1983 930 Rebuilt Engine Leaking

[cool4engineer]

After rebuilding my engine, I noticed there is some oil dripping off from between the head and piston area. Initial break-in was done and oil changed at 1k miles. The leak is not very noticeable but there is oil presence on that area. Is that normal? Should the heads be re-tightened?

[aerodyn930]

Try to take a photo of the area, No the heads do not need re-torquing, If indeed it is a leak at the head to cyl. junction your engine should be removed and that area inspected, something is not right.

Lou/ AERO DYNAMICS

[totle]

I had a oil leak on mine as well after a rebuild. It turned out to be that the base gasket on cyl #4 had shiftet (probably during assembly) and caused the leak.
Had to take out the engine again, and replace gasket. Now she is all dry :-)

[zcoker]

I do not think that it will be leaking oil at the head-to-cylinder section, more like combustion gases....but I could be wrong. It could be coming from the rocker shafts, as those cause major leaks that go all over the place if not installed correctly.

[Schwarzeritter]

1. You should put the car up on a lift and have a inspection.
2. If you find that it is super obvious then it's not a problem. You found the leak.
However if it is one of the speculative ones, clean the suspected area really well.
turn the engine on, let it just idle a bit 5-8min. Leave, and inspect again.
3. SOL and as Lou said, you'll have to remove the engine and inspect it up close and personal. =(

Good luck-

[JFairman]

If you see an oil leak at the head to cyl. junction than thats likely where it is coming from.
It would be impossible for oil leaking from a rocker shaft(s) to come out the bottom of the cam tower then go 3.5" along cylinder head cooling fins towards the cylinder with air flowing by and then straight up against more cooling airflow and gravity to where the cylinder and head meet.

Did you have the cylinder heads resufaced? Were the cylinders new or if used cleaned up at the mating surface?, and did you lap the sealing surface of the head to the top of the cylinder?
Were the deck hights the same and did the cams turn freely with no binding or sticktion after the cam towers and heads were all torqued down while no rockers were installed yet?

What kind of head studs were used? and how much torque was used to tighten them.
I have read and heard many different head stud torque ratings from different engine builders saying from 24 to 36 foot pounds on stock dilivar head studs so now I don't know whats best there or if thats what's in your motor.

It wouldn't hurt to check and retorque them while adjusting the valves next time so you never know if that will help until you try it.

A combustion leak would usually make some noise under full throttle. I've also read that part of the reason for the dilivar studs expansion rates in relation to the cylinder and head expansion rates is to keep oil from seeping out from the head and cylinder head mating surface while the engine cools down from operating temperature.

Do you see oil on the spark plugs on the cylinders that are leaking? If yes than rings or valve guides and seals may be leaking, and more so if the oil level is at the top of the safe range on the dipstick.
It may be better to have the oil level at the bottom of the dipstick safe range so it isn't draining back from the oil tank and filling up the case, the bottom side of the cylinders and pistons, and exhaust valve guides and lower part of the cam towers as high.. overnight after running.

[iamchappy]

I found mine is leaking from the through case bolts after the rebuild, drips and runs down the case and headstuds. You may want to look there also...

[cool4engineer]

Here I include two photos with the oil leak. I also noticed that the largest amount of oil is around the air deflectors. The oil seems very dark and also more viscous than standard oil. Heads were re-surfaced and new valve guides installed when engine was rebuilt. Head Studs were the ones used in 993. This situation is only happening in one side of the engine and also there is a small leakage on the last bolt of the lower valver cover.

Thanks for your advice, Guys!!!

[zcoker]

I've seen that strange kind of leak on many 930's around that same area but cannot say where it comes from, also dark like that. If you pull the plug boots, you can test for oil leaking from inside the plug cavity from the rocker shaft ends; below this area is direct access to the area you have pictured - through the fins it would flow from topside. I cannot see it as coming from between the head and cylinder, especially if you had it resurfaced. If it were leaking between the head/cylinder, you'd have other major issues like no compression and/or combustion gases spewing out.

[WERK I]

Originally Posted by cool4engineer

..................snipped to save space............

Yep, that looks like the infamous cylinder-to-head "weep". I would go with JFairman on this. Was there any resurfacing on the heads and cylinders during the rebuild? Also, are these the original 930 cylinders or some other vintage?
How many other cylinders are weeping?

[911st]

What about an oil return tube?

Others: oil pressure switch, oil cooler seal, pressure fed tensioner lines, or crank case breather...

Not my area.

[onboost]

You'll love this one...

Also check the the crank seal at the pulley. I've seen these leak after a build, or with age. Only drips when parked, when the engine is running, the fan has enough draw to pull the oil up and through the fan... it distributes it across the cylinders, does not all burn off then appears as a mystery leak on the cylinders. worth a look see..

Paul

[jpnovak]

Which cylinders is the leak on?

It is nearly impossible to have an oil leak between the head and cylinder. There is no oil there unless your rings, valve guides and valve guide seals are completely shot! I hope not on a rebuilt engine.

If the leak is on the 4-6 bank look at the top of the motor for the oil pressure sender or internal thermostat. It is quite common for oil leaks to run down the top of the cylinders and appear like they are coming from that area. There is not much that can leak on the 1-3 bank up top of the case except for the breather cover. Given the viscous, black nature of the oil I think you have a secondary leak somewhere that is picking up the dirt and grime as it is blow across the engine by the cooling fan. You may want to look inside the engine oil cooler from below with a flashlight and see if the top is gumming up. This add to the cooling problems later down the road of time if not cleaned.

If the leak is on #1 or #4 then you would look specifically at the cam seal between the chain housing and the cam tower. A leak on the inside (toward the case) would run down the cylinder cooling tin to the location you have pictured.

You may want to consider pulling the alternator/fan assembly and having a look under the engine cooling shroud.

[DPHANS]

Hi guys
Even I had that type of oil leak, The engine that I had was a 3.o single turbo totaly rebuild, and this engine start to leak after 4 weeks. and when I did a valve adjustment I also tighten the rocker arms shaft, after that the oil leak was gone.

DPHANS.

[zcoker]

...and if it was blowing that much oil from between the head and cylinder, it will be a mosquito fogger out the tail pipe.

Originally Posted by jpnovak

Which cylinders is the leak on?

It is nearly impossible to have an oil leak between the head and cylinder. There is no oil there unless your rings, valve guides and valve guide seals are completely shot! I hope not on a rebuilt engine.

If the leak is on the 4-6 bank look at the top of the motor for the oil pressure sender or internal thermostat. It is quite common for oil leaks to run down the top of the cylinders and appear like they are coming from that area. There is not much that can leak on the 1-3 bank up top of the case except for the breather cover. Given the viscous, black nature of the oil I think you have a secondary leak somewhere that is picking up the dirt and grime as it is blow across the engine by the cooling fan. You may want to look inside the engine oil cooler from below with a flashlight and see if the top is gumming up. This add to the cooling problems later down the road of time if not cleaned.

If the leak is on #1 or #4 then you would look specifically at the cam seal between the chain housing and the cam tower. A leak on the inside (toward the case) would run down the cylinder cooling tin to the location you have pictured.

You may want to consider pulling the alternator/fan assembly and having a look under the engine cooling shroud.