dr bob

Sorry--

The Hylomar seals the threads fine without depending on the pressure on the aluminum washer. That let me set the bolts at lower torque without worrying about leakage.

Imagine that the bolt 'pulls' on the rear faces of the block threads, pressure against the front faces of the bolt threads. There's a little gap between the rear of the bolt threads and the front of the matching block thread. Makes a spiral path for coolant to pass through. A dab of Hylomar on any thread will block that path and effectively seal the bolt. I coat the whole thread anyway, including the faces of the selaing washer, just because. Hylomar stays somewhat flexible in use, so the difference in thermal growth between the block and the bolt doesn't cause breaches in the seal. With the sealing done in the threads, the torque on the bolt can be less than wha's normally needed to seal with the aluminum washer.

Teflon thread sealing paste is almost as good, and is readily available from hardware stores in the plumbing department. Where Hylomar firms up some, the thread sealing paste stays as paste. It's generally enough for this duty, but is really intended for use on tapered threads where the gaps get smaller as the bolt gets tighter. It has the benefit of the teflon as a thread lubricant so it will be easier to get the bolt out later. At the same time, that thread lubrication means you can get the correct pressure on the threads well before the spec'd torque on the bolt.

That lubrication on the threads, be it from Hylomar, Permatex, teflon paste or from anti-sieze, might be a contributor to the OP's failure. It may have allowed too much pressure on the threads at lower-than-spec torque. That may not have been an issue in steel threads, but in that aluminum boss it's possible the pressure was too much.


I should remind folks that while this works fine for me, no warranty is implied and all that. I come up with ideas and theories about what should work, and try them on my own car. This method works for me just fine, and lets me remove tthe drain bolts absolutely painlessly. It was obvious to me at the first removal that the factory's original tightening torque was more than I was willing to do again. It took a much stiffer pull than I'd anticipated to break the bolts loose, and there was risk of rounding the 13mm bolt heads then. That was after the initial assembly by Fritz with all new parts.

blown 87

This is just a theory on my part, but when I see RTV on a European engine I suspect Joe Bob and Billy Bob have been playing with the Craftsman set they got at the yard sale,

When I see Hylomar, I think this engine was worked on by some one who had a clue.

Hylomar is good stuff for sealing gaps of .010 or less on most fluids.

RTV is hack stuff for the most part, and we see lots of it, and the crappy work that goes with it.

polecat702

Castings by nature are porous. My former student says that they use the Aluminum putty on engine castings to fill in cracks, and irregularities, then they have the parts remachined. They are sent for heat treating, which in effect is annealing the stresses out of the material. I guess the heat treatment is the key, for a lasting repair.

FWIW, I can reach up and touch either side of my 928 engine where the drain plugs are located. That being said, I would clean the area where the plug casting broke off, take the broken part, and tack it into place and weld it up. A small scratch TIG tourch will fit in that area just fine. Have it done by a competent welder, with zero problems. You shouldn't have to pull the engine. Have the ground from the welder as close to the work as possable, and disconnect all the brains in the car.

blown 87

That is good news, do you have contacts that can do this in the DC area?