stihl 660 chain oil leak

[Rob Stringer]

hello all, my stihl ms 660 has recently started leaking chain oil (shortly after a couple of days milling oak). I've removed the clutch to look at the oil pump etc. and can see no oil leaking from there when I run it but oil is pouring out from underneath the chainsaw. Took the oil hose and pickup out and its covered in chain oil but has no visible cracks. Was wondering if anyone had any ideas what the problem might be and if theres anything else I should check? Thanks, Rob S

[spudulike]

There isn't too much that can go wrong with the oiler mechanism. A few things to try -

 

Make sure the oiler pickup pipe has no splits in the end that forms the grommet seal with the pump.

 

Make sure the small seal is fitted between the pump and the oil outlet that connects with the bar mount oil channel.

 

Check for cracks in the oil tank and oil pump.

 

If I couldn't find anything, I would pressurise the tank and check for leakage.

 

My guess is damage or the small sealing washer is missing/split.

 

Worth making sure the bar oiler hole isn't blocked as well.

[Richard Thompson]

I know it's not ideal but if I'm looking for a leak I put fuel in the tank as it's thinner than bar oil and will find any small holes easier it also washes the tank out. I then empty out the fuel and replace with chain oil once a repair has been sorted but any thin cleaning solvent will work just make sure that it won't melt the saw ( I don't use acetone as I have melted a strimmer tank before)

[Rob Stringer]

I know it's not ideal but if I'm looking for a leak I put fuel in the tank as it's thinner than bar oil and will find any small holes easier it also washes the tank out. I then empty out the fuel and replace with chain oil once a repair has been sorted but any thin cleaning solvent will work just make sure that it won't melt the saw ( I don't use acetone as I have melted a strimmer tank before)

 

Thanks for the replies.I also sometimes use fuel to clean up the tank but in this case it'd be gushing out of the bottom of the saw so i'll give it a miss..I ran the saw with the clutch removed and could see there was nothing leaking from the oil pump or that side of the saw but oil was gushing out from underneath somewhere between the oil tank and the oil pump. The problem is I cant see exactly where and I dont want to start replacing the wrong parts..

[spudulike]

Thanks for the replies.I also sometimes use fuel to clean up the tank but in this case it'd be gushing out of the bottom of the saw so i'll give it a miss..I ran the saw with the clutch removed and could see there was nothing leaking from the oil pump or that side of the saw but oil was gushing out from underneath somewhere between the oil tank and the oil pump. The problem is I cant see exactly where and I dont want to start replacing the wrong parts..

 

Reckon the small sealing ring on the oil outlet is missing then, either that or the seal on the oil pickup pipe is split - the parts are relatively cheap, the MS660 has potential to earn lots in a day.......need I say more!

[Rob Stringer]

yep, looks like I need to order some parts..