comments:

Do these ‘‘plugs’’ not pop out in cases of extreme cold thus
saving the block from cracking during the contraction of the
cast iron??

–
1968 3.8S
Zurich, Switzerland
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9

In reply to a message from The Jag Man sent Mon 8 Jun 2015:

To put simply, do they pop out when the coolant is extremely
cold? Generally not. and if they did it may not necessarily
save the block. And it would be entirely coincidental and
unintended.

The manufacturer gives the Lb’s per sq ‘’ reuired to pop out a
properly installed one and it’s impressive.

I have a quite rare and interesting SS Jaguar block here. the
only problem being one side bowed out and cracked despite have
2 ‘’ freeze plugs’’ on that side.

Rolls Royce use them in Jet engines which haven’t been water
cooled for some time. The Moss gear box remote has one.

They are used to facilitate manufacture of the casting and
istalling cores [ Hence ‘’ core plug’'].

But this post confirms the problem … that is calling them ‘’
Freeze plugs’’ does cause some people to think that’s what they
are.

The weeping ones are usually steel and as Hubbard Spring
says, probably barrel plated.
Brass ones are far less likely to have the problem. Mild steel
barrel plated ones will corrode far quicker than the cast iron
block. And the brass one will in effect never corrode.–
The original message included these comments:

Do these ‘‘plugs’’ not pop out in cases of extreme cold thus
saving the block from cracking during the contraction of the
cast iron??
Next time one of the other plugs starts weeping, I will add
an additive and hopefully save myself a lot of work :))
Gerard

–
Ed Nantes SS
Melbourne, Australia
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10

In reply to a message from The Jag Man sent Mon 8 Jun 2015:

not from what I have read, many blocks cracked from
freezing, never heard of one being saved by a ‘‘popped out’’ plug.

Your story reminded me how tightly they are in there, even
when very corroded, I think I HAD to resort to slide
hammers, cause there was no way the buggers would pry out.

cant remember what they are called but there is a strap that
can be self-tapped into the block either side of the plugs
to positively restrain them, maybe for racers?–
The original message included these comments:

Do these ‘‘plugs’’ not pop out in cases of extreme cold thus
saving the block from cracking during the contraction of the

–
Tony
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11

In reply to a message from awg sent Tue 9 Jun 2015:

It’s unlikely racing makes core plugs more prone to popping …
incorrect installation however… a more likely candidate.–
The original message included these comments:

cant remember what they are called but there is a strap that
can be self-tapped into the block either side of the plugs
to positively restrain them, maybe for racers?

–
Ed Nantes SS
Melbourne, Australia
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