Can I vent my crankcase breather into the air filter?

[tonytoller]

While cleaning the engine room recently I noticed a few drips of oil from the rocker cover breather pipe which just hangs down in the engine bay (Volvo KAD42 diesel). This makes an unnecessary mess in the bilges and my first thought was to guide the pipe into a plastic bottle which I can then empty from time to time. Then I thought back to my old Mini and remembered that the breather was connected to the back of the air filter casing - problem sorted!

Can anyone tell me if there is a problem doing this. Why don't Volvo do it as standard? Perhaps the air intake will cause a vacuum in the crankcase instead of just relieving pressure?

 

[paddy01]

This is the way it's done on my friends 5.7l V8 OMC petrol, the 2 oil breathers (1 from each rocker cover) feed back into the flame arrestor / air filter.

Paddy

 

[paddy01]

I should point out that I'm a mechanical idiot who most people won't trust with a rubber hammer... seek professional advice etc.. I just make the tea and take the blame...

 

[Trundlebug]

Maybe the reason they don't do it is to help prevent engine runaway.

If the engine gets a bit hot or an oil control ring goes, the breather would be feeding oil fumes back to the air intake, which would enable the engine to run off the oil fumes even if the fuel is shut off. That will only happen with a diesel, not a petrol.

Then you have a problem - engine runaway. RUNAWAY!!!

 

[DAKA]

Maybe the reason they don't do it is to help prevent engine runaway.

If the engine gets a bit hot or an oil control ring goes, the breather would be feeding oil fumes back to the air intake, which would enable the engine to run off the oil fumes even if the fuel is shut off. That will only happen with a diesel, not a petrol.

Then you have a problem - engine runaway. RUNAWAY!!!

My Cummins-mercruiser are designed to vent back to the intake, they actually by-pass the air filter.
Before they get to the intake they do vent through two purpose made oil recovery bottles (which drain back to the sump).

I cant see an issue with your modification if it enters outside the air filter other than an increased use of air filters and bit of extra cleaning of the filter housing between filter changes, but a lot of short journeys could cause an oily mess in the air filter housing.

 

[volvopaul]

No you cannot, if you do that and by the sounds of the amount of oil/mist coming out the pipe your engine is showing signs of bore and piston wear, you will block up the intercooler matrix causing the engine to work harder and run without the correct air /fuel ratio, oil will then settle in the bottom of the intercooler casing and drip out all over the engine mount and starter motor as there is a very small drilling in the casing to allow moisture to escape naturally.

To overcome this properly a kit can be made up whereby you fit all the components from the kad 32 engine and have the proper breather filter kit which separates the oil mist and returns it to the sump, but its £350 per engine in parts alone!

I have done a few kad42/43 engines now and it really works well.

 

[Latestarter1]

While cleaning the engine room recently I noticed a few drips of oil from the rocker cover breather pipe which just hangs down in the engine bay (Volvo KAD42 diesel). This makes an unnecessary mess in the bilges and my first thought was to guide the pipe into a plastic bottle which I can then empty from time to time. Then I thought back to my old Mini and remembered that the breather was connected to the back of the air filter casing - problem sorted!

Can anyone tell me if there is a problem doing this. Why don't Volvo do it as standard? Perhaps the air intake will cause a vacuum in the crankcase instead of just relieving pressure?

Never route emgine blow-by into air inlet on a diesel engine particularly a motor equipped with a charge air cooler. You will end up with your air side swimming in oil in no time and charge cooler will become choked with partly carbonised crankcase combustion products leadind to rapid drop off in engine performance.

Simple solution is as you suggested, go to chemist and obtain plastic bottle, technical term is 'puke bottle' works a treat however you still get oil film arounf engine compartment.

Walker Airseps are piece of dung, designed for, and only work properly on Detroit strokers.

Racor CCV system is nice set up. I assume they must do kit for yout Volvo.

 

[tico]

Fully concur with LS1... My Fords breathed a bit heavy and gave a grimy engine bay... also clagged up the intercooler and killed performance.

The cure involved leading a hose from the rocker cover breather to a plastic bottle (1Ltr milk container) which had ~1" holes cut in the sides. End of hose wrapped with foam inside the bottle to act as a filter.

Not the most elegant but worked a treat.... allowed the blow past to vent but filtered most of the oil out thus keeping engine bay clean and preventing clogging of intercooler.

Just change the foam and bottle each season or when claggy with oil.

 

[burgundyben]

Never route emgine blow-by into air inlet on a diesel engine particularly a motor equipped with a charge air cooler.

I might change that on my Perks this winter then.

 

[Hurricane]

While cleaning the engine room recently I noticed a few drips of oil from the rocker cover breather pipe which just hangs down in the engine bay (Volvo KAD42 diesel). This makes an unnecessary mess in the bilges and my first thought was to guide the pipe into a plastic bottle which I can then empty from time to time. Then I thought back to my old Mini and remembered that the breather was connected to the back of the air filter casing - problem sorted!

Can anyone tell me if there is a problem doing this. Why don't Volvo do it as standard? Perhaps the air intake will cause a vacuum in the crankcase instead of just relieving pressure?

Try another approach.
I bet you are using Volvo engine oil.
I had similar problems on a pair of D12s
We switched to a better quality oil - Shell Rimula and the problem went away.
IMO and I'm certainly not an expert, the Volvo oil foams more than better quality oils.
Maybe others can comment.
It worked for us.
Might be a very cheap solution to your problem as well.

 

[paddy01]

See, I knew there was a reason they won't let me twiddle the spanners....

 

[Latestarter1]

I might change that on my Perks this winter then.

Ben

All engines breathe, fact of life, however Fairey boats are particularly prone due to 15 degree shaft angle, regardless of engine model #6 whips up a storm in the crankcase. Fords had their breathers piped to skin fitting on the hull side leading to nasty oil stain.

Here is pic of Cummins 260 fitted in Fairey Spearfish, I came up with simple arrangement in pic. Draw blowby from the 'quiet' area in the front gear case. Simple K&N air compressor filter as vacuum break, then pipe back to air filter in a loop with 'puke' bottle at lowest point to collect condensed residue then uphill to air filter.

Most of the components came from aquatic suppliers and do not cost $$

 

[tonytoller]

Thanks for all the tips

Thanks Volvopaul but the engine I noticed dripping was rebuilt last January, so I don't think that's the problem and is only a few drips - but even that's is too many. It also looks like connecting a breather to the air intake is a no,no, so I'm going to go for the plastic bottle arrangement but also try using Shell oil as suggested by Hurricane.

One other thing. Someone suggested it's a good idea to run the engine room extractor fan all the time to aid circulation. I have done this quite a bit and the outlet vent has accumulated plenty of oil staining, so it must be helping. Does anyone else have a view on this?

 

[Latestarter1]

Thanks Volvopaul but the engine I noticed dripping was rebuilt last January, so I don't think that's the problem and is only a few drips - but even that's is too many. It also looks like connecting a breather to the air intake is a no,no, so I'm going to go for the plastic bottle arrangement but also try using Shell oil as suggested by Hurricane.

One other thing. Someone suggested it's a good idea to run the engine room extractor fan all the time to aid circulation. I have done this quite a bit and the outlet vent has accumulated plenty of oil staining, so it must be helping. Does anyone else have a view on this?

All engines breathe regardless of lube oil used, fact of life. This is why actual blow limits are listed on manufacturers technical spec sheet.

In my practical experience excessive blow by CAN be down to over dilligent owners. Regardless of make always best to run a marine engine nearer the LOW mark than MAX marking. One can go back to basics, drain and refill motor with correctly calibrated quantity of lube oil and never be tempted to add a little extra just to be on the safe side. Has the opposite effect.

 

[DAKA]

Regardless of make always best to run a marine engine nearer the LOW mark than MAX marking.

Point of order sir !


About a year ago I posted to suggest all D3 owners should not run on full oil and the rest of us should consider running on 2/3 dipstick as well, my post was pissed on from all directions including your self.

 

[burgundyben]

Regardless of make always best to run a marine engine nearer the LOW mark than MAX marking.

That's useful, my port engine does that automatically...

 

[Latestarter1]

Point of order sir !


About a year ago I posted to suggest all D3 owners should not run on full oil and the rest of us should consider running on 2/3 dipstick as well, my post was pissed on from all directions including your self.

Must be getting more old and stupid than I thought.........Rarely post much regarding Green motors as I know little about them and dislike the D3 on sight.

However, you say I was a detractor so I must defer to your point of order sir!

 

[DAKA]

Must be getting more old and stupid than I thought.........

You certainly dont come across that way .

Although technically accurate my comment was only meant tongue in cheek

Cheers
Pete

 

[Greg2]

Now I really wouldnt want to disagree with volvopaul as he knows far more than I ever will but on our last boat which had KAD42's the breather pipe went into the back of the air filter. It was like that when we bought it and I thought it was supposed to be that way. Now I am wondering if it was a previous owner modification??

On the issue of air circulation I was also advised to have plenty and fitted extra fans as a result.

 

[IDAMAY]

Related Matter

I have Cummins 5.9 QSB fitted with the aforementioned Walker Airsep "dung". These recirculate crankcase air through a coalescing filter which removes oil mist. At 600+ hours these now need replacing but the Cummins quote for the filter elements is approx £225 plus VAT and I need two! Anyone know of a supplier of alternative, more reasonably priced filter elements for these engines or is it possible to clean the elements?