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Hi all.

I'm experiencing a strong gassy smell coming from my NB when I drive it. It seems to be coming from somewhere under the car, although I don't know where from. I don't think it's the air conditioning unit, even though we only had it fitted just around 4 months ago. Everything feels tight and the unit still produces nice cold air.

The engine, gear box and diff oils were all changed around 2,000kms ago, so I'm not sure if this would be the problem. I'm at a loss to where it may be eminating from. My only remaining guess is possibly the exhaust.

Besides the air con, the only thing that's been changed in recent times, was a new muffler to give her a bit of a growl, but I feel because this is behind us and we only smell it when we're in motion, I've kind of ruled that out as being the culprit.

Has anyone else experienced any similar troubles? Anyhow, as usual, I'd really appreciate any assistance from the mechanically minded of you out there please.

Thanks again.

When you say gassy I assume it smells somewhat like gas as in LPG, or natural gas from the stove?
Rather than USA style "gas" meaning petrol.


Anyway, assuming the LPG one, I would doubt it's the aircon, my understanding is that aircon gas is odourless (which is part of the danger working with it)

A muffler is unlikely, especially in motion, I was driving my car with no muffler fitted for a few days and no exhaust fumes (ones I could smell anyway) entered the cabin, moving or stationary.


I would suggest that it may be to do with the recently changed gearbox oil, gear oil often has a rather unique smell, somewhat like onions or garlic, and it tends to cling very well to things (my girlfriend is a mechanic who specialises in gearbox rebuilds, he clothes often stink of gear oil)

I would suggest it's possibly some spilled on the gearbox (common since yo fill them until it slightly overflows from the fill hole then wip off the excess)
or possibly just that when the mechanic has done it the stink has got into the air vents and fabric and needs a bit of an air out.


My suggestion, put the vents of fresh air, fan on full, aircon on, and windows down. Do that for a while and see if it helps clear the smell.

hks_kansei wrote: (my girlfriend is a mechanic who specialises in gearbox rebuilds, her clothes often stink of gear oil)

Excuse me for stating but that sounds HOT!

Well it seems it may be coming from the gearbox. I don't why or how, but the mechanic seems to think that's the culprit.

I drove it around this morning to get it to the point where the smell is obvious, and took it straight down to him. He smelt it immediately, and said, "yep, it's a gearbox oil smell".

I just don't understand how it could be fine one day and then have this horrendous smell eminating from it the next.

We've been all over it and can't see any leaks, and the oil has been replaced yet again.

He seems to think it may have something to do with the breather, but he can't be sure until he pulls it out. More expense!!!

Again, any advice or knowledge that you could pass on would be greatly appreciated.

Cheers, Wayne.

Could the gbox oil be leaking from around the shifter area. People always put some oil in the turret there.

Don't know yet Bruce. I'm going to take the console out this afternoon and have a look from the top, and see if I can see anything.

Thanks for your suggestion too. I don't know mate. It really is turning into a bit of a nightmare at this point. Everytime we go to a mechanic or specialist it seems to cost us $50 here and $100 there, and still no solution.

It's cost us around $300 so far with changing all the oils, and having the air con checked out etc. plus labour costs.

I shouldn't complain. I know there are many people far worse off than us, but being pensioners and not flushed with funds, it does start to wear a bit thin. Anyhow, the joys of owning an MX-5 I guess.

Thanks again mate.

Wayne.

I did have a long detailed response typed, but it seems to have gone into the ether.



SHort version is, when the console is off check for leaks, and also check if any of the carpet or sound deadener (ugly brown fluff stuff) is damp or discoloured.

Perhaps somebody spilled some gearbox oil.

Also note that that area gets quite warm as it traps exhaust heat, so as it warms up the smell would likely get stronger.

"It seems to be coming from somewhere under the car"..............what about from the boot???

Is your battery ventilated to the outside???............this is a standard feature on the NB8A and I suppose other models.

When I bought my car it had a "ring-in" battery and wasn't ventilated and I could smell gas when I opened the boot. I bought the genuine Mazda battery and had the ventilation tubes fitted and now no problems.

Stock on NA

Worth a look, but batteries tend to vent hydrogen and acid fumes, which tend to smell very different to gas (LPG/Natural gas)

Battery gases tend to be pretty acrid smelling.



Even so, worth a look since it should have the tubes attached even if it's not the cause of the smell (NB battery located under carpet on far righthand side of boot)

Can't believe no one has mentioned the gear stick inner/outer boots yet. They've probably started to split and perish - since they always do.

http://www.mx5parts.co.uk/gearlever-shift-boot-lower-mk1-25-p-259.html
http://www.mx5parts.co.uk/gearlever-shift-boot-upper-mk1-25-p-258.html

A leaking gearbox rear seal might also be the culprit, and can sometimes be hard to spot...

That's what I mentioned.

bruce wrote:That's what I mentioned.

Yea true you did.
The OP sounds like he needs a little bit more detail on the specifics though - since he's taking it to the mechanic for 100 bucks a pop.
He needs to read between the lines to know that its probably because of splitting rubber boots - and that they're basically a consumable on the car.

Anyhoos - hope you find it 5isalive. Grab a screwdriver and pull that centre console... Its only 4 screws on an NA - NB should be much the same.

Could be the Catalytic Converter some times when they go you can get a rotten egg smell
Do you get a rattle under the car, have you lost performance, do you use more fuel than you used to
These can all be signs

ndragun wrote:Can't believe no one has mentioned the gear stick inner/outer boots yet. They've probably started to split and perish - since they always do.

http://www.mx5parts.co.uk/gearlever-shift-boot-lower-mk1-25-p-259.html
http://www.mx5parts.co.uk/gearlever-shift-boot-upper-mk1-25-p-258.html

A leaking gearbox rear seal might also be the culprit, and can sometimes be hard to spot...

speaking from experience ,if the boots are split you WILL get a strange smell at running temperature from hot gear oil and grease.
NB8B should only have grease in the turret and not a lot of it.
while you are in there, check the 4 bolts holding the turret to the gearbox as they are known to loosen themselves.
to get the cosole off there is one screw each side of the console towards the front.
two screws in the centre console
one screw under the window toggle switches
i found OM boots about 1/3 cheaper to buy direct from JAPAN through ebay