Drooling Head Gasket

I have an 85 R80RT. A few days ago, I noticed that the left head was shiny with oil around the head gasket - that area is normally as dry as a bone. The head gasket has no visible cracks or breaks in it.

I wondered if the head was not properly torqued, so I loosened and re-torqued each nut to 33 NM. Nothing seemed amis until I got to the upper exhaust rocker tower. The nut there came loose with way too little effort. I re-torqued that nut and the remaining nuts and noticed that that upper forward stud was showing one more thread than the other three cylinder studs.

After re-setting the valves, I buttoned everything up and cleaned the outside of the head with carb cleaner. The next day, I had oil around the head gasket. Today, not only oil on the head, but a fine mist of oil on my left boot.

I had been hoping that there was some sort of screwup last time the head came off (at least a year ago - stupid leaky pushrod seals). Now, I'm wondering if that upper forward cylinder stud is pulling out of the case.

I do suspect that the left head is a bit warped. I never could get the left rocker cover to stop leaking until I switched to a silicone gasket. I heard somewhere that the left head was cast in a way that made it more prone to warping. Is that true or just rumor?

I know I'm going to have to pull everything apart - and, if the cylinder stud is pulling out, I'll want to have a pro fix it. I have not had enough experience with helicoils or timeserts to have a go at that by myself. If the head is warped, how should I check it? What constitutes too warped? It does not look like there's much room to mill the head flat - is that even possible?

In the meantime, what do you all think? Anything else I should be looking for?

MonoRT said:

If the head is warped, how should I check it? What constitutes too warped? It does not look like there's much room to mill the head flat - is that even possible?

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A good machinist can check it to see if and how much it is warped, and can plane it if needed. You might talk to Ted Porter about it- I'd suggest he would be a very good candidate to do the work as well. He is working on the heads on my RS currently. Among the number of things he's doing, one is checking them to verify that they are flat and plane them if they are not within the recommended tolerances (mine had terminal leaks at the valve covers, which can be a symptom of warped heads).
http://www.beemershop.com

Just to throw in my zwei Pfennigs, Ted has done work for me in the past as well. He's happy to talk to knowledgable owner on the phone too. Give him a call and see what he has to say.

Were you able to attain the torque value needed on that stud?

Yes, I was able to get 33NM on the stud that I was worried about. Perhaps that's a good sign as far as the stud goes? If the stud was really messed up, I imagine that I could have just kept tightening the nut without reaching 33NM.

I will want to open it up again and check to see how easy it is to back off the nut on that stud. The first time round, I could have backed that nut off with a palm ratchet - no problem.

The bike continues to spray a mist of oil on my left boot.

It sounds as though the stud with the loose nut @ the ex. rocker tower has stripped its threads in the engine case. Remove the nut and unscrew the stud from its thread. If it withdraws easily, you may have found the source of your leak. If that's the case, it's not a big deal to Heli-Coil the hole. BMW even makes the correct length replacement thread insert. Good luck!

Sounds like the thread to me. It is typically the forward upper one. After three helicoils (one doubled) I had to replace the block.

This area of the motorblock (I heard certain years only) are SOFT!

I would not recommend helicoils. To use timeserts for the top front is a bit tricky to get the opening for the oil flow correct but a much better bonding with the block.

/Guenther ('89 R100GS happy with a '81 block)

I have out of town visitors this weekend and that may keep me away from tools and the garage... However, if I remove the rocker cover and find that nut loose again, I will suspect that the stud is pulling out of the case. I hate to admit this, but I have never had to heli-coil anything myself. Early on in my ownership of this bike, I pulled the left rocker cover stud loose, but I paid a local mechanic to fix that. That local mechanic now lives in Idaho, so he's not an option.

I'm sure that I can find some you tube videos on the use of heli-coils or timeserts (which is better? - I don't want to start an oil thread!). I am concerned about drilling out the old hole correctly. The engine would still be in the frame, so I can't think of any jigs that will help me drill straight. Those studs are pretty long, so if I drill/tap out the old hole off square, it would make quite a difference at the end of the stud.

Would I need a new stud? Steel is way harder than Al, so I would assume that the steel threads might survive the pulling-out process. I just looked at the original pulled-out rocker cover stud (my mechanic replaced it with a Subaru part!) and it looks new except for some discoloration of the plating where it was threaded into the head.

I guess I'm just asking if anyone has any tips. Learning from other people's experience seems more efficient than making my own mistakes.

I'm sure Cycleworks sells a tool/jig for drilling straight. I know there's one offered in the Airmail made by HPD. Website is:

http://www.hpd-online.com/stud-tool.php {address is wrong in Airmail!!}

Something that would work well I think is if there was an old cylinder that could be cut down so that only maybe the outermost 3-5 inches was left. Once that is slipped on and the other three studs are run in a ways, the remaining hole acts as a drill guide.

But you're right...only go down that path if that's what's happening. You got 33Nm (~24 ft-lbs) on the nut...what's not to like? If it's loose again, well, that will be the answer.

The first helicoil was put in by a Ducati mechanic free handed (well, I put pressure on him because I was about to leave for a rally). Lasted only 4k miles. Then a good BMW mechanic in town used a self made jig (like one as Kurt described). A large helicoil was inserted first and a smaller one next. That lasted 37k miles. In between on the other side a helicoil was inserted by my good mechanic with a jig and it was still good after 40k miles.

My impression: If done with the right jig by a professional it may last a long time.

/Guenther

Cycle Works has the jug for sale or rent.

Mmmm... . . I know you've science'd your way through this by process of elimination, but your comment about a mist of oil on your left boot caught my attention ... is there a chance that your oil pressure sending unit is the culprit? Perhaps spraying up onto the head? Yeah, I know, slim to none, but they have been known to fail.

Yes, those oil pressure switches do fail and drip/spray oil on your boots. I even bought a 24mm crowfoot wrench to make those switch changes easy. That would have be too simple and cheap. My current oil pressure switch is nice and dry.

I did get a chance to check the tightness of the upper exhaust stud nut. It came loose with very little effort - with my hand choked right up to the ratchet head on the wrench. Nuts! Also, if I moved the torque wrench (a dial type) sloooowly, I could only hit 30NM - the target torque kept sneaking away from me.

Well, I guess I know what's wrong... I really like my bike, but sometimes I think it's mocking me. The pushrod seals on the right side are getting leaky. The pushrod seals on the left side with the bad stud are dry. Sigh.