First post here after lurking for a while. Recently picked an NB 2.5 MK2 (2004) with 140K miles. Bought it off my Dad who had no issues and as soon as I get my sticky mits on it, it’s all gone wrong…
First drove it up from Liverpool to Bristol and no issues. Been on a few shorter drives in my few weeks of ownership and again no issues.
Doing some motorway driving recently and noticed the temperature gauge was maxed out. Stopped off on hard shoulder to let it cool and carried on - same thing happened.
I topped up the coolant and got home (slowly) and when I checked the next day, the car would judder and stall after a few seconds. I noticed the ignition coils had melted. Ordered a new set along with new spark plugs and managed to get the old coils out (piece by piece) with some compressed air shot in for the remainders. Car now idles and seems to run much better,
Take it for a test drive and the power seems very low. Since done a compression test and got the following numbers with the throttle fully open:
Cylinder 2 and 3 are clearly very low and I noticed a bit of oil in Cylinder 4 when changing the spark plug.
Adjascent cylinders with low compression could be a head gasket issue, but it could also be a miriad of other issues. My next step would be to do a leak down test but I’m just looking for some guidance or advice on anything else I can do or what people have done who have had a similar issue.
I smell cracked piston rings but what came first with the damage?
Hypothetically.
You may have to end up lifting the head…but I guess you suspect that anyway.
If you need a replacement mill talk to Prestige Mk2.5 Spares Specialists on PhartBoak.
They are pretty cheap.
I don’t think these engines financially merit strip rebuilds.
2/3 hours out with help, 4 to 5 hours in.
Been there…but my Mk1 right enough.
All assuming it’s not terminally porous around the chassis rails, sills, and arches of course…
In which case…?
If you do need a head gasket, please shell out for a pukka Mazda effort.
Probably, my money would be on a gasket failure across the central land between cylinders 2 and 3 caused by overheating. Cause of overheating could be lots of things including excessive blow by on cylinders 2 and 3. If you have a bore scope then you could see what the piston tops and the cylinders look like. If not then the only way is head off at which point you should be able to clearly see the problem. Anything else is guesswork.
The trouble is there is an expectation that for a given set of symptoms there will be a quick, easy answer. In most cases you need to spend time on diagnosis until you can narrow down the cause and even then there may be multiple reasons. The probability is that you’ve got it right but there is hardly ever a guarantee….
In reality every day is a learning day even for some things which appear simple at first glance.
I really really hope I’m “amateur” wrong for the guy.
The presence of oil is mostly what I do not like.
Bad, expensive memories.
I deserved it really for track-caning an old tired engine
If the engine got hot enough to melt the coils then the blown head gasket could well be the result of a warped head between cylinders 2 and 3. Either way the head needs to come off to investigate further.
I would find your local mx5 people and have her checked, sounds like a blown head gasket or head warp, its not as expensive as you think to get the head removed and re skimmed and fitted, but why did she over heat in the first place , that needs to be solved also, i highly recommend fitting a aftermarket temp gauge to these roadsters that does work correct , the problem with the OE gauge is that they are dampened and stop at 70 odd to give “that piece of mind” at dead top,the roadsters run at around 98 degrees( hence the great heaters) if they ever start to move off top dead on the OE gauge , get parked up sharpish and turn her off you are getting into around 120 and climbing, and its a alloy head on these engines, so it does not take much to warp one.
sorry but the lesson here is keep an eye on the gauges, we have all been there at some point, but sort out the reason that caused her to over heat so it will not happen again.
M-m
My '93 Mk1’s gauge has registered a “2pm” all it’s life.
It does not overheat? Perhaps just different.
Think the Mk.2.5 does 12 O’clock TDC right enough.
Don’t wholly trust 5 gauges much from what I’ve read over the years!
Its not different ,The needle as been removed at some point and re fitted incorrect, remove the needle, run the roadster to operating temp( when the fan kicks in) and push the needle back on at TDC , but if you are use to it there for the reference it is giving ,then leave it be, they are all set to TDC at the factory.
M-m
