Oil Pan Bolt Fell Off.

[George7941]

I was changing the oil in my truck (the one in my sig) a week ago and noticed half my oil pan had a coating of oil on it. Further inspection revealed the leak to be from the oil pan gasket and I noticed the second bolt from the front, driver side, had fallen off. I replaced the bolt and torqued all of the bolts (most had loosened up) to 18 ft.lbs, the recommended torque. Hopefully that took care of the leak.

I have had the truck since new and the pan has never been touched before. GM needs to start applying loctite to these oil pan bolts. I used the red 262 loctite but I dont know how effective it is going to be since there was oil contamination.

On a side note, I thought the auto industry had switched over completely to metric fasteners but these pan bolts were 5/16C threaded. I suppose this has to do with the roots of this engine which go back to the mid-fifties.

Anybody owning the 4.3l V6 should check their pan bolt torque.

 

[defektes]

When I did the intake manifold in my 4.3 every bolt was metric.

That is odd, loctite like you said would be a must.

How many miles on yours?

Good thing you cought it before any more bolts fell off.

 

[George7941]

I only have 52k km (33k mi) on the truck.

Only other problem I have had with this truck was with the thermostat, it started opening too early. Truck was under warranty but I did not even bother taking it in, I changed the stat out myself.

 

[onion]

Sure that bolt wasn't an 8mmX1.25?

Almost exactly the same size.

 

[George7941]

Positive. I was so sure it was going to be metric, I started threading in a M8 bolt and noticed binding after a couple of turns. I then took off another pan bolt and noticed the three slashes (grade5), confirming an imperial-sized bolt.

 

[defektes]

I love this engine, like the old 5.7 its easy to work on.

Keep an eye on your coolant level, I had intake mani failure 123k miles in. Other than that this truck has been bullet proof.

 

[George7941]

It must have been a plastic-framed IM gasket that failed on your truck, no? Did you use a Felpro replacement gasket?

I assume that my 2006 truck does not have the plastic-framed gasket. I do keep an eye on the coolant level and it hasn't budged in three years, and, no, Dexcool does not evaporate any more than any other coolant.

Perhaps the oil pan bolts became loose because the cast aluminium pan is a structural part of the engine-transmission assembly (the oil pan forms the lower half of the engine bellhousing and the tranny is bolted up to it) and is thus subject to a lot of stress.

 

[mechtech2]

18 ft lbs sounds extremely high for any pan bolt.
Distortion or breakage is inevitable.

 

[George7941]

18 ft.lbs felt high when i was torquing the pan down but I kept cranking till my torque wrench clicked. I check the calibration of the wrench with weights about once a year to ensure accuracy.

I have the GM service manual for the truck and 18 ft.lbs (25 Nm) is what it calls for. The pan is a ribbed cast aluminium pan that is a structural part of the engine-transmission assembly and perhaps that is why the torque figure is so high. Certainly a stamped steel pan would distort under the torque.

 

[mechtech2]

George - That makes sense. There are indeed a number of cast pans and pan spacers that are structural.
You were smart to use a torque wrench. This would be one thing that it is essential.

 

[lipadj46]

The torque values on my oil pan bolts are 16 lbs so that does not sound crazy. I have a heavy cast aluminum pan though.