Do steel cylinder head studs break?

[LeRoux Strydom]

I have done some searches and found lots to read here about how to replace these studs. The Dilavar head studs (black in color?) on my 78 SC were replaced with the steel types (shiny color) about 40k miles ago. As far as I can tell, the heads were never re-torqued after that. I now have a small oil leak on #6 cylinder (exhaust side).

I guess this weekend I will pull the valve cover and try to re-torque the nuts on those studs. My question is: are these steel studs known to break?? I am not in the mood to have to send the car in to get the studs replaced again, not to mention the costs. I am therefore hoping that the re-torque will solve the leak unless a nut is obviously loose inside the valve cover. Also, is it OK to just re-torque the nuts on the exhaust side, or better to do both intake and exhaust sides at the same time. Torque to 33 Nm?? Can I take the valve covers off without draining the oil?

Another issue while I'm asking: One of the oil return tubes (between #4 and #5 leaks a bit. Can I try to rotate the tube to see if it will seal again or should I bite the bullet and replace w/ the collapsible type?

Any help/advise is appreciated.

LeRoux

[Jdub]

I would be very interested in knowing if there is a way to prevent the natural corrosion between hex nut and stud from causing undue twisting forces on the stud itself. Would one lightly tap the hex head to break the corrosion, or maybe turn back a 1/4 turn, then turn in to torque?

John

[yelcab1]

Sure,

Try retorque the head nuts, if they still leak I would think the studs somehow have stretched. Once they do that, they don't hold well any more. By opening the valve covers (exhaust side), you will automatically drain the oil, so you might as well drain it first. The engine alone only holds a few quarts, the oil tank holds the rest.

You can try the oil return tube turning trick, but I would just byte the bullet and replace it. I would think you are causing more problems than solving it by turning the tube. Maybe the other side will start leaking too.

[LeRoux Strydom]

Thanks so far. What about only re-torquing the exhaust side and not the intake side?

LeRoux

[Superman]

I say retorque them all while you're at it. I have retorqued mine three or four times since the rebuild last spring and the last time I did it, none of them moved. Previously, I was able to tighten a couple.

If the looseness has allowed the cylinder head to bang against the cylinder top, then you may have a leaking situation until the heads and cylinder tops can be flycut.

No, the steel studs don't break, as a rule. I would be very surprized if one of yours is broken.

Sure, try to turn your oil return tube. Worth a try.

[88911coupe]

When you say "retorque" does that mean just adj your torque wrench and tighten again OR are you suppose to back the bolt off an then retorque? Sorry if this is a dumb question.
Later

[Superman]

YOu can back them off a little if you want, but the goal is just to get them to the proper tension. I would turn them clockwise only, unless they seemed troublesome.

[LeRoux Strydom]

Thanks Super

I am still unclear on draining the oil before taking off the exhaust valve cover (can you tell this is my fiirst time?). Wayne's 101 book says that even when taking out an oil return tube, only "some" oil may leak out. Surely this will also be the case when removing the bottom valve cover? I'm planning do an oil change anyway, but would like to have the oil warm when draining but the engine cold when doing the head stud nuts.

Did the re-torquing solve an oil leak on your engine after the rebuild or wasn't it leaking? I am pretty sure that the nuts on mine cannot be that loose since I do not hear any blowby when the engine is cold, and the leak is more of a "sweat" on #6, but enough to create a mess on the heat exchanger. I'm glad to hear that the steel studs do not break as a rule, but will only know for sure this weekend.

LeRoux

[B.Lane]

I would think using the proper lock tight should eliminate a need for retorque. Do the studs stretch? and is that why to retorque? just wondering becasue i am about to reassemble my 3.0.

[Wayne 962]

Loose head studs cause compression leaks - not oil leaks. Look for your oil leaks elsewhere (see 101 Projects, Project 13, I think)...

-Wayne

[LeRoux Strydom]

Originally posted by Wayne at Pelican Parts
Loose head studs cause compression leaks - not oil leaks.
-Wayne

Wayne

believe me, I have studied your 101 book cover to cover. I had the car up on lifts yesterday at my Porsche mechanic to try and identify the oil leaks. We found a sweating oil return tube and oil leakage between the cylinder and head of #6 piston, obviously at the bottom being blown backwards from the fan air. The head stud visible at that piont was also wet with oil. The tech said the oil was leaking between the cylinder and head, to look for loose or broken studs and to retorque. Are you suggesting this to be a wild goose chase? I have already been looking forward to tightening up those puppies to 33Nm - even bought a 5-65Nm torque wrench at $70 for the job. I would hate to do all that and still have the leak. My thoughts were that if a stud is broken or loose enough that oil could seep past the nut/washer in the head, down the stud and out the side of the cylinder?

I will post a picture of the mess later tonight.

Anybody else on the issue of draining the oil first?

LeRoux

[yelcab1]

Loose head studs DO cause oil leak (and maybe compression leak as well). My did, and went away after I rebuilt the engine. In my case, the loose head nuts came from stretched head studs (so the nuts became loose). Oil leaks in the exact same location you have.

[LeRoux Strydom]

OK, here is a pic of what I am talking about:


Any other views on whether loose studs can cause a leak like this? Or is it another leak somewhere above? Buggered if I can find it, though.

LeRoux

[dbanazek]

I bet you have a leak from the top. thermostat o ring, breather hose, oil cooler....

This would be easy to ID w carbs, w CSI it will be a chore.

[Thomas Owen]

First of all, there should not be any significant amount of oil in the combustion chamber to leak between the head and cylinder.. Between cylinder and case, perhaps. I believe that is what Wayne is referring to when he says there will be a compression leak here. Unless, of course, the engine has other internal problems that allow the oil past the piston...
Dave is probably right, look above this cylinder for the root of the problem.
Question about lower valve covers... When there is oil in the engine you have to raise one side of the car (tilt) before removing the lower cover on that side. Adjust valves on that side, replace covers and raise the other side. Oil will pour out otherwise.
Regards,

[B.Lane]

I had an oil leak that appeared to be from the heads as well once...As it turns out, i had filled my car with to much oil...the oil was making its way into the intake and worked it's way past the intake gaskets. (in need of replace ment as well as everything else). It was dripping all the way down to the exhaust. In any event, i drained my oil and refilled with 20/50 race and made sure i didn't over fill. The problem stopped after that.

[Superman]

At least three of my cylinder heads were bouncing on the cylinder tops, even though only one head stud was broke. So yes, I strongly suggest retorquing often after a rebuild. The compression leaks did result in a dried carbon/oil film on the heads, like I see in the picture. Oil leaks closer to the case are almost certainly from something like theromostat o-ring.

Bottom line: Wayne and nearly everyone else is right. Retorquing may not seal up the compression leak. Oil and compression leaks are dealt with most effectively during a rebuild, less effectively between rebuilds. Once a cylinder head has been beat up, it may no longer be flat enough to seal. There is no real seal between the heads and the cylinders. There is an aluminum ring there, but I cannot believe that it would do anything to seal compression. Porsche cylinder heads and cylinders are metal-to-metal joints.

Sure, retorque them. When you have the engine out next, fix some other leaks. Rebuild time is the only real hope for a leakless engine.

[LeRoux Strydom]

Thanks for the advise and combined wisdom, everybody. I will soldier on, try the retorque and see if the tech can find the real source of the leak. Maybe also do a compression test. I must admit to overfilling the oil about 4 months ago when ownnership was still new, this may still be the residues of that episode which did leave a huge puddle on the garage floor, although the engine has been steamcleaned subsequently and is still wet in this area.

Thanks again.

LeRoux

[LeRoux Strydom]

A follow-up on the situation.....

I opened up the valve covers on #4,5,6 side. No studs were broken, but I was able to tighten 5 head stud bolts by maybe a 1/4 turn each before the torque wrench clicked, all on the intake side ! The bolts on the exhaust side were all tight to spec. It also looked as if #6 rocker shaft was sweating oil (see photo below), but maybe this area became wet from the leak somewhere else, I'm not sure. The other rocker shafts were dry as a bone. I tightened up the rocker pinch bolt a little just to be sure, although it is impossible to get a torque wrench in there. I replaced the covers with new gaskets, silicone-beaded on the bottom cover.

I also replaced an oil return tube, and used the trick with two hose clamps on the two tube halves, levering them apart with a wide screwdriver blade to slide the tube open. Even though the circlip fits nicely into its groove with room to spare, the O-ring on the case side does not appear to seat fully compared with the other tubes, but it does not leak a drop (see photo). Should I try to slide the tubes halves open more to get the O-ring more fully into the case?

I must admit to a fair degree of satisfaction after the job, especially when I drove the car about 30km afterwards and no oil dripped on the floor overnight. I will see if the oil leak onto the heat exchager has stopped once I have driven it for a few days, maybe it was only something stupid as a valve cover gasket.

The oily mess on the heat exchanger:


#6 rocker shaft - does it leak, or is oil being blown in there from somewhere else?:


The new oil return tube - notice that the O-ring is visible in the case. Should I try to push it open more, even though the circlip is in the groove with room to spare?


Thanks for any advice/comments.

LeRoux

[cstreit]

I would think you'd want to back off the head stud nuts a bit before re-torqueing... Otherwise you might get a false reading from the torque wrench just trying to overcome the friction of the threads, and the nut against the washer...