Core plug - cylinder head

[widdowson2008]

A very kind gentleman checked my fluid levels (and generally tightened up various loose bolts) for me this morning and being the meticulous and eagle eyed sort of bloke he is, he spotted THIS.
There appears to be a minor leak on one of the cylinder head core plugs (inset pic).
He recommended that I get it replaced ASAP, and being paranoid where coolant leaks are concerned, I agree with him.

Couple of questions (3 actually).
1 – Has anyone else noticed something similar to this?
2 – Where is the best place to get it replaced (circa Chesterfield)?
3 – What is involved in replacing it?

[Allans]

It's a 'pan' shape core plug Steve. They're pretty straight forward to remove and refit. There're various methods - pick your favourite. Tap it sideways and pull it out with pliers is pretty straight forward. Obviously tap the new one in square. You could find a socket that fits inside the 'pan' to help you do this. In the photo it looks like you have removed the manifold - the access will be easier. A Mazda main dealer should be able to get a core plug for you. Or match it up elsewhere.
This advice is from the 'net:

To remove a core plug take a punch and a hammer, and knock on one side of the coreplug, until it turns in the hole. Then grab hold of the other side with a pair of pliers. Twist and pull to get it out. Be extremly careful not to knock the plug into the engine block. You might not get it back out, and it might get stuck in such away that you won't get a new core plug in...To install a new core plug, get a socket that fits exactly inside the plug (which might be hard to find) and use an extension and a hammer, to drive it back in the hole. Take extreme care to make sure the plug is driven straight into the engine block. If it's not straight a leak will occur.

[Northern Bongolow]

can you remove a second hand one and refit out of an old cylinder head (same model of course). or do they distort when removing,and a new one needs to be fit eveytime.

may have the odd spare in my shed,still in the old head.

[Allans]

I may have a few used heads myself... It'd be good if it worked Ady. But personally I wouldn't risk a used one. It could loose the tension. I'd use a new one.

[Northern Bongolow]

thanks allan. .

[widdowson2008]

In the photo it looks like you have removed the manifold - the access will be easier.

[/quote]
Thanks Alan. Just to clarify things, the head in the pic isn't mine. It's Kirstys old head before I chopped it up. I was using the pic for identification purposes.

[Northern Bongolow]

just tried to remove a head core plug from an old head using the tap with a punch method.
im sorry to say that it repeatedly didnt work,this maybe is because the head plug is so small,or because the head casting is very rough behind the plug,this doesnt allow the plugs i tried to be tipped out. the hole it sits into is quite shallow in its machined section,and the rest of the hole is left very rough.
so the way i got them out is a bit fred dibnah but it worked very well.
drill a hole in the centre of the plug and insert a large woodscrew(3 inch works well) then drag it out while keeping it square to the hole sides,this method does not damage the machined hole,so should allow a nice fit for the replacment.
hope this helps you steve.

[helen&tony]

Hi Ady
That's exactly the way they used to do it years ago...I read that in a book / manual in the 60's...I had a suspected core-plug leak , so I read it up...turned out to be a cracked block.......Punch/ drill a hole, and screw in a self-tapper, and lever it out with a pry-bar / nail-bar and a block of wood as a fulcrum on the block (claw-hammer's good). Use a fine drill, though, on a turbo engine...don't want swarf in the turbo cooling passages ( I don't know how fine they are)...most swarf will wind out on the drill...but you know Murphy's Law!!
Cheers
Helen

[widdowson2008]

Got new core plugs.
Whilst I've got the coolant system down, it was suggested that I change the engine sensor and thermostat, at the same time, so got them as well. Only got to fit 'em now.

[munroman]

Got new core plugs.
Whilst I've got the coolant system down, it was suggested that I change the engine sensor and thermostat, at the same time, so got them as well. Only got to fit 'em now.

Well, if you need any help with the cooling system, some guy on here did some fantastic work on explaining it with fancy diagrams!

[widdowson2008]

NOTE: THIS OLD POST HAS BEEN EDITED. I HAVE RETRIEVED THE MISSING PHOTOS AND INSERTED THEM IN CORRECT PLACE (I THINK)

Coreplug before removal showing position of pinhole.




The old core plug had been pressed in to the extreme depth of the hole. This made it impossible to remove by tapping on one edge as Alllan had suggested - the plug could not rotate.
A hole was drilled in the core plug, a screw inserted, and the whole thing levered out using the screw.

If anyone tries to remove this particular coreplug, extreme care must be taken NOT to disturb the adjacent (very fragile) switch. In my case, I had bought a new switch anyway. Just as well because the connector had separated from the old switch and was on the point of failure.
Ady tells me this switch controls several vital functions (via the ECU). Perhaps he could elaborate.

Core plug removed. Pic shows rough edge of casting at the bottom of the core plug hole.





New core plug fitted.




Removal of the old core plug was quite straightforward as Allan had said it would be.

The old plug had corroded away at the point indicated in the pics. There is actually a pinhole in the plug and the only reason it had only weeped (and not spewed coolant out) was because the plug was seated at the bottom of the hole with the pinhole hard up to the rough casting. Could have been a disaster if eagle eye (Ady) hadn't spotted it last week. Not an area you would think to check. (Well not me anyway)

[Velocette]

Coreplug before removal showing position of pinhole.


The old core plug had been pressed in to the extreme depth of the hole. This made it impossible to remove by tapping on one edge as Alllan had suggested - the plug could not rotate.
A hole was drilled in the core plug, a screw inserted, and the whole thing levered out using the screw.

If anyone tries to remove this particular coreplug, extreme care must be taken NOT to disturb the adjacent (very fragile) switch. In my case, I had bought a new switch anyway. Just as well because the connector had separated from the old switch and was on the point of failure.
Ady tells me this switch controls several vital functions (via the ECU). Perhaps he could elaborate.

Core plug removed. Pic shows rough edge of casting at the bottom of the core plug hole.



New core plug fitted.


Removal of the old core plug was quite straightforward as Allan had said it would be.

The old plug had corroded away at the point indicated in the pics. There is actually a pinhole in the plug and the only reason it had only weeped (and not spewed coolant out) was because the plug was seated at the bottom of the hole with the pinhole hard up to the rough casting. Could have been a disaster if eagle eye (Ady) hadn't spotted it last week. Not an area you would think to check. (Well not me anyway)

I had a core plug of that type replaced on my old R Series Maestro and if I remember rightly they used Loctite or Hylomar on it.

[widdowson2008]

I had a core plug of that type replaced on my old R Series Maestro and if I remember rightly they used Loctite or Hylomar on it.

Didn't use Loctite or any other 'gluey' stuff on mine because the fit was quite tight and the hole quite clean and free from crap. Been running like that since March this year and no leaks as yet.
Theoretically, it shouldn't need any sealant, but I would agree that the use of a sealant is of no detriment. Sort of belt and braces approach, and that aint a bad thing on a Bongo.

[Velocette]

I had a core plug of that type replaced on my old R Series Maestro and if I remember rightly they used Loctite or Hylomar on it.

Didn't use Loctite or any other 'gluey' stuff on mine because the fit was quite tight and the hole quite clean and free from crap. Been running like that since March this year and no leaks as yet.
Theoretically, it shouldn't need any sealant, but I would agree that the use of a sealant is of no detriment. Sort of belt and braces approach, and that aint a bad thing on a Bongo.

These pan shape core plugs are relatively new to me, I remember the old domed ones that you smacked in the middle.

[widdowson2008]

I had a core plug of that type replaced on my old R Series Maestro and if I remember rightly they used Loctite or Hylomar on it.

Didn't use Loctite or any other 'gluey' stuff on mine because the fit was quite tight and the hole quite clean and free from crap. Been running like that since March this year and no leaks as yet.
Theoretically, it shouldn't need any sealant, but I would agree that the use of a sealant is of no detriment. Sort of belt and braces approach, and that aint a bad thing on a Bongo.

These pan shape core plugs are relatively new to me, I remember the old domed ones that you smacked in the middle.

They are actually slightly domed. Bit like frying pan with a domed bottom. I'll see if I have a pic. Meanwhile, I have some pics of head core plugs to post - back in 5.