Oil dripping from air filter housing

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KeithL
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Oil dripping from air filter housing

Post by KeithL »

On our 1098cc engine we have a hose from the breather pipe of the rocker cover to the air filter housing. After a run we also have a small amount of oil dripping from the bottom of the air filter housing, presumably having been sucked through the pipe. At an auto-jumble recently they had an original air filter housing like ours but the pipe into the air filter housing was enclosed at the end but with a small hole in it, unlike ours which is 'straight through' with no restriction (see photo). Is this why oil is being sucked in? Should the inlet pipe into the air filter housing be restricted in some way to reduce the chance of oil being sucked in?
DSC04667.JPG
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philthehill
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Re: Oil dripping from air filter housing

Post by philthehill »

There is very little suck by the air filter at the breather pipe inlet but you may have plenty of blow from the rocker cover.
What is the condition of the air cleaner in the area of the breather inlet pipe - is it oily?
To check the amount of suck at the air cleaner breather inlet - run the engine at a reasonable amount of revs and placing your finger over the end of the air cleaner breather inlet pipe see what the vacuum feels like.
If little vacuum you have got engine blow by - possibly worn rings, valve guides/seals.
I would fit the later air cleaner with the reduced breather inlet as a matter of course.
BMC did put various restrictors in place to limit engine blow by including a restrictor in the rocker cover breather outlet to limit the amount of oil/fumes exiting the engine.
After various attempts and ways of reducing engine breathing BMC/BL did fit a breather valve and breather pipe direct into the inlet manifold to overcome heavy engine breathing.

StillGotMy1stCar
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Re: Oil dripping from air filter housing

Post by StillGotMy1stCar »

Can’t answer your question, but here is a picture of hose end you described. Brace yourself it is rusty.
Air filter housing (640x480).jpg
Air filter housing (640x480).jpg (197.48 KiB) Viewed 1819 times
Regards John
KeithL
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Re: Oil dripping from air filter housing

Post by KeithL »

StillGotMy1stCar wrote: Mon Jun 18, 2018 11:17 am Can’t answer your question, but here is a picture of hose end you described. Brace yourself it is rusty.
Air filter housing (640x480).jpg
Regards John
Thank you John - at least I didn't imagine it.

Out of interest how big is the hole? I did think I might make my own restrictor.

Keith

KeithL
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Re: Oil dripping from air filter housing

Post by KeithL »

philthehill wrote: Mon Jun 18, 2018 11:11 am What is the condition of the air cleaner in the area of the breather inlet pipe - is it oily?
No, it isn't oily. The oil just seems to run down the side of the housing and drip out the bottom.

I will check the amount of suck.

StillGotMy1stCar
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Re: Oil dripping from air filter housing

Post by StillGotMy1stCar »

Sorry for a metric measurement but a 3mm drill bit fits it perfectly.
My engine is the later type that once had the Positive Crankcase Ventilation system fitted but was removed by someone, so not sure it would be of any use if you restrict it. It would most likely start leaking more from the rear crank scroll.
Regards John
KeithL
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Re: Oil dripping from air filter housing

Post by KeithL »

StillGotMy1stCar wrote: Mon Jun 18, 2018 2:47 pm Sorry for a metric measurement but a 3mm drill bit fits it perfectly.
My engine is the later type that once had the Positive Crankcase Ventilation system fitted but was removed by someone, so not sure it would be of any use if you restrict it. It would most likely start leaking more from the rear crank scroll.
Regards John
Thanks for the sizing. Good point about the oil leaking though.

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geoberni
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Re: Oil dripping from air filter housing

Post by geoberni »

Hi
My Series II was fitted with a 948cc many years ago and I just took a look; it has a Filter housing with the restrictor as in John's photo.
3mm looks about right.

And I wouldn't know what a Positive Crankcase Ventilation system was ... :-?
Berni
Basil the 1955 series II

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philthehill
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Re: Oil dripping from air filter housing

Post by philthehill »

Thanks for the reply to the question regarding air filter element condition.

Fitted to most BMC/BL vehicles at one time or another.

The cost of a new replacement valve is horrendous at around £70 plus so if the diaphragm was split/damaged or other damage occurred a previous owner may have decided to ditch the valve.

https://www.moss-europe.co.uk/valve-ass ... soc=515715

The valve is an important means of reducing oil leaks from the rear main area and other places and I would recommend it is reinstalled.
They do come up for sale on 'e' bay now and again. You will need the bracket, manifold adapter and hose pipe if not already in place/acquired.

https://www.ebay.co.uk/itm/MG-midget-br ... Sw32xa7LOZ

pgp001
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Re: Oil dripping from air filter housing

Post by pgp001 »

You might be interested in what I have just done with great success.

viewtopic.php?f=4&t=68271

Phil
StillGotMy1stCar
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Re: Oil dripping from air filter housing

Post by StillGotMy1stCar »

I thought the restrictor was part of the PCV system but as Berni’s 948cc engine wouldn’t have that system the restrictor must have been more widely used. Thanks Phil, I will reinstate the valve when I get my pickup back on the road.
Regards John
KeithL
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Re: Oil dripping from air filter housing

Post by KeithL »

pgp001 wrote: Mon Jun 18, 2018 7:29 pm You might be interested in what I have just done with great success.

viewtopic.php?f=4&t=68271

Phil
I had been following that post but I don't think I have a breather port on my carburettor to do what you did.

pgp001
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Re: Oil dripping from air filter housing

Post by pgp001 »

You can use a 1¼" SU carb from a mini which is what I now have fitted, but it is quite possible to drill your existing one and add the connection yourself.

My original carb was well worn in the the throttle spindle anyway, so it was well worth doing for that reason alone, but I get a great feeling of satisfaction now every time I look under the car and find no oil slick. :D

Phil
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