964 Oil leak and knocking on first start up???

WMRiceman · 09-04-2010, 02:19 PM

I finished up my 1990 964 rebuild this morning. I turned it over for 3 30 second intervals and then started it up. I hear a terrible knocking sound from what might be the right side (4,5,6,) and I see oil coming from the front of the engine. I pulled the engine out and slowing started taking it back apart.

The oil is coming from the top of the engine. The oil pressure sensor is dry and so is the crankcase ventilation tower. When I saw it on top of the right chain housing I thought I had it but if you look at the middle section where it is pooled up, a chain housing leak would not make it over the hump and into the valley. Maybe the case seam on top of the number 8 bearing? The front main seal and intermediate cover are dry. There is some oil on the right side of the top of the engine but I'm not sure if it was blown there by the fan.

The knocking has me puzzled as well. I now have the engine back on the stand and I rechecked the right side timing chain and the position is still correct, .050 in. I pulled the plugs out and it spins freely with no interference. I am guessing I'm going to have to split the case again to find out where this knocking is coming from?

I truly appreciate any advice you smart folks can give. I have been reading post on this forum throughout the rebuild and I have learn so much. I'm just very disappointed with myself right now with this rebuild. Everything was going so smooth; no surprises and now this. Please help.

Flat6pac · 09-04-2010, 05:18 PM

looks like you might have oil coming out of the main oil galley, something in the picture doesnt look right in the plug on the galley. The chain box picture would be an extension of that leak.
Bruce

WMRiceman · 09-05-2010, 10:33 AM

Thanks Bruce, I'll go take a look at it now. I put some JB Weld on that plug at rebuild. Mark

WMRiceman · 09-05-2010, 04:53 PM

I took off the JB weld I put on that oil plug to see if something was apparent but not really. I have attached a few pictures of the plug with it cleaned off. I'm going to reapply JB Weld. I would think with as much oil as I had leaking out, I would have seen something. There was no sealant on this plug when I took it apart.

Good news is the knocking doesn't seem to be mechanical. The heads look fine and no sign of any thing hitting. Maybe ignition and knocking from the wires being wrong It is hard on a 964 to screw up the wires; I never took the wires off the distributor but I guess I could have. The wire length makes it hard to put them on the wrong plug. The distributor belt is not broken.

I have ordered gaskets and sealant and I'm going to try this again. I'm not confident since I didn't find anything obvious. The number 8 o-ring from the gasket kit seemed tight when I put it on but if was the only one in the kit even close to being the right one.

BURN-BROS · 06:26 AM

I would look at the 4,5,6 chainbox. check for cracks or warpage. The chainbox routes oil for the tensioner where you are experiencing the leak. The knock you heard may be the tensioner.

Edit: The pooling of oil is higher up so it's likely the leak is at the case seam.

This should not have contributed to the knock so I would check my clearances again.

JFairman · 09-06-2010, 08:20 AM

It might be a good idea to remove the other JB weld epoxy blob above the #8 nose bearing oil feed hole and nearby and below the fan housing roll pin that is still there in the second set of pics.. Clean oil away with brake clean and compressed air, prep scuff, and redo it with 24 hour slow hardening JB weld (not the 5 minute JB weld stuff which will delaminate and warp from the heat) or devcon marine epoxy.

If it slowly leaked oil maybe the engine fan air flow sucked oil upwards and through it causing that pool of oil sitting under the fan housing.
...just a thought from looking at your pics..

WMRiceman · 09-06-2010, 09:48 AM

Thanks for all the advice. I have been out in the garage studying the case all morning. I'm thinking now that I had a case seam leak. In the pictures, you can see where Porsche machined a cut out around one of the cross bolts. I put too much orange lock tight on my halves thinking that the left over would just wash away. I filled up that little groove with lock tight. I had to dig it out when I took it back apart. Instead of the oil traveling back to the internals of the case from the matting, it would have pushed its way out of the case. Just an idea, I'm not going to use nearly as much case sealant next go around. I've been reading post that say little is better. I'm going to tighten up the outer fasteners first next time and then move to the through bolts.

The knock sounded like detonation. When I spun the car over with the DME relay out, nothing but smooth spinning. Once it fired up, very bad knocking. I checked the valve timing before I took it back apart with the chain tensioner in place and not a mechanical tensioner and it was a little off but not by much. .045 in. not the .050 as prescribed. The chains were nice and tight when I took it apart. The chain tensioner seems to hold onto some oil and keep it tight. When I put it back the first time I had to compress the tensioner some to get some oil out just to compress them.

Now here is an idea. I didn't fit the knock sensor bar with the cylinders before tightening up the heads. I latter put the bars on and I had to work to get the bolts to line up, They were tight with a lot of side pressure. The manual says to tighten up the bar to just 7 ft lbs. Crazy idea but if the bar was too tight the computer might have thought I had knocking under normal running condition and started retarding the timing. Could this cause the knocking? I'm going to fit the bar loose before I put the heads back on.

One last thing. I didn't take the cam tower off the heads. I was planning on re-installing the three heads and cam tower as a unit when I put it back together. Anyone see a problem with this. Thanks again for all you help. I have been reading every post I can on through bolts and tightening techniques. I followed the book on the RTV on the through bolt o-rings, not the second time. That stuff was everywhere. I'm going to follow the factory manual this time and just oil them. I would love to get some the the green ones and not the blue ones in the kit but can't seem to find them. Thanks again, Mark

WMRiceman · 10-02-2010, 06:26 PM

Problem Solved. I took the engine back apart and used only a very light coat of 574 on the case half and all is well. No knock or oil leak this time around. Thanks for all the help. Mark