First day at track. Questions on overheating.

[m962b]

I was fortunate enough to realize my dream of taking my 78 911 on palm beach international raceway for some hot laps, nothing serious, last Sunday. The car did really well. Handling exceeded my expectations, etc.

However, I overheated the car after 4 laps and I wasn't driving it too hard. I lost all oil pressure even though I'm running 20w-50. With all of that said, she cooled down nicely and ran like a champ on the way home. I burnt out the alternator right as I for home though. So heat may have been the culprit there.

I have an entirely stock 78 sc with no mods except a factory turbo whale tail with the ac grille bolted on.

The temp was a pleasant 70 degrees.

What gives?

[ginot912]

do you have a front fender cooler?
that is some serious overheating, not being that hot or pushing the car for too long.
Thermostat working properly would be my first guess. remove and test in hot water.

[Dave at Pelican Parts]

Keep an eye on the oil pressure for a while. A buddy of mine wound up losing his 2.7L motor that way. After overheating like that, the oil pressure started a one-way journey downward...

I don't know what could have caused yours, though. Your SC should have the "trombone" cooler, so checking the t-stat would be a good idea. But even without an external cooler, I don't think 4 laps in mild weather should have been able to overheat that much!

Could there be an oil pick-up problem? There's something about the early SCs and the oil pickup... I think if one of the sump plates is put on the wrong way around (which isn't hard to do) the pickup doesn't work very well?

--DD

[campbellcj]

Maybe timing is way off or something like that?

Think about changing the oil ASAP as it's probably cooked.

[ErVikingo]

As a fellow owner of an SC and a driver at PBIR, I have some suggestions.

First off, since the overheat was so bad that you lost oil pressure, I would send a sample of the oil for analysis and have someone with knowledge also look at the old filter. You want to identify what level of damage might have happened internally (main bearings perhaps).

I don't use multigrade oil on my car. I stick to Valvoline Racing straight 50.

The trombone is totally deficient for performance driving at a track. On the road it works since it is not as intense. I started by replacing mine with a Turbatrol. Slight improvement but still not a real radiator type cooler. I then added a front mounted radiator cooler. End of my concerns.

If you do not want to add a front spoiler (to hide a center mounted cooler) I suggest you replace the trombone with a Fluidyne cooler and I would run lines to the driver's side and mount a second one there.

Now, what else could be wrong that caused such high temperatures? Have you tested your thermostat? Is your timing and mix appropriate?

If you have the stock gauge, I recommend you change to the graduated one so you can tell when its time to quit before things get expensive. In my book, up to 215 is OK, after that drop the revs and try to get as much air as possible. If it keeps on climbing, SHUT IT OFF

[m962b]

New oil and filter (oem) was installed with 10.6 quarts of oil about 2 weeks prior.

Normally temperatures are perfect.

Oil pressure dropped to nil, but once cooled, about 20 minutes later, it was fine. No smoke, no leaks.

Idle stayed steady. A hair high for the time it was hot, then stabilized.

I have managed to do something to my alternator since.

I reckon an upgraded oil system is in my future.

[cstreit]

Originally Posted by m962b

Oil pressure dropped to nil, but once cooled, about 20 minutes later, it was fine. No smoke, no leaks.

How long was it at Zero? That does not sound good to me.... Was that at idle, or all the time?

[Bill Verburg]

Originally Posted by m962b

I was fortunate enough to realize my dream of taking my 78 911 on palm beach international raceway for some hot laps, nothing serious, last Sunday. The car did really well. Handling exceeded my expectations, etc.

However, I overheated the car after 4 laps and I wasn't driving it too hard. I lost all oil pressure even though I'm running 20w-50. With all of that said, she cooled down nicely and ran like a champ on the way home. I burnt out the alternator right as I for home though. So heat may have been the culprit there.

I have an entirely stock 78 sc with no mods except a factory turbo whale tail with the ac grille bolted on.

The temp was a pleasant 70 degrees.

What gives?

You don't hear about this much these days but there was an issue w/ '78/78 SC oil scavenge system that caused symptoms like what you describe, one would think it would have been fixed by now but...


What could be happening is the oi is collecting in the crankcase and not being returned to the oil tank, it happens at high rpm, eventually the oil tank empties and oil pressure goes to zero.

There was a TSB 7/79


The problem was the oil pickup


The fix was a venturi-like sump pickup around the oil pump scavenge pickup
part # 930.107.314.00

there was also an earlier TSB 9/78 that was also aimed at this issue, this involved a change in the oil by pass pistons and was incorporated in mid '78 production, an early '78 SC might not have had the retro fit

items changed
safety valve(in the side of the cc) spring # 901.107.531.00 and screw cap #999.604.026.02
pressure relief valve(mounted vertically) spring #930.107.531.01, screw cap #999.064.026.02 and spring guide #930.107.533.00 these parts have been used right up through the 964s

One other possibility that would also cause the listed symptoms is that the oil sump cover may have put on wrong during the last oil change

[ErVikingo]

Good point Bill and one overlooked as i thought that was a universally known issue. I remember making that upgrade with the different pickup and sump cover.

I would look at oil analysis and filter. I had a similar situation once and it had spun the mains. I still have engine case with the hole where the rod came out at home as a sad reminder.

[m962b]

Oil pressure was at zero while driving. I could rev it up and get it to about 1 or 2, but that was all.

I hoped that the oil simply thinned out due to heat and loss pressure accordingly.

[txhokie4life]

Pull the filter and have it and the oil analyzed.

Running with 0 pressure and only getting 1-2 bar at revs is a sign something has more clearance than it should. This is highly unlikely to be an oil viscosity issue.

Mike

[Dave at Pelican Parts]

Yup, there's a good chance that you need a rebuild...

--DD

[ONQRACIng]

Hate to say this but, bad connection on sender? Maybe a wiring issue? Never overlook the obvious.

[KTL]

Could be a bad sending unit like Andrew suggests. I had one go bad on my '87 and it would behave the same way. The only reason I felt the sender went south is because my car sat in the garage for many months. So there was no opportunity for the engine to develop an oil pressure problem while running, like an overrev or overheating or whatever.

Could be a coincidence of overheating and a bad sender occurring at the same time, but probably not likely. If you can get a known working sending unit, try swapping in the replacement unit and see if the oil pressure is different.

Checking the oil filter is very wise too because if there is a serious problem inside the engine, you don't want to run it any more and damage the rods or the crank. It's very easy to cut open a filter to look at the paper element for debris. This dude is not necessarily an authority on engine repair, as evidenced by his shameful mess of a workbench. However he's got a nice trick to cut open filters w/out a specialty pipe cutter-like filter cutter

https://www.youtube.com/watch?v=KFXYN5ZN9S8

[ONQRACIng]

Great Video!

I was only putting the wiring statement out there to ensure that all rocks were overturned prior to going into a "rabbit hole".

Seems I alsways go down the most difficult or least likely path, only to find the answer is simple.

keep us posted.


Andrew

[glewis80SC]

Similar issue with my 80SC at a track day once, temp all ok until pushing it on track. Turned out I mounted my sump plate 1/4 turn off during pre-track oil change that restricted flow and cooling. It was that simple...operator error.

[KTL]

Originally Posted by glewis80SC

Similar issue with my 80SC at a track day once, temp all ok until pushing it on track. Turned out I mounted my sump plate 1/4 turn off during pre-track oil change that restricted flow and cooling. It was that simple...operator error.

I've heard of this but can't visualize what the problem is caused by. Do you know of a Pelican thread that covers this issue? I'd like to see what the wrong way is.

[glewis80SC]

Originally Posted by KTL

I've heard of this but can't visualize what the problem is caused by. Do you know of a Pelican thread that covers this issue? I'd like to see what the wrong way is.

I dont have a pick or know of a thread, my understanding is it restricts the venturi effect. When you take the plate off, funny to say, but it is straight forward which is the correct position.

[Bill Verburg]

Originally Posted by KTL

I've heard of this but can't visualize what the problem is caused by. Do you know of a Pelican thread that covers this issue? I'd like to see what the wrong way is.

The oil scavenge pump pickup should have a piece that looks like a screen w/ a whole for the oil pickup on one side and a dimple. This piece comes off w/ the sump cover, and provides a venturi area that prevents the cavitation issue I described above.
In the parts books they call it a strainer 930.107.314.00, these were only installed in a few late '79s and then in all '80 up

the older part # was 901.101.380.01 should be updated to the 930 part #

if the strainer isn't installed right it restricts high rpm oil flow into the pump

[Dan J]

Ding, Ding, Ding, Once again Bill V is the winner here
Classic symptoms of scavenge pump pick up issue
If it's a mostly stock 78 chances are it still has the original pick up screen
Did the oil pressure come back after it cooled down?