Oil breather pipe

[Mark R]

 

Hi all,

 

Yet another engine related post regarding my BMC 1.8! I currently have an oil filler cap with an integrated breather pipe connection on it. There is no breather pipe on the rocker cover itself. Currently the breather pipe doesn’t lead anywhere so when the engine has been running the rocker cover can become misted with oil over time. Attaching a 1/2” fuel pipe to the cap, where should this pipe terminate? Should it terminate at a through hull fitting or elsewhere?

 

On a side note, is there anything beneath the metalwork in the area marked by the blue ‘X’?

 

Mark

[Ken X]

I suspect you could change the rocker box cap for one with an integrated breather which wouldn't leak.

 

As to the blue X there is canal water under it.  It is the uxter plate and forms the top of the swim.  Best not to be drilling any holes. 🙂 The swim narrows the subsurface hull allowing the prop to pull water back.

[dmr]

Right below that blue X is the canal, water!!! never be tempted to drill any holes here 😀

[Jen-in-Wellies]

6 minutes ago, Mark R said:

Currently the breather pipe doesn’t lead anywhere so when the engine has been running the rocker cover can become misted with oil over time. Attaching a 1/2” fuel pipe to the cap, where should this pipe terminate? Should it terminate at a through hull fitting or elsewhere?

Definitely not in to the canal. Pollution and all that. If no one comes up with the proper place for it to go, run the hose in to a suitable bottle and remember to empty the oil out every so often. It's what happens with a lot of racing car engines, where the usual oil breather route isn't available.

 

7 minutes ago, Mark R said:

On a side note, is there anything beneath the metalwork in the area marked by the blue ‘X’?

The canal is below the metalwork in the area you've marked! The hull tapers in to the prop and rudder at depth, but the counter area above is in the water to a typical depth of a couple of inches.

[Tony Brooks]

I think that you have another breather on one of the side covers on the engine under the exhaust manifold. This one may well have a mesh oil trap in it, so it is worth taking the side cover off and ensuring it is clean. This one may have a hose on it terminating on the air filter

 

I would put a longer plastic hose on the breather and lead it into an old pop/milk bottle sitting on the baseplate. It can then be changed for a clean one, now and again.

 

The crankcase pressure it is venting MIGHT indicate that the engine is getting on a bit, but if it starts easily from cold and only burns minimal oil I would not worry about this.

[Mark R]

Cheers all,

 

I did think that it might be the canal, I'll keep my drill well away from there. 

 

11 minutes ago, Ken X said:

I suspect you could change the rocker box cap for one with an integrated breather which wouldn't leak.

 

As to the blue X there is canal water under it.  It is the uxter plate and forms the top of the swim.  Best not to be drilling any holes. 🙂 The swim narrows the subsurface hull allowing the prop to pull water back.

 

@Ken X having looked I've not seen anything I think would suit, is there such a thing? Is it a generic part? I have a oil cap for a BMC engine (no breather pipe attached) and that doesn't fit the aperture on the rocker cover. The cap you see in the photo doesn't seal to the rocker cover very well and tends to pop up slightly with the engine running.

[Tony Brooks]

2 minutes ago, Mark R said:

Cheers all,

 

I did think that it might be the canal, I'll keep my drill well away from there. 

 

 

@Ken X having looked I've not seen anything I think would suit, is there such a thing? Is it a generic part? I have a oil cap for a BMC engine (no breather pipe attached) and that doesn't fit the aperture on the rocker cover. The cap you see in the photo doesn't seal to the rocker cover very well and tends to pop up slightly with the engine running.

 

I have a feeling that Calcutt have fitted those caps to 1.8s. You could always change the rocker cover for a normal B series one (petrol or diesel) that would take a standard cap. Look carefully in case a rubber sealing O ring has been lost.

[Ken X]

To be honest I am more familiar with petrol BMCs than diesel. I assumed a cap with an internal breather would be available.  Other, more experienced, members will doubtless give better advise.

 

In the short term I would go along with Jen and Tony and pipe the cap into a collection vessel of some sort.

[Tracy D'arth]

BMC breathers were on the front tappet chest cover under the manifold with a gauze inside, and petrol engines; on the top of the rocker cover. The cap with a breather on is an old one, later ones were plastic and pushed inside the cover neck, no breather. Calcutt used the old parts for some reason.

I would check and clean the side breather, route the pipe to either the air cleaner if it has one or into a plastic bottle, and replace the rocker cover with a later one with later plastic cap.

[Mark R]

@Tony Brooks, it's always been like that, I don't think anything is missing,  I just think the seal is mishaped after years of service. I was hoping a new ribbed seal would be available but my searches have been fruitless. I might look at changing the rocker cover eventually but the plastic bottle idea seems more than ample!