Hello. I wanted to see how difficult and what is involved with welsh plug replacement with the engine in the car. I am planning to change the engine coolant and was thinking about a broader cleaning of the cooling system such as pulling the radiator and cleaning it out. I also thought about removing the welsh plugs in an effort to clean out the engine passageways better since I have heard build up can occur there.

I'm not trying to make this a major job. Just trying to be thorough if I reasonably can. I am hoping I can reach some or all of the plugs from below once I drive the car up on ramps. Does that sound reasonable to anyone?

Also, what is involved in removing and replacing, and is it fairly easy while lying under the car? I think what I need to do is drive a flat blade screwdriver into the center of the plug and pry it out. After digging, spraying and whatever else I can do I expect I need to rinse out the block and then install new plugs in place by using a socket of roughly the same size OD as the ID of the bore of the plug and tap it into place. I have read that adding some loctite (blue I assume) is a good idea.

Let me know if any of this sounds wrong or simply a bad idea.

Thanks,

Eric

 

I can't quite remember the exact layout/location of the plugs on a 4.2 six so these are general remarks...not Jag specific.

Removing is the easy part. Installing can be tricky. It takes quite a bit of force to drive 'em home and that means enough room to swing a hammer and hit the plug square-on. Not always convenient, sometimes almost impossible....especially if working on your back from below!

You can buy freeze plug installer tools that allow to to approach the plug at a slight angle. Sometimes they work sometimes they don't, depending on access/location of the plug

Cheers
DD

 

The casting plugs are situated in each section of the block near a stud for the cylinder head. Most machine shops use black gasket sealing compound to seal the plugs while installing them. The original purpose of the plugs is to seal the hole used to remove the casting sand from the mold during manufacture.
Some plugs are easier to access than others but you might remove the ones that you can and flush the block.

bob gauff

 

Most of the crud accumulates at the rear of the block. There is also a small diameter plug towards the back, RH side of the block, and when I took mine out it was completely blocked up !

As Doug says, removal is easy, but replacing core plugs with the engine in the car can be very difficult because there is no room to swing a lump hammer. Don't remove unless you're sure you can put one back in.

 

One idea: are you familiar with those pneumatic palm hammers you can find at home centers (Lowes/Home Depot)? Would there be enough room to use one of those, and, if so, is it a good idea or are those things too aggressive? I have never used one, I have pneumatic nail guns, but if they fit it could be an option...

I've heard a number of times about them being full of krud when people rebuild their engines so I can only assume non rebuilt engines have at least some blockage in there.

What would you recommend to use to clean out the block (again remembering it'll still be in the car)?

Thanks for the help!

Eric

 

wow, I personally would not mess with those freeze plugs, especially if they are not leaking.
might cause you to have to remove the engine just to replace one miserable plug. Moreover, that's a job you do when rebuilding the engine and the block is going to be boiled, it's not a general maintenance item.

instead, you can use a product like Prestone Super Flush, to flush and reverse-flush the engine block and radiator without removing anything but installing a "T" adapter in one of the 5/8" heater hoses, it does a decent job of cleaning the crud inside the coolant passages inside the block. Otherwise you probably heard it before: "leave dirty, dirty enough".

 

^ The most important bit of advice yet :-)


Cheers
DD

 

I really would go out of my way NOT to take them out.
I've no experience of this engine but plenty of welsh plugs.

 

If you really insist on removing the welch plugs,then take off the carbs and manifold, and the exhaust manifolds then you can reach them all from above. They will be rusty inside. It is a really good idea to remove them and clean out the block as these engines suffer badly from rust "mud" which rots the long cylinder head studs.
The idea of a socket is ok, but be careful it is not too snug, as when you beat the welch plug in, it reduces in diameter and traps your socket !! Good luck.

 

Well, I finally got the car up on ramps and took a look under there and have decided it is not easily done. I was thinking, for some reason, that it would be clear under the intake manifold, but found plenty of other things in the way on the bottom side as well.

So I went by the car parts store and got a flush kit and other cleaning liquids and will go that route.

Thanks all for the feedback.

Eric

 

best decision you ever made! :-)) Flushing the system will do fine, check out the Back-Flush kit made by Prestone, it does a very decent job of cleaning, all you have to do is install a "T" adapter to one of the heater hoses, then you connect a garden hose to the "T" and the water pressure and Super Flush chemical does the job. Note that there are kits for 1/2", 5/8", and 3/4" hoses.

 

Just giving a status update on what I did as well as looking for opinions.

As stated, I decided to just flush the system out. I did get one of those flush kits where you splice into a heater line, but after looking at the water flow circuit I didn't think it was going to be that beneficial so I haven't used it yet. I did remove the drain plug on the back left side of the engine (if seated in the car). I had the car on ramps. When I unscrewed the plug, coolant came out with a good amount of force and was fairly clean so I thought that was a good sign. After it all drained out I proceeded to flow water through the expansion tank and let it run out the drain plug hole. It continued to come out with good force. There didn't seem to be any build up around the drain plug hole so I was happy with that as well. I then took the hose and stuck it up to the drain plug hole and let the water back flush through the system until it overflowed out of the expansion tank. I let it run like that for a little while. I then reinserted the hose in the expansion tank and turned the engine on, with the heater at full blast. I walked around the front and revved the engine some and noticed the force of the water coming out of the drain plug hole increased as well. I ran it like this for a while, monitoring the coolant gauge. After a few minutes I revved it again, but I noticed the water coming out of the drain plug hole didn't splash like it did before, so I am assuming it was not coming out at a greater pressure. My question is, does this sound right? Why would the water not come out with greater force when the engine is revved? I didn't think much of it at the time, but when discussing with a colleague at work the next day it did strike me as odd. Any thoughts? Is that right or is something wrong? I filled the system up with water and the Super Flush chemicals. I will attempt the same test when I drain the water out this weekend.

Thanks.

 

I was reading through this thread trying to solve a problem. I have coolant pouring out on the back side of the engine. We have checked all hoses and radiator, plus replaced water pump. The only thing we can think is a freeze plug. You said you can get to it from above. I really don't want to pull the engine and underneath looks like you have to drop the transmission. Can anyone help me with how to get to that Part of the engine. It leaks above the transfer case.By leaks it pours out I mean.

 

Presumably you have an XJ6 4.2. All the welch plugs are on the side of the engine. The older engines once had one at the rear of the block but later engines have a plate with gasket secured by four screws. If you can look with a mirror and torch you should be able to see it.

 

We have a S Type and noticed coolant pouring out this morning.. found the freeze plug on the ground.. needing instructions on how to get to it to replace it.. do the heads need to come off? Is there any easy way to do this?

 

If it's a 1960s S-type, the engine had fewer core plugs than the later long stud blocks for the 4.2 litre engine. However they are different to the later plugs, being a dished washer that is quite difficult to insert and secure, The plugs fit against a lip in the core plug hole and one then has to thump the centre to get the plug to expand slightly to make the seal. I did the ones on a 2.4 litre engine way back in the 80s. The later ones are a doddle in comparison

 

Generic comments, I hope!! Never know when my post are recorded or lost in cyber space. Very irritating!!


1. Do no remove plugs in situ. Unless they leak or there is a major over heat issue suggesting a block full pf goop. Replacing them will be major challenge, and the chance of failure quite possible. "Up that creek" seems to ft.

2. Jose's option is a good one to an extent. I've done on other critters. I think I still have a kit t do it. Alas, spewing on to the ground is not good for the environment and the glycol is poison to critters.

3. If you are up that infamous creek, there might be a way back. At one time, plugs were sold that relied on a seal and a bolt to expand them in to place, with a BFH not needed. The space thing.

4 Driving a nail into wood is one thing. Palm slapper might be OK there. But steel into iron. that friction thing. Not to be relied on, albeit, it just might work.

5. Decades ago, a little plug on my well worn 58 Pontiac Star Chief began to leak more and more. At the back of the left head of it's V8. Very close to the fire wall.
Pull the head/ or, bodge. Circumstance dictated the latter. I stood on my head in the driver seat well. drilled a few little holed in a small circle at the level of the plug in the
fire wall. Managed to pry out the center and then the plug was there. Luckily it came out rather easily. Very rusty!! A flush and ready for the new one. Luckily, a straight shot. Put some Permatex red on the plug and drove it home. I made a plate and affixed it to close the hole. Permatex black as a gasket... It survived for a time til it tossed a timing chain. Bye, bye Pontiac. You are killing me.

Carl .