Help on SC engine issue, please!

[AlexJ]

Hi all!

I just finished restoring my 1982 SC.

I was planning to restore the engine as well but a few weeks after I started this project I discovered the mechanic who normally did its maintenance and he told me that this engine has been repaired 11.000 kms before it was stopped.
Stronger head studs, chain tensors and a few other bits were replaced.
As it was some years ago he couldn't be very precise about this repair.

Because of this, I decided not to open the engine and save some money on this restoration.
Important to say that this engine has been stopped for 3-4 years. After I purchased the car (almost 2 years ago) I sprayed WD 40 through the spark plugs holes to preserve it, while the restoration was going on.

On the engine, I replaced all the seals, gaskets, oil pressure pistons, sensors, etc. and inspected it with one of those micro cameras that go through the spark plug holes to check any damage. Apart from some superficial rust on the valves, everything looked correct.

After the engine was assembled in car, it started properly, no smoke, oil pressure on normal values, and sounded good. I used a cheap engine oil to run the first kilometers (15w40) in order to clean any dirt. I was planning to change to proper oil after running the first 500 kms.

Now I started to run the car and after my first longer trip, there are some facts that I would like to share:

- When cold, it starts well, normal oil pressure (4-5 when cold idle), no smoke. Only fuel pump is a bit noisy.

- After running it for a while, it reaches what I think is the normal running temperature (3rd mark on the temperature gauge), it loses power, oil pressure drops to 1 and hardly increases when I accelerate, and white smoke comes from the exhaust.
- Idle drops to around 600 rpm and hardly stays running

Before these facts, can anyone give me an opinion about what probably is happening on this engine?

[kodioneill]

Maybe too much oil in the tank.

[Bob Kontak]

I wonder if you have too much oil in the car? There are a lot of threads on this but when you car rests oil drains into the case - not all but several quarts. When you warm it up the pump moves the bulk of it into the tank in the rear fender.

If there is oil on the stick when the car is cold I am pretty sure there is too much oil in it. Check the oil with the car level and running at idle and warm.

If the oil level is between the min and max marks on the stick when cold I would drain two quarts out before starting and then check it as it warms up. Hope this is all your issue is.

[AlexJ]

Thanks Bob and kodioneill...

I really wish you were right, beleive me.
The related situation happened twice - last two runs. On the first time, first thing I checked was the oil level... It was above the minimum mark. I refil it and same happened...

Just one thing I didn't understand: if there is too much oil, the pressure also drops?

[Bob Kontak]

Your temperature at the 3rd mark is 120C. I do not see that unless running it pretty hard. Normal driving is 100C but I have a front oil cooler.

You are now running thinner oil than 20W-50, correct? You have not reached the 500km oil change point.

Pull the bellows off between the air sensor and the throttle body off and check if it is dry on the inside. That will confirm if you have been sucking oil into your intake. It may take a half hour maximum - on and off - depending on where your band screws are positioned. If easy access - 5 minutes.

Let us know what you find. I would like to see the "too much oil" hypotheses confirmed or eliminated.

When it warms up describe more thoroughly the loss of power. Is it mis-firing, smooth but sluggish?

[AlexJ]

Bob, sorry but I wrote it wrong on my other post.

When it first happened and I check oil level, the oil level was BELLOW minimum mark.
I then refill it and now, when hot, it is half way between min and max marks.

I am now using 15W40 oil - quite cheap one... hope it is not losing its properties (viscosity) when hot... ??? Since I started to drive it, I only covered around 100 Km.

One detail (I don't know if this is normal): if I pull off the oil filler cap the idle changes... if I cover it with my hand I feel it sucking and idle changes...

I think I understand where I should check for oil... Do you mean inside the air box? Can I check it through the pop-off valve?

Sorry for all these questions but I really didn't sort out where do you mean I should search for oil...

When I said "loss of power" I din't mean mis-firing. I feel a slight vibration on the engine and it simply doesn't rev up.

[rootmatt]

How about a different idea. You replaced a lot of seals and gaskets. Is it possible that you cured a good sized vacuum leak and the engine is now running too rich? That might explain why it's happier when it's cold. Also, how fresh is the fuel?

[Reiver]

a change in idle when you remove the oil cap is normal. Feeling some blow by (pressure coming out of the res) could simply be that your rings are not seated yet allowing your case to get more pressure than normal....that should lessen as your rings seat on break in.

[James Brown]

start checking for air leaks and if you can get some fuel pressure readings and check out the warm up regulator. might be CIS related

[AlexJ]

Originally Posted by rootmatt

How about a different idea. You replaced a lot of seals and gaskets. Is it possible that you cured a good sized vacuum leak and the engine is now running too rich? That might explain why it's happier when it's cold. Also, how fresh is the fuel?

Its fresh... just bought it...

[AlexJ]

Thank you all for your suggestions...

... but there is one thing that is making me a bit confused...

Either if it is a "too much oil" possibility or a "CIS issue", could these two cause an oil pressure drop?

[Bob Kontak]

Originally Posted by AlexJ

"too much oil" possibility or a "CIS issue", could these two cause an oil pressure drop?

I do not believe either issue would cause an oil pressure drop. The oil pump spins at engine speed.

I am writing a lot here because I don't exactly know what to tell you. :-)

You did mention the car "does not rev up" but in an earlier post you mentioned that the oil pressure does not increase with RPM when it starts to run bad. I am thinking it does increase in RPM but only at a slow responding increase. If it does not rev at all then that is why it is at 1 bar but I think you are getting enough increase in RPM where you or I would want to see the corresponding increase in oil pressure.

This summer I drove my 81 for eight hours in 100F temps with the AC on. All highway speeds. After a couple of hours my oil pressure would not go above 2 1/2 marks on the pressure gauge - it was as if it hit a stop. I had never seen this before and it has been acting normally since. The oil temp was 110C - about 10 higher than normal. Maybe the pressure gauges can act up with age/heat? However, I had no performance issues.

Regarding the excess oil - the simple question is how much oil have you put in there in total - including re-fills - and were the front cooling lines full when you filled the tank originally?

Regarding my sucking oil comment the lower hose in the pic connects to the back of the bridge between the air sensor and throttle body. That is why the rpm drops when you pull the cap off. You are sucking un-metered air. The rubber bridge has to come off to check if oil has been sucked in.

However, I am not absolutely sure if oil can be sucked through that tube even if over filled in the tank. There may be baffles that prevent this? Someone should know.

[ChrisBennet]

I assume you are, but just humor me here; are you checking the oil level *while the car is idling* on a level surface?

[ChrisBennet]

In my experience, "warmed up" on these cars is on or around the first mark on the temp gauge; around 8 o'clock. The "3rd mark" on the temp gauge (10 o'clock) is on the hot side IMO unless you are stuck in traffic or someplace with really hot weather.

Smoke: You see this when the oil level is too high. It gets sucked into the engine from the tank through the hose the goes from the oil tank fill pipe to the somewhere above the throttle body (I forget exactly).

Power loss: you would see this if the crankcase is full of oil (think of running in water up to your knees).

Just a theory: Oil gets hot -> oil gets thin -> pump can't pump it fast enough -> oil pressure drops and crank case fills up with oil -> power loss results.

Check the front oil cooler with your hand (careful not to get burned). Is it hot? If it isn't, then the oil thermostat isn't opening which might explain the too hot oil (see above theory).

[Bob Kontak]

Nice post Chris.

Alex does have an oil cooler on his car. I found a pic in one of his resto threads.

Alex, to repeat what Chris is asking, are you checking the level when running? Hot thin oil will drain into the case much faster than normal when the engine is shut off.

Also, how much oil have you put in the car? You should remember.

[woland]

Alex, I read :

"I am now using 15W40 oil - quite cheap one..."

15W40 or 15W50 are ok but you shell use a decent mineral oil or semi-syntetic
I remember that more than twenty years ago my 5 cylinder Audi was ruined using cheap oil: When hot, the pressure was alvays very low, then the engine began burning oil from the exaust, then the car was good to trow away.
After this exeprience I always thought that an engine costs much much more than few gallons of good oil. I use motorcycle oil because bikes have much rpm than a sport car. I have no oil consumption and the engine always fires istantly

[AlexJ]

thanks guys... I think I will write a check list from your comments and tomorrow I will start all over again and add some pictures or probably a film of what is happening...

- Oil lines and oil cooler were empty.

- engine oil used: 15w40 mineral - already 15 litters used

- last oil check - running hot (100º) at idle, flat surface, shows half way between max and min marks

- when it is running ok, normal oil pressure readings - for example at 2000 rpm 5 on oil pressure gauge. When problems start, at 3000 rpm, oil pressure gauge hardly reaches 1 - 1 and 1/2... revs up slowly and hardly passes 3000 rpm always with low oil pressure - around 1.

- on last run, oil lines were hot so I assume the thermostat is opening

[SC-targa]

Make sure the oil drain/screen cover on the bottom of the crankcase is installed in the correct orientation.

[boyt911sc]

Originally Posted by AlexJ

thanks guys... I think I will write a check list from your comments and tomorrow I will start all over again and add some pictures or probably a film of what is happening...

- Oil lines and oil cooler were empty.

- engine oil used: 15w40 mineral - already 15 litters used

- last oil check - running hot (100º) at idle, flat surface, shows half way between max and min marks

- when it is running ok, normal oil pressure readings - for example at 2000 rpm 5 on oil pressure gauge. When problems start, at 3000 rpm, oil pressure gauge hardly reaches 1 - 1 and 1/2... revs up slowly and hardly passes 3000 rpm always with low oil pressure - around 1

- on last run, oil lines were hot so I assume the thermostat is opening

Alex,

I've done numerous oil change for 911 engines (SC's & Carrera's) and never once used a full box containing 12 quarts of oil. Between 10 and 11 quarts is where I usually stop filling the oil tank. The final oil check is when engine is at operating temperature and idling on a level floor.

Unless you have a large aftermarket auxiliary cooler would it require 15 quarts of oil. Start checking your oil level cold and once the oil stick gets some oil on it consistently (do the checking multiple times) stop adding oil. Run the engine briefly and stop it. Check the oil level again. Do not allow the oil level to reach above the 'minimum' level marker when oil is COLD!!!!!!!

I would check my oil when the engine is cold and watch where the oil 'mark' at the oil stick. Then another check after driving the car for a while and look at the oil mark between the lower and upper dots on the stick. After a while you'll get familiar how your cold oil would expand when heated. A fully warm engine should have the oil level somewhere between the 2 markers (preferably at mid point).

Tony

[Bob Kontak]

Originally Posted by AlexJ

- Oil lines and oil cooler were empty.

Alex - Unless the oil cooler lines and front cooler were removed from the car and drained out they were full.

That is a couple liters extra on on top of the 15 liters (15.85 quarts) already in the system (some has blown out through your exhaust pipe).

Also, you said the oil lines were hot. Were the ones in the front hot or the ones in the rear hot? That makes a big difference.

I am leaning towards over-fill.

I don't think you need a list, I think you need to drain the tank and case and put 9 liters/10 quarts in and no more.

Use a Mahle filter also.