OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Peculiar Oil Leak on Briggs & Stratton Quantum (?)

Good-day to you Gentlemen - my very first Post!

I'm gettng a peculiar little oil leak re-occurring on a Briggs & Stratton Quantum XTS50-powered Rover Mulch n' Catch that I purchased brand-new back in 2006, but which hasn't really done all that much work since, due to my preference for the lighter pushing-weight of my 2-strokes. In case it's helpful to the really clued-up Quantam'ites amongst you, the leaking motor's Identification Number is:
12F802-3179-B1 05050658
The following photos should give you some idea of the location of the leak. The motor itself has done about five hours of work since the leak was last cleaned away:








As you can see, the leak appears to be occurring primarily around the base of the Oil Filler Tube, but it is also extending forwards in a thin band along the gasket-line between the Crankcase and the Sump (but only on the Exhaust side of the motor). For some weird reason, it appears that the leak (or at least oily vapours from it) are somehow finding their way up on to the top of the Dipstick! If you have a good look at some of my photos, you can see how oily the top of the Dipstick is, yet how clean the rest of the motor's upper surfaces are. The motor's missing plastic trim-covers, by the way, were all removed (but not replaced) prior to the last time I cleaned away the leak (ie. about 5 running-hours ago). So it might be significant that the upper surfaces you see in the photos are not smeared with oil, in contrast to the top of the Dipstick...

Anyway, due to the preponderence of oil around the base of the Dipstick, the instinctive first inclination of many might be to suggest that the leak is being caused by crankcase oil seeping past the O-Ring at the base of the Oil Filler Tube when the motor is running, due to vibrations from (presumably) worn blades...

Well, I suppose the true cause could end up being something like that, but due to the fact that the blades aren't all that worn, and that the O-Ring in question (which is in a non-wearing application) is still in perfect condition, I'm therefore very interested in whether anyone has seen a similar leak in a Quantum before that was being caused by something else entirely...(?)

This is a terrific forum by the way! It's funny how little-ol' Australia with its small'ish population can often end up producing the best forum in one particular category or another (Woodworkforums.com being another very good example...)

Just by the by, is it possible to change the "justification" when typing a post, from the default "centred"-type, to something like "left" or "full"?

Best Wishes & Many Thanks in advance,
Mike.

Hello Moby Mick and ODK members and Guests,

A genuine welcome to the ODK forums.
Your comments on this site are most encouraging to all of us.

I'm not the technical expert here.
To me, your engine's problem seems to stem from excessive crankcase pressure -
most likely through a defective crankcase breather valve...

Our Forum engineers - Grumpy and Gadge - will offer advice to you.
Others members are, as always, welcome.

I'm not sure on the 'justification' issue. Administrator Deejay should be able
to help there.

I hope you enjoy your voyage here Moby Mick.
------------------------------------------------
JACK.

Hi Moby Mick, your engine was made on 6 May 2005, and its "manufacturing plant" is not a plant at all, but an administrative center at Briggs' head office. These factors lead me to suspect you have an early Chongqing engine, which in general is not a good thing to have. From what I've seen and heard Briggs did get that plant working properly, but it took several years.

Oil leaks from multiple places simultaneously are often a result of crankcase pressure, typically caused either by excessive blow-by (combustion gases leaking past the piston rings into the crankcase) or an obstruction in the positive crankcase ventilation system. Hence I generally agree with Cyberjack, though I add the possibility that your engine has leaky piston rings due to them potentially being poorly made, poorly fitted, or both. Alternatively the bore may have been poorly machined.

Dear Jack and Grumpy,

Many thanks for your two excellent replies; The scales literally fell from my eyes as I read them. Yes, of course - excessive crankcase pressure!
It makes so much sense now that you have suggested it, for several reasons...

Firstly, if we are talking about oily vapours under pressure (rather than oil in liquid form) it would be so much easier for them to defeat the O-Ring in question (still in perfect condition!) at the bottom of the Filler Tube...

Secondly, pressurised vapours would have no trouble making it up to the top of the Filler Tube and defeating the seal up there under the Cap (as evidenced by the photos)...

Thirdly, it would explain why the problem has persisted since I changed the oil 5hrs ago, even though I swung over at the time from SAE30 to 20W40 in the hope that the thicker product would cure the leak (in the event that the O-Ring was indeed the culprit). Vapours obey no viscosity laws, regardless of the rating of their parent oil...

Fourthly, it would account for why the thing's Plug has been consistently dark around the cylinder-end of the threaded section, since the motor was brand-new. Have a look at this photo that I took just this arve:



This is more or less how the Plug has looked since new. The electrodes actually used to be even darker than what they appear to be in the photo, but the recent change to the thicker oil seems to have agreed with them, which would be consistent with the "blow-by" theory...

Now, with regards to the cause of the said excessive pressure, it surely can't be a blocked Breather (surely?), because the problem has been there since the motor was new, and I've always been reliable with the oil-changes since then anyway. Nonetheless, does anyone know offhand whether they are serviceable? I had it off 5hrs ago and never gave it a second thought at the time, because I was distracted with "O-Ring"-type thinking...

At any rate, I like the "Chongqing-Crap-Manufacture" theory a lot, because something like a slightly "out-of-round" Bore would transcend any counter-arguments citing the motor's newness and lack-of-wear, and would readily explain the dark Plug colour since new. I actually took the Mower back under warranty only 6mths after purchase back in 2006 to complain about the Plug-colour (thinking that it could be indicative of excessive mix-richness), but the mower shop couldn't find anything amiss. I'm now wondering if the buggers bothered to check the compression? Well, it's a good excuse to buy myself a Compression Guage I suppose. That would surely be the best first step in determining whether the culprit is the Breather or Blow-By... Hmmm... Maybe I should also try putting 2-stroke oil in it...(Joke!)

Once again, Many Thanks Gentlemen, and if I don't speak to you again before Christmas - Best Wishes to you both!

Moby (but with an imagined "W" between the "O" and the "B") Mick...

Mick, you can inspect the positive crankcase ventilation valve if you want to: it is built into the cover over the valve chest, on the side of the crankcase. You can find it by back-tracking the breather hose that goes into the carburetor. Here is the instruction on it from the Briggs manual:


If the valve is clear, and the valve chest is clean, I think you can be fairly sure it is a blowby issue.

Thanks a'Muchly Grumpy for another excellent reply!

I will check that valve sometime over the next week or so. In the meantime I'll start sniffing out what's available out there in the way of Compression Testers, in anticipation of the valve appearing to be in proper order when inspected. I'm fairly certain from memory that the Valve Chest was quite clean when I had the Breather off 5hrs ago. Anyway, we shall see. I'll post again when I know a bit more.

T'will be a fairly underwhelming feeling if it turns out to be Blow-By, considering that the Mower was not much under $600 to buy. C'est la vie, I suppose...

Well, I hope Santa brings you something very nice as a reward for being so generous with your time throughout the year to me and quite obviously a plethora of needy others!

So Best Wishes Again!
Moby Mick

Compression testing is not all that good a diagnostic tool on side valve Briggs engines, Mick, because of a patented Briggs feature called EasySpin. This holds the intake valve very slightly open during the entire compression stroke, believe it or not. Briggs therefore recommends that you assess compression on those engines by turning the engine backwards with spark plug lead disconnected of course until you find compression, then flipping the engine backwards against that compression, and observing whether it stops rotating then bounces back. A decent bounce-back is treated as evidence of satisfactory compression. Those who are inclined toward more elaborate techniques can do a leakage test instead, with the engine just past top dead center on the compression stroke, so that both valves are completely closed. This test can be rather effective, provided you have the equipment to do it, and the knowledge to interpret the results.

Some people do perform compression tests on these engines, but the result is sensitive to just how fast you spin the engine, because of EasySpin.

Right you are of course Grumpy - Compression Release, for easier starting...
Okay, so scratch a Compression Tester as a Christmas present to myself!
Well, not to worry - On with the show...

So I opened the Valve Chest up this morning, and as you can see from the photo below, it's as clean as Kleenex in there:



As for the Breather itself, it works perfectly. I blew into the disc-valve opening, and could feel air come out of both of the small liguid return holes at the bottom, as well as the vapour outlet at the top. In order to check the Breather Passage, I then blew into the top of the Oil Filler Tube and could readily feel the air coming out of the Passage where it enters the Valve Chest. Finally, to check the Breather Tube, I removed the Air Cleaner Base, and stuck a Blow Gun into the Carburettor end of the Tube, and was able to feel air entering the Valve Chest at the other end. So the whole Crankcase-ventilation setup appears to be working fine...

Now, as regards compression, I performed the backwards-bounce test as you suggested, and the amount of bounce that resulted seemed quite exemplary. So I'm scratching my head again...(?)

Just by the by, do you happen to know whether this vintage of Quantum is happy to run fully-synthetic oil in it? Some older car engines don't seem to be. I ask because I'm just thinking that some synthetic oil might palpably decrease the amount of vaporisation that is occurring in the crankcase, to the point that even if blow-by was still happening, it might no longer result in the leaks in question...(?)

Well Best Wishes for now,
Mick.

It's something of a mystery at the moment, Mick. If you remove the cap from the oil filler tube with the engine running, does it puff much?

Briggs recommends SAE30 oil, not multigrade, but it must conform with API standards such as SG and its successor standards. It makes no difference whether it is synthetic or not. You are currently using 20-40 multigrade, which will be increasing the oil consumption compared with straight SAE30. However this doesn't usually cause oil to come out from sealing surfaces. At the same time, I have to point out that a side valve Briggs engine is not a Honda: I've never personally seen one that was actually oil-tight, though I don't doubt they exist.

Please report back on how much huffing and puffing goes on with the dipstick removed, then perhaps we can talk about whether there is actually anything wrong.

That's not to bad of an oil leak for about five hours use I;ve had oil run down the side of the mower from the same leak in less than 30min of run time. The dipstick Oil Filler Tube never seem to seal right on the briggs I've worked on and use,the plastic tube seems to warp over time and not seat right. I pull it all off clean it and put a new o'ring on and plenty of Three Bond to seal it...If oil weep out of crankcase gasket seem excessive I will pull the motor and re torque crankcase bolts ...As grumpy has said a Briggs engine is no Honda oil and fuel weeps seem to be the norm from the working on them I've done.. Hope that may help all the best in working it out.

Roger on that Oil-Cap-removal test Grumpy - I'll get back to you sometime after the weather breaks enough up here to take the unit outside and give it a run...

Thanks for the crossed-fingers Chris. If this is anything like par for the course with Briggs, then like I said earlier - it's all a bit underwhelming for an owned-from-brand-new mower...

Gents, I had a 3rd or 4th-hand Classic-type 200-series a few years back, and I can't remember it having oil leaks anything even remotely like this one has. Mind you - from memory - I think the Oil Filler was a short-little, all-metal, screw-in affair, that screwed directly into the lower crankcase (so there were no O-Rings involved at the bottom, nor rubber seals up at the top under the lid...) Hmmm...

Anyway, we'll see where it all goes from here. Will get back to you when I can Grumpy.

Best Wishes and Thanks Again,
Mick.

Hello Grumpy,

Well, I took the machine outside this afternoon, and performed that Oil-Cap-removal test you requested several times. The result each time was that the motor didn't miss a beat at any stage, nor huff and puff or chug in any way shape or form. I imagine that you will interpret that outcome as meaning that there is probably a pretty good seal being formed in the bore by the piston rings...

Just by the by, I was a little surprised by just how many small oil droplets were getting flicked up high enough to make it out of the top of the Oil Filler Tube when the motor was running with the Cap off. There was truly a steady supply of them!
I can see now from looking at the Exploded Parts Diagram for this motor that it does indeed have a dedicated Oil Slinger, but I was still surprised by the amount of spray because I was hitherto under the mistaken impression that only the I/C variants ran Slingers. In light of this, and given that it appears that the Rings and Bore are probably in good order after all, I'm swinging back to thinking that the problem could be due to liquid-form oil, after all. Or in other words - a case of poor sealing from the O-Ring (albeit still in perfect condition) at the base of the Filler Tube, as well as from the Seal under the Cap...

Mind you, that still wouldn't explain why the Plug has been running dark since the thing was new - The "oil vapour" theory works better with that issue...

Any further thoughts would be most welcome!

Best Wishes for now,
Mick.

Mick, the "huffing and puffing" I was asking about, was the extent of gas blowing out of the oil filler when the dipstick was absent. The engine should not run much differently with the crankcase open: on cars, the idle speed used to pick up a bit in the old days before automatic idle speed adjustment, but you'd never notice such small effects on a mower engine.

From your description, there isn't a lot of blow-by happening, since if there were, you'd see something like a thin sphere of oil mist around the open end of the filler tube. If you've ever seen a tired old car engine idling with the filler cap removed, you'll know what I mean. Of course the amount of gas expelled from the filler increases exponentially when the engine is under load. Those of us old enough to remember the "road draft tubes" running downward from car engines prior to Positive Crankcase Ventilation, and the vast cloud-banks that used to roll out from under old cars when they attempted to go uphill, will never forget the image.

It sounds as if the only issue is that there is a mismatch between your expectations, and your engine's design and manufacturing standards.

Just to put the blow by to bed for good I'd pull the air filter and if it's dust dry there is no blow by or very little...Looking at the plug to me it could just out of tune or the mower/engine doesn't get a good workout and needs a load and worked hard..Also O-Ring's can and do fail they get flat spots and go hard not easy to see with the naked eye not here but in high pressure hydraulic systems they can and do just blow out...All engines resonate at a certain frequency that's why steel parts break/crack and fall off an engine that oil filler tube sure don't just sit there doing nothing it vibrates like crazy wearing out the O-rings... And those O-Rings have been working as a wearable part from the 1st day you fired up your mower...Oh yeah how does the engine actually run? out of curiosity what makes you pull the plug to see the burn has it not run right from new? Hope that helps its got me thinking to

You can say that again Grumpy!... The thing may not have been quite as expensive as a Honda, but it was certainly a lot dearer than a Sanli or a Gardenline, and I didn't see any oil leaks on my neighbour's example of the latter-brand when I changed her oil a while back (and the factory-supplied oil that came out of it was as thin and black as Coca Cola...)

Good thinking Chris - I did that just now, and it's clean and dry in there.

She runs very well. Doesn't hunt around for revs at all, and doesn't bog down too much when you hit the thick stuff - just changes exhaust note a little. Always starts first pull if you prime it, 2nd or 3rd pull (depending on how long since the last mow) if you don't prime. Idles very happily too, and going by sound and feel when you shut her off, she feels like there's plenty of compression up her sleeve.

I started keeping an eye on the Plug once I realised that the Carb could not be adjusted in any way (because the needles are all preset, unfortunately...), and I also wanted to see whether the Plug changed colour after the "run-in" period and the first "5hr" oil-change. Not too long after that - when I noticed that the Plug colour wasn't changing to "tan", I pulled apart the Air Filter and noticed that the factory hadn't quite packed it properly; one edge of the pleated paper cartridge was snagged on the edge of the gauze from the pre-filter, and this had allowed a "free run" onto the paper cartridge for a large amount of dirt and debris. I thought then that I had found the plug-colour problem, but kept checking the Plug all the same to see whether it came good (which it didn't...). I've toyed with the idea from time to time of running a slightly warmer Plug in the thing, but have never got around to seriously trying to do something about it.

I note your O-Ring comments, and they are fair. I suppose when I think of O-Rings actually doing some work, I think of the spindle O-Ring on a hot-water tap, which has real movement and (admittedly lower) temperature to contend with, in addition to a constant supply of muck coming down the spindle from below the tap-handle.
To my mind, the O-Ring on my motor's Oil Tube mustn't be quite thick enough, because there doesn't seem to be much resistance and effort required to pull the Tube in and out of the parent-orifice for it in the crankcase. I actually contacted Briggs a couple of months ago to ask whether they knew if the "spare part" version of the O-Ring was merely just the same thickness as the factory-installed item, but since I got redirected to Briggs here in Australia, they unsurprisingly ended up being a little in-the-dark regarding the specifications of both O-Rings - original and spare. Someone in my predicament wouldn't know if there had been a change somewhere along the way in the specification due to warranty claims and feedback, and in point of fact - the same might have happened to the Oil Tube itself, which could have grown in diameter by a smidgen since I bought my mower. Heck, I haven't even mentioned the Seal under the Oil Cap yet...

Well, I better get myself organised, because there's certainly some mowing to be done with the weather we've been having lately here in Brisbane!
Best Wishes for the New Year to both of you if I don't talk to you again before tomorrow!
Mick.

Mick, the Gardenline and Sanli both use chonda engines, which as far as the base engine is concerned, are rather accurate copies of Honda GXV series engines. Hence they don't ooze oil unless something has gone wrong. The only thing I've heard of happening to them more often than to genuine Hondas in that respect, is sludge-blockage of the PCV system. In most cases the PCV system is the same as on genuine Hondas (the exception being that a few of them use a flexible flap valve instead of a disk valve: a variation I dislike). Hence it seems that chonda owners are much less prone to changing the oil, than Honda owners. Personally, I can't blame the chonda manufacturers for making a product that appeals strongly to degenerate bogans: that is largely out of their hands.

I have never expected side valve Briggs engines - the bargain-basement items in their product range - to perform like much more expensive engines, and hence have not been disappointed by them. I used to own one, and up to that time it was by far the best mower engine I'd ever used. (Let's not dwell on what I'd used previously, in case I offend some keen collector of one of them.) Then I got my first Honda, and have never used anything else since. In due course, if I live long enough to need another mower, I'll be looking at chondas. I can no longer tolerate either side valve engines, or Honda prices. Of course I'll expect to put up with a few teething troubles with the kind of mowers that have chonda engines, but once those are sorted, I think I'll be happy.

I'll close this thread.