Classic cars forum & vehicle restoration.
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jp928
Joined: 07 Jun 2016 Posts: 249 Location: Australia
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Posted: Tue Aug 22, 2017 7:39 am Post subject: Vintage welch(sp?) plug removal |
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Looking for advice based on experience...
26 Rover 9. Completely overhauled engine 20 years ago, only got running in the last 9 months. One of the core plugs in the head is leaking - light yellowy-green sludge , very slow weep. May be coming through a crack or pin hole in the plug itself. It has a hex hollow, ~9/16"/14mm across flats.
Any advice on trying to remove this please? Engine has been up to temp ~6 times.
thanks
jp |
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peter scott
Joined: 18 Dec 2007 Posts: 7119 Location: Edinburgh
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Posted: Tue Aug 22, 2017 8:56 am Post subject: |
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A piece of hex bar or a bolt with a nut welded onto it.
Peter _________________ http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon |
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Kenham
Joined: 12 Mar 2012 Posts: 209 Location: Kent
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Posted: Tue Aug 22, 2017 8:59 am Post subject: |
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I presume it is a threaded plug, I would drill a hole near the thread and gradually increase the size of drill until just touching the thread and try to collapse the plug. If you can do this a few times around the plug it will free off, I doubt the block will be very thick so don't resort to too much force with a hammer. Try to keep the hexagon intact . All sounds easy of course. Best of luck |
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Kenham
Joined: 12 Mar 2012 Posts: 209 Location: Kent
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Posted: Tue Aug 22, 2017 9:03 am Post subject: |
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I'm thinking it is seized in the thread. Spark erosion is the way to go if you can find someone local to do it. Not impossible to do yourself if you believe what you see on youtube! Never tried it myself though. |
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jp928
Joined: 07 Jun 2016 Posts: 249 Location: Australia
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Posted: Wed Aug 23, 2017 2:56 am Post subject: |
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Obviously I wasnt clear enough - I havent actually leaned on the plug yet - still working up a suitable tool to get a good grip on it. Was worried about doing damage with too much torque on it. Scraping on the end a bit, looks like it not brass - more a silvery look like iron or steel. Will try a shortish bar with a bolt through the end to limit the torque at first.
thanks
jp |
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jp928
Joined: 07 Jun 2016 Posts: 249 Location: Australia
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Posted: Sat Nov 04, 2017 7:29 am Post subject: Welch plug removal |
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Well it certainly is stuck in the threads! Very strange weep, seems to be actually coming through the plug material, and it isnt going to get better, so I started on it. The edges are not very stable, but I managed to get a punch mark on it, so I started drilling. After ~5mm it seemed to get very hard, and since I didnt know what might be behind the plug (in the way of head casting), I decided to move to the centre recess. I went to put a punch mark in the centre (spring loaded punch), and the punch tip went clean through! The plug was so soft I managed to remove most of the centre by just working a screwdriver tip around. Looks like there is part of the head casting on each side of the threaded hole. 90% of the plug is now gone, but the remains are stubbornly embedded in the thread grooves. The lower part is coming out slowly via a small sharp driver and a bit of hammering, but the upper part is going to be more difficult, just due to visibility and access issues. Currently soaking in penetrating oil. Might try a bit of heat next to see if it will dislodge anything.
jp 26 rover 9 |
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jp928
Joined: 07 Jun 2016 Posts: 249 Location: Australia
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Posted: Mon Nov 06, 2017 3:56 am Post subject: |
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Finally got it out. Lots of brutality with, unfortunately , a small chisel - only thing to hand with a sharp edge, 1/4 wide that I could get into the threads with. A normal cold chisel wouldnt get in there. Took several sessions of chipping away at the stuff stuck in the threads before I could get even a tiny bit of a plug started, and then gradually got enough of the tap started to lean on that a bit, out, in again, run the plug in a bit more , then the tap again. Tried a bit of heat, but it didnt seem to help much. Painful contortions required to get at the top threads, but all done now. First plug I tried seems to be undersize, or its bottoming inside - even cold it leaked as soon as it saw water. More research and measuring required on the plugs, but that should be easy, I hope.
jp |
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Clactonguy
Joined: 20 Mar 2018 Posts: 104 Location: clacton on sea
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Posted: Wed Mar 21, 2018 1:44 am Post subject: welch plug |
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though original was obviously rusting away hence leaking. these if threaded ? are actually harder to remove than modern 'Push in' types.
ideally block should be on a bench for working on so access and visibility is at best.
however can understand trying to fix in situ.
pity no images.. we need to re-tap threads and use a new plug with correct thread and size.
also I would coat threads in a sealer to prevent seepage around thread/corrosion. as you have tried re-tapping and. no luck sealing -suggest we check plug is correct? ( owners club?) thread and size . again use a sealing compound such as plumbers and engineers use for threaded components in a high temp environmental situation.
the worry here if plug is too deep and we are forcing it in too far? we may cause other issues. hope it turns out well. |
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jp928
Joined: 07 Jun 2016 Posts: 249 Location: Australia
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Posted: Wed Mar 21, 2018 2:58 am Post subject: |
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Re deepness, I have relieved some of the end threads to prevent bottoming. Used some sealant, but its not 100% sealed yet - very very slow weep still. Thread spec is good, based on tap fit, and plug spec. There are very few owners I have found who could verify the thread - advised by somebody it is 3/4 BSP IIRC. Many engines seem to have these holed plugged with something that looks like aluminium, but the outside has been cut off flush, but the result looks like its been hammered flat. My spare engine has such in the head on both sides, and the lower block as well. Another car in QLD is the same.
This is now a minor issue compared to sorting out the radiator - tossup between a new core from UK (GBP800 shipped, + fitting here), and fitting a modern radiator behind a honeycomb facade.
jp |
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