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DISCUSSION => Engine + Driveline => Topic started by: P. Kennedy on June 12, 2009, 05:00:42 PM

Title: Valve cover drill out problems
Post by: P. Kennedy on June 12, 2009, 05:00:42 PM

OK, so once upon a time, I put heli-coils all around the valve cover to try and solve the common oil leak.  Didn't work so well, so I'm in the process of redoing it.  All but 2 of the old heli-coils came out with easy drilling, but I actually broke drill bits in 2 of the cyl. head holes down low near the passenger side shock tower.  The drill bits that broke were cheap crummy ones, so I went to ACE and got some cobalt bits that says "for Stainless and hardened steels."

I'm not making any progress with the allegedly better drill bits, and I'm using a honking, corded Milwaukee drill with gobs of torque (probably what broke the cheap bits.)  I seem to be only "polishing" the broken off pieces of bits down in the holes.

Suggestions?

TIA

Title: Valve cover drill out problems
Post by: 1991 E30 M42 on June 12, 2009, 05:58:57 PM

I had that issue when I did the head on my Mercedes, I got a long skinny punch, about 1/8" wide, and broke the end of the drill bit into smaller pieces and vacuumed them out

Title: Valve cover drill out problems
Post by: cravo on June 12, 2009, 05:58:59 PM

I have the same problem... Is it a "common thing" in the M42 engine?
From time to time, the spark hole of the 2nd cylinder get´s filled with oil...
I´ve already swapped the valve cover seals, but the problem remains...
Tips are welcome ;)

Title: Valve cover drill out problems
Post by: P. Kennedy on June 12, 2009, 06:34:29 PM

Quote from: 1991 E30 M42;73541

I got a long skinny punch, about 1/8" wide, and broke the end of the drill bit into smaller pieces and vacuumed them out

Thanks a bunch.  I will give that a shot

Title: Partial success
Post by: P. Kennedy on June 13, 2009, 10:29:34 AM

The "punch" technique worked, but I blasted all the way through the bottom of the threaded valve cover bolt housings.

JB Weld, drill & tap time!

Title: Valve cover drill out problems
Post by: 1991 E30 M42 on June 13, 2009, 01:47:28 PM

I wouldn't even worry about making the hole blind again, I have a few that are all the way through

Title: Valve cover drill out problems
Post by: gearheadE30 on June 13, 2009, 02:18:05 PM

Quote from: cravo;73542

I have the same problem... Is it a "common thing" in the M42 engine?
From time to time, the spark hole of the 2nd cylinder get´s filled with oil...
I´ve already swapped the valve cover seals, but the problem remains...
Tips are welcome ;)

You sure the seals are seated correctly? I had the same problem and put new gaskets in, and even with some stripped bolts it worked fine. Did you check the torques on all of the bolts?