[Vwdiesel] Bolt hole mania
val at swamps.roc.ny.us
Mon Feb 7 15:19:57 EST 2005
Imagine if the protologist decided to chase your threads!
What you describe is basically what I seek to do on every head change.
It is noteworthy to discuss assembly lubricants. One needs to look at
the reason for the lubricant.
Years ago I always reassembled with Never-sieze. But then I began to
notice that I never broke a headbolt removing it. And that never-siese
has metal particulates in it. Not necessarily good to have swimming
around in a newly reassembled (or rebuilt) engine. So then I considered
grease. The Tribologists at work chastized me. Light machine oil they said.
The purpose of reassembly lube in a head bolt, is to assure uniform
torquing without "sticktion". Admittedly, I've had a bit of "chattering"
of the socket/torque wrench when reassembling heads. They said I should
use light weight oil. 10 or 20, but not more than 30, in the summer.
Even in the coolant passages, I asked? I was asked if I ever had a broken
headbolt in a water passage. Admittedly, no. Although there was one
REALLY eaten away with corosion headbolt on one VW diesel I did work on.
(It was run, in the summer,with tap water, and no antifreeze. And the
head gasket leaked for several years and probably 60K miles before rebuild.)
Again, I was told to simply use light machine oil. If using engine oil,
pick the non-detergent kind, but it doesn't really matter.
Cam shaft, lifters, use assembly lube (grease). Connecting rods, use
oil on the threads. Optionally grease on the bearings, but the
prefered technique was to pump up the engine oil prior to restart.
One race car engine rebuilder I got tutored from bought STP. Never as an
oil additive, but rather as an assembly lube. The tribologists approved
that, but they preferred machine oil. They argued that the VI improvers
in STP oil treatment were not needed. And VI improvers are not
lubricants, and don't offer the protection of oil. So why not just use
oil. (Trivia, 10W50 oil has less "oil" than a can of 30 HD, because the
VI improvers in the 10W50 "displace" the oil in a can.
Getting to heads...the machine shop I've used for heads for the last decade
tells me that most gasket manufacturers are now recommending "ground" heads
(looks like it's bead blasted), as smooth heads (yep, the polished grind)
tend to burnish the gasket, and eventually that creates failures (leaks)
between the metal and the burnished material.
I have to say that I've experienced fewer 60K mile failures of head gaskets
after the new finish.
At one time gasket manufacturers were recommending head gasket prep
sprays, also, but that has passed, at least for VW/Volvo diesel heads.
Bentley has always said put the head gasket on dry. But consider that
there are different gasket manufacturers, and if you use one other
than VW's, you want to find out their recommendation.
Oh, that race engine rebuilder...his shop looked like a kitchen. Well,
perhaps more like an operating room. Sheets all over the place.
Clean room booties over shoes. Filtered air. The works. He maintained
that the cost of the precautions were small compared to the cost of
contaminant induced failure. (Reminds me of a certain surgeon I know.
He wore full face masks long before they were very popular. He maintained
that infection was far worse than a little discomfort for him while
Enough for now. Back to the science of APDs (avalanche photodiodes)
for single photon counting...a different kind of Quantum mechanics.
> The head gasket job continues:
> Having cleaned up the surfaces of the head and block, it's time to do the
> bolt holes.
> The bolts that came out looked pretty crusty, so I went at the cleaning with
> some intent.
> Ran a chase bolt in and out each by hand and discovered that some did not
> want to permit bottoming. Filled all holes with solvent and left to soak.
> Sucked out the solvent with the shop-vac and a trachor made of clear vinyl
> tubing. got quite a bit of particulate stuff. (visible thru the tubing).
> Ground a couple of slots in a head bolt wih the B&D and a thin cutting wheel.
> Dipping in solvent for each hole, and rinsing after each, chased the threads
> to the bottom of the holes. Sucked them dry again.
> refilled with solvent and brushed the threads by using a cute little tooth
> brush made by Butler G.U.M , with a bristle group about the size of a pencil
> eraser (which I trimmed a bit shorter).
> Screwed this in and out of each hole to clean the threads. Sucked them dry
> again, lots more particulates.
> Put in more solvent, sucked again, still getting particulates.
> Looked in with a penlight, there's crud at the bottom of the holes.
> Put in more solvent, using a long, flat blade screwdriver (3/16" blade),
> scraped the bottom of the holes. sucked again. lots of junk, one piece
> plugged the tube.
> Refilled and sucked again twice until no more junk visible.
> Chased all holes again and then flushed again, no more junk.
> Now threads appear shiny inside the holes.
> One more job before assembly.
> Will chase each hole with a bolt sprayed with "fogging oil" Used to
> winterize outboard motors.
> Dont want the threads to be completely dry when the new bolts go in.
> Will suck each again to be sure no oil puddles on the bottom.
> I hope you will excuse my "anal" attitude about this job. Perhaps it's
> because I endured prep and colonoscopy inspection last week. The doctor made
> much of ensuring the hole was squeeky clean for that too.
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