Freeze Plugs

Dear sir, As I removed the head from "Blanch", (54' XK 120 DHC) to replace the head gasket, I noticed some seepage from the center freeze out plug on the carborettor side of the block. I am thinking that now the head is off, I should replace all of them because I do not want to take the head off next year. 1. What is the best course of action to remove the plug? how about a dent remover? or a die grinder?? 2. Can a plug from NAPA or a regular auto parts store be used without loosing points later in life, or do I need to send for a special plug? 3. what seals the plug, plugs silicone?? 4. what is the best means of installation ? a large socket that fits the lip of the plug or the center of the plug ?? Does anyone with experience wish to comment? - Respectfully, E.W. Blake

Mr. Blake, The way I have removed old core plugs is by drilling a hole in the center big enough for a small pry bar (or screwdriver) to fit into it. I then just pry it out. The core plugs are a standard size and can be gotten at a regular parts store. You may try to find stainless to reduce later rust. I have used no. 1 Permatex for sealant with no bad effects as yet. I am sure other sealant work also. The way to set the new core plug is to set the plug all the way into the flange. Then the plug is struck in the center until it deforms. The plug spreads out as it deforms sealing the hole. I usually use a ball-peen hammer with the round end toward the plug. - Cleo Bay, XK120, XK140

E.W. - Sure, any good auto parts store freeze plugs will work. I prefer NAPA, because they're reliable and usually have what I want when I want it. Dorman (convex, not U-cup) is the preferred brand for me. You mentioned a concern 'later in life' with 'points' - I presume you appreciatye that leaky freeze points garner more points than dry ones, as they're more authentic! Just kiddin'! Dorman also makes an adjustible line of freeze plugs that don't have to be hammered in; a turn of a wrench pulls two circular cups into one another such that the iner one causes the outer one to expand, seal, and lock in place. Not original, but you don't have to remove the exhaust to install, service, or replace them,!!! Food for thought!! Best to get it back on the road and Drive It; these cars are not to be coddled! Enjoy! - Larry Schear, Twin Cam, Inc.

I remove and install freeze plugs exactly as described by Cleo. I would only add one note. To help ensure a quality seal, I clean the seating with a wire brush attachment on a drill along with sandpaper and knife or screwdriver. If these parts have not been replaced from new on these XK engines, I guarantee that some of the plugs are ready to rust through at any time. For those who are interested, examine some of the plugs to note signs of the tell-tale dripping or weeping down the block. Hopefully you won't see this. If the engine is ever removed for heavy duty servicing, freeze plugs should routinely be replaced. The small one at the rear of the cylinder block on the XK 120 engine is very difficult to access with the engine in place. If it leaks you remove the engine or drill through the firewall. - Bob Oates

Time to talk about core plugs again. The plugs in the engine block, head and intake manifold are called core plugs because they fill a hole where the sand "core" was supported in the mold during the casting process at the foundry. They are also sometimes called freeze plugs because if the water freezes they have been known to pop out and maybe save the block from cracking, but there's no guarantee of that. They are also called Welch plugs but I don't know the reason, perhaps Welch was the name of the inventor or a major supplier. The XK block has three large ones on each side, plus a seventh at the back, plus one or two small ones. My XK120 has only one small one, down by the starter motor. I believe very early XK blocks had a second small one but I don't know exactly where it was. The head has two hidden by the exhaust manifolds (same as the small one in the block), plus the three in the spark plug valley (threaded with copper washers). The intake manifold on mine has a large one at each end, but other manifolds may be different. On Mark V and earlier pushrod engines, some of the plugs are the same as for early XK engines. If you see one weeping, it most likely means it has rusted thin from the inside and is ready to crumble away. These things are plain steel and not very thick, like 3/32" (2mm). The writer of the manual seems to think you can dimple them out, but I removed the ones on my XK120 by hammering a screwdriver through the center and twisting them out. It is easy enough to reach the ones on the sides with the intake and exhaust manifolds off. The one at the back of the block is difficult to get even if you take out the gearbox tunnel, and of course E-type and most saloon owners don't even have that option. Obviously if you have the engine out for any other reason now is the time to replace that one. Also remove the block drain petcock, and the block heater plug if you have one and can get it out. Blank off your intake and exhaust valve ports, then flush all the side plug holes with the garden hose, while sticking a stiff bent wire in there to loosen up the crud. Try to avoid flushing large amounts of crud up into the water pump (or better yet take it off). Flush down from any and all the ports you have opened in the head. New plugs are available from Moss, Welsh and other Jaguar parts sources, and possibly your local auto parts vendor. Mine are shaped like a satellite dish, but on some more modern engines they may be like a round layer cake pan. You may find the diameter is a bit oversize and you may need to grind it down on a bench grinder. Use core plug sealant from your local parts vendor, and be sure it hasn't separated in the tube. Put a large diameter socket on the plug so the hammer force is around the edge and hammer it in, convex side out. - Rob Reilly - XK120 FHC, Mark V saloon

I would like to add that it is advantageous to use brass core plugs. Seal easier and NO corrosion. Available everywhere quality engine parts are sold - George Badger

I would definately second George's recommendation on using the brass softplugs. I have blown the steel ones out of the side of the block, even with Permatex sealer. The brass plugs conform to the opening much easer and the Permatex helps seal around all the little pits in the cast iron blocks along with being less prone to rusting out. I have also found using a long bolt makes it easier to compress the plugs, especially with the engine installed. - Larry J.

If you have any questions or comments send e-mail to: ted@jag-lovers.org
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