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Welch plugs 2.5L V8

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Icos
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Joined: Tue Oct 02, 2018 11:53 pm
Location: Melbourne, Victoria, Australia

Welch plugs 2.5L V8

Post by Icos »

Hi, I have a leaking Welch plug in the block just above the engine mounting bracket drivers side RHD, could anyone tell me the diameter of that Welch plug, it’s one of six, 3 per side.
Is it possible to replace them, or any of them without removing the engine out of the bodywork?
Any idea where they are sold, thanks!

Vortex O'Plinth
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Location: Gloucestershire

Re: Welch plugs 2.5L V8

Post by Vortex O'Plinth »

As far as I recall these plugs are 1 1/8" diameter and the Jaguar Part No. is C26004 - perhaps someone else could verify? I replaced one on my SP engine and got access by removing the exhaust manifold; I think access might be more restricted on the saloon? A web search will throw up any number of core plug suppliers, but in any case, David Manners can supply them.
Nick

"Don't bother with the Air & Space Museum - there's nothing to see.......".

Christopher Storey
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Re: Welch plugs 2.5L V8

Post by Christopher Storey »

Nick is quite correct : the part number is C 26004, and they are currently in stock at manners for £ 1.32 or SNG Barratt for £ 2.06

tjt77
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Re: Welch plugs 2.5L V8

Post by tjt77 »

Replacing the welch plugs in situ is very challenging.. there are however 'repair' plugs that are easier to fit in tight spaces...so consider this as a possible 'practical' solution to resolving the problem....these are made of a rubber compound with a threaded shaft through them and washers either side..( they fit rather like a cork in a bottle) which is tightened by an external wing nut to expand the plug to seal the hole up.. .its a question of whether there is sufficient room for you to be able to remove the leaky one (there are a number of ways to do this .. again..the main challenge is very tight space to access .. most bang a hole through the old plug with sharp instrument and lever the plug out.. others drill a hole and use a self tapping sheet metal screw .. and either a short piece of metal with a hole for the screw to go through and use as a lever.. or just vice grips or some other suitable tool to act as lever on the screw..) if you can get the old one out...you should be able to fit 'repair 'plug in there..
Fitting correct 'as original plug' is going to be close to impossible as they are locked in place by flattening the convex part with a suitable diameter flat faced tool (3/4" round bar stock the most common) and hammer, and it has to be hit squarely in the middle to expand evenly and lock in place and have an effective seal ..before this can be done the hole where the plug sits in has to be absolutely clean.. almost impossible to achieve in situ.. the 'repair' plug wing nut is relatively east to clinch up in tight spaces... also the repair plug negates the need to fully clean out the lip the plug sits within and eliminates the problem of flattering the plug so it expands to seal against the sides of the lip it fits within...
For an effective repair ALL the welch plugs should be carefully inspected ..if one is leaking, others are likely not far behind.. I'd avoid long journeys until this is addressed properly. dropping the front subframe assy out of the car would give much better access to the plugs on sides of cylinder block..( exhaust manifolds will still obstruct them to some degree.. these can also be removed in situ if necessary .. but its not fun)
For a long term fix, consider engine removal and replacing ALL of the welch plugs .. If you have access to a car hoist, removal and replacement for front subframe is about a 2 1/2 hr job..
regardless ..this is one of the more 'unpleasant' and time consuming jobs that occur .. its never fun working with 'interference' fit parts in very tight places from underneath the car.. good luck..

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