Why is oil in 964 throttle body ?

[964Cab]

I have a '90C4 911 (964) and I had oil dripping from the throttle body over electrical wires that exit from the alternator. Upon taking the throttle body off I found a significant amount of oil in the throttle body itself. There is one large 1" diameter oil hose that feeds the throttle body. What the heck is oil being feed to the throttle body in the first place ?
I assume with oil in the throttle body that this could influenec idle, etc. Wouldn't it be better to feed the oil (breather hose I guess) into the valve cover gasket (ala a PCV set up) ?
Has anyone else found oil dripping from their throttle body ?

[Bill Wagner]

I've seen this happen when the oil has been over filled.

Good Luck,

Bill Wagner

[964Cab]

Bill (et all), take a look at these pics of my oil in the throttle problem, what do you think ?

08-11-2001, 06:00 AM

[Britwrench]

The usual reason for oil in the throttle body is overfilling.

If oil level is ok, check the oil thermostat is working and the front oil cooler in the right front fender gets hot. If not, the oil will run into intake. Also check condition of all the breather hoses under the right rear fender and make sure they are not filled with oil mayo if you only use the car on short trips.

[964Cab]

Oil not over filled, I'm real careful about that. I have however been monitoring the open end of the oil tank breather hose (not connected to it's factory location on the input to the throttle body) and I am finding a film of oil coupled with a misty oil smoke. The tail pipe doesn't emit any oil smoke but the above noted oil tank breather hose does. Was having the throttle body eat those oil/misty fumes from the oil breather hose an air-pollution-emission related process ? I think the older 911s had the oil breather hose connected not to the throttle body but instead to the intake air filter unit where at least the filter blocked the oil from getting into the throttle body and fouling the air-fuel/misture process. I must admit I don't fully understand the whole oil tank breather system (not to be confused with the still intake and not problematic engine crankcase breather system),

Many thanks...

[This message has been edited by 964Cab (edited 08-17-2001).]

[Britwrench]

Why is breather hose not connected to factory spec? The breather system is part of an integrated air intake and emission set-up. It's possible you have a breather problem.

Also check the condition of the air filter and make sure it is not blocked.

Check compression/leakdown, you might just have a piston blow-by problem.

[964Cab]

I thought about that (piston blow by) but I have no other indications of piston blow by such as weak idle and weak hiway performnace or for matter I don't have oil in the exhaust fumes.

I think maybe a oil tank bypass valve is bad as I think Porsche MotorSports has been having a problem with a breath tank divertor valve during their racing at higher rpms. Here is their info:
http://www.us.porsche.com/national/motorsports/technical/oil.htm

PS: I don't of course have a 3.8 racing car, just a '90 Cab964 and a hi miles 993 Cab. It's my 964Cab that has the oil in the throttle body problem.


[This message has been edited by 964Cab (edited 08-18-2001).]

[Britwrench]

Yes, but you don't have a 3.8 RSR and don't drive in the same rpm range....

If there is oil in the throttle body it has to come from somewhere..double check the breather pipes are not blocked or sludged up and I would still check the compression...

[964Cab]

Strange, I never noticed it before, but I have smoke coming from the dip stick tube !

[Britwrench]

The dipstick tube is connected to the oil tank.........
You still have a pressurisation problem.

[964Cab]

I ck'd all about the oil tank area and I don't see any pressure valves; just tubing in and out of the oil tank. Do you think by having that oil tank breather hose off the intake throttle body has created a problem ? I just can't stand the idea of pumping oil into the throttle body. Right now I have that 1" bore oil breather hole in the throrrle body blocked off. The oil tank breather hose is now not feeding anything and of course it's emitting pulsating oil-film smoke, just like the oil dip stick hole is emitting (with the dip stick out of course). Car runs wonderful, idles perfect (now that I got the oil out of the throttle body).

BTW: I have not changed in any way the engine oil breather hose system. I've altered only the oil tank breather system which originally was feeding the throttle body.


Many thanks,
'90C4Cab



[This message has been edited by 964Cab (edited 08-22-2001).]

[Britwrench]

Would you say the puffs of smoke are like the symptons of a broken ring, causing excessive crankcase pressure?

If you disconnect the breather hose to the throttle body, it may have upset the vacuum/pressure balance of the system.

Could you refit the parts as they should be and try it?

[964Cab]

Thanks for your help. I can re-connect easily I a left a 1 foot extension of 1" I.D. hose (1 1/4" O.D. hose) on the input bore to the throttle body (blocked off of course). I also have added a two foot breather hose to the original breather hose that was originally into the throttle body (it comes from the oil tank itself). I just fret about re-connecting it because the just noted oil tank breather hose is also emitting the same pulsating oil-filmy smokey smoke that's coming from the oil tank dip stick hole (dip stick out of course.

I'd hate to inject into the throttle body with oil again. I'll try a short duration TEST by re-connecting the breather hose to the throttle body and see what effect that has if any on the pulsating smoke coming from the oil dip stick hole.

Many thanks,

I'll try the TEST tomorrow but I need to get a 1" to 1/2" hard plastic coupler to mate the two extra breather hose extensions. Car runs like a bat out of hell though, idles like a champ and you'd never know it has a problem. Lots of oil pressure on the dash gauge, ok oil presure at idle. No smoke out the exhaust, no drop in oil on the dip stick. Just have one small oil leak from that hard to get at chain cover gasket that's hidden by the blower fam heater duct stuff. A few drops a day drop, that's all.

Patrick




[This message has been edited by 964Cab (edited 08-22-2001).]

[silver911rdb]

I know this is a really old thread…But did you figure out the problem? I have a 964 with a 3.8l that is having the oil backed up everywhere after running it high rpm on the track. Does anyone have any details on the Porsche Motorsport bulletin mentioned above? “ http://www.us.porsche.com/national/motorsports/technical/oil.htm“

The link is no longer valid

Thanks

[jgrosjean]

I have the same problem. The oil collects in the bottom of the intake manifold and drips on the plastic engine cover. No smoke in the exhaust or fumes coming out the oil filler with the cap off.

[mikedsilva]

Originally Posted by silver911rdb

I know this is a really old thread…But did you figure out the problem? I have a 964 with a 3.8l that is having the oil backed up everywhere after running it high rpm on the track. Does anyone have any details on the Porsche Motorsport bulletin mentioned above? “ http://www.us.porsche.com/national/motorsports/technical/oil.htm“

The link is no longer valid

Thanks

Not sure about that link... but last year I rebuilt a 964 engine that was a little tired. The oil fill cap was taped down with duct tape!

When running, there was quite a bit of blowby and pressure coming from the oil tank. During disassembly I found quite a lot of oil that drained out of the intakes...

Then when I got to the pistons, I found the top ring on each piston was cracked.

[silver911rdb]

Originally Posted by mikedsilva

Not sure about that link... but last year I rebuilt a 964 engine that was a little tired. The oil fill cap was taped down with duct tape!

When running, there was quite a bit of blowby and pressure coming from the oil tank. During disassembly I found quite a lot of oil that drained out of the intakes...

Then when I got to the pistons, I found the top ring on each piston was cracked.

My engine was rebuilt with new pistons and cylinders. One odd thing I noticed is that when filling the oil tank, the oil was very slow to go down the filler tube. I had to pour it very slowly so it didn’t back up. That isn’t normal is it? I’m used to the earlier 911’s where I can just squeeze the oil bottle and fill as fast as possible.

[Bill Verburg]

Originally Posted by silver911rdb

My engine was rebuilt with new pistons and cylinders. One odd thing I noticed is that when filling the oil tank, the oil was very slow to go down the filler tube. I had to pour it very slowly so it didn’t back up. That isn’t normal is it? I’m used to the earlier 911’s where I can just squeeze the oil bottle and fill as fast as possible.

Normal

I put the rear of my 993 ~10" up in the air to facilitate the oil fil process

[Peter M]

Originally Posted by silver911rdb

My engine was rebuilt with new pistons and cylinders. One odd thing I noticed is that when filling the oil tank, the oil was very slow to go down the filler tube. I had to pour it very slowly so it didn’t back up. That isn’t normal is it? I’m used to the earlier 911’s where I can just squeeze the oil bottle and fill as fast as possible.

My 993 was the same. My recollection is that the later cars have a gauze screen in the filler tube that the earlier cars didn't have.