Crank Case Breather

[Breals]

My crank-case breather pipe seems to be ejecting a fine mist which is coating everything in my engine hole with oily goop.

 

There doesn't seem to have been any significant drop in oil pressure since the engine was serviced, so I don't think there's anything terrible wrong. Should I be concerned, and are there any suggestions for preventing the mess in the engine hole?

[Alastair]

This can be cause for concern - or not . . .

 

First thing to do, is clean or change your oil filter.

 

Next, check that you are getting piston-ring blow-by into the oil . . . AFAIK, the only way to test this properly is a compression test (hello, mechanics, can you advise here?)

 

is your oil pressure going up too much?

 

I had a similar problem - cleaning the oil filter and changing the oil sorted it.

[Speedwell]

Isn't your engine a BMC1800 ? The breather should feed through a rubber hose into the air intake behind the air filter so that the mist is burnt by the engine. I imagine most engines have a similar system.

Arthur

[khaffra]

Isn't your engine a BMC1800 ? The breather should feed through a rubber hose into the air intake behind the air filter so that the mist is burnt by the engine. I imagine most engines have a similar system.

Arthur

Most engines feed the crankcase breather back into the air filter, If this is a problem put the pipe into an old beer can or something similar and the oil will stay in their ( do not seal this up though it must have a hole in it to release the pressure), you can also gauge how much oil is coming out of the engine then as well as a little bit of oil goes a long way when it is just a mist.

[Breals]

Thanks. I should mention that the oil and filter were changed in November last year.

 

I will look for an obvious point for the hose to attach to the air intake. I don't think there's a proper air filter, its just a square section tube of metal, open both ends. Being a novice, I would have thought that doing this might have harmed/clogged the engine.

 

A little bit of oil does go a long way; it had been getting into the bilge, and when I pumped the bilges on Saturday I left a huge oil slick, to my shame and horror!

Edited February 13, 2006 by Breals

[dor]

Has this just started suddenly? If so, then you need to look for a reason. Could be something causing excessive crankcase pressurisation, i.e. piston blow-by. Or maybe there is another vent somewhere that has become blocked.

 

You haven't left the dipstick out have you? - I did that once and I had loads of oil spread around the engine 'ole.

[Breals]

No, its always been like this, but I hadn't equated the mist coming out of the pipe with the gunge building up in my bilges. I can't remember whether the pipe was originally tucked inside the air intake though.

 

I'll check my dipstick forthwith!

[Noah]

Piston ring blow-by and excessive mist spray out of my (Kubota) crankcase breather. I believe my problem was caused by cylinder-bore glazing, possibly as a result of running at, or near, tickover for long periods. Since I've owned the boat I've changed the oil more regularly (with the correct spec. oil) and I've given the engine an occasional thrashing. The misting problem has now virtually gone, as has the exhaust smoking. I once rebuilt a smokey 1200cc motorbike engine that had been owned by a "very careful" elderly rider. The crankcase breather was connected into the air filter, which was dripping with engine oil. When stripped, the cylinder bores were badly glazed, due to the "pottering about" that the bike was used for. I remedied with a glaze-buster hone.

 

Just my experiences, but a possible cause of the problem. My crankcase breather now emits just a very slight oil mist which I have directed into a plastic bottle stuffed with rags. This oil mist used to coat everything in the engine bay. If the dipstick is removed with the engine running, there is just a slight spitting of oil. If I removed it just after I bought the boat, I would get covered in oil because of the crankcase pressure.

 

Noah

[Breals]

Just my experiences, but a possible cause of the problem. My crankcase breather now emits just a very slight oil mist which I have directed into a plastic bottle stuffed with rags. This oil mist used to coat everything in the engine bay. If the dipstick is removed with the engine running, there is just a slight spitting of oil. If I removed it just after I bought the boat, I would get covered in oil because of the crankcase pressure.

 

Yes - this rings true with me because my dipstick popped out (steady!) last sunday, and virtually all my oil gushed out into my bilges (luckily I heard the hiss and stopped the engine). The diagnosis was excess pressure in the crankcase, and the advice from the mechanic was 'live with it until the engine dies, then call us and we'll fit a lovely new Isuzu unit'. Because reconditioning the current engine wouln't be cost effective.

 

But what do you mean by 'glaze-buster' hone?

Edited February 24, 2006 by Breals

[John Orentas]

Yes - this rings true with me because my dipstick popped out (steady!) last sunday, and virtually all my oil gushed out into my bilges (luckily I heard the hiss and stopped the engine). The diagnosis was excess pressure in the crankcase, and the advice from the mechanic was 'live with it until the engine dies, then call us and we'll fit a lovely new Isuzu unit'. Because reconditioning the current engine wouln't be cost effective.

 

But what do you mean by 'glaze-buster' hone?

 

 

If your gearbox and other parts are ok there is no reason at all why reconditioning your engine or fitting an exchange unit would not be very cost effective, though I would concede that a new engine unit would be more profitable.

 

As Noah says it may only require a little attention, perhaps new rings and the bores cleaned up, hones come in various types but a basically a number of small grindstones fitted in some sort of contraption which fits into a drill it re-textures and removes the work hardened areas of the bores.

 

As I have said rather too often run your engine hard when you get the chance.

[khaffra]

Have you checked your breather pipe hasn't got an obstruction or is kinked as it shouldn't blow your dipstick out very easily. If there is that much pressure in there it should be almost pouring oil out of your breather.

[lymmranger]

Some engines can, over time, gunge up and block the breather system.

 

For example, (yes I know its a petrol) the old Vauxhall Cavaliers used to have a breather from the crankcase up to the rocker box where it passed through a mesh filter. If this filter was not changed it would eventually block, as would the rubber pipe to the crankcase. This would result in a very smoky engine which regularly blew out the dipstick (and subsequently the oil). Changing (or even discarding) the mesh filter and unblocking the pipe took 15 minutes and resulted in a much improved engine.

 

The point I am making is, that there can be many reasons for excessive oil pressure. You need to talk to as many owners of the same engine as you can. This will quickly build up a picture of common faults and may even result in a quick (cheap) fix!

 

Having said that, I would agree with the comments so far. A breather pipe should NOT just be lying around. It should be connected to something, to allow recirculation. This is usually at the intake side of the air filter to allow the filter to remove any impurities. You would be strongly advised to modify your installation to reinstate this! A visit to the local breakers yard should provide you with all the parts you need for next to nothing. Again ask questions of local boaters who I sure would be more than proud for you to have a look at their engine. This will soon allow you to work out the best way of doing the job.

 

Good luck and let us know if you discover something unusual...... We all learn something new every day!!!!!!!

 

[Sir Nibble]

I've just spoken to my mate Owen who runs "Amber diesels" next door to me. I showed him your posts and he is confident that your problem lies with an obstruction somewhere in the breather system. The logic goes that there is no way to blow the dipstick out if the breather is unobstructed, and that degree of blow by would show up as difficult starting, lack of power and clouds of smoke.

[Breals]

The breather pipe had (has) a dip in it where it sags (currently it is connected to on old defunct bilge pump outlet). If the oil condensed in this and collected at the low spot, that might have blocked the pipe while the engine was running. Tomorrow I'll sort this pipe out and try linking it to the air intake as suggested.

 

I've just befriended an engineer at Diglis, so I hope he'll be able to have a look and give me some advice. But I don't want to spend much on the engine as it's never going to be completely satisfactory, I feel!

Edited February 24, 2006 by Breals

[Keeping Up]

The breather pipe on my engine was originally made of plastic, but I had to replace it last year when it cracked and split. I used a length of rubber cooling-system hose that I bought from Halfords, ie it was designed to carry hot water, and now I find that the outside of the hose always seems to be oily. Does anybody know if rubber hoses are oil-permeable?

[Guest]

Some engines can, over time, gunge up and block the breather system.

 

For example, (yes I know its a petrol) the old Vauxhall Cavaliers used to have a breather from the crankcase up to the rocker box where it passed through a mesh filter. If this filter was not changed it would eventually block, as would the rubber pipe to the crankcase. This would result in a very smoky engine which regularly blew out the dipstick (and subsequently the oil). Changing (or even discarding) the mesh filter and unblocking the pipe took 15 minutes and resulted in a much improved engine.

 

The point I am making is, that there can be many reasons for excessive oil pressure. You need to talk to as many owners of the same engine as you can. This will quickly build up a picture of common faults and may even result in a quick (cheap) fix!

 

Having said that, I would agree with the comments so far. A breather pipe should NOT just be lying around. It should be connected to something, to allow recirculation. This is usually at the intake side of the air filter to allow the filter to remove any impurities. You would be strongly advised to modify your installation to reinstate this! A visit to the local breakers yard should provide you with all the parts you need for next to nothing. Again ask questions of local boaters who I sure would be more than proud for you to have a look at their engine. This will soon allow you to work out the best way of doing the job.

 

Good luck and let us know if you discover something unusual...... We all learn something new every day!!!!!!!

 

Lada's did exactly as you describe and I am told that VW Golf/Polo were the same (no personal experience). I would guess from the way this engine is misbehaving that something isn't brathing somewhere.

[John Orentas]

Apologies to everybody but it must be said that if an engine is pressurising it's crankcase, or breathing heavily it means that exhaust gasses are getting past the pistons, there is nothing subtle about the cause and there is not likely to be any subtle cures either.

[Alastair]

It can also be coolant (if you aren't running an air-cooled engine). If it is coolant, chances are some of the oil will resemble mayonaise.

[khaffra]

Apologies to everybody but it must be said that if an engine is pressurising it's crankcase, or breathing heavily it means that exhaust gasses are getting past the pistons, there is nothing subtle about the cause and there is not likely to be any subtle cures either.

 

John

All crankcases get some pressure in them and if even on a good engine the breather becomes blocked it will blow out the next easiest thing, To blow out the dipstick would require an awfull lot of pressure that should not be possible without a breather problem ,

 

I had a motorbike that got its breather pipe kinked that went to the airbox, that was a perfectly good engine and created enough pressure to blow out the oil seal by the sprocket.

[John Orentas]

John

All crankcases get some pressure in them and if even on a good engine the breather becomes blocked it will blow out the next easiest thing, To blow out the dipstick would require an awfull lot of pressure that should not be possible without a breather problem ,

 

I had a motorbike that got its breather pipe kinked that went to the airbox, that was a perfectly good engine and created enough pressure to blow out the oil seal by the sprocket.

 

"All crankcases get some pressure in them".

 

Sorry, doesn't work like that, no blow-by equals no pressurisation. I can take the filler cap off my car and no gas is emitted at all, and that has done 120,000 miles.

 

Since you mention motorcycles some used to have timed breathers so there was actually a slight vacuum in the crankcase.

[khaffra]

"All crankcases get some pressure in them".

 

Sorry, doesn't work like that, no blow-by equals no pressurisation. I can take the filler cap off my car and no gas is emitted at all, and that has done 120,000 miles.

 

Since you mention motorcycles some used to have timed breathers so there was actually a slight vacuum in the crankcase.

 

Your crankcase has no pressure because of your crankcase breather pipe, try blocking it up and your crankcase will pressurise and will blow the easiest thing out of the engine, no matter how old the engine is this will happen.

[John Orentas]

Your crankcase has no pressure because of your crankcase breather pipe, try blocking it up and your crankcase will pressurise and will blow the easiest thing out of the engine, no matter how old the engine is this will happen.

 

 

I think we should agree to differ.

[lymmranger]

steady John.....

 

time for another pill!!!!

 

 

seriously though, the Cavalier problem I previously described was a common fault, caused purely due to a blocked breather system.

 

It resulted in dipsticks blowing out, seals popping and I have even seen filler caps popping off. Clearing the blockage fixed the problem instantly with no lasting effects on the engine.

 

You are quite correct though, exhaust gases blowing past sloppy piston rings will have a similar effect

[Cafnod]

Hi Breals

Are you moored at Diglis basin? We are in Worcester tomorrow (Saturday) to do some work on our boat, which is moored at Lowesmoor, possibly we are there Sunday too. If you would like an on the spot second opinion PM me and I will give you my mobile number.