My oil pan after 110k

[JHZR2]

Here is the oil pan from my 91 BMW 318i with about 110k. I dropped it because some folks on the M42 forum I frequent had been seeing problems where the upper oil pan bolts were working loose and falling out. If enough fall out, there is the potential for the gasket between the upper oil pan and the block to shift, causing the oil pump to suck air... I had to do an OC, so figured Id pull the pan while I was at it, remove the bolts, thread seal and re-torque them.

None had fallen out... two were completely loose, one was easy to turn with just a finger, and the rest were OK.

Here is my oil pan and pics looking inside the engine from underneath:

The last two really arent that color. The metal is clean as can bee silver, the oil was amber, and I shot with flash and high iso settings on a P&S, and got this yellow tinge to the metal. Everything is VERY clean.

I did run Auto-RX just before this change, look at how the gunk in the pan is loose and mobile...

JMH

 

[Kestas]

Maybe add lock washers under the head of these bolts?

 

[40ford]

What brand and weight oil were you running?

40ford

 

[JHZR2]

I'd have to get longer bolts then... they are bolts that have washers already attached... just small bolts that can only be torqued to 89 in-lbs. I figured that thread sealant (high temperature) was the best option... If I hve to open the pan up again sometime, I might just get longer bolts with lock washers - thats a good idea!

Thanks,

JMH

 

[JHZR2]

Originally Posted By: 40ford
What brand and weight oil were you running?

40ford


Ive been running rotella syn 5w-40 for the most part, but lately it is schaeffer's 5w-40.

JMH

 

[mechtech2]

Bolts lose tension as the gasket compresses over time.
Or, the pan was dropped to check out the bottom end after the flood, and not tightened properly.
I hate leaks, and probably would use a little premium sealer on the gasket, then tighten the bolts normally.

 

[Drew2000]

Maybe clean the bolts/holes with brake cleaner and apply blue Loctite to the threads on reassembly.

Drew

 

[deepsquat]

a lot of junk in the pan ...but the crank and rods look very clean

 

[JHZR2]

it really wasnt any junk... just looks nasty. The spots on the third pic down are actally discolorations of the metal, there wasnt really any mass there. The other stuff fortunately wasnt more than what a swipe of a paper towel could wipe away perfectly.

It was the consistency of what you get in an AT or diff drain plug though, FWIW... Makes me think that a magnet might be a nice thing to have in there. Wonder if I should have epoxied a super-strength magnet in the pan!

JMH

 

[dwendt44]

89 in/lbs isn't much torque. Only a tad over 7 ft/lbs.
No wonder they loosen on their own.
There are torque charts out there, my guess (and that's all it is)is that you can up that a bit.

 

[paulo57509]

What do the BMW forum users do to keep the bolts from loosening?

I don't really like lock washers (the split type) because I feel they don't really do anything. Bolts stay tight because of the stress induced in the mating threads. The spring force in a split washer isn't enough to maintain the stress required in the threads to keep them tight. They become flat washers way before the specified torque is applied. They're designed to "dig" into the bolt and the pan (in this case)? At that point, it's too late. The fastener is already loose.

Considering that the gasket would compress somehat over time, and would allow the fastener thread stress to relax somewhat, I would opt for some kind of thread locking compound, making sure the bolt and hole threads are squeeky clean.

 

[JHZR2]

it isnt a lot of torque. I did nt look at a chart, but a respected engine builder claimed 10-20% over that would be fine for these metric 8.8 bolts.

I used thread locking compound, instead of loctite. A lot of members used loctite. My reasoning was that I wanted something designed for higher temperature, but that didnt have such high force requirements to break/overcome at disassembly. The only loctite that fit the high temperature requirement was the red stuff, which held too tenaciously (worried about breaking the bolts at disassembly). Thread sealant is really designed for another application, but it prevents vibration loosening at temperatures up to 450F.

JMH