Help a novice with an oil leak

RBC2404 · August 23, 2019, 02:53:57 PM

Hello,
1st time poster here. FYI: I have enough knowledge and experience with chainsaws to make me dangerous lol. My one stihl saw (MS 251C) has developed a leak from what initially appears to be coming from the bottom. Specifically what is labeled as a 1143 791 5900 - Stihl Stop buffer from the parts diagram I found. What I don't know is what this part does (I've Googled it I promise). I am asking because I was hoping to not disassemble it any more than necessary but I will if I have/need to. Could this part be where the oil is leaking from? Also please let me know if you need any other information (pictures, etc)
Many thanks,

RBC

samandothers · August 23, 2019, 10:06:15 PM

Most of my saws will leak some bar oil. If you run them they get hot then there can be pressure built up in the tank that may push some out. The saw case usually has some oil in the bottom.
I am not a repair person nor would attempt much repair. Just sharing some things I have read. Since some of it came from the internet consider the source!

RBC2404 · August 24, 2019, 04:49:59 AM

Thanks for taking the time to reply. I can assure you that this is not normal - if I fill the reservoir up and let it sit it will be empty when I go to use it again. It's leaking a large amount. I'm hoping to wait another day or so for an answer as to this parts function, otherwise I'll continue to take it apart and try to verify if its the leak as I'm currently using my larger stihl but its much heavier and frankly bigger than what I need for the wood that I need to saw now. I fell a 3ft diameter tree last week and needed that 25" bar but what I have left is little stuff and that's over kill lol. Thanks again!

Al_Smith · August 24, 2019, 07:37:02 AM

It's a blind shot in the dark attempting to trouble shoot anything over the internet .However as a rule and depending on the design it's often the case bolts becoming loose causing a leak .I have IPL's
but none cover the three numbers series and certainly nothing on this model .Some times if you store the saw on its side the leak stops or at least slows down .Doesn't cure the problem but leaves less of a mess .
I think given enough time they all leak to some degree .I wouldn't suggest storing the saw on the kitchen table which most likely would spark rather lively conversations and a predictable out come which would not be good if you get my drift . ;)

Al_Smith · August 24, 2019, 07:39:08 AM

Geeze I must have hit the wrong button and changed the font size on the previous post, disregard .I'm not shouting .Phat Phingers

thecfarm · August 24, 2019, 09:42:57 AM

On the kitchen table part,depends if you live alone. :D

Al_Smith · August 24, 2019, 12:02:03 PM

I don't have a wife ,she has passed but I have a cutey live in ..What I don't have is a dog house which most likely would be my next abode with the chainsaw until I atoned .

Al_Smith · August 24, 2019, 12:04:35 PM

You have to excuse my sense of humor. It gets the best of me some times . 8)

RBC2404 · August 27, 2019, 11:50:49 PM

I appreciate your responses and humor =)

Tropical Sawyer · August 28, 2019, 02:35:13 AM

Is the "stihl stop buffer" between a part of the saw which is on the anti vibration side and a part of the saw on the crankcase side? I think it may just be a rubber stop to prevent vibrations getting into the handles when you are really leaning on the saw in the cut and the mounts are stretching sideways.

From the diagram, it looks like there could be a path from the "stihl stop buffer" to where the oil pump is. It may be that one of the inlet or outlet lines may have come off of the oil pump or an o ring may have gone bad.

Not really sure though, the best way to find out would be to have a look at the oil pump and see whats going on.

Air Lad · August 28, 2019, 06:52:27 AM

Could do a good degrease over the area . dry off .and then check periodically for the wet spot to zero in on the cause

RBC2404 · August 28, 2019, 08:56:47 AM

That sounds possible. I've tried to attach pictures - one of the entire side:

And one - zoomed in on the part from the lower left portion of the photo:

RBC2404 · August 28, 2019, 08:58:20 AM

Wow it worked! Let me know if that helps you help me. =) now I need to figure out how to take this apart. Looks like I'll have to remove the handle to start with.

Air Lad · August 28, 2019, 03:31:45 PM

That wet bit is nowhere near the oil tank.Bit strange. Looks like residual oil that has landed there through operation

RBC2404 · August 29, 2019, 04:42:25 PM

That enlarged circle area had blobs of oil laying in it. I had to dry it out so you could see the part. I'm thinking the poster above that mentioned that a hose might have come off or something could be right. There are parts for the oiler behind the clutch (think that's the silver circle in the expanded view) so I'm hoping to find something when I remove it. I found a decent video on how to break it down. I'd take it to get serviced but they are saying 6 weeks around here and I don't have time for that. I'm not exaggerating when I say that there are pools of oil on the floor. I've had this for years, I know what a normal amount of oil is...

lxskllr · August 29, 2019, 05:43:25 PM

You may have already found a pic, but here's an IPL for the saw...

Stihl MS 251 Chainsaw (MS251 C-BEQ) Parts Diagram, Oil Pump

I agree with Air Lad that I doubt that blowup is the source of the oil. My guess is it's just collecting there.

Michael · August 30, 2019, 03:49:02 PM

That buffer stop has nothing to do with the oil leak.

RBC2404 · August 30, 2019, 06:32:35 PM

Indeed it wasnt leaking there.

Thanks so much for the parts diagram.

So I took the clutch cover and clutch out. It appears just below the Worm gear (which looked fine) is the oil pump in a plastic housing. Now I cleaned everything out (incredibly dirty down there) and put it back together and oddly it doesn't seem to be leaking anymore. However I think the oil pump is bad as I don't feel I'm seeing as much oil come off the bar when running it (against a piece of cardboard. Is there a good rule of thumb about this?

Another question regarding this picture - does everything look right? What is the red stuff I'm seeing around the shaft? It just doesn't look right to me but I really am going on instinct.

Tropical Sawyer · August 31, 2019, 08:02:47 PM

If stripping down the saw and reassembling it fixed the leak, something like an oil line may have just come slightly loose. Did you have a look for o-rings and seals while you were taking it apart?

I have no idea what that red stuff would be. The only thing I can think of is red loctite, but I have no idea why there would be so much.

As for the amount of oil, not sure if it is the way to do it, but I usually run the saw through a log. Then pull the chain up out of the bar and see if it is wet with a film of oil. If the tangs of the chain have a film of oil you won't be damaging your bar as you cut. If you can see oil on the tangs I would then suggest running it for a while before looking at buying a new pump. When I've done oil pump work before, it seems like they take a while before they really start pumping oil as much as they did before. Maybe they need to purge air from the system?

Anyway, sounds like you fixed the problem!

DelawhereJoe · August 31, 2019, 08:52:50 PM

High temp rtv silicone possibly, it gets used on some forced air pool heaters. Someone may have used it as a gasket on that saw at some point.

Al_Smith · September 01, 2019, 08:40:37 AM

I personally wouldn't get concerned about it .Chainsaws ,old Harleys just leak they can't help themselves .On the other hand Fords, Chevys and even Hondas leak after enough time .I had a Cadillac that leaked and have no doubt so would a Rolls _Royce but I 've never owned one .Just buy a bag of oil dry and don't store the saw on the kitchen table unless it's in a kitty litter box .A fact that could lead to rather lively conversation to say the least . 8)

realzed · September 01, 2019, 01:55:54 PM

If you are expecting to see oil 'sling off' and are using Stihl oil these days.. I would say you are expecting to notice something that really won't happen a lot - or at least like it might have a few years ago.
The newer bar oils especially the Stihl variety that I am familiar with, are designed to stay on the chain and bar as much as possible through the composition they build into the oil formula.
In addition the newer Stihl saw oil pumps are also designed to put out as complimentary frugal amount as possible to save the environment..
Together it makes for the easy proof of good bar and chain oiling of 'days gone by' a lot harder to gauge - but a supposedly a better situation if you are a 'tree hugger' verses a 'tree cutter'..

RBC2404 · September 01, 2019, 09:57:23 PM

It is red and rubbery however I don't think it is from anything anyone did to the saw. I bought it new 5 years ago (?) I think...

I am not convinced that it is putting enough oil on the bar. Running it against cardboard (for 20 seconds or more) to catch the spray doesn't give me very dark/visible lines... I'll try looking at the chain and bar itself. I can also fire up my larger saw and compare the two.

DelawhereJoe · September 01, 2019, 10:23:13 PM

With my 362 it doesn't use as much Stihl oil as it does with tractor supply brand bar oil, I don't know if the tractor supply oil is just thinner but it looks like it does a better job oiling the 25" bar I have because the chain stays wetter.

joe_indi · September 02, 2019, 04:08:45 AM

RBC,
Chances are that this 251 has carried over a fine tradition from the previous generation of this class of saws.
See the picture? The part having a red arrow is the tube that connects the oil tank to the oil pump.
The connector on tube that connects to the oil pump (the part marked in blue) has the tradition of coming off the oil pump and making a mess.
The Stop Buffer that you see covered in oil is a result of this. Just push the tube's end (marked in blue ) back onto the pump and it should stop leaking

Al_Smith · September 02, 2019, 07:32:38 AM

This bar oil business gets a lot more hoopla than it deserves but it does make for lively conversation .They've choked down the amount of oil as if it were the wreck of an oil tanker ,which it's not .Conversation about what's the best brand ,they all work .If you feel you must pay more go for it .
Some swear by salad oil ,some swear at it .I use it for salad myself but I cook with peanut oil .I doubt bar oil would go good on salad .
I live at one of the major cross roads of the country.I-75 and US 30 .I would venture to say ,in this county more oil falls on the roads in one day than all chainsaws drop in an entire year .On the other hand stingy on bar oil makes for sales of bars and chains which is another way to look at it .