MX-5 OC Forum

 Great result Harvey

I'd say so too...always nicer to rebuild than take a risk on a 2nd hand unit. Satisfying knowing you've basically got yourself a new engine...plus the fun of pulling it all to bits.

 Yes, Stripping the engine and rebuilding it was quite good fun and very satisfying. Getting the engine out and back in again was not. Just waiting for a  lottery win so I can build a huge workshop with a 4 post lift. I might be waiting some time!

Harvey

Lokisdad:

Smokey start up? - not any more! After the rebuild the engine started first time yesterday. Very satisfying.

Very encouraged by this. Thanks for sharing.

My 80,000 mile engine turned into a soot-chucker/oil guzzler after the winter lay-up. Good oil pressure, good compression and she starts and runs reasonably well, just a smelly exhaust and oil/soot on the tailpipe and rear bumper.

I was quoted £25 for big end bearings and £40 for rings (excluding VAT) by a local trusted machine shop/engine builder. Bearing this in mind and your experiences reported here I am sorely tempted to re-ring the pistons and fit new big-end shells myself rather than taking a chance on another used engine of unknown provenance.

Hi niggle. If your engine was OK before the winter lay up I'd be tempted to try a good flushing oil and something like Wynns Engine flush before you embark on a complete strip down. If you do strip it down be wary of very cheap parts. I know you need a mortgage to get Mazda rings ( or half a mortgage for the same thing from MX-5 Parts) but I am told they are high quality parts and should last.  If you dont have a lift it's a bit of a swine getting the engine out, although probably no worse than any other relatively modern car, so you dont want to be doing it all again in 20k or 30k miles.

Good luck whichever way you go

Harvey 

I have tried soaking in ATF a couple of times to no avail. I am going to try carburettor cleaner next and if that doesn't work then I will overhaul the bottom end after the tax disc expires in November.

I am led to believe that the bearings are ACL and the rings are NPR, both reasonable quality AFAIK. I have only done 7,500 miles over the last three years so another 20K would be more than adequate for my planned remaining period of ownership - a nice Mk3 2.0 Sport is on the cards sometime in the next year or so.

 I'm surprised by these engines gumming their rings like this. It's the sort of thing that was common in the 60's, especially with old motorcycle engines (aircooled; heat), due to the poor oil that was available. Decoke at 20 or 30K and re-ring at 60K. My dad had a new engine in 1965 at 60K in a car he'd owned and had serviced from new. Perhaps these have been run on poor oil in the past. The problem is that once the rings stick in the grooves they no longer do their job and piston blow by then adds more heat and burned deposits to completely seize them. I'd use modern high spec fully synthetic oil in these engines without a doubt.  

 I think you are right Rich about using fully synthetic oil. I plan to do a couple of hundred more miles in mine and then change to some really good stuff. Currently, on the advice of the old boy at the Mazda garage, I'm running on normal mineral oil so the new rings can bed in properly. He reckons that modern fully synthetic oils are so slippery that the essential wear needed to bed everything in does not take place. I'm new to MX-5 ownership but I do get the feeling that these engines do run quite hot and benefit from either very good quality oils and/or frequent oil changes including flushing. Am I right?

Harvey

Regular oil changes are essential for all engines. Good semi-synth oil and a new filter every 6k is about perfect. There's really no need for super-pricey oil and certainly no need to replace it any more frequently...this isn't a race engine, it's designed to be an everyday drive.

Hi Harvey, yes I would. Why hold back? What's your engine worth? I get Mobil fully synth from Halfords, £24 on offer last time, bought a couple for the MX and the Mazda 6. I've used fully synth for nearly 30 years on anything half decent that I've serviced myself from our Astra GTE in 1984. Even use it in the lawnmower.

Why try and guess how good another oil will be or use mineral because that was the oil in the days the car was produced? Back in those days the API standard was SF. Would we hunt that down from a classic car oils supplier and insist it went in because the car came with it?

We've seen how limited those old oils were. SG was introduced a few years later to stop black death blocked oilways from contamination from oil which could not cope with modern engines and motorways. Engines were being run hotter and leaner and faster and producing far more power for their size than ever before.

Ford suffered particularly with the pinto in the Cortinas and Capris. But all that was a looong time agoo. Why chain yourself to that technologoly for the sake of a tenner? If it makes anyone feel any better btw, the vast majority of "fully synths" are refined from dino oil anyway, think of them as a super refined mineral oil rather than anything different, but superior they are.

http://www.mobiloil.com/USA-English/MotorOil/Synthetics/What_Is_Synthetic_Motor_Oil.aspx

Hi Harvey,

I am hoping to be in Carmarthen over the weekend visitig me Mam. If you need A hand with anything  or A second opinion pm me your address and I'll call in. 

Regards

Simon

 Hi Simon. Hopefully I'm OK with everything at the moment and not planning to do anything more on the car until winter. However if you want to call in for a brew and a chat. you're more than welcome. I'm about 15 mls from Carmarthen and about 3 mls SE  of Newcastle Emlyn. If that's not too far out of your way let me know and I'll pm some details

Harvey

Hi Harvey

Ye be good excuse to have A drive, good road from Carmarthen to Newcastle Emlyn. Look forward to meeting you

Regards

Simon

Rich M:

I'm surprised by these engines gumming their rings like this. It's the sort of thing that was common in the 60's, especially with old motorcycle engines (aircooled; heat), due to the poor oil that was available. Decoke at 20 or 30K and re-ring at 60K. My dad had a new engine in 1965 at 60K in a car he'd owned and had serviced from new. Perhaps these have been run on poor oil in the past. The problem is that once the rings stick in the grooves they no longer do their job and piston blow by then adds more heat and burned deposits to completely seize them. I'd use modern high spec fully synthetic oil in these engines without a doubt.

Me too. My car has been run on Mobil 1 0W-40 with very regular oil changes from the time of import into the UK in May 2006 until my last oil change earlier this year. I had been lucky enough to grab Mobil 1 on promotion at Asda for the best part of three years. Asda seem to have stopped selling Mobil oils recently so I used some Fuchs 5W-40 fully synth from Opie oils instead. The engine barely used any oil at all until it was laid up late in 2011.

Not sure if it is a change of oil chemistry that has gummed the rings up or whether a brief period of lean running due to a split crossover hose that has caused the spring oil control rings to overheat and lose their temper. Pot #4 seems to be the cuplrit, possibly no coindidence that this end of the engine runs hottest in the absence of a coolant re-route?

niggle:

Rich M:

I'm surprised by these engines gumming their rings like this. It's the sort of thing that was common in the 60's, especially with old motorcycle engines (aircooled; heat), due to the poor oil that was available. Decoke at 20 or 30K and re-ring at 60K. My dad had a new engine in 1965 at 60K in a car he'd owned and had serviced from new. Perhaps these have been run on poor oil in the past. The problem is that once the rings stick in the grooves they no longer do their job and piston blow by then adds more heat and burned deposits to completely seize them. I'd use modern high spec fully synthetic oil in these engines without a doubt.

Me too. My car has been run on Mobil 1 0W-40 with very regular oil changes from the time of import into the UK in May 2006 until my last oil change earlier this year. I had been lucky enough to grab Mobil 1 on promotion at Asda for the best part of three years. Asda seem to have stopped selling Mobil oils recently so I used some Fuchs 5W-40 fully synth from Opie oils instead. The engine barely used any oil at all until it was laid up late in 2011.

Not sure if it is a change of oil chemistry that has gummed the rings up or whether a brief period of lean running due to a split crossover hose that has caused the spring oil control rings to overheat and lose their temper. Pot #4 seems to be the cuplrit, possibly no coindidence that this end of the engine runs hottest in the absence of a coolant re-route?

 Hi,

It'd be a shame if overheating has ruined an otherwise good engine. I don't know whether the split xover hose is a water pipe or air induction pipe, did it boil over?

If it's an induction pipe and it was running lean but coolant and oil were still fine I wouldn't expect it to damage the oil rings, but if it boiled over and ran a while the bores and rings could get very hot very quickly.