NB Burning Lots of Oil

[jjbradders]

Hi all
I've recently completed a complete restoration on a 1999 mk2 mx5. Took about 18 months and finished this June, in that time the car has covered about 1500 miles.

In that time, it's emptied the entire sump twice, fortunately picked up at home rather than on the road.

I'm guessing it's going to be due to the valve stem seals or piston rings. The rings were replaced and the bores honed but I didn't touch the valve stem seals. It smokes all the time which I think points (sadly) towards the rings. There's no leaks and oil pressure is excellent.

Any help much appreciated
Cheers
James

[fatjon]

There are lots of possibles. I would start with wet and dry compression tests. Normally I would be saying gummed oil control rings but not if it's had all new rings, assuming they were fitted correctly and able to move around as they should. How much was honed out of the bores, maybe too much or the finish was bad? I tend to resist just honing and re-ringing unless the wear is really minimal. A compression test will give you something to work with at least but will not take oil control rings out of the equation as they have a negligible effect on compression, just a massive effect on smoke!

Valve stem oil seals usually only leak under vacuum so they are unlikely to be the main culprit as you suspected.

[therevday]

Ive got a 1.8 mk1 thats just started to smoke like hell!!! I left it ticking over last night and when I came back to it I expected Micheal Jackson to jump out and sing thriller Mine started with smoke when it was first started and cold. I suspect valve stem seals.Compression test has to be first port of call.I can only drive mine now at night,everyone near where I live thinks we have had fog

[fatjon]

therevday said:

Ive got a 1.8 mk1 thats just started to smoke like hell!!! I left it ticking over last night and when I came back to it I expected Micheal Jackson to jump out and sing thriller Mine started with smoke when it was first started and cold. I suspect valve stem seals.Compression test has to be first port of call.I can only drive mine now at night,everyone near where I live thinks we have had fog

That is oil control rings. Classic symptom on the MX5 engine. Valve stem oil seals have a little puther for the first few seconds and on the over run and briefly AFTER a quick rev, whereas the gummed up oil control rings really belch out huge clouds of smoke that will not go away until it's warm and especially bad at idle and curiously less when driving (less vacuum above the piston during induction when the throttle is open). They get stuck in the groove and cease to scrape the bore. The vacuum above the piston sucks up the oil through the ring gaps in the compression rings and bobs your smokey uncle.

[therevday]

Fatjon any ideas on how to unseize the oil control rings? Id rather not pull the engine apart unless I really have toWe had the head off last year to do the head gasket. the bores looked fine.

[jjbradders]

Thanks for the advice!

I've set about stripping the engine down and should hopefully have the block out the car in the few days, hopefully this will work.

Thanks again
James

[fatjon]

therevday said:

Fatjon any ideas on how to unseize the oil control rings? Id rather not pull the engine apart unless I really have toWe had the head off last year to do the head gasket. the bores looked fine.

There is no way. Don't get sold any snake oil. They will be set solid with gum and hard carbon locking them into the groove so instead of jiggling around freeish they are fixed or quite hard to move. The carbon also blocks any oil they scrape from escaping. I took mine off the piston then spent a good few minutes on each piston cleaning out the groove, replaced them with new ones. Pain in the arse job but there's no shortcut. I suspect using better oil and changing more often maybe the key to avoiding it. For some reason it's more common on Mk2 engines, which is weird as I can see no difference in the bottom end that would account for it.

[MX-5 Lazza]

I suspect it's something Mazda realised too as from the launch of the Mk2.5 they started specifying full synthetic oil rather than semi-synth as specified before.

[anonymous-user]

My NA is burning oil when reaching high revs and briefly afterwards (judging from the stink it creates) but nothing really visible from the exhaust at any time - does that point to valve stem seals rather than rings? If so, can I replace those without taking the head off?

[cjb44]

fatjon said:

There is no way. Don't get sold any snake oil. They will be set solid with gum and hard carbon locking them into the groove so instead of jiggling around freeish they are fixed or quite hard to move. The carbon also blocks any oil they scrape from escaping. I took mine off the piston then spent a good few minutes on each piston cleaning out the groove, replaced them with new ones. Pain in the arse job but there's no shortcut. I suspect using better oil and changing more often maybe the key to avoiding it. For some reason it's more common on Mk2 engines, which is weird as I can see no difference in the bottom end that would account for it.

I agree, although in the past on other engines I have filled the bores with diesel and left for a couple of days and this has shifted any carbon gumming the rings. Diesel is a great product for shifting anything that has rusted or is grubby. Road laying pavers are all fitted with diesel spray kits to clean down the machine at the end of the working day!