Catch can full

[Pinz712M]

Pretty new to driving an old 911, but is it normal that the oil catch can gets full.

I have a 1973 RSR tribute with a 2.8.

I had it for about 200 miles and today the catch can spilled oil all over the garage for the 2nd time. I am talking a full quart of oil in the catch can.

First time I thought they put too much oil in. So I made sure I checked the oil level while running.

Is this normal, did I put too much oil in to begin with? Bad venting somewhere?

Thanks
Christian

[scootergt3]

a catch can coming from what? your oil breather hose on top of the engine or from your oil tank?

[Pinz712M]

From the oil tank

[Rodney Nelson]

Are you talking about changing your oil? If so, typically around 12 quarts. So, if you don't have a large oil container it will overflow.

[Pinz712M]

No, after driving for a while the catch can is full and spilling oil.

[Sboxin]

Originally Posted by Pinz712M

Pretty new to driving an old 911, but is it normal that the oil catch can gets full.

I have a 1973 RSR tribute with a 2.8.

I had it for about 200 miles and today the catch can spilled oil all over the garage for the 2nd time. I am talking a full quart of oil in the catch can.

First time I thought they put too much oil in. So I made sure I checked the oil level while running.

Is this normal, did I put too much oil in to begin with? Bad venting somewhere?

Thanks
Christian

We have had the same issue with a 3.8L 964 engine in the 911 race car . . . mostly, I didn't
check/empty the catch can often enough . . .

Something else is we only fill the oil to 1/2 inch above the low mark to keep from blowing
oil out of the tank into the catch can. But, we still get oil in the vented catch can.

Most likely you have just filled to too high a level when changing the oil.

Do you have a drain to empty the catch can? Is the can only a one quart/liter size?
Is the can connected from the tank and also to the case breather - or does the
can end at the tank and have it's own air vent?

Others on this Forum may be more helpful and definitely more knowledgeable . . .

Regards,

[scootergt3]

is it the factory oil tank or a front mounted aftermarket one?

[Pinz712M]

From what I can tell, it’s the factory oil tank.

By catch can, I am being generous in saying that. It’s an old Porsche quart size oil bottle.

I don’t see any venting anywhere, the oil bottle catch cans has a “breather hole” in it

[RWebb]

dump the catch can out and recycle the oil

it should take a while to fill up

post pics & mileage, etc. for more info

[pampadori]

can you get us a picture or two of what you're talking about and how the thing is plumbed?

I added a catch can to my 3.0 because I no longer have the factory CIS and airbox. I ran the vent line from the crankcase to the catch can and then the other fitting on the catch can to the oil tank. My catch can also has a vent with a filter on top of it.

I can drive VERY hard for a couple of weeks and not have more than a couple of tablespoons worth of fluid in the catch can. Not really oil either, it smells more like moonshine.
I have less than 15K miles on my motor rebuild so probably not a lot of blow-by, which I think is what normally gets blamed for what you are seeing.

[Rawknees'Turbo]

One possibility of a rapidly filling catch can from oil tank and/or crankcase breather cover is excessive blowby past the pistons rings - the pressure this creates in the crankcase pushes the oil out.

One way to test is to perform a cylinder leakage test (leakdown test) and put your ear near the oil tank's fill spout (cap off) and see if you can hear any hissing (blowby past rings).

Another way to sort or test is to run the engine with the oil fill cap off and look to see if there is an excessive amount of oil vapor, or even oil mist, coming out when you increase the revs some. If there is not excessive blowby then you'll just see some wispy vapors, but nothing alarming.

[Rodney Nelson]

I have never heard of a catch can? Where does it come from? What is it? How about a picture?

[3rd_gear_Ted]

The oil tank fill neck is the highest point, vent line should originate there.
I located a Jaz catch can with a vent in the left rear wheel well for no oil fume mess in engine compartment. Hose runs from oil tank with thru fitting into wheel well along top of engine compartment

[Sboxin]

Originally Posted by Rodney Nelson

I have never heard of a catch can? Where does it come from? What is it? How about a picture?

Oil breather catch can in photo of 3.8L 964 race engine - yellow rectangle . . .

Breather hose attached from oil filler where original breather hose connected oil tank to
engine case breather at rear of engine - [case connection] Wrong - intake connection is blocked and hose does not
connect to engine intake - catch can has air filter on top to allow pressure equalizing (as
I understand the system) The catch can has a turn cock fitting on the bottom to remove
accumulated oil.

I hope this photo helps . . .
Regards,

[Speed metal]

So is this a necessity? (Running a catch can) Can't the breather on the top of the block go to the breather fitting on the oil tank?

[Sboxin]

Originally Posted by Speed metal

So is this a necessity? (Running a catch can) Can you run the breather from the oil tank to the intake instead?

IMHO of course - - but I don't think you will pass emission testing with a catch can system if you happen to be
in one of those areas. These catch cans I believe are used on modified high
performance engines - like the OPs 2.8L engine . . . and our race engine with cams and
12.5 CR pistons and dyno tuned ECU chip by Mr. Wong . . .

Regards,

Roy T

[RWebb]

Originally Posted by 3rd_gear_Ted

The oil tank fill neck is the highest point, vent line should originate there.
I located a Jaz catch can with a vent in the left rear wheel well for no oil fume mess in engine compartment. Hose runs from oil tank with thru fitting into wheel well along top of engine compartment

right, I also have a Jaz can - not optimal

Grady Clay* laid out the factors for a catch can in an old thread - OP needs to post pics...




* as usual...

[Rawknees'Turbo]

Originally Posted by Speed metal

So is this a necessity? (Running a catch can) Can't the breather on the top of the block go to the breather fitting on the oil tank?

In stock trim, most road cars, including 911s, vent the crankcase gases (oil tank, too, with 911s) back to the intake in order to be burned in the combustion chambers. This is not ideal from a performance standpoint, as the oily vapor can promote detonation, and also gums up intake components over time.

[Rodney Nelson]

Originally Posted by Sboxin

Oil breather catch can in photo of 3.8L 964 race engine - yellow rectangle . . .

Breather hose attached from oil filler where original breather hose connected oil tank to
engine case breather at rear of engine - case connection is blocked and hose does not
connect to engine intake - catch can has air filter on top to allow pressure equalizing (as
I understand the system) The catch can has a turn cock fitting on the bottom to remove
accumulated oil.

I hope this photo helps . . .
Regards,

Thanks Sboxin! You learn something everyday.

[Rawknees'Turbo]

Originally Posted by Sboxin

Oil breather catch can in photo of 3.8L 964 race engine - yellow rectangle . . .

Breather hose attached from oil filler where original breather hose connected oil tank to
engine case breather at rear of engine - case connection is blocked and hose does not
connect to engine intake - catch can has air filter on top to allow pressure equalizing (as
I understand the system) The catch can has a turn cock fitting on the bottom to remove
accumulated oil.

I hope this photo helps . . .
Regards,
. . .

What do you mean by the part I highlighted? Maybe I'm reading it wrong, or the setup on your engine is entirely different than what is on my 1987 Turbo, and basically all internal combustion engines that I'm familiar with, but you absolutely do not want to block the crankcase vent or pressure will rapidly build in the case (from piston ring blowby, heat, and the movement of the crankshaft, connecting rods, intermediate shaft, oil pump, etc.).