Venting a Mitchell overdrive

[daveymc29]

I have been running a Mitchell O.D. in my roadster for ten years or better. It performs flawlessly except from day one it has leaked fluid out the vent line. I have raised the end of the vent as high as I can get it without boring a hole in the floor pan somewhere. Back some years we went to the Portland meet with a friend that had a Mitchell and his pumped fluid up the speedometer cable so much that it leaked down onto the floor inside the cab. Someone mentioned using a fuel filter in the vent line. I'm going to try that cure and wonder if there is something more I should know? Do I mount it horizontally or vertically? Should I go ahead and bore a hole in the floor pan and run the vent up into the area behind the seat and put the fuel filter near the end of that line? Any other suggestions and/or cures for this leaking. I filled the O.D in TX and when I got to CA it was almost totally empty, perhaps half a cup in the box when I drained it. I use a synthetic gear oil, 140 weight. Should I use something different?

Thanks for any assistance. I am pulling the O.D. out of the car and checking the inside of it for possible problems and to remove a small piece of flexible plastic hose I managed to pump in there years ago when changing the oil.

[quickchange]

Talk to Mitchells , they are a great company, Just done 2000k in mine , no loss of oil , the breather tube is fastened to floor boards on my delivery . yes keep it as high as pos , if its pushing oil out then must be building up pressure, I cant see what a fuel filter would do ? contact them for advise. Zero degrees here in NZ this morning . % weeks till the salt , get your hair driers out.

[Fred K-OR]

Originally Posted by quickchange

Talk to Mitchells , they are a great company, Just done 2000k in mine , no loss of oil , the breather tube is fastened to floor boards on my delivery . yes keep it as high as pos , if its pushing oil out then must be building up pressure, I cant see what a fuel filter would do ? contact them for advise. Zero degrees here in NZ this morning . % weeks till the salt , get your hair driers out.

Going to be a 0 here in Oregon and Washington with a 10 to the left of the first 0! Heading on Tues to the NWRM in Walla Walla, Wa where those two right 0's may be a 10.

[Synchro909]

The vent tubes on both of my Mitchell O/Ds are full of oil but the oil level doesn't drop much between services which is when I check it. I just top it up if it needs it and keep driving. I have wondered though as to whether it should do that but figure "If it ain't broke....."

[daveymc29]

I never really worried about the oil in the vent tube until over the last couple of weeks it seems to have changed. I park over some cardboard pieces and after a medium drive, say a couple of hundred miles, when I come in and park over a clean cardboard I will find roughly a cup of oil has come out of the Mitchell. I'll give them a call tomorrow and maybe run it up there for their opinion. How does the top of the box come off? Anyone had it apart?

[Brentwood Bob]

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Stupid question, but is there an obstruction at the casing?
I thought the mitchell used 30 weight, but checked the installation instructions and the spec is 75-90w.
So your 140w may be the issue.
Good question for mitchell?????
Bob

[Tom Endy]

We have probably a couple dozen or more Mitchell overdrives running around in my area where during installation we cut the vent tube to a length of about 2 inches and put the relief valve on the end sticking straight up. I saw no need to have the relief valve on the end of two feet of tubing. None have had a problem of porting oil out through the tube and valve.

Possibly the valve is defective and not opening to allow any pressure build up to vent off, or the excessive length of tubing interferes with the venting.

The Ryan overdrive in my Victoria works on much the same principal as the Mitchell and it has a metal vent valve that screws into a threaded boss on top the housing. I have not experienced any problem with oil porting out of it during the 20 plus years I have had it.

Tom Endy

[Synchro909]

Originally Posted by daveymc29

I never really worried about the oil in the vent tube until over the last couple of weeks it seems to have changed. I park over some cardboard pieces and after a medium drive, say a couple of hundred miles, when I come in and park over a clean cardboard I will find roughly a cup of oil has come out of the Mitchell. I'll give them a call tomorrow and maybe run it up there for their opinion. How does the top of the box come off? Anyone had it apart?

Please let us all know what they say.

[waxhead]

Any updates on this??

[modelAtony]

Mitchell states , do not use syn oil.