1275 breather issues

[KoppaK]

Has anyone got any real world advice on slowing down the oil drip from the back of a 1275 Midget engine fitted with hif44. The engine isn't in its first flush of youth but didn't lose anywhere near as much oil when it was fitted in the Midget it was pulled it from. The breather sysem at the moment comprises of a pipe from the timing cover canister to the carb, non vac side of butterfly and a small pipe from rocker cover into air filter.I'm thinking I may need to add a pcv valve and go to the manifold but which valve and how ? I have a refundant servo connection in the ally manifold already so maybe could use that ? Gratefull for any assistance on this, cheers John

[MikeNash]

Dear KoppaK,
I'd check that timing cover canister first; it could be blocked. See the troubles I had here!
http://www.mmoc.org.uk/viewtopic.php?f=4&t=59324
I don't think you can too have many CLEAR breathers!
Regards, MikeN.

[KoppaK]

Thanks Mike, already been there, it's clear

[bmcecosse]

The PCV is the way to go, esp as you have the servo connection handy.

[philthehill]

I have suggested previously that the mini clutch housing bolt on breather is attached to the unused fuel pump aperture on a 1275cc 'A' series.
Here is a link to a photo of a Minor fitted with both a 1275cc engine and the mini breather.

http://www.pioneer-automobiles.co.uk/Mo ... _1505.html

http://www.minispares.com/product/Class ... sic/clutch housing breather.aspx|Back to search

[IslipMinor]

The standard in-line Midget 1275 breather system is a hose from the timing cover oil separator to the carburettor, a blank rocker cover (no connections of any kind) and a 'vented' oil filler cap. With the open breather to the air filter, or any other open breather, you cannot create the essential 'partial vacuum' needed to restrict oil seepage through the rear scroll.

The 'closed circuit' breathing system draws clean air through the filter in the oil filler cap, down through the head and crankcase and into the timing cover and through the hose into the inlet system and out through the exhaust. The filler cap is designed to pass a restricted amount of air, so that the 'suck' from the carburettor connection maintains a slight vacuum in the crankcase and helps to keep the oil inside the engine. Neutral or even worse positive crankcase pressure will almost guarantee a leak through the rear crank scroll.

This only applies to in-line engines, transverse engines in Mini's etc. had a 'proper' rear crankshaft oil seal, so were not as prone to leaks.

There is a rear crankshaft oil seal conversion kit, but it does not have a good reputation, and Peter May, for example, does not recommend it very highly at all. He will sell you one if pressed, but it comes with a very severe health warning!

There will be plenty of alternatives suggested, but we have exactly that set up on our 1380 and it has worked very well for 50,000+ miles. It is not 100% drip free, maybe 98/99%!!

[KoppaK]

Now thinking about this, the engine came without a rocker cover and I have fitted an alloy one there is a very small hole in the centre of the chrome cap about 2 mm, a standard midget cap wouldn't fit it.

[bmcecosse]

Fit a cover with a breather pipe...

[IslipMinor]

Which cover? Timing or rocker cover? The 1275 engine never came with a vented rocker cover. We've been round this before, not again please.

[bmcecosse]

1275 S. Always had a vented rocker cover. It works!

[IslipMinor]

As I said, Mini engines had a proper rear seal - we are talking about in-line engines. They need a working closed circuit breather system to minimise oil seepage through the rear scroll.

[bmcecosse]

Absolutely, which the PCV applies to best effect.

[KoppaK]

It's a alloy rocker cover with a tube out of it approx 12mm id that goes to a pipe on the back of the K&N filter.

[IslipMinor]

The pipe from the rocker cover to the air filter creates an 'open' breather' system and completely defeats the objective of the purpose of the engine breathing.

The in-line A-Series engine needs a good, working closed circuit system - either the earlier PCV connected to the canister on the timing cover (1098 engines had the pipe from the front tappet cover canister to the PCV), or on the later 1275 engines from the timing cover to the side of the carburettor. It sounds like you have at least some of the later system - timing cover to HIF44.

Try blocking the outlet from the rocker cover, make sure that you have a clear 'vented' oil filler cap and see if that reduces the leak.

There is no oil separator on the rocker cover and venting from it into the K&N air filter may have partly/completely clogged the filter with the oily fumes - I would check this as well.

[KoppaK]

Ok thanks, I'll give it a try

[smithskids]

The medium speed diesels I used to work on had crankcase extractor fans fitted and used to run at 1/2" water gage vacuum. Some of the Blackstone engines used a venturi system worked by the turbo air pressure to create a vacuum in the crankcase also. This was to prevent crankcase explosions and reduce oil leaks. Bigger engines even had crancase explosion doors fitted with non return valves .

[KoppaK]

Update: I changed the rocker cover for a MG Metro one I had in the back of the shed with the original type MG cap which hreathes but not sure if it's enough/too much. Fitted an inline Volvo Amazon PCV I had kicking around and ran the car for approx 20 minutes while I reset the carb etc. Couple of drips while it was running then about 10 after it was switched off so much better, get the feeling it's as good as it's going to get, will get a better idea once it's properly on the road I guess.