Smoking a little when idling, More on acceleration

Hello! So I’ve been having an issue with my Mx5.

On Idle smokes a little bit hesitant on acceleration and loads of smoke. Coolant Level hasn’t really changed at all over the last few weeks. I check this daily. HG has been done recently etc…

Any help or recommendations would be appreciated!

  1. My model of MX-5 is:Eunos Mk1 Na
  2. I’m based near: Worcester
  3. I’m looking for technical help or recommendations on: Diagnosis

Hi D, Just pop the colour of your smoke on here as it will help others to offer a diagnosis.

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Colour of smoke, hope that helps :slight_smile:

Ive just uploaded a picture :slight_smile:

Hmm picture with bluish smoke suggests oil being burnt. Coolant gives white smoke (steam).
Have you (in increasing amounts of effort)
a) checked oil level
b) checked for emulsion on the inside of the oil-filler cap
c) checked the PCV valve has not jammed open
d) checked for oil on the spark plugs.

If no emulsion (from blow-by with worn bores or damaged rings or piston), and PCV rattles OK and you can only blow through it one way, then I would suspect either worn inlet valve stem seals or head-gasket oil leak either of which will be shown on the plugs.

If the worst case, then seek professional help.

Could be oil or coolant vapour. Put some paper close to the exhaust exit to catch any droplets. If they are oil you will soon find out. The smell also will tell you if it is oil. It looks a bit like smoke rather than steam in the picture which suggest oil. If it’s oil burning it could be either an oil control piston ring that is worn or has failed, or the head gasket. If it is coolant vapour it is most likely the head gasket. Are you able to do a compression test on the cylinders? this would give you more information. Also look at the spark plugs. If the electrodes are oily it is most likely an oil control piston ring.

Initial best guess from your symptoms and picture would be valve stem oil seal/s.
They just get a bit old and worn out like us all.
If you get that confirmed then you might as well have the valves/seats etc done as well depending on your budget and the love of your car.
You say you have had a new head gasket recently so you may have had other work done?
Then a potential piston oil ring problem…
Just my initial opinion :+1:

Valve stem seals have been done all round btw.
I’ve had the valves all lapped and done too.

Update: which is really strange, so I’ve been checking the coolant level over the last month hasn’t moved, until after the post I made earlier which is typical.

The reservoir has completely gone :weary:

Oh dear!
The picture (difficult to tell of course) did look like blue oil smoke.
But based on your update and extremely low level (empty?) coolant tank would point “towards a head gasket failure”. Even though it’s recently been replaced. Cheap one? Or perhaps not fitted/ torqued down properly.
If it was all done by a garage get it back there safely and get them to fix it. :+1: (warranty more than likely within a year).

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Hmm, maybe it was white to begin with, but if the engine continued to overheat without enough coolant it would soon become blue.

A colleague of mine lived at the top of a hill up from the seafront in Brighton and one of his favourite stories is of a crash that took almost ten minutes to resolve. He had this sequence of photos, and the smoke from half-way up was white and near the end when the police finally arrived was blue. The problem was a broken track rod and two drunken drug dealers were fighting each other for control of the car weaving up the street, slamming into parked cars on either side.

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Agree entirely. :+1: A fair few more questions need to be asked and assessed perhaps.
As if it did over heat with the guage rising and then “sort of drop back” that would indicate loss of coolant too.
Then the engine would continue to over heat and subsequently burn oil.
Let’s hope not! :slightly_smiling_face:

Thanks everyone for their replies, today i have done a Compression check, which has come back good. Im wondering if its a crack in the cylinder head…

I have done compression test and all cylinders are good, something that did happen last night was that the coolant in the overflow disappeared. Ive topped it up and I’m monitoring it too see if it happens again. Im starting to think a crack in the cylinder head maybe?

Personally I think you have reached the point to put your hand in your pocket and seek a professional opinion/assessment.
You could run it and monitor it yes, but to what potential detriment?
Certainly if you are thinking a cracked cylinder head. :flushed:
Just my opinion. :+1:

Im just trying to diagnose as best as i can really, I’ve spoke to my mechanic, so hopefully some testing soon! price isn’t an issue atm, its more trying to find someone by me that can do the work/take it on…

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When the valve stem seals were replaced, did the head come off. ?
I’ve seen (on TV) this job done leaving the head in situ.

How many miles ago were these replaced.
Was there any smoke before this ?

Some good news! Compression looks good! Which means it’s not the rings/pistons.

On to the next part still diagnosing…

It still could be the oil control/scraper piston rings. The top piston rings which provide the compression seal may still be functioning ok. There could also be a leak in the cylinder head gasket between the oil and coolant galleries that would not necessarily affect compression. Have you looked at your spark plugs yet? Are they oily, sooty or clean?

If there is cross contamination between the oil and water systems i would normally expect emulsification of both the oil and coolent content.
Perhaps it would pay you to have the cooling system pressure tested.