Pressure in oil

[911Jarle]

Hello!

I've got a bit of pressure releasing when I take off the cap.
Something to worry about?

It's very cold outside, something like -10 to -20 every day for a month or so.
Could it be the breather has frozen or something?

Cheers, Jarle

[911Jarle]

Originally Posted by 911Jarle

Hello!

I've got a bit of pressure releasing when I take off the cap.
Something to worry about?

It's very cold outside, something like -10 to -20 every day for a month or so.
Could it be the breather has frozen or something?

Cheers, Jarle

Forgot to mention. It's a 1979 SC, 3.0.



Cheers, Jarle

[JJ 911SC]

and the RPM goes down???

[911Jarle]

Originally Posted by JJ 911SC

and the RPM goes down???

Hey!

A bit difficult to say. Since the cold weather started I have a had a problem with rpms beeing a bit sticky. It idles to high around 1800 rpms. At 1800 rpms the difference when taking off the cap is not noticable. I know there is a valve of some sorts that slows down the rpm drop between shifts, and I was reckoning that was the source for that problem.

Today though, I noticed there was a bit of pressure in the oil reservoir. Never noticed that before.

Maybe I should try to disconnect that valve? See what happens?

I've looked around for cracked hoses etc. have not found anything.
Ideas anyone?

Cheers, Jarle

[911Jarle]

Originally Posted by 911Jarle

Hey!

A bit difficult to say. Since the cold weather started I have a had a problem with rpms beeing a bit sticky. It idles to high around 1800 rpms. At 1800 rpms the difference when taking off the cap is not noticable. I know there is a valve of some sorts that slows down the rpm drop between shifts, and I was reckoning that was the source for that problem.

Today though, I noticed there was a bit of pressure in the oil reservoir. Never noticed that before.

Maybe I should try to disconnect that valve? See what happens?

I've looked around for cracked hoses etc. have not found anything.
Ideas anyone?

Cheers, Jarle

Hey guys!

Noone knows what can be the source for pressurising the oil reservoir?
Anyone experienced this before?

Thanks!

Cheers, Jarle

[T77911S]

pressure?

the oil tank is vented to the back of the "turtle" that connects the Air flow meter (AFM) to the throttle body (TB). there should be a vacuum, not pressure, in the oil tank and you should notice a drop in RPM's when the cap is removed. there may be a spark arrestor in the line from the oil tank, it may be clogged or frozen. there are 2 hoses, one to the back of the engine and the other to the turtle.

if the high idle does not drop, your aux air regulator (AAR) may be bad or stuck. an easy first check is to check for power on the connector going to the AAR.

[lindy 911]

Check the oil tank breather hose where it connects to the intake. Not the crank case breather hose, the other hose at the neck of the oil tank. The fumes from the oil tank are routed into the intake tract and burned in the combustion process. I think there is a check valve where the hose enters the intake tract. The check valve could be frozen with condensation and not opening.

Lindy

[Drisump]

My understanding of the question is that, when you remove the oil filler cap, you notice there is a some pressure exerted on the cap. This begs the question, at 1800 rpm, why are you removing the cap....you can't, with any deal of accuracy, check the oil. I would deal with the idle issue. I can't say that I know what pressure would be felt removing the cap at 1800 rpm as I never have. Good luck PS. as T77911s says, there should be a small amount of vacuum resisting removal, not pressure exerted on the cap.

[911Jarle]

Hey!

Thanks guys!

What I will do today, is that I will put an electrical heater under the rear hatch today.
Leave it there to heat the engine compartment up for several hours.
Hopefully it should though it..

Regarding the auxillary air valve, what does it look like? If I disconnect it, that should have an effect on idle if it works?

Thanks for the info guys! Hope it's a bit warmer where you are

Cheers, Jarle

[911Jarle]

Originally Posted by Drisump

My understanding of the question is that, when you remove the oil filler cap, you notice there is a some pressure exerted on the cap. This begs the question, at 1800 rpm, why are you removing the cap....you can't, with any deal of accuracy, check the oil. I would deal with the idle issue. I can't say that I know what pressure would be felt removing the cap at 1800 rpm as I never have. Good luck PS. as T77911s says, there should be a small amount of vacuum resisting removal, not pressure exerted on the cap.

Correct when I remove the cap, there is a bit of pressure.
Agree, it is likely that more rpms will create more blowby and fumes even on a good engine.
Sometimes it does idle around 1200 rpms will try to remove the cap when that happens..

Thanks!

Cheers, Jarle

[T77911S]

no, disconnecting it is not the ing to do. first and easiest is checking for power at the connector. then you can ohm the AAR itself, should be around 30 ohms. if that is good then it needs to be removed and cleaned.

it is located on the same side as the oil tank, between runners 5 and 6.


if you indeed have pressure, it can very with rpm. just because the rpm goes up, does not mean the pressure will. some pressure comes from the piston moving down, it tries to push air out of the block, but there is also a piston going up that is trying to pull air in. they may or may not counter act each other.
as the engine gets old, you start to get comprssion blow past the rings, like mine. that can create a lot of pressure. it gets to the point it will start to blow oil out of the hose going to the air intake. mine was/is so bad, it filled my decel valve full of oil. there should be a restrictor inline with that hose. it can collect moisture, i suspect yours is frozen.

gotta go, water pipe at work just broke

[911Jarle]

Hey guys!

Thanks for helping, problem is solved.
Put an electric heater inside the engine bay for two hours.
closed it up with some warm cloth..
After that absolutely no pressure after 20 mins of driving and idling.

Still idling to high, that is probably the aarv. Will check that this weekend...

Thanks people, easy fix!

Cheers, Jarle

[BernieP]

When I drove my 1980 Euro SC year round this would happen when it got very cold. It would pressurize the crankcase and force oil past the rear main seal. Water condenses in the oil system and would freeze some where in the breather system. Removing the oil cap would relieve the pressure, once the oil got up to temp. it would boil off the water and all was fine till the next cold snap.

Bernie P

[911Jarle]

Originally Posted by BernieP

When I drove my 1980 Euro SC year round this would happen when it got very cold. It would pressurize the crankcase and force oil past the rear main seal. Water condenses in the oil system and would freeze some where in the breather system. Removing the oil cap would relieve the pressure, once the oil got up to temp. it would boil off the water and all was fine till the next cold snap.

Bernie P

This sure seems like it was the case!

Good info this is!!

Cheers, Jarle

[teenerted1]

sounds like it isnt getting hot enough to boil off the water

[911Jarle]

Originally Posted by teenerted1

sounds like it isnt getting hot enough to boil off the water

At -20 or -25 it probably doesn't get hot enough for that...
Agree, sounds like it...

Cheers, Jarle

[T77911S]

just pull that hose off, clean the arrestor in the line. i did not think about, but the presssure could blow the rear seal, good call.

i cant keep the water out of mine. its full of that white foamy crap. i even had water in the valve cover last time i pulled them. if and when i get the 3.0 in ill clean all that out real good.