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In February, I finished up a head gasket job and obviously reinstalled cam housing with new gasket, as well as the end cap. On the end cap I even put Holemar sealant.
Recently, oil has been leaking in the rear area; it collects onto the engine # stamping then drips down, eventually hitting hot exhaust. Stinky!
On first look, it appears to come from the new headgasket where head meets block at engine # stamp.
On closer inspection, after wiping and driving, the cam tower above gets oily. Then, I wipe again and see this:
Seriously? Oil coming from under the bolt? What do I do with that?
I’m almost certain that you’ll find that bolt has nearly stripped all the threads in the head and due to that is not holding firm. It’s easy to overtighten those bolts causing this if they were not chased and spotlessly clean before bolting on the cam tower amhik.
Could be what MAGK944 said, however there is an oil passage to the camshaft very close to that exact spot.
Often the oil pressure pushes out the gasket around the oil passage and then it starts to leak more and more.
Either way, head or cam gasket, you're going to need to pull the cam tower first. Check the gasket and replace if damaged.
When reinstalling the cam gasket, do not use a gasket adhesive. The factory (or Victor Reinz) gasket has a graphite coating at the ends that allows for a difference in expansion between the head and the cam tower. If you use an adhesive then the gasket may tear.
I’m almost certain that you’ll find that bolt has nearly stripped all the threads in the head and due to that is not holding firm. It’s easy to overtighten those bolts causing this if they were not chased and spotlessly clean before bolting on the cam tower amhik.
I'm trying to remember if that bolt was a little hard going in; may have seemed a bit tight, though it's a tough spot and I do recall having issues fumbling with elbows and such. Not much leverage! I did use all new bolts though.
I definitely didn't overtighten it, using a smaller torque wrench set to 15 ft lbs. But no, I didn't clean the hole. In fact, I never do; I don't have--nor can I seem to find--any "chaser" tools. They are such a mystery! Everyone talks about them.. but.. where are they? There certainly isn't an affordable set like regular tap&die stuff.
If the threads are indeed leaking, I'm guessing I need to remove the cam tower, drill that hole, and tap to a slightly bigger thread, find a bolt that works?
PS: I didn't use any adhesive here, only on the end-cap cork gasket. And cam gasket is under that bolt head.. or.. is the suggestion that a failed gasket would help steer oil up the bolt hole threads?
...I don't have--nor can I seem to find--any "chaser" tools. They are such a mystery! Everyone talks about them.. but.. where are they? There certainly isn't an affordable set like regular tap&die stuff....
I guess they may be known by a different name but yes they are taps designed to reach to the bottom of a thread, like the final tap you would use to finish cutting a thread. Relatively cheap to buy a set, I use mine on almost every thread I take a bolt out of just to clean up the thread, then I carefully clean all the crud out afterwards. It’s just cheap insurance.
If you don't have the old female threads cleaned out properly, then some of your torque goes into the friction of the dirty threads and thus you do not get the joint tight enough. You should be able to run your bolts in with your fingers if the female threads are properly cleaned.
If/when you take the cam tower off you might want to confirm that there is not a scratch on the head or the cam tower that is deep enough to allow oil to get past the gasket.
Also, there is a chance the leak is coming from the gasketed fitting at the rear of the cam tower. There is some discussion of this near the end of the article here: https://newhillgarage.com/2013/06/25...tem-explained/
Also, you might want to check your head surface with a straight edge to make sure it has not bowed due to an overheating event. Check the cam tower while your at it, although it being bowed would be a real surprise. You could dry fit the cam tower without a gasket and check that location with a feeler gauge.
I have always wanted to "chase" threads and clean, but could never find these tools; thanks for the info on making your own Harvey. In fact, I do recall reading this before, just forgot exactly where.
I had a 'head job' done before re-installing, incl. "flattening" whatever that is. When I got it back, I did notice 2 scratches north of this area. I couldn't feel them though. I found out after that the machinist is known for drinking (the infamous Drunk Machinist)
Yesterday, I wiped the area and shortly after the first start of the day, the oil returned. I wiped again, took those pics, drove around doing errands a few times, and it kinda stopped leaking (a little you see in the pic but no more). Perhaps the leak mostly occurs in the transition from stone cold to warm.
With my torque wrench, I will check the torque on that bolt today (cold engine). This is one of two bolts that needs an universal elbow + extension: perhaps this throws off the torque wrench? I've always wondered what effect elbows & extensions have when using a torque wrench.
When I installed these bolts, I followed the official pattern. Would removing this bolt out-of-pattern (and reinstalling) be a problem? And if not, could I remove the bolt and do anything with cam tower installed?
Last edited by Dan Martinic; 10-14-2018 at 10:04 AM.
Reason: Clarification
I'm putting a head back on myself and a couple days once I get it back from The Machinist. Thanks for sharing your experience here, I'm sure it might save my butt in some way.
"I definitely didn't overtighten it"
Ha! With a 30+ year old aluminum head there will be problems with threads. I had the same issue with my cam tower. I lucked out by cleaning the threads and changing the bolts. I had the head off so it was accessible. That's an M8X35 bolt.
I'm starting to see how dirty or corrupt threads can cause problems, though it's unclear how I can *over* tighten if the torque wrench clicks and I stop? Maybe under-tighten. Then again, I'm not exactly a machinist. Not even a drunk one lol
I bought the car at 69k US miles and I haven't removed the cam tower till recently. Not clear how the threads could get so dirty or bad if most of their life they've been fastened and the bolt pretty clean. I was going to reuse the bolts but one got a bit rounded on removal so I just replaced them all.
Now I have nice used ones to home-make chasers from. Anyway, I'm gonna go check torque on that one now...
Ok, I went out and put my smallest 1/4" torque wrench on it. This allowed me to use a 6mm bit in a bit holder--a very short (almost too-short) setup so no elbow needed.
I had one-ratchet-click's space of movement. At 20NM setting, I was able to turn it three times (one ratchet-click, back, one ratchet-click again, back, one more ratchet-click) until the little torque wrench clicked the torque value.
I don't know how much the bolt turned, but at least a bit. Given it's one of the last outside bolts in the tightening pattern, I'm assuming I haven't messed up the others. I guess I should have pulled all the caps and checked torque on them all in order. But that would have required too much patience and professionalism, neither of which I have tonight.
Update to follow if the leak stops. Driving my son to hockey soon
The problem is that torque values are based on clean threads.
Any oil or such in the threads reduces the friction between the threads on the fastener and the threads in the hole.
So the amount of friction that the torque wrench 'sees' is lower than it should be for the amount of 'pull' being applied to the threads.
It's a bit counterintuitive, but it's very real.
Wait: are you suggesting that since oil has been riding up those threads, I've just over-torqued this bolt? Yikes
But wait: I'm in the habit of putting Copaslip anti-sieze on everything--including these originally! That would mean everything I fasten is over value??
Well, the hockey drive shows no oil leaking from the bolt, though I could swear there's a little collecting along the edge where head meets block right on top of engine number stamping. Above that looks clean still. Tomorrow's drive to work will be a better test. So will daylight + a proper work light!
10-13-2018, 03:12 PM
Oil leaking from cam bolt? really?
