Where is the "Hidden" oil????

z13racer · 10-12-2013, 12:36 PM

Howdy,

Where can leaked oil hide? How much can hide? How do I determine if it is hidden oil or freshly leaked oil?

Here is the story. I have a 1983 911SC.

Last night in a rush to take the GF to sushi I made a small catch can for oil that was leaking out of the oil filler vent hose. The fit for the hose into the opening in the small plastic brake fluid bottle was very snug; apparently too snug.

After driving a 6-8 miles I had to pull over and shut the car off as smoke was pouring from the rear of the car. I popped the deck lid and saw fair amount of oil sprayed against the firewall and all over the crank-case vent hose area. Right away a significant puddle of oil formed directly under the sump near the motor/trans junction. Additionally, the bottom of the car was coated with oil.

It looked bad so sushi was off the menu and flatbed ride was now on the menu.

Today I thoroughly cleaned top and bottom of motor. Then checked oil level: none showing. I filled until oil was on dipstick. Then unhooked diz and cranked until I saw good pressure on gauge (3rd bar). Reconnected diz and fired car. No issues. Idled for 10 min and noticed puddle of oil under car. Thought the worst! However, pressure was great and oil level constant.

I've driven the car a few short times around the hood and it keeps dripping a significant amount of oil, but level on dipstick is the same and oil pressure is very good.

So where is this dripping oil from?? Blown gasket/seal or "hidden" leaked oil that I could not get cleaned up????

Ideas. Suggestions.

Worried,

Scuzzy

mreid · 10-12-2013, 12:45 PM

Oil cooler. Classic symptoms.

z13racer · 10-12-2013, 12:48 PM

Been under the car and oil cooler looks clean. No leaks from bottom side. Don't know how oil could get to other side of trans.

RSTarga · 10-12-2013, 12:56 PM

It sure sounds like you are overfilling. Are you checking the oil with the engine above 180 degrees and at idle?

tonythetarga · 10-12-2013, 12:57 PM

excuse me if I am stating the obvious...but it sounds like you filled oil while the car was off. If that is the case you have seriously overfilled the car and it is pouring out of the vent line for that reason.

mreid · 10-12-2013, 01:01 PM

I just re-read your original post and I think Tony is correct. I just assumed you were checking/filling with the engine running, warmed up, and on a level surface.

z13racer · 10-12-2013, 01:06 PM

I've checked the oil level with the car hot and running.

z13racer · 10-12-2013, 01:07 PM

I had to add 7.5 qts of oil.

z13racer · 10-12-2013, 01:09 PM

I have to go to work. I will check back later.

Thanks for the input.

LEAKYSEALS951 · 01:28 PM

did you add the 7.5 quarts before or after you noticed the oil leaking from the oil filler vent hose and jury rigged the can.

BTW: never jury rig something and take a girlfriend on the test run -especially a dinner date! NEVER

addendum..after re- reading you original post, it looks like you added it after your "blow out". Did you add oil before the blow out? Sounds like there was too much to begin with, it caused you to want to address the leaking oil on the vent tube by placing the bottle, which somehow pressurized itself so much that when it blew, a whole bunch of oil came out, causing you to have to add a lot to get it back to normal. If that is the case, the car should be fine, just keep driving it with a good eye on the pressure and the oil level until it all drips/burns off. It may take awhile.

R

Richard Burns · Richard Burns's Garage

I suggest that you drain all of the oil out of the car that is out of the tank and out of the sump (engine). Replace the oil filler vent hose correctly fill with 8 litres of oil. Start the car and check oil pressure if O K go for a short drive to get the motor up to normal running tempereture. Park on a level surface do not turn the motor off now check the oil level on the dipstick it should be about half way between the marks showing low and fullif a little low then add say half a litre and recheck hte dipstick. Do not be worried when the car loses revs when the oil filler cap is removed it is normal. In future only check the oil level when the car is hot and idling I suggest each time you return from a drive check the oil before you put it in the garage.

theiceman · 10-13-2013, 12:39 AM

yeah sounds like this car needs baselineing.
how long have you owned it ?
ever change the oil before ?
as pointed out above there should be no oil showing on the dipstick before you cranked it.

start over and remove your " catch can "

z13racer · 10-13-2013, 03:02 AM

Thanks for the input guys.

I think the issue is with the seal at the crank/flywheel. By preventing the crankcase pressure from venting in to the tank, or actually letting the pressure vent from the tank, I have popped out this seal.

The oil now circulates through the system and escapes between the motor and clutch draining out of the bottom of the bell housing.

Thoughts?

And yes I have changed the oil before. I've owned it for almost 3 years. I just replaced, with help, all lower studs and have installed 993cup/964 profile cams. Additionally, I've discarded the CIS and gone with a 1st generation Megasquirt.

The car runs perfectly. I just spaced on thinking out the consequences of my little catch can improvisation resulting in this mess. I will begin pulling the motor tomorrow. We will then see if my theory is correct.

GaryR · GaryR's Garage

You put a catch can on without it having a vent to atmosphere?

This is similar to what should be used, if anything..

z13racer · 10-13-2013, 05:34 AM

Yep.

Hose fit into brake fluid bottle very snugly and I did not consider the need to vent from there. D'oh!!!

mreid · 10-13-2013, 05:38 AM

Unfortunately, I think your theory is correct. Good luck with the drop!

GaryR · GaryR's Garage

Quote:

Originally Posted by z13racer

Yep.

Hose fit into brake fluid bottle very snugly and I did not consider the need to vent from there. D'oh!!!

Did the car start to run badly just before it blew the oil out all over the place? I had a blocked vent line and the car would run ok for 5 minutes and then start bogging down, let it cool off and it would do the same thing.. luckily for me nothing blew out.

dad911 · 10-13-2013, 05:56 AM

Quote:

Originally Posted by z13racer

Thanks for the input guys.

I think the issue is with the seal at the crank/flywheel. By preventing the crankcase pressure from venting in to the tank, or actually letting the pressure vent from the tank, I have popped out this seal.

The oil now circulates through the system and escapes between the motor and clutch draining out of the bottom of the bell housing.

Thoughts?

And yes I have changed the oil before. I've owned it for almost 3 years. I just replaced, with help, all lower studs and have installed 993cup/964 profile cams. Additionally, I've discarded the CIS and gone with a 1st generation Megasquirt.

The car runs perfectly. I just spaced on thinking out the consequences of my little catch can improvisation resulting in this mess. I will begin pulling the motor tomorrow. We will then see if my theory is correct.

Why did you add the catch-can? Were you getting increased oil out the breather? If so, do a compression test & leakdown before you drop the engine.

z13racer · 10-13-2013, 05:57 AM

The car ran great the whole time I had the catch can attached.

z13racer · 10-13-2013, 06:05 AM

I had a very short hose on the filler vent with a stainless steel mesh filter mounted to it. I was getting some oil dripping from the filter into the engine bay when I would drive aggressively on twisty roads with rapid elevation changes. So I figured a catch can would be an adequate solution.

Just did a compression test before the stud/cam/tensioner replacement 2 months ago. Car is running great. Pulls hard all the way past 7K rpm.