Author Topic: Valve cover drill out problems (Read 2679 times)

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

1991 E30 M42 · « **Reply #1 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

cravo · « **Reply #2 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

P. Kennedy · « **Reply #3 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

P. Kennedy · « **Reply #4 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!

1991 E30 M42 · « **Reply #5 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

gearheadE30 · « **Reply #6 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?