GMK

Need the expert's advice here. Had a my 1991 C2 engine top end rebuilt this winter. I've done approx. 5500 km since I got the car back, and took the engine tray off today to inspect the underside of the engine.

The right side of the engine was dry, but I notice some oil leakage on the left side, see picture below.

I've not noticed any particular oil consumption when measuring from the dip stick.

So what say the experts here? Should I take my car back to the workshop?

All advice appreciated! Thanks!

RallyeChris

The valve covers could just use a re-torque. I have found my billet aluminum valve covers get a tad "sweaty" after track days or a couple thousand street miles. No drips or anything. But, I might catch a whiff of burning oil, only to find the sweat has accumulated. My valve covers and gaskets are only about 3500 miles and about 3 years old. A quick tweak with the 10mm keeps them dry for a while. It is possible that your gaskets are settling-in and a simple re-torque will alleviate your concern.

GMK

Hey thanks for the quick response RallyeChris. I sent an email to the German workshop that did the rebuild, will be interesting to hear from them. You're explanation seems logical.

The Norwegian workshop that adjusted the valves and changed the oil 2000 km after rebuild did mention oil leaks on the left side. They replaced the gaskets, but the left side still leaks. Not sure how I feel about this so close after the rebuild.

RallyeChris

If the leak on the left side is still persistent after replacing the gasket again, it is possible that the cover is warped if original. The original covers were/are known to warp over time. This is why the previous owner of my car went to billet aluminum units. He hated leaks of any kind.

John McM

My engine was fully rebuilt 16,000 km ago. It leaked about 500km after the rebuild and was a 50/50 call on taking it back to the OPC until an independent told me that 964s are difficult to keep leak free. Right now I'm dropping my engine to get the gearbox synchros fixed and will look for source of the leaks.

J richard

Check the rocker shafts, a common source of leaks on rebuilt motors. I would not rebuild a motor without rocker shaft seals for this reason.

onceover

Also, I would advise against using the engine gray as it causes the engine to get too hot.

GMK

Gents,

Asked the German workshop that did the rebuild. It is a well known workshop here in Norway (I think one of the un-official Porsche dealers here uses the workshop extensively for all of their engine work), and I know they are very experienced with Porsche 964 engines. They made two points that made sense to me:

1) The German workshop had used silicon in addition to the valve cover seals. The Norwegian Porche Centre that adjusted my valves and re-tightened the rocker axels after 2k km, removed the silicon under the argument that the silicon could loosen and clog up the oil lines. When I asked the workshop about this, they said that their extensive experience showed that almost all valve covers warp over time, and while the offiical Porsche manual does not specify silicon in addition to seals, they argued that it was needed in order to keep the valve covers tight. They had never experienced problems with silicon clogging up oil lines.

2) As for the leakage, they said that it was most likely coming from the rocker shafts, so 10 points are given to Mr J richard. Their experience was that the specified torque number given in the official Porsche instructions was too low. They consequently used more torque than specified in order to avoid leakages. They could not give me an "updated" torque-number that they use though.

Onceover, II've seen some of the tray vs no tray threads that pop up here, and I'm actually on the "use under tray-side", as I do believe that the aerodynamic benefits of keeping the tray out weighs the "drawbacks" of potential over heating. Note though, that I'm living in Norway, and I can count on one hand the number of days above 20 degrees C that we've had this summer.

Returning to thread topic, I think I'll contact the Porsche Centre here in Oslo again and ask what torque they used on the rocker shafts and if they possibly should tighten them a bit more. I'll keep you updated.

J richard

The issue with the rocker shafts is that they are fresh mating surfaces when new, and once removed (even in the same bore and orientation) they are just not mated up. Be careful to fight the urge to over tighten them. If you break a pinchbolt you have a job on your hands. Most important to make sure they are at the right depth.

The sure fire solution is to use the RSR rocker seals that slide into the slot behind the expansion sleeve. Otherwise just inspec them to make sure that they are tight and haven't walked in their bores to uncover the slot, or you will have a large leak.

GMK

Hey thanks again for response J richard.

I looked up the rocker arm assembly in the 964 manual, but were unable to find the expansion sleeve you refer to. And where can I find RSR rocker seals?

J richard

I'm referring to the ends of the rocker shaft itself. As you tighten the Pinch bolt (Allen) it wedges the the ends of the shaft and expands to tighten in the bore. The rocker shaft seals fit in the groove to seal the bore. I've found this as one of the most prevalent leaks on a 911, I don't know why Porsche didn't put them in from day one. They are a Porsche motorsports part 911.099.103.52, you need two per rocker shaft. Not sure where to get them on your side of the pond, I'd start with the dealer. You want to use 20ftlbs on the bolts.