I am worried now

Technical Area Engine, Transmission, Exhaust etc
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  1. My model of MX-5 is: NC
  2. I’m based near: Cheshire
  3. I’m looking for technical help or recommendations on: Smoke

I have just had the thermostat changed (plus new coolant) and a new car battery fitted literally last week.

Today I cleaned the car and took it out on a drive. When returning I noticed the exhaust trim a little coaked up. I rev’d the engine to 5000 rpm and saw quite a bit of white smoke coming out of the exhaust.

Usually I would worry but I dont think it happened before the thermostat was replaced. It has been serviced recently as well.

Could it be the engine sorting itself out from being running incorrectly for probably years before I bought the car due to the thermostat being stuck open?

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How long was your drive, did it get properly hot? White smoke suggests water vapour/steam. Usually seen after a cold start, occasionally and ominously when there is a head gasket leak. None of the recent work involved removing the cylinder head presumably?

It’s possible there was a lot of condensation in the exhaust and you have just been boiling that off.

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Could it have been coked up before you left?

If you’ve been running cold then you’ve been running rich so that might be the cause. Take the car out for a good long drive to get everything up to temperature. I’d say at least half an hour to an hour which should allow the ecu to relearn all it’s stuff [you’ve had the battery off] and get rid of any remaining moisture in the exhaust system. Don’t be too gentle with it either, these engines like to rev and giving it some welly will warm things through nicely.

White smoke is hopefully just the build up of moisture from your recent drive added tot he fact that it’s not exactly tropical right now. Other causes of white smoke are usually coolant getting into the combustion somehow. Check your coolant levels regularly.

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Both those explanations above I was thinking too.

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5

And inspect the dipstick & oil cap for beige coloured “mayo”.
In all probability…it’ll be absent.

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Thanks, I think the moisture from running rich and the new thermostat is now allowing the engine to run properly and it is cleaning it out. I will keep my eyes on it. I will also check the oil and see what colour viscosity it is.

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Checked the oil, the colour is fine albeit a bit black and it is down to the minimum level, so definately needs a top up anyway. So I will order some now from amazon lol. Hopefully the problem will resolve itself.

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I won’t be the only one to tell you this, that oil level should be kept up at the max mark if you want your engine to last the course.

Do make sure you are reading it correctly first. Manual says check the level around 10 mins (or thereabouts) hot engine after switching off.
I check when engine cold, left overnight. Keep to the max mark

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The car was cold and it was on the bottom line, so I ordered 2 litres. Will hopefully be enough to top it off.

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Most likely water in the exhaust evaporating I agree. Could be head gasket even if the oil is ok, it depends on the position of failure. Sounds very much like it’s going to be simply water in the exhaust to me anyway. As suggested drive it 20/30 miles or more so it’s really up to running temperature and you should be golden.

I use an OBD reader and whilst the water comes up to 80 degrees in about 5 miles the oil temperature lags behind by a good 30/40 degrees and takes at least 12/15 miles to reach temperature.

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This is what I am hoping with the thermostat changing how the car is running. It has only occurred since having this done last week.

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It’s more likely to be that you just haven’t noticed it before.
All engines produce steam - to a degree.

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Mrbarry,

I have an OBD reader and the Torque Pro app in my 2.0 NC1.
I can’t for the life of me find an Oil Temp option there ?
Which app are you using ?

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I had the thermostat changed around 3 wks back because the perceived wisdom on here suggested my temp of mid 60’s was low. It now runs mid 80s and the last two tank fill ups have increased my MPG from 250 per tank to 280. I’m amazed it made that much difference but thinking about it, if the electronics tell the ECU the engine temp is low, it may supply more fuel in a choke like situation.
I can’t think of any other explanation… ?

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Replacing the thermostat is a job I’m going to have to do as well. My NC runs at a steady 68 degrees and fuel trims are nothing excessive but I’m getting sooty discolouration around the exhaust trim.

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I use car scanner. It’s a free app. I use a Vgate iCar pro wireless adapter that was around £18. It’s highly impressive in all honestly.

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Thanks :+1:

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Min to Max is only about 0.8 litre so don’t go pouring loads in straight away. I’d put 0.5 litres in, wait a bit for it to drain into the sump then recheck the level and add small amounts at a time to bring it to the max level.

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There is no oil temperature sensor output on the nc engine so how can this happen.

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If so much oil has gone missing then you need to find out how many miles it was since you last checked it.
Keep an eye on it from now on as it sounds like you have a problem.

Oh and check your coolant level. They are a b ugger to bleed off and quite often the water level drops some time after work is completed as air is expelled in the system after it’s been emptied.

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