Cylinder Head Bolt Failures

Cylinder Head Bolt Failures
by Gene Ritacco
reprinted from Die Flusternde Bombe
in Rocky Mountain Chapter
Motorsport Report
May 1997

The Bombe received this letter from Brian Philpott: In the November 1992 issue of the Roundel, a mechanic member said he "has seen a number of cylinder head bolt failures in early 325/525i engines. The hex heads sometimes shear off and wedge beneath a camshaft lobe resulting in serious damage. Torx style bolts were a phased into production in April 1989."

I have a 1988 325iS which has done 75,000 miles. It has just encountered the "serious damage" problem described above. One of the hex heads broke off and wedged under the camshaft lobe. This caused a large hole in the cylinder head. Repairs to replace the cylinder head, exhaust valves, intake valves, etc. cost me $3,000.

I think it may be a good idea to have the head bolt replacement recommendation listed in the Bombe (or in this case, the Motorsport Report) so that other members can get theirs replaced. The parts only cost about $32. Two other mechanics have said that they have seen this same problem with BMWs of my vintage. I have written to BMW NA regarding this issue as I think they should have done a recall, or at least some sort of advisory, for these faulty head bolts.

Brian, here's the tech tip for everyone to learn from, from the Novermber 1992 Roundel, page 75:

"The bolts should be replaced one at a time, reusing the old washer. Torque the bolt being replaced to 22 foot pounds, then tighten the bolt again by moving the torque wrench 90 degrees, then tighten it again another 90 degrees. Owners of modified 'eta' engines might do well to consider this update also. Make certain after removing each head bolt that prior to installing each new one that there are no fluids collecting in the head bolt hole. Otherwise you may experience "hydro loc" which will result in the engine block splitting allowing coolant and oil mixing requiring replacement of the engine block (engine!). Lightly lubricate the new bolt threads and washer for a smooth torque and use the specs specific to the new bolt."