persistent oil leak

[akrockhound2]

I bought my '03 Dmax new. Starting at 4,000 miles there has been a recurring oil leak from one of the side main bearing cap bolts. Dealer repaired it about 5 times under warrantly (now 70,000 mile) I am doing it myself about every 6 months. More of a nuisance than anything else except my local mechanic wonders if something is "wrong" with the main bearings and whether "things are moving around in there".

We've tried fixing it per the GM service bulletin and using every thread sealer on the market. It keeps coming back.

I tried going to GM Nationwide 1-800 number before the warranty ended to try and get a GM engineer on the phone to tell me whether I should be concerned about this. That lead no where - the GM phone person basically blew me off.

My question is this - Can anyone direct me to a Duramax diesel engineer who currently works for GM with the hope that I can get a definitive answer on the cause and cure for this problem?

[DmaxMaverick]

Have you tried a copper washer under the bolt head? It should seal it and wouldn't effect bolt torque any significant amount.

[akrockhound2]

I haven't because my mechanic says the soft copper would be crushed and otherwise make it difficult to get the 52 ft-lbs of torque.....still begs the question why only this bolt leaks (but not the rest of the main bearing cap bolts) and why do I need to take extra steps with this one?

[DmaxMaverick]

The copper is supposed to crush (which is what causes it to seal), and 52 lb/ft is not excessive. Use brass, if copper doesn't sound reasonable. I'd use copper, and apply some blue Loc-Tite between the bolt head, washer, and block, as well as on the threads (belt and suspenders).

The only thing that sounds probably, with it leaking like it is, is a defect at the bolt-block interface. Perhaps a porosity issue. Copper, under significant pressure, will "liquefy" and fill gaps. Steel won't do this, considering the pressure involved. If the leak continues, after applying a good sealing method, I'd suspect a block crack, casting flaw or main cap defect. Not much else to consider.

[akrockhound2]

I'd suspect a block crack, casting flaw or main cap defect. Not much else to consider.


That's exactly why I wanted some solid information from GM about this BEFORE it went off awrranty but as i said they blew me off completely....It's enought to make me angry.

[bobt]

I would think that if you have had this problem since 4000 miles and the dealer has repeatedly tried to fix it, you have ample historical documentation to show the problem existed before the warranty expired, regardless of what the ultimate cause is.
Bob

[akrockhound2]

My question remains the same. Does anyone know how to get hold of a GM DMAX engineer? Is the only option really to go through the generic 1-800 number?