Engine core plugs.

I have decided to keep my 124,000 mile '96 300 tdi rather than upgrade to a newer TD5. The main decision factor is avoiding the increase in car tax at the end of the year (assuming it goes ahead).

So one of the things I need to do is to keep it reliable (which it has been all its life). At 70,000 miles I had to have the core plugs at the side of the engine replaced as one of them was seeping and another was nearly on the way.

My friendly mechanic said that they are two core plugs at the back of the engine block and cylinder head that you can't get to. This has been niggling away at me and I wonder if there is anything I can do short of taking the engine out to give me piece of mind.

Is it possible to get to the core plugs enough to fill up with chemical metal or something similar? Has anyone had any problems with the rear core plugs failing?

V8 has them at the back as well, when I has mine replaced on my old 3.5 RR it was only the ones on the side that was giving problems I understand the the rear ones are smaller and don't give a problem (saying that someone will say they do).
So if they don't leak don't touch

It sounds like someone ran it with the wrong volume of antifreeze rust inhibitor at some point which has lead to them corroding early

I haven't heard of these being a problem and have not had a problem myself.

Regarding filling them, if you could get them degreased and you could fill them that might stop the leaking, but it might not do to well with the expansion/contraction and if you ever did need the core plugs they ain't going to work.

I,conversly,have just dismantled a 300 with the rear core plug in a **** state,probably as said due to wrong coolant mix.How to get to it without dismantling?No ideas,sorry

I had a 300tdi, back in 2002 my baby blew big style on the A20 in France, 82mph one minute, black smoke and steam next! The core plug at the back of the engine let go and the engine ceased. seems the guy who owned her before didnt use anti freeze and so........new engine.