I’m looking for technical help or recommendations on:
Preventing engine smells from coming through air vents
Prior to my ownership, my Mk1 had a major oil leak from the CAS / Cam area which was repaired and most of the oil cleaned off the back of the engine and transmission.
When cruising, air coming through the vents is as it should be, ie clean & no smell. Ditto when stationary and engine is cold.
Once engine is at operating temp however, while cruising air is clean but when stationary, immediately get a fumey/oil smell coming through the air vents. Popping the bonnet up and same smell.
Have ruled out coolant leaks (smell is not sweet) and have replaced the gear lever gaitors to prevent odours from the transmission.
Suspect it is the old oil that is heating up and resulting fumes coming through the bulkhead / in to the cabin air intake.
I’m going to clean off as much of the oil but would it help to tape over some of the holes in the bulkhead as shown in the pic?
I would check the thermostat is opening properly, could be running a bit hot. Mine recently did the same & it has no oil leak. Fitted a new stat & all is well again.
Aren’t those holes for the windscreen washer bottle (in non-ABS car). The holes go into the scuttle, not through the bulk head. As I recall, you have a UK SE, which had ABS, and a relocated washer bottle.
You can stick tape over them, won’t make any difference.
I would check that the carbon canister (EVAP canister) and purge valve is working. The canister reduces emissions, by taking fuel vapour from the fuel tank, into a canister of activated charcoal. Periodically, the purge valve allows the fuel to be pulled into the inlet manifold. If the valve (solenoid valve) malfunctions, the charcoal will become saturated, the the petrol will off gas, creating a petrol or “engine” smell.
Check the rubber seal along the top of the scuttle is intact and properly fitted; this is important in sealing the engine bay.
Check the rubber grommet around the loom as it passes through the bulkhead is intact.
Yes, ABS and yes, have taped the holes and no difference. I had hoped the smell was coming through those in to the scuttle.
I thought about getting the underside & engine bay steam cleaned to remove all traces of oil & gunk.
I’ll check the EVAP. Quick Google shows it can be deleted or replaced, but not emptied / charcoal replaced it seems. Not sure how to check it’s working as it should be.
Gently warming the canister will regenerate the activated charcoal. It should be maintenance free. If there is a problem, its with the solenoid.
I would not recommend removing this. I had a car where a previous owner had stripped this out, supposedly to save weight. It just looked like something was missing, and I wa left with a tube plugged with a nail.
In the firewall, you will have numerous orifices (throttle cable, brake master cylinder, clutch master cylinder, loom, heater hoses), where fumes could enter. Its an old car.
Maybe you have an oil leak dropping onto the exhaust.
It’s quite crowded at the back of the engine bay to check for old oil.
If I take off the exhaust heat shield / manifold cover (if that’s what it is), would that give better access or am I best off looking from underneath? I am not savvy with the spanners mind.
Drove it this morning and the smell is definitely coming in through the heater air intake when stationary. Absolutely fine when driving.
When mine had a CAS oil leak the passenger footwell became somewhat smokey.
After fixing it I would still get a weird smell. Due to various things it was a while before I got it MOT’d, and was told I have a PAS leak (which I still haven’t managed to locate and that was 3 years ago ).
Could you be smelling burning power steering fluid?
Since the back of the engine is as you say somewhat crowded, maybe a long stick with a rag/towel wrapped round it that you can just poke down behind?
Thanks for the reply, to be honest I’m not certain but don’t think it’s PAS related unless the pipework is routed near the exhaust?
As it is only an issue when the engine is hot.
When idling at cold, no smell, but idling on a hot engine, bad smell. And that’s only when the blower is on, when off there is nothing coming through in to the cabin.
I’m going to see if I can get it on some ramps at some stage and have a good look around.
Oil leaks on old MX5s are hard to track. Cam cover gasket, CAS O-ring (yes, I know it was replaced), sump gasket, crank seal. I have a leak someplace, enough for the care to do a little wee on my drive, but not enough for me to start tearing into the engine.
Clean off the engine with an engine degreaser, and put some sheets under the car to monitor for any spots
Progress today. Removed the exhaust heat shield and got the degreaser in as many of the nooks & crannies as I could. Rinsed it all off and went for drive. Much better. I’ll go for another run tomorrow and it’s sorted.
I had a Mk1 a few years ago. One day when starting it I could smell burning, like oil. I upped the bonnet and yes there was a feint trace of smoke rising off the exhaust manifold. Switched off and had a look around, couldn’t find a thing.
Way before this I had changed the cam cover and CAS gaskets so it was all leak free for months.
The mystery still remained many start ups later, no more oily smells. Couldn’t understand it, my engine bays are usually sparkling clean so an oil leak easy to spot.
That’s interesting Mick, much the same for me, ie no obvious signs of a leak but unlike yours, my engine bay is not gleaming!
I may change the bonnet seal just in case that’s allowing engine air in to the skuttle and in to the cabin air intake. But definitely improved giving it a degrease. Got some TFR arriving later and will give that a go along with a a good rinse too.
).
it’s sorted.