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MG MGA - Oil Leak from Air Cleaner

Hello
This year I made a few long distance trips and every time noticed some drops of oil under the left side of the engine (1500). After long investigation I understood that the source of leakage was the front air cleaner.
I know Barney’s article of the Crankcase Ventilation and I understand that after some time of idling it could be minor oiling but I didn’t noticed any drops of oil last year.
I have to mention the engine is 900 miles as rebuilt and has a great compression and clean draft tube.
I have some ideas but no one seems me proved:
1. I increased idling speed from 800 rpm last year to 1000 rpm this year. Suction inside the air cleaner increased and began to draw some drops of oil.
2. I use FRAM paper air filter elements. Last year they were new and could absorb some amount of oil. Now the filter is wet because of oil from the valve cover and can’t absorb any more oil and it leaks from the canister.
I’d like to hear some other ideas from you.
Thank you,
Nick
Nikolai Skliadnev

Can you post a photo of the connection hose setup from rocker cover to air filter canister to be sure it is the original setup?
Mike
Mike Ellsmore

I suspect you are right with number 2. I am surprised it is enough to drip onto the floor though. Could it be that those drips are from the draft tube? Also the tappet covers can weep a bit of oil and they in the same area.
Neil McG

I had the same problem as Nick. The front filter eventually gets enough oil via the rocker cover breather to leak onto the left chassis rail below. We checked everything on the engine and couldn't come to any conclusion, so as I am using an alloy rocker cover with a breathable cap, I closed off the pipe from cover to air cleaner, and no more problems. BTW, the draft tube on the engine was completely clear.
Gary Lock

Mike,
There are photos of the vent hose. I think it’s correct.
Neil,
Oil drips exactly from the air cleaner canister onto the left chassis rail below and from the rail onto the floor as Gary said and it’s not from the draft tube or from the tappet cover.



Nikolai Skliadnev

Another photo.


Nikolai Skliadnev

Nikolai

Just a minor observation, the length of the vertical section of breather pipe where it attaches to the rocker box seems excessive to me. Mine bends almost immediately after the end of the metal stub tube on the rocker box. Does it clear the bonnet when closed? Just wondered if the bonnet bends the pipe, blocking it?

Steve
Steve Gyles

Thanks Nikolai,
Hose appears correct, can you post photo of draft tube just to confirm orientation. What are the actual compression figures? If these are all good maybe the installation of an impingement plate or demist pad in the rocker cover off take is the only way you will stop oil carry over when the car is stationary and the draft pipe is not evacuating sump gases. A change from paper filters to the K&N type material may help.
Mike
Mike Ellsmore

Nikoli

Lots of questions from myself and Mike. What does the inside of the rocker box look like? Any signs of creamish looking sludge inside the vent cap area?

Steve
Steve Gyles

I tried using paper air filter elements but changed to the original style after the front paper element oiled up to the point that the engine was not getting enough air through the front carb. If you drive these cars much you soon realize that they drip oil from various places no matter how much you try to stop it from dripping.
Ed Bell

Mike,
Thank you for advice. I will try to take a photo of the draft tube tonight but it seems to me it’s impossible to change orientation of the tube. I made a compression test just a few days ago. The compression is 160 – 165 psi depending on cylinder.
Steve,
The breather hose doesn’t touch the bonnet, really it’s not so high as it looks in the picture. I also opened valve cover a few days ago. It’s absolutely clean and looks like new.
Thank you Ed.
Do you have any explanation of this?

Does anybody else use paper air cleaner elements and do you have any leakage from the canister?
Nick
Nikolai Skliadnev

Nick

My canister is dry. When in forward motion air goes into the filter canister, up the tube and into the rocker box, so in theory oil fumes should only come down the tube when stationary. Is the draft tube blocked?

Steve
Steve Gyles

Nick - I have K&N filters on mine for last 11 years and have not so far noticed any oil in the filter housing, although they do blacken quite quickly after being cleaned. It sounds like there is excess pressure in your crankcase forcing oil spray from the rocker box ( valve cover) into the vent pipe. good luck - Cam
Cam Cunningham

If the paper filters create more pressure drop than the draft tube creates suction, then you will get backflow.
A fix could be to detach the tube from the filter, plug that hole, and put a separate small air filter on the tube, or on the rocker box inlet.
Or change from paper filters!
Art Pearse

Art x2

If the paper filters create more pressure drop, change from paper filters!

Also Ed x2

If you use K&N or original filters they are oiled to start with! A few more drops is not a problem.

But, if you do have an engine breathing problem it needs to be fixed. Pretty much involves checking that the downdraft tube and breather hose are clear. Seems like you have the correct cap anyway.
Neil McG

Steve and Neil
The draft tube and breather hose are completely clear. I think Art is right; paper filters create more pressure drop. Do you use «original» type air filter elements?
Thank you.
Nick
Nikolai Skliadnev

I have K&Ns in one car and put originals in another. The K&Ns were fitted when I got the car 8 years ago and I have never noticed an oiling problem (But I haven't looked especially). The original filters have been in the other car for a year or so and again, no known problem.
Neil McG

This thread was discussed between 12/05/2014 and 15/05/2014

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