Hi,
On my newly purchased MX5, I went to remove the plug leads. All but one would not come off the sparkplug. Three leads actually broke on the process . Had to end up breaking the plastic shroud still attached to the plug with a small screwdriver and picking out the rubber seal with a hooked pick.
Happily all off now, but a new set of leads needed. Are there any tips for ensuring this doesn’t happen again. Little dab of copperslip on the rubber seal perhaps?
Sounds like they were due for renewal anyway, new ones should be OK.
Do not use copperslip, or any other metal loaded grease! It will short out the spark. Best to just keep it all squeaky clean, don’t leave anything sticky to trap sooty diesel dust etc.
If you have the leads with the modern full-cover metal-shielded plug-end with the spring that grips the metal part of plug body, do not apply any kind of grease or goo to the insides, especially not WD40, just make sure it is all spotlessly clean. Only a silicon grease (eg MS4) can survive the high temperatures without denaturing.
In the past, this sort of thing was one of the rare occasions when WD40 was sometimes actually beneficial in not quite setting as a waterproof glue. Back in the old days (1960s) of dodgy Austin Mini electrics I found that the original WD40, once it had been applied to the distributor cap and leads inside and out, would guarantee the car to start in the dampest of conditions, whereas before with the same leads etc it was touch and go and depended on which way the car faced with the prevailing (damp) wind. Just keep it off all of the insulator of the plug, and especially avoiding near the metal body where it will cook to a nasty hard brown crust. But now, as a result of half a century of motoring experience, I avoid the use of WD40, and don’t even have a can of it.
You have been very unlucky here.
The leads usually survive far worse than this - oil in the plug wells for example.
Were the leads original Mazda?
Get a replacement set of leads, clear the spark plug holes of any debris and oil and fit without any kind of lubricant. At this stage very easy to check that leads will come free from plugs without a problem. They are usually quite a snug fit but a vertical pull from the top of the moulded part that seals on the cam cover with equal pressure using both hands has always worked for me.
If you have an oil leak from the cam cover gasket into the plug wells a new gasket will need fitting.
Rhino666, Hi thks for your advice. So i’m in a bit deeper than just just replacing spark plugs and leads. When I pulled No.1 plug the end was all rusty and I could see some water in the bore. So I’m suspecting a head gasket failure 
Compression test showed 90, 60, 60, 110 psi
Cam cover removed and found water in the cam cover. hopefully posted a picture below.
Do others agree??
We start a separate thread on my investigations
This time with photo hopefully. Yep sucess!
I was going to say that stuck spark plug leads could be caused by overheating, I’ve seen the leads melt themselves to the head/plugs. This coupled with your watery oil could well indicate head gasket failure, from experience the head has probably warped though so get it flat checked before refitting. If it has wrapped, give the valves a good lapping in too.
Rusty looking water, not looking good that.
That is common for cars that have been started for a short time to be moved around,… condensation… get her serviced and back together using new seals including the CAS, get that oil out and fresh in 10/30-10/40 semi synth for your MK 1 only , NOT fully synth as you may get as info it is incorrect, as for the HT leads sounds like they were well past there best , no need to blob any kind of lube etc on as it will work as a barrier , i would also check the pots are clean in the coil pack and not tarnished because by the sounds of it they may be, if so a bit of wire wool in there and spin it with a screw driver to make new and fresh, but do it off the roadster.
But compression does look poor?
M-m
Hi Gary
Robbie makes a good point re possibility of overheating and the stuck plug leads - was there any sign of melted/deformed rubber/plastic.
Whichever way you go with this that head needs to come off. The head sets are much, much cheaper than when I looked a few years ago.
I found this…
Not sure if this set is any good for this application but good feedback and lots sold. Seems to have everything needed including valve seals which I would think would definitely need replacing after being cooked.
Once the head is off you will be able to check if warped and see condition of valves.
Hopefully the previous owner may be able to tell you what caused the overheating. If it was a water cooling problem hopefully restricted to top end. If it has been starved of oil could be crank damage or choked oil rings.
I hope this is an easy job for you and your son but if there is any kind of bottom end damage, I would recommend a replacement engine.
Good Luck
Rob
Lets not fast forward to THE HEAD NEEDS COMING OFF, REBUILD IT, FIT A NEW ONE… just yet,OP is there signs of oil in the cooling system buddy.
M-m
Gary has already said that there is water in two of the cylinders - it is regrettably clearly more serious than condensation.
Add the compression test results and there can be little doubt in my opinion.
Head gasket failure usually means water in the oil but not always - it depends where the gasket has been breached.
All, firstly thank you from a newbie for all your help and advice.
Rob, the ebay link is very helpful £36 vs £93 from mxparts.
M-m, no signs of oil in the water. No signs of emulsified oil in the than cam cover or dip stick.
As the car has been standing for about 6 weeks the compression tests without oil in the cylinders may be a bit misleading??
Anyway, this was always going to be a father and son project. i’m sure we can fix it. its to nicer car to scrap! We get to work on it next Wednesday, head off and figures crossed its not warped.