Is it piston rings??

T

tomdmx

Well-Known Member
Joined
14 Jan 2012
Messages
157
Visit site
Reading through some forum responses I realised that my engine produces a bit of blue smoke....initially starts with some then settles down but still smokes a little (steady flow at higher revs)...the oil has dropped very little for a 24hr period (i mean not even noticeably)..it is an old lister 18hp twin so should I be worried? We are setting off to the french canals in summer so want to make sure all is ok....
 
Blue smoke is burning oil. Sounds to me like rings, I assume it's an air cooled Lister. The smoke is worse when cold because as the engine warms up, the piston swells in the liner & slows the oil loss a little. If it is an air cooled engine, should be an easy job to do. I wouldn't want to be in a French canal with an engine that starts to blow more oil out of the exhaust than fuel!
 
That's what I thought but then read some posts on here saying that its rings that need changing...so got a bit worried...but thanks for the reassurance :)
 
Could be valve stem seals. Rings don't increase oil loss as they warm up, but the hot oil does get thinner, so that if the rings are below spec it passes them more easily. With the engine warm, check if there is much blow by, by removing the oil filler cap. If it is blowing out gas and some oil spray, then it is almost certainly rings. If you strip it you can easily check the rings, by removing one, and inserting it in its bore, then measure the ring gap. Manufacturer will giuve a secified maximum for this. engines will run well beyond it, but with reduced efficiency. Ovality in the bore can be checked with the head off, using an inside caliper. Worn bores will be larger side to side than fore and aft in relation to the crankshaft.

If there is apparent blow by, block off any other vreaqthers, and block the oil filler opening with aq rag for around 8 = 10 seconds. if blow by is present, then there will be a pressure build which will release with a whoosh when you remove the rag. If it does prssurise, then the rings are shot.

Have fun!
 
Last edited:
So, this is a water cooled lister...it has two decompressor valves....i have removed the oil cap under load and no spitting out at all...
 
tomdmx said:
Reading through some forum responses I realised that my engine produces a bit of blue smoke....initially starts with some then settles down but still smokes a little (steady flow at higher revs)...the oil has dropped very little for a 24hr period (i mean not even noticeably)..it is an old lister 18hp twin so should I be worried? We are setting off to the french canals in summer so want to make sure all is ok....
Click to expand...

It is an old tech. low power engine, slow reving and with a heavy flywheel. I was fortunate enough to spend a lot of hours steering a brand new Willow Wren built narrowboat in the early seventies with a new air cooled Lister twin. From new it smoked a little on start up, also when increasing revs after idling for a while. This was considered perfectly normal. If your engine starts readily, does not consume oil at an unaceptable rate and performs well I doubt it is in need of major work. I posted on this forum about our three cylinder Yanmar which consumed oil dramaticaly. It was running on light oil for the newer Yanmar engines. A change to a good old fashioned 20/50 suitable for both petrol and non turbo diesel engines fixed it. Perhaps an oil change to an old generation heavier grade oil and some careful measuring of oil consumption may allow you to put your mind at rest-or not! Good Luck.
 
You must log in or register to reply here.

Share this page

Top