Roche993

Don, this is a great thought. Might just explain why you throttle was not working when you had it running!

dgmattingley

So the saga continues.

After checking all the wires and connections I could think of I was unable to find any evidence of fried electronics that would've caused my engine to refuse to shut down. So I buttoned everything back up, turned the key, and the starter just made a "whoosh" noise. The crank didn't turn. Hmm, maybe the starter did get stuck somehow, and failed? There is a lot of stress placed on the starter when building oil pressure at 30 sec intervals before the first time you start the fresh engine.

For good measure, I disconnected and then reconnected the starter, and then gave it another go. The engine roared to life immediately, and after about 5 seconds I turned the key and...it shut right off. I have a rebuilt starter from EBS on its way.

But wait, there's more. After the obligatory 20 min run-in of the new engine, I shut it down again and went to take a peak underneath. Uh oh. A large puddle of oil. So, while I've proved I can rebuild a 911 engine that fires right up, it's an engine that won't shut off and leaks oil like a sieve! The puddle was "healthy", about 12 inches in diameter. Back up on jack stands, I found the origin of the leak -- the base of cylinder 2 was thoroughly soaked. Ugh. So after about 5 hours of work I got the engine back out. And after another 5 hours I got it back on the engine stand and torn down to the cylinders.

First I rotated the crank to TDC for piston 2 so I could pull up the cylinder and take a peek at the o ring. It looked fine as far as I could tell, at least there was no obvious sign if it being fouled or torn. There really isn't anywhere for that o ring to go, so apart from getting badly twisted I'm not sure how it could fail so completely. It didn't appear to be twisted at all.

Looking at the through bolts, the two at the bottom of cyl 2 were soaked with oil, which doesn't necessarily indicate a failure, as a leak from the cylinder would also cause that. With a flashlight I could see a very very thin coat of oil on the top two through bolts that sit directly above cylinder two. It's so thin that it's imperceptible in a flash photo, and it wasn't bad enough that there was any evidence of oil dripping down the case. All the other top through bolts were totally dry. This leads me to believe it could actually be that all four center through bolts are leaking, which are also the first four to be torqued in the case sealing sequence. Although this seems rather unlikely, after inspection it also seems very unlikely that it's an issue with the cylinder base o ring. Even if the o ring was fouled, I wouldn't expect it to fail so completely and the bottom of the cylinder to be so evenly coated with oil. However, the extent of the leak seems to be more than would conceivably leak through the through bolts in 20 min, even if the o rings were badly fouled. What conclusion to draw? Other possible culprits?

The only other thing I can think of is that the head studs were not torqued all the way, but they sure were on tight when I removed them So my plan of attack is to replace, one at a time, the o rings in the four through bolts around cylinder two, replace the o ring at the base of cylinder two for good measure, and then button everything back up.

Below are pics of the base of cyl 2 before and after I removed the engine.

Ed Hughes

Did you use green (Viton) o-rings for the thru bolts? For earlier motors, at least, they are the hot ticket, as many have torn the reds in assembling a case.

That does seem to be coming from the cyl base, however.

trophy

That really sucks Don....

is there any damage to the case or the cylinder that could be causing the leak?

I have been watching you thread with great interest, I am pulling down my engine at the moment ready for a rebuild...

dgmattingley

Yep, they're the green ones so I unfortunately I don't have that excuse.

Not that I know of, but I'm going to give it a careful look when I take the cylinder completely off. The case and cylinders were all checked out and within spec and hadn't leaked like this before, but who knows.

geolab

Hi Don, wish you courage,
Just a quick question;
Did you tighten the cam housings on the cylinder heads before tightening the cylinder heads to engine ?
or did you tighten the cylinder heads, and later tightened the cam housings ?
What about the knock sensor bridge ?

dgmattingley

Hi Geo,
Thanks. I tightened the cam housing bolts first, with the head nuts only very lightly snugged, then I did the torque sequence for the head nuts of 17ft-lb and 90 degrees.

Mike J

Hi Don,

Hey, in your last picture in post #77, at the base of the cylinder, it almost looks like a deviation or dent of some kind - its right at the bottom of the base. It would be the way the picture is taken - not sure.

I think what George is getting at is, if the cam carrier is not flat, it could pull a barrel out of alignment and then when torquing the barrel's down, they can not not be perfectly aligned with the base of the case. however, you had them held down on the case (lightly snugged), so unless the carrier is totally twised it should be ok. I assume when you inserted the camshaft it rotated freely in the cam-carrier, no binding?.

Did you examine the base O ring carefully for defects? Perhaps there is a small imperfection that was allowing oil to pass?

Did you also put the knock sensor bridge on loosely before torquing down the cam carrier to the heads?

Cheers,

Mike


Can you check the flatness of the cam carrier to head interface?

dgmattingley

I see what you mean in the photo, but I think that is just an effect from the dripping oil. Something to check I guess.

The camshaft rotated freely and I installed and removed it without issue, no binding or any problems.

I did not put the knock sensor on before installed the cam carrier to the heads.

Do you think I should consider taking the carrier and heads apart?

Thanks for the feedback.

axl911

I ran into the same problem on my 993 rebuild. Leak started slowly, but by the end of the week I would have 8 inch puddle of oil parking the car after I drove it.

Ended up pulling the engine and replacing the cylinder base gasket and thru-bolt o-rings. MAKE sure you use the green viton thru-bolt orings and not the crappy blue ones. Mine o-rings seemed fine when I pulled it out, but a small nick could have caused the leak.

The rings fixed the oil leak. I didn't break apart the cylinder heads by carefully removing the whole thing in one unit.

When doing the thru-bolt, install the orings dipped in oil very carefully using the tool so the oring doesn't get scratched by the thru-bolt threads. Also insure the orings are seated properly on both sides with a "snap" before tighten down the thru-bolt and nut.

dgmattingley

Interesting. was your leak at a particular cylinder or through bolt or from multiple locations? Did you use any sealant at the cylinder base? I did use the green ones, but this was my first time installing these so I can't say whether I didn them correctly. I did oil them up and used a pen cap like described on pcarworkshop.

axl911

Mine was just like yours. Can't tell whether it was base gasket or thru-bolt o-rings so I replaced both. I thought I was careful first time. But on 2nd time, I inspected each o-ring and made sure each are seated fully. And only use plastic/non-sharp/non-metal part to seat each gasket/oring.

I don't recall using any sealant on the base gasket. Only oil to put them on.

Be very careful with dirt and debris. Only a small piece of dirt can pinch the gasket and cause a leak. Be careful when installing the gasket/o-rings. If they are twisted, pinched, or not seated properly and relaxed they can leak. Lube 'em up plenty.

Didn't read through your thread, but did you machine or change your cylinder and/or case?

dgmattingley

No machining to the case or cylinders, just jet washed and deglazed.

I thought I was careful, too, but looks like I wasn't careful enough. The hardest part is maintaining patience when all you really want to be doing is tearing down a back road or goosing it at the track. Thanks for the tips.

Ed Hughes

I'd actually use the proper Silicone grease, which is a paste. Dow 55 is what I used. Not easy to find, but I thought it to be worth it.

Mike J

Similar idea, but I used Dow Corning 111 on all the O-rings. I also used some Curil-T on the cylinder base gasket to case seal to "help" the Viton O-ring.

I do not think its necessary to split the carrier/heads (just yet). Have you had a good chance to examine the base O rings for any damage? How about the through bolt O rings?

Keep at it, you are almost there!

cheers,

Mike