300Tdi coolant leak from Engine block

Hi frinds
P gasket was leaking on my 300Tdi conversion. Which replaced around couple of weeks ago. I noticed some coolant leak again and thought P Gasket is still leaking then I replaced the P Gasket again with TRV this time.
Today I have noticed that coolant is leaking again. I inspected under the P Gasket housing with a dry tissue paper and it was completely dry. Then I have noticed coolant is leaking from the Engine block right above where the coolant engine block nut. I cleaned that round cap on the engine block dry then after few minutes minor drop appears itself while vehicle is stationary.

I am uploading the picture where coolant is leaking on that round seal on Engine block. Please advise what could be done to stop that coolant leak.

You can replace these caps.
They are called Core plugs,
Need to be able to swing a hammer,have you got enough space ?

Hi thanks for your reply, it has some space but not enough. Could you please provide any instructions how to replace these core plugs or refer to any manual?

I have just watched a video on YouTube for replacement. I have just renewed the manifold gasket and P Gasket and Red coolant. It’s seems like I have to remove everything again OMG. Can I reuse the Coolant if I manage to drain it slowly and use a filte to put it back in again. Or could that core please could be replaced without removing the Manifold. As the manifold bolt were fitted with coils I don’t want to disturb the manifold bolts again.

This core plug can be removed using a long flat faced chisel/drift and a lump hammer. Ease it out. The trickier part due to space restriction is to install a new core plug squarely so the new plug is square and seals water tight. It's not much work removing the manifold et al to ensure a 100% plug fit. Plus, buy a few plugs if this is your first time as it's easy to bugger one up on refit. Use a smaller socket to drive home the plug.

Yes you can re-use the coolant if new/clean.

New core plug time, not got enough time/skill/money? drain coolant down, clean properly (not polish) by roughing it up and dry core plug face, then get some liquid metal on it.

I think that bolt head underneath the leaky plug is the engine block coolant drain.

lynall said:

New core plug time, not got enough time/skill/money? drain coolant down, clean properly (not polish) by roughing it up and dry core plug face, then get some liquid metal on it.

I think that bolt head underneath the leaky plug is the engine block coolant drain.

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see I could have said this… must be getting better at refraining from teaching new members bad habits….

But best get some metal putty. Easy to use on every liquid

Hicap phill said:

see I could have said this… must be getting better at refraining from teaching new members bad habits….

But best get some metal putty. Easy to use on every liquid

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Me being lazy would bang a bottle of K seal in it!

I will try to replace it, bit scared hope that won’t drop into the Engine. I think someone already applied some sort of putty on it instead of replacing the cap. May be I could smear it with some TRV

As a temporary fix [that will most likely last forever[ you could buzz back the core plug and apply a good layer of JB Weld. But be careful when buzzing back as the plug's already leaking so the metal is already worn to near paper thin around the holes.

If you plan to change the core plug search for this on YouTube, there are plenty of tutorials showing you how to do this. It's not a difficult job. I usually heat mine up first to aid cracking the rust/muck around the plug.

Singr07 said:

I will try to replace it, bit scared hope that won’t drop into the Engine. I think someone already applied some sort of putty on it instead of replacing the cap. May be I could smear it with some TRV

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Cannot go in as there will be some sort of casting behind it.

lynall said:

Cannot go in as there will be some sort of casting behind it.

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I think the "core plug' is tapered so it cant fall inwards. In the global south we call them a welsh plug though

Lucky it's that one that's leaking as there is one at the back of the motor as well

I have had one blow out 30 mins of driving after picking it up from my mechie who replaced them as preventative maintenance so they need to be secured somehow

On the P gasket replacement - an old hand in the business told me to soak it in warm water for an hour or two before putting it to work

lynall said:

Me being lazy would bang a bottle of K seal in it!

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Hi folks

Thanks for your precious time.

I have replaced this cap without removing manifold. I knocked the old one out carefully with a 36inch long crow bar without damaging the Engine block edges.

This new cap’s steel is slightly thicker may be 1-2 mm and depth is also couple of mm bigger. I have smeared TRV around the inside edge.

Original cap was fitted around 2mm insides the recess, but this new cap doesn’t go in like the original one and I tried striking it with big hammer. This cap is still sticking out around 1mm. I hope these won’t pop out with coolant temperature.

Please provide your opinions.