Nissan Patrol 4x4 (Africa)

Afternoon all,

So I picked up another coolant leak on my TB42 Carb Y60 GQ
At the end of last year, I replaced all coolant pipes except the radiator hoses, and all heater hoses. So I first checked there to see where the leak was coming from.
I next moved on to tracing the leak, took of my exhaust manifold heat shield and intake piping as it seemed to be coming from there/that area.
Couldn't spot the source of the leak, but it looked like it was between the rear of the block and the gearbox bellhousing, which was confusing. Basically it was coming from somewhere high up on the engine, and running along where the bellhousing and block meet.
(made no sense to me that there would be any leak or failure points within the bellhousing, on the rear of the engine block. (is this correct, is there anything there that could leak coolant?
)
I then checked my radiator cap and oil filler cap to see any signs of a blown head gasket. Found no signs.
I then prayed it wasn't a crack in the block, and couldn't see any signs or indications that that was the case.

Confused, I remembered I have my TB42 EFI engine sitting in my braai room, so decided to go have a look there as I couldn't see between the engine and firewall on the car where I suspected the leak was coming from, I could barely fit my hand back there...

What I discovered was that there is a Welsh plug on the head of the engine rear by the firewall. I suspect this is where my leak is coming from.

Now my next question is:

Where do I get a replacement Welsh plug?

How do I go about removing the old one and installing the new one??
There's not much space there at all....
Would I have to take it in somewhere?

Any advice or recommendations would be much appreciated, thanks!

Unfortunately I doubt this could be done without removing the engine, or at least the head.

Welsch plugs are sold by most spares shops. You just need to know the size.

To remove it, smack it with a screwdriver or chisel just inside the rim (if you try do it on the rim you will gouge the hole it fits in and cause problems getting the next one to seal). It will probably turn sideways, and then you fish it out with pliers.

To re-install, you apply shellack sealant (best) or loctite around the edge and smack it in. The ideal tool to do this is a punch that fits nicely into an installed plug and has a shoulder at the right depth to prevent knocking it through and also ensures that it is square, but it can be done with a socket if you are careful.

Shellack sealant can be bought from the plumbing supply section of the big hardware shops.

I probably have a punch as I once replaced welsch plugs on a TB45. I can courier it to you if you undertake to send it back once you are done.

Oh, I would recommend replacing all the welsch plugs in the water galleries if one is leaking. IE all the ones in the head and the upper 150mm of the block.

Oh, I can't remember for sure but I think there may be a plug in the back of the block behind the flywheel?

Peter is correct. That engine will have to come out.....because....If one is rusted, they all will be.

You may as well do them all, and while you're there, I'd inspect the water pump as well, since corrosion of the pump and impeller could also have occurred. I'm assuming you are running a PROPER ANTI-FREEZE MIX, yes? Because less than a 50% mix WILL cause rust and corrosion.

Hi guys,

Tanks for the replies and advise, much appreciated!

I was hoping that it wouldn't be the case of having to remove the engine, but it was a very slim chance that was going to be the case....unfortunately

I guess now, this is the motivation to get a bunch of other stuff done, while I'm at it....time for some serious maintenance!

May just tackle the EFI conversion, cooling system refresh, water pump, gaskets, belts etc etc while I'm there...

I think there may be 2 Welch plugs on the flywheel side of the engine, from what I've read at least, so I think like you mentioned, there is at least 1.

I've hear that using brass plugs is best over the steel ones etc, to prevent and resist corrosion, any recommendations on this?

@jakeslouw
yes I have been running a coolant mix, not just water.

I would use brass as a first choice.

Be careful with brass. Make sure you run a suitable anti-freeze to prevent galvanic corrosion of the aluminium head.

If normal welsch plugs are correctly fitted with a suitable sealant, they will be fine.

Peter Connan wrote: ↑11 Jul 2023 16:11 Be careful with brass. Make sure you run a suitable anti-freeze to prevent galvanic corrosion of the aluminium head.

If normal welsch plugs are correctly fitted with a suitable sealant, they will be fine.

Thanks, I did read about that, didn't realise it could pose such an issue.

I have my 4.2EFI sitting here, was going to transfer all the components across to my carby engine...
I have a little extra cash coming my way soon, and the TD42 is now starting to temp me if this engine has to come out anyway....
ah decisions decisions

after digging further, the top Welsh plug on the head at the rear of the engine is NOT leaking, so it must be one of the ones behind the flywheel on the block of the engine......