3.9 V8 Rover Block Core Plugs

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Ian Anderson
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3.9 V8 Rover Block Core Plugs

Post by Ian Anderson »

Good evening all.

The engine in the Gt40 has had leaky core plug on coolant. Left side of engine just above engine mount. It has been done twice now by garages to fix MOT advisories.

Well MOT on Thursday and another advisory as the damn thing is leaking again and the one further to the rear on the same side is starting to weep too.

So how hard are these things to fit and get to seal,properly? What is the trick?. Or do I get it machined for screw in plugs?

Do you have to ream out the hole to ensure perfectly round for a watertight fit?

Or use a sealer and if so which one?

Ian


Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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Re: 3.9 V8 Rover Block Core Plugs

Post by ChrisJC »

It depends why it's leaking.

I had some rust through from the inside, even though I used that fancy pink antifreeze.

Consequently, I took the engine out and changed them all for brass core-plugs rather than plated steel ones.

Chris.
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Ian Anderson
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Re: 3.9 V8 Rover Block Core Plugs

Post by Ian Anderson »

Thanks Chris,
Last replacement was done December 2019 so less than a year, so doubtful it is rust through.perhaps the one further to the rear which appears to be original and is now,weeping.

I think I will attempt this myself this time as the professionals have not got it right.

Do they go in dry or need a sealer added?

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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Re: 3.9 V8 Rover Block Core Plugs

Post by GDCobra »

Did mine a couple of years ago and seem OK so far (fingers crossed) they had rusted through from the inside, coincidently (or not) just after I changed the anti-freeze. I did put a bit of sealant on them but I think most got wiped off on entry.
You need to make sure the hole is good with no gashes in the side from previous plug removal.
I think the key to this is getting them in square, I did try doing mine with the engine in the car but could not get a good square entry so took the engine out in the end, only way to do it properly on my case.

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Re: 3.9 V8 Rover Block Core Plugs

Post by ChrisJC »

I used a good smear of sealant when I did mine.

I also took the engine out and did the lot, and found a couple more that were not far off perforation!

I rather think that the pink antifreeze is acidic if you make it too strong.

Chris.
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Re: 3.9 V8 Rover Block Core Plugs

Post by GDCobra »

ChrisJC wrote:
Mon Nov 16, 2020 9:37 pm


I rather think that the pink antifreeze is acidic if you make it too strong.

Chris.
Must admit I did think that as mine went after I used that stuff, switched back to blue after

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Re: 3.9 V8 Rover Block Core Plugs

Post by Ian Anderson »

I have heard on another forum that the core plugs should be Aluminium not steel or copper as heat expansion is all wrong and causes leaks.

So I tried mine with a magnet and the magnet sticks!

Purchased fro Rimmer so I thought they would be good, but hey who knows!

Anyone have a source of Ali core plugs or is this bloke wrong on that?

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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Re: 3.9 V8 Rover Block Core Plugs

Post by SimpleSimon »

Genuine LR plugs never had any issue and a smear of Wellsel, Shellac, Permatex etc when fitting, theres some moody aftermarket ones out there :cry: G48 coolant the preferred its non OAT etc
TVR Chimaera RV8 Mods & Megasquirt

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Ian Anderson
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Re: 3.9 V8 Rover Block Core Plugs

Post by Ian Anderson »

Ok Car is coming out of hibernation and time to her this core plug sorted.

Quick question what pressure radiator cap are you using? Mine is a Stant marked 21 to 25 psi which to my mind may be high and causing higher pressure than normal in the system causing the core plugs to weep!

Cheers
Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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Re: 3.9 V8 Rover Block Core Plugs

Post by ChrisJC »

Both of mine are bog standard P38 Range Rover ones, but I don't know what pressure they are set to...

Chris.
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Re: 3.9 V8 Rover Block Core Plugs

Post by Richard P6 »

Ian Anderson wrote:
Mon Apr 19, 2021 7:48 pm
Quick question what pressure radiator cap are you using? Mine is a Stant marked 21 to 25 psi which to my mind may be high and causing higher pressure than normal in the system causing the core plugs to weep!
Mine is 15PSI
Rover P6 4L V8
Megasquirt MS1 EDIS
5 Speed

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Ian Anderson
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Re: 3.9 V8 Rover Block Core Plugs

Post by Ian Anderson »

Thanks Chris and Richard.

Thanks to Amazon I have 3 coming in different pressures. Trial and error I guess but willl start with the 7 lbs then 11 and then 15.

Certainly be easier on the core plugs so long as it does not boil, but it seldom gets into the mid 90’s

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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