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Dart Oily Plugs

daimlernorm
Posts: 12
Joined: Tue May 02, 2017 5:48 pm
Location: Preston Lancs England

Dart Oily Plugs

Post by daimlernorm »

Hi, I recently decided to check my spark plugs, I noticed that the two front plugs
on each bank (nearest radiator) had a lot of oil on the thread of each plug, can anyone
advise the cause & remedy, the other 6 spark plugs were fine.
Thanks in advance
Norm

Vortex O'Plinth
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Re: Dart Oily Plugs

Post by Vortex O'Plinth »

Since the oil is on the threads it probably got applied as you removed the plugs. The usual cause is oil collecting at the bottom of the plug tubes due to leakage where the tubes are threaded into the head. This is a common problem with no very easy solution. The only way to stop the leakage is to unscrew the tubes and seal the interface with the head, either with sealant at the base of the tube where it abuts the head or by using a thread sealant when reinstalling. The tubes are not always easy to remove without distortion and most people with the problem just put up with it.
Last edited by Vortex O'Plinth on Tue Apr 17, 2018 10:04 pm, edited 1 time in total.
Nick

"Don't bother with the Air & Space Museum - there's nothing to see.......".

silverdart
Posts: 285
Joined: Sat Feb 13, 2016 10:49 am
Location: West Midlands

Re: Dart Oily Plugs

Post by silverdart »

As Nick says, The oil probably reached the plug thread as you unscrewed it.

If the engine ran smoothly before you removed the plugs, it suggests there is nothing to worry about.

Dave.

classiclife
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Re: Dart Oily Plugs

Post by classiclife »

Hello,

Rather than start a new thread I thought I would raise this one again.

Now that I am ticking some jobs off on my list (V8-250 saloon), I changed the spark plugs today as part of the service and noted that in some of the tubes there was a tad of oil and I understand it is one of those things - grin & bear it.

However and of note some of the spark plugs could be undone by hand, giving the impression they had not been tightened as much as they should be - in fact I would say merely pinched tight. I accept there does need to be an awareness of alloy head cross threading, but having owned alloy head cars in the past my plugs were certainly not able to be undone by hand !!

Is this purely a case of the PO not tightening them enough or could there be some other reason ?? The plugs were obviously seated okay as no rough running or other negative factors experienced.

Perhaps it is me looking too deeply at a non-existeng underlying issue, but just wanted to mention it should anyone have a view.

The plugs in the car were N5C and I have changed these to BP6ES.

Thank you in advance.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

Ian Slade
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Re: Dart Oily Plugs

Post by Ian Slade »

You don't have to grin and bear it, remove the rocker covers, then carefully remove the tubes and replace the "O" rings, or you could just try giving the tubes a nip up. When you tighten down the nuts on the rocker cover you also attempt to pull the tubes out of the head, oil finds its way to where you don't want it, always has done. :roll:
Owner since the 70's, Genghis is slightly to my left.

classiclife
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Re: Dart Oily Plugs

Post by classiclife »

Thanks Ian, that seems a logical and straight forward fix when the covers are off next time around.

Regards.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

faeton
Posts: 103
Joined: Mon Feb 29, 2016 9:31 pm

Re: Dart Oily Plugs

Post by faeton »

To remove the tubes I keep two old nuts that hold the rocker cover down .Screw one down upside down . the other on top right way up . Get two pairs of stilllsons or grips and tighten both together , put one pair of stillsons on bottom nut and unscrew , I have used this method dozens of times ,never failed . Using grips directly on the tubes can damage or collapse the tube . When replacing use a silicone fluid on the copper seal . Loctite on the thread is good but could cause difficulty next removal . The threads on these tubes are very fine , care must be taken not to cross thread

Dave

classiclife
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Re: Dart Oily Plugs

Post by classiclife »

Thanks Dave, appreciate you describing the process and certainly makes sense.

I guess from what you are saying, that there is no permanent fix and a job that needs doing from time to time. Think I can live with that !!

Regards.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

Ian Slade
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Re: Dart Oily Plugs

Post by Ian Slade »

Yes, the copper "O" seal hardens over time, I annealed mine ( heat to red heat with a blow lamp and drop in cold water) softens them nicely, though you may only be able to do this a couple or so times as they get thinner every time, but last about 7 years
Owner since the 70's, Genghis is slightly to my left.

Pinto
Posts: 44
Joined: Sun Oct 09, 2016 8:25 am
Location: Sunshine Coast Queensland Australia

Re: Dart Oily Plugs

Post by Pinto »

Hi All from down under,
What a coincidence, only yesterday I removed the plugs on my V8 saloon to do a compression test and found oil in some of the plug tubes, so this series of posts has told me where the oil is coming from, I will live with the problem.
As a matter of interest the plugs fitted by a PO are NGK BP5EY set to .030".
Regards,
David B.

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