Disco 3.9 V8 Welch plugs

**Sprite001** · 27th May 2012, 01:49 PM

Hi there again
Got my 3.9 V8 engine running today and It runs real good, until I looked under the car and found a small puddle of green water !!
Upon closer inspection I found the water was leaking from the welsh plug on the R/hand bank.
I was wondering if it is possible to replace all 4 welsh plugs from under the car? And what I have to remove to make the job a little easier.
So if anyone out there has done this job before, could you please give me some guidance.
Thanks again
Phil

**bee utey** · 27th May 2012, 02:06 PM

Well for starters you need good access to the welch plug, normally I fit them using a slightly smaller-than-cup-size socket and a lump hammer. If you think there's any way you have enough room to swing a hammer, maybe by using a socket extension, then it is possible. Personally I would only replace the leaking plug and then keep the corrosion inhibitor up to spec from now on.

It'sNotWorthComplaining! · 4th June 2012, 05:43 PM

you lucky you don't need to do the welsh plug on the rear of each head

**haydent** · 4th June 2012, 06:28 PM

I've done all the ones on both sides on my 3.5 with the motor in. At times I would undo a motor mount and starter and exhaust as well as jacking the enjin up a bit just to give you that bit extra room.

But as recommended just start with the leaking one and hope its one of the easier to get to...

**haydent** · 4th June 2012, 07:05 PM

Actually I just remembered something I did. As it can be hard to get the old ones out particularly due to lack of space to swing a hammer. I got around this by using a long rod in my case from an old jack as a long punch that could reach through under the wheel guard from the outside beside the car.

This way plenty of room to swing the hammer to hit the plug, spinning it around a bit so you can then grab it to get it out.

There's pics of me doing this on one of the other thread about this job.

**Sprite001** · 5th June 2012, 04:54 AM

Thanks for that
Got the old ones out over the weekend ,now I am about to put the 6 new ones in. The front ones will be the hardest, did you put any sealant around the plugs before you installed them?
Cheers Phil

**p38arover** · 5th June 2012, 06:47 AM

Originally Posted by Sprite001

Upon closer inspection I found the water was leaking from the welsh plug on the R/hand bank.]

Welch! Welch! Welch! NOT welsh! Gawd, how often do I need to say it on this forum?

Now to fix the thread title!

**blackbuttdisco** · 5th June 2012, 07:33 AM

Never thought I'd see the day that an English Ninja would be supporting the Welsh.

PS, my wife is Welsh .

**haydent** · 5th June 2012, 01:39 PM

Originally Posted by Sprite001

Thanks for that
Got the old ones out over the weekend ,now I am about to put the 6 new ones in. The front ones will be the hardest, did you put any sealant around the plugs before you installed them?
Cheers Phil

i did use some maroon colored sealant in yellow tube with antlers on it i think. if you really want the brand i can get it but its common in auto shops. its thick though.

i may have done some with and without, cant remember. try with first but if too hard try without.

It'sNotWorthComplaining! · 8th June 2012, 08:05 PM

Originally Posted by p38arover

Welch! Welch! Welch! NOT welsh! Gawd, how often do I need to say it on this forum?

Now to fix the thread title!

Core plug

From Wikipedia, the free encyclopedia
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A core plug that has been corroded from improper engine maintenance.

Core plugs, sometimes wrongly called freeze plugs or frost plugs, are [ame="http://en.wikipedia.org/wiki/Plug"]Plug - Wikipedia, the free encyclopedia[/ame] that fill the [ame]http://en.wikipedia.org/wiki/Core_%28manufacturing%29[/ame] holes found on water-cooled [ame="http://en.wikipedia.org/wiki/Internal_combustion_engine"]Internal combustion engine - Wikipedia, the free encyclopedia[/ame].
The [ame="http://en.wikipedia.org/wiki/Sand_casting"]Sand casting - Wikipedia, the free encyclopedia[/ame] cores are used to form the internal cavities in the [ame]http://en.wikipedia.org/wiki/Engine_block[/ame] or [ame="http://en.wikipedia.org/wiki/Cylinder_head"]Cylinder head - Wikipedia, the free encyclopedia[/ame](s), usually forming the [ame]http://en.wikipedia.org/wiki/Engine_cooling[/ame]. The traditional plug is a thin, domed, disc of [ame]http://en.wikipedia.org/wiki/Ferrous_metal[/ame] which is pressed into a machined hole in the casting. Alternatively a non-ferrous metal such as [ame="http://en.wikipedia.org/wiki/Brass"]Brass - Wikipedia, the free encyclopedia[/ame] offers improved corrosion prevention. In some high-performance engines the core plugs are large diameter [ame]http://en.wikipedia.org/wiki/Pipe_plug[/ame].[1]
Core plugs can often be a source of troublesome leaks as a result of internal cooling system corrosion. Ease of replacement depends on accessibility. In many cases the plug area will be difficult to reach and using a mallet to perform maintenance or replacement will be nearly impossible without special facilities. Expanding rubber plugs are available as replacements when access is a problem.
Freeze plug

A true freeze plug is an expansion plug located in the side of an engine block that is supposed to protect the block against freeze damage. Water expands when it turns to ice, and if the coolant does not have enough [ame="http://en.wikipedia.org/wiki/Antifreeze"]Antifreeze - Wikipedia, the free encyclopedia[/ame] protection it can freeze and crack the engine block. The freeze plugs (there are usually several) are supposed to pop out under such conditions to relieve the pressure on the block.[2]
A variety of [ame="http://en.wikipedia.org/wiki/Block_heater"]Block heater - Wikipedia, the free encyclopedia[/ame] called a "freeze plug heater" can be installed, replacing the freeze plugs, to warm the engine before start up.
Welch plug

The Welch plug was originally designed by the Welch Brothers of the Welch Motor Car Company of Pontiac Michigan in the early 1900s.
"At that time core holes in the engine blocks were fitted with pipe plugs. During one of these run-ins a pipe plug backed out. In order to get back on the road one of the brothers drove a quarter or half dollar into the hole. From this they developed the Welch plug, some with the help of my Great Grandfather Martin Hubbard. They then patented the plug and the M.D. Hubbard Spring Company become the sole manufacturer of the Welch plug for the life of the patent."[3] The Welch plug being the domed disk which is fitted against a shoulder in the core hole and then the dome struck with a hammer to collapse the dome and expand the disk to seal the core. Other core plugs are a dish design when pressed into the casting hole the tapered sides form the seal. These core plugs do not require the shoulder inside and are the principal design used in modern engines.[4]

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