75 911S: New Project Questions, Oil and Smoke - Oh my!

[E_Swift]

I couldn't settle with one aircooled project, so while I continue to piece together my early 66 912, I happened across a 75 911S that had also been sitting in dry storage for almost two decades.

It was partially stripped down for a repaint that never happened, so it came non-running and with boxes and bins of parts. In other words, a very fun puzzle for someone like me.

While I was able to get the engine started without much coaxing beyond ignition system basics, there was no alternator pulley or belt to be found so I did not run it for more than 20 seconds until tonight when I fitted these parts.

I should mention, since the car sat for so long, I did a pre-emptive oil and filter change - well, tried to... More on that later.

The good news is that now with a newly replaced oil pressure gauge, there is plenty of indicated oil pressure at startup and the generator light turns off. Whew. Annoyingly, the tachometer isn't currently reading and concerningly, the oil tank gauge is pegged high. Everything else seems to be working there.

Now, when I did the pre-emptive oil change, I drained a total of up to 9 quarts out of the combined sump and oil tank. This seemed low, but with an unfamiliar engine, I filled it just over 10 quarts of quality oil (my understanding of the minimum spec) and intended to revisit the level once the car was warm. Which attempting to achieve raised another entertaining issue. I should point out that the car has an oil cooler plumbed ahead of the passenger front tire - does not seem entirely factory - the parts look 90s era so I am thinking that was done at the same time the hydraulic Carrera tensioners were fitted, and perhaps when the pre-75 exhaust was installed to eliminate the thermal reactors. Always good to take a chance on a car with no paperwork whatsoever, I might add.

So with what would seem to be plenty of oil and reasonable pressure, I allowed the car to idle for perhaps 10 minutes and walked around looking for leaks, smells, puffs of smoke... During this time the idle oil pressure slowly dropped to near the bottom of the gauge, which was not especially concerning, and I could just see that the oil temperature started to read on the temperature gauge - maybe 125F. handheld IR temp readings on the oil tank, front cooler, oil filter, and sump all reading around that level - careful probing of the cylinder head temps yielding values around 180F. Seems reasonable for a car just starting to circulate oil to the coolers I thought. Next thing I notice is smoke billowing out of the dash area. Hmmm.. Pushed the car out of the garage, shut it off, readied the fire extinguisher, started hunting for the source. Thinking maybe a pinched wire or short on the aftermarket radio - though it doesn't really smell like burning plastic or fried electronics. Smoke peters out, source not located but seems to be under passenger dash. Stripped out carpet, kick panel, map pocket... no clear source. I should mention blower motor is not currently in the car, so clearly not involved.

Started the car up again, shortly thereafter, the chimney started pumping again. Faint smoke from passenger rear quarter as well, ahead of the oil tank, but no clear source. No leaks - oil lines, coolers, bottom of engine is dry. Smoke is not blue, white. Stops slowly as engine cools. I am sure this car has or had plenty of nice accommodation for mice at some point. Did they get in the heater and now I am slow roasting their bedding material? Any good way to clear that passage? Any other theories? I'd like to get it up to temp safely to check the oil level but the smoke and inconsistent oil level readings have me spooked.

With engine idling, flat surface, oil clearly warming and if I trust the sensor only to about 125F (Where is this sensor located - is it remote to the engine?), the dipstick doesn't even register - maybe just a touch of oil on the end. This is with the VDO gauge still pegged high. Is the engine somehow underfilled? What should it read when it is warming up at idle on the dipstick? On the dipstick above the min but below the max? I would have thought the dipstick level and gauge both would read low and then rise with temperature.

[timmy2]

Only time to read oil level is when engine is at full operating temp. Car running on a flat surface.
Most only fill to 1/2 way on the dipstick when hot. Nothing shows on my dipstick when cold.

[ADDvanced]

Originally Posted by timmy2

Only time to read oil level is when engine is at full operating temp. Car running on a flat surface.
Most only fill to 1/2 way on the dipstick when hot. Nothing shows on my dipstick when cold.

^ this. Found out the hard way on my car, had to clean the whole intake system. You've probably overfilled it. My car likes to run 180-220ish, and often times the gauge/dipstick won't register anything until it's quite warm.

[ossiblue]

If the oil level gauge is pegged "full", the sender is likely bad or the wire to the sender is shorted to ground. As others have said, the gauge is useful only when the diving, not at idle, but it should never be pegged high, which I interpret to mean the needle moves immediately to the highest point and remains there with no fluctuations, ever.

[Trackrash]

Welcome. Did you know that it is good form to post a picture of your car? Sounds like you have a fun project.

Some cars have had an issue with the wires to the dash lights burning, since they are un-fused. Don't think that is your problem, but worth checking.

It sounds like oil has gotten into the exhaust heat exchangers. That would explain it coming into the cabin through the heating ducts. Pull the carpet back in front under the dash. See if the smoke is coming from the heater duct. This could take quite a while to burn off if that is the case.

Probably a bad wire to the oil tank sender. The oil tank gauge on the dash is a good idea, but in reality not much practical use as the oil level will vary quite a bit during operation.

The oil level should be checked when warm using the dipstick on level ground. I usually have mine at the lower end of the stick. Too much oil and it can get into the intake making a mess. Remember the tank holds almost 3 gallons when full, so no reason to fill it all the way up.

[E_Swift]

I appreciate all of the feedback. Mixed results today, but progress nonetheless!

Originally Posted by afterburn 549

I am no one but welcome here-
Without seeing your car.................
the "mid years" are bred with some problems.
Most the oil leaks are on top of the engine and will require a new set of skills to get at them (partial engine drop probably)
The oil sender, T stat, and vent hose are the culprits.
Porsche being air cooled is pumping air and in your case- air, oil and smoke into the cabin because it all runs dwn onto the exhaust.
You will probably have leaky valve covers also if they have not been addressed.
There is a list of "mods" that need to be addressed in the mid-case years as far as the engine. (magnesium )
The valve guides were inferior and will make the engine smoke badly.Too.
The oil tank level never works very well unless you install the oil mod and the cam oil restrictors.
You will find loads of advice here , from a load of great people !

Thanks for the pointers. I am seeing mixed reviews on the oil restrictors for these early engines with the lower volume oil pumps, but will consider it. The valve covers seem to be dry and with the various upgrades that have been made, someone clearly cared about the engine at some point. Still, plenty of opportunity for improvement left!

Originally Posted by timmy2

Only time to read oil level is when engine is at full operating temp. Car running on a flat surface.
Most only fill to 1/2 way on the dipstick when hot. Nothing shows on my dipstick when cold.

Your last comment there gave me the confidence to actually run it long enough to get up to temp. Indeed, when I finally got it up past 180F, the oil started just barely showing on the dipstick. This tells me I had not overfilled, and it took a quart and change to get it 1/3 to 1/2 of the way between Min and Max on the dipstick.

Originally Posted by ADDvanced

^ this. Found out the hard way on my car, had to clean the whole intake system. You've probably overfilled it. My car likes to run 180-220ish, and often times the gauge/dipstick won't register anything until it's quite warm.

I don't think there is any way I could have overfilled, but the smoke does indicate something got into the heater boxes at some point. I let the car smoke away up on to about 210F and it has started to dissipate. Whether the oil burning off within the heaters is from seepage or a previous overfill - I am not certain. I will say that I am happy that the car doesn't smoke at startup, nor upon minor rev or decel. It isn't fully driveable because of body panels, glass, and lights needing to be fitted, so I can't really do a full shakedown yet.

Originally Posted by ossiblue

If the oil level gauge is pegged "full", the sender is likely bad or the wire to the sender is shorted to ground. As others have said, the gauge is useful only when the diving, not at idle, but it should never be pegged high, which I interpret to mean the needle moves immediately to the highest point and remains there with no fluctuations, ever.

I found a spare gauge in the parts that were included, and swapped it in. What I found is that both gauges behave the same, seemingly regardless of whether the sender wires are connected or not. This is not my highest priority, but it someone can point me to a good wiring diagram for a 75, or has experience troubleshooting, I am all ears. I have attached a photo of the back of the gauge, there is one terminal with nothing connected to it, but it is on the opposite side of the gauge and also appears to be a redundant ground connection- I do see one loose wire looking back through the gauge hole, but it is far too short given its current routing to connect, and I'd rather see a wiring diagram before creating more problems I have to chase down!

Originally Posted by Trackrash

Welcome. Did you know that it is good form to post a picture of your car? Sounds like you have a fun project.

Some cars have had an issue with the wires to the dash lights burning, since they are un-fused. Don't think that is your problem, but worth checking.

It sounds like oil has gotten into the exhaust heat exchangers. That would explain it coming into the cabin through the heating ducts. Pull the carpet back in front under the dash. See if the smoke is coming from the heater duct. This could take quite a while to burn off if that is the case.

Probably a bad wire to the oil tank sender. The oil tank gauge on the dash is a good idea, but in reality not much practical use as the oil level will vary quite a bit during operation.

The oil level should be checked when warm using the dipstick on level ground. I usually have mine at the lower end of the stick. Too much oil and it can get into the intake making a mess. Remember the tank holds almost 3 gallons when full, so no reason to fill it all the way up.

Dash lights are burning bright, so that is something on the positive list. Smoke is/was definitely originating from heater boxes under engine. I will have to warm it up again tomorrow and see if it continues, or whether it is all vaporized now.

I expected a photo would be a nice element of an introduction, but the car is really not a looker, frankly embarrasing now. It's by no means an original barn find, and it wasn't completely spared by the 80's/90's with a really poor paint job. On the plus side, I have been inside and out of it, and with my experience on early cars, very happy to report there is no corrosion of note here. Attached a representative overview of how it looked at time of delivery, as well as the vast swath of parts that accompanied it.

[ed mayo]

What terminal is the green white wire hooked to ,,,'G' or +

[E_Swift]

So, I have two main questions after tonight's exploration:

Of the two remaining gauge issues, I'd like to get the tach working. I poked at some threads this morning while I was waking up and didn't see a very clear tutorial given my basketcase starting point. I have attached a photo just below of the multiple unconnected wires in the driver's side of the engine bay. I am guessing that something here needs to tie into the coil or distributor. I would be grateful for any guidance.



Next, while I am provisionally feeling good about the cylinders and valve seals due to so little / nonexistent smoke from the exhaust - I do have to say I feel like I can hear what I would call a tapping coming from the engine. I haven't grabbed stethescope yet, but feel like it is coming from the passenger side more than the driver's side. The fact that it doesn't seem to dissipate with rising temperatures makes me think it isn't just an overdue valve adjustment.. Without a tach, it's hard to say if the rate is once or twice per revolution. I am hoping all I need to do is adjust the valve lash, but have to admit the solution could get quite a bit more invasive. Any other thoughts before I look under the valve covers at the valve adjustment?

[911obgyn]

If the engine has not been run in years there is probably rust on the valve seats. Only on a few that were open you can run it and it will dissipate but Italian tuneups need windows.

[E_Swift]

Originally Posted by ed mayo

What terminal is the green white wire hooked to ,,,'G' or +

Green/white is connected to the "G" terminal on oil tank level side of gauge.

Originally Posted by 911obgyn

If the engine has not been run in years there is probably rust on the valve seats. Only on a few that were open you can run it and it will dissipate but Italian tuneups need windows.

Are you thinking the rusty seats would produce the tapping sound, or the smoke? My impression of an italian tune up is a spirited drive to "clean out the carbon" so to speak?

For reference, here is the sound:

[SalParadise]

What's the original color? Silver?

[ADDvanced]

Here's what I would do:

- Fresh oil/filter
- replace the seal on the sump sensor ($3-6 or so, the cork gasket)
- Fresh trans fluid (swepco)
- Replace your rubber brake lines with these, cheap piece of mind and upgrade:
https://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2016.cgi?command=DWsearch&description=PEL911-SSDOT1
- Bleed brakes
- Get it on the road and see what happens

[E_Swift]

Originally Posted by afterburn 549

Without knowing who has done what you will have to sort out the issues.
The noise from the engine is very hard to tell from here if it is valve train or exhaust.
My concern for you is the original copper guides are in there and will be beyond lose.
You will have to pop the covers and check them.
Oil restrictors- a lot of research went into them here years ago by some very smart people on this board.
Most agreed they were a good thing but that was with the oil mod and the rest of the updates in my case.
I am not sure about a "stock" set up.
Most agreed the cams were getting more oil with the restrictors and less of a foam job .
My valve train never changed after the break-in as far as cam wear.
Its your car.Do as you wish.
Your engine will really benefit from SC or 964 cams.
Something to remember if you take it apart.
Did you get any paperwork with the car?

By "oil mod" do you mean upgraded pump and bypass mod, or something else?

Originally Posted by SalParadise

What's the original color? Silver?

The much more desirable Bitter Chocolate! Any grey or silver you're seeing is dust.

[E_Swift]

Originally Posted by ADDvanced

- replace the seal on the sump sensor ($3-6 or so, the cork gasket)

To clarify, do you mean the sump plate gasket - or is there a sensor down there I'm not yet familiar with?

[SalParadise]

All I can say is that it's fantastic that you have it running. My '75S Targa has not run in years. What's the build date on the door?

[ADDvanced]

Originally Posted by E_Swift

To clarify, do you mean the sump plate gasket - or is there a sensor down there I'm not yet familiar with?

The one on the oil tank for the oil level sensor. They always disintegrate and leak. Easy fix.

[ed mayo]

If you have the wires on the proper terminals of the gauge, then a simple test is to pull the power wire at the level sender and alternately ground it and unground it, the gauge should go full scale in each direction. If it does the problem is the sender.

[E_Swift]

Originally Posted by SalParadise

All I can say is that it's fantastic that you have it running. My '75S Targa has not run in years. What's the build date on the door?

Thanks! I am very happy with how well it starts (instant cold start-up) compared to the way the mechanical pump and rebuilt Solex's behave on my 66. Unfortunately, it seems that the sticker on the door jamb did not survive the classy 80's or 90's metallic purplish blue makeover. PM me if you wan the chassis number to put the car in context. Given that I am on the west coast, I assume the car came with CA emissions, but I suppose I should buckle down and get a Kardex to be sure (and also know all the original options present).

I got several car-loads of parts with this car, many of them redundant. Some for a SWB 912, others for a 72, others for a 77 911S. It's been a real education sorting through several generations of headlights, gauges, and even the removable body panels.

Originally Posted by afterburn 549

Yes -The SC pump and the mod inside the case.
However, if you are that far, there are several other things that need to be addressed on the inside.
Personally, I like the Mag case.
But love is in the arms of the beholder.

If/when the engine gets dropped, I will complete all remaining upgrades. I wouldn't have purchased a middie if I didn't like seeing an underdog win the fight!

Originally Posted by ADDvanced

The one on the oil tank for the oil level sensor. They always disintegrate and leak. Easy fix.

Thanks, mine seems to be holding for now, but I will order one to have on hand to replace at my next service.

[Walter_Middie]

I'd like to get the tach working

The distributor has a single wire that goes from the points to the CDI trigger terminal. The CDI has a +12V power input. Then the CDI has a +460V power output directly to the ignition coil. Finally, the CDI ground, this is a metal tab on the case.

A way to remember is "B" for Battery, "C" for contact (the points) and "A" for ACHTUNG, don't electrocute yourself! The other coil primary terminal goes to ground of course.

The contact "C" also includes a black with a purple stripe wire at a white plastic wire junction - this is the wire that drives the tachometer. It runs forward from the CDI box on the left side of the engine bay.

[E_Swift]

Originally Posted by Walter_Middie

The distributor has a single wire that goes from the points to the CDI trigger terminal. The CDI has a +12V power input. Then the CDI has a +460V power output directly to the ignition coil. Finally, the CDI ground, this is a metal tab on the case.

A way to remember is "B" for Battery, "C" for contact (the points) and "A" for ACHTUNG, don't electrocute yourself! The other coil primary terminal goes to ground of course.

The contact "C" also includes a black with a purple stripe wire at a white plastic wire junction - this is the wire that drives the tachometer. It runs forward from the CDI box on the left side of the engine bay.

This was very helpful, Thank you. I thought I had it fixed a few times, but it turned out that the shielded signal wires for A and C were shorted to their shield/ground. Once I sorted that out, fired right up with a working tachometer!

Here is a shot of the ugly but functional short term solution:



Is there a good source for those shielded CDI wires, or perhaps a reproduction factory loom? All these wires are too brittle for my liking!

In the picture, I have circled in red one currently unidentified connector - anyone know what it is?

The blue circled fan or pump - can I remove it without plugging anything mechanical at this point? It isn't electrically connected or plumbed to anything underneath at this point...and I am not in California or subject to any visual emissions inspections..

Finally, I had a chance to mount the hood, original driver's door, washer tank, fuel filler cover, and a few other small things like a shift knob that doesn't have any auto-rotating feature.




The windshield, bumpers, and lights await - not much left before it is road legal.