Crank case to cylinder block oil leak

[ajs350]

I have a small oil leak that is coming from the tunnel to the left of the cam chain housing. I first thought it was the bolt I'm pointing to in the picture but the oil is coming from the tunnel. Is this indicative of a broken gasket or can I get away wilth removing the valve cover and retorquing the cylinder head cap nuts?
Thanks
Ross

[daves79x]

Ross:

More than likely you will find that the stud won't torque because it's pulling out of the case. Pretty common. Can be Helicoiled, but lots of stuff has to come apart to do it. Take the valve cover off, once you have eliminated all external possibilities, and see what happens when you try to torque the head bolt. If you can live with an under torqued head bolt, you might get it to stop by cleaning up the washer really well and smearing some Hondabond or similar on it. See what you find.

Dave

[Jeff Bennetts]

Its a long shot but I have seen the stud acorn nut replaced with a regular open nut, this allows oil to seep down the stud, you'll know after pulling the cam cover off.

If the stud is pulling out of the case like Dave has suggested a long shot fix is to clean the stud the best you can with some brake cleaning fluid and compressed air then apply some Permatex loctite for assembled fasteners to the stud and let it wick its way down the stud to the block, wait a couple days and try to retorque the stud cap.

[bobcat]

Refer to the 79 shop manual or service bulletins concerning "sealing the intake side cyl. studs" ! oil appears at the front
but could be leaking from the rear and flowing downhill (tunnel)to the front .
bobcat

[daves79x]

Ross:
The stud that is leaking is also not blind. The threads go into the crankcase. Honda used sealant on all of them, but it is necessary on some of them, including the offending one. It could be coming up out of the case threads, but if you see it wet up into the head, it is likely the previously speculated issue.

Dave

[ajs350]

Thanks for all the suggestions. I'm going to clean up the tunnel as best I can and take it for another ride to see from which direction the oil is coming from. With that I can decide what to do next.
Is it possible to remove the stud without taking the head off?
Ross

[daves79x]

Ross:
Yes, you can remove the studs sometimes without removing the head, but don't fear removing the head if the time comes. The only real issue is the cost of the head gasket.

Dave

[ajs350]

I have the valve cover off and the engine tilted and see oil on #4 inlet stud up to about 1.5 inches above the crankcase. The picture below shows this although you can see where I have wiped the stud with my finger removing some of the oil. The stud appears to be dry higher up. The #4 exhaust stud looks similar.
I looked in the manual for "sealing the cylinder head studs" but could not find anything. How do I view service bulitins?
Am I right to assume from this that oil is wicking up from the crank? If so what is the best method to tighten these 2 studs?
Also I removed the 2 acorn nuts and found a copper washer under each. Do I need to aneal these before retorquing?
TIA
Ross

[daves79x]

Ross:
Those studs are not blind. You will need to remove them (if more than one) and use thread sealant on them. Honda used some, but on the '79s it was sparingly. If your leak is for sure from the crankcase, that's the cure.

Dave

[Jeff Bennetts]

If its only the one stud I would try the permatex thread locker for pre-assembled fasteners, what do you got to lose?

Permatex Penetrating Grade
Threadlocker Green

PRODUCT DESCRIPTION S.I.N.: 834-300
Permatex Penetrating Grade Threadlocker Green is a
medium strength anaerobic threadlocking material that cures
between engaged threads to form a unitized assembly that
resists virtually all leakage, shock and vibration. The product
is a single component, anaerobic liquid that cures in the
absence of air and when confined between close fitting metal
surfaces. Because of its low viscosity and capillary action, the
product wicks between engaged threads and eliminates the
need to disassemble, apply product and then reassemble. The
high prevailing torque provides vibration resistance to
adjustment screws. Ideal for all threaded engagements less
than or equal to 1/2 inch in diameter. The product can also fill
porosity in welds, castings and powder metal parts. Excellent
chemical resistance with a temperature resistance range of
-175°C to 150°C (-65°F to 300°F). OEM Specified. NSF
White Book registered.

http://www.permatex.com/documents/tds/a ... /29000.pdf

[ajs350]

Thanks Guys. I bought some of the Green Permatex so will try that at the bottom of the studs along with Hondabond at the top between the acorn nuts and washers.
The washers seem to be copper so do they need annealing beform retorqueing?
Ross

[Jeff Bennetts]

Thanks Guys. I bought some of the Green Permatex so will try that at the bottom of the studs along with Hondabond at the top between the acorn nuts and washers.
The washers seem to be copper so do they need annealing beform retorqueing?
Ross

You should'nt need any sealer for the washers and acorn nuts, I guess you can anneal the washers and reuse them but I always buy new ones, they aren't that expensive.

Make sure you clean the stud and the area around it, brake cleaning fluid would be good and use some compressed air too, do it until the fluid doesn't pull any more oil from the block.

[NobleHops]

This is a great tip and I am very interested to learn if this is successful in this case. As Jeff said, not much to lose for trying! I wonder however if it wouldn't wick a little bit better if the engine was good and warm when the Permatex was applied.

Hope it works Ross!

N.

[Jeff Bennetts]

Just make sure all the oil is cleaned from the stud and block area.

[ajs350]

No luck I'm afraid. After just a few miles today oil began weeping from the tunnel next to #4 cylinder.

I'll take the valve cover off again and I'm assuming that if I put 2 6mm nuts on the stud I can turn the lower one and it will force the stud to unscrew?

Is there any particular thread sealant you would recommend?
Thanks
Ross