Recently one of our own members had an engine failure in an nexpected way. It has often been said that when opening an M42, expect to find a bolt laying inside. When we opened up this member's engine (Febi Guibo) what we found scared not only us, but also a well known engine builder. The motor had 160k miles on it.
As many of you know, our pans hang awfully low. They tend to get bashed a bit, not to mention our high strung motors and similar owners high strung driving style leads to lots of vibration. All leading to lots of loose bolts, especially since Germans it seems do not know how to torque a bolt, they are about 10-20% below torque compared to other manufacturers using similar size bolts.
My thanks to Metric Mechanic for letting Febi and I pull his pan to get this information.Basic rundown of what happens.When BMW designed the M42, they made the oil pickup bolt to the oil pan,
which bolts to the block. This is sealed by an ear of the pan gasket. When the bolts come loose and fall out, the front edge of the pan, can slide forward, allowing the pump to suck air from the oil pan. When this happens there is no way to prime the pump, or get any oil to flow. Run too long like this and the engine will grind to a halt. Also, there was no oil leaking from this engine, so do not use this as a gauge to see if yours has the problem.
Every M42 owner should consider doing this!I will make it as simple as I can. It is possible to do with simple hand tools.
Sorry for the cheesy Photoshop graphics, but they get the point across.
Note* All pictures can be clicked for a higher resolution version. As always you do this at your own risk.
How to diagnose and prevent.First thing to do is drain your oil. (17mm)
Jack up the car, be sure to block the tires, use stands or ramps, not just a
jack.
With a 10mm wrench remove the lower oil pan. If you are lucky you will not be missing any bolts. I will be adding part numbers and specs for the
bolts later for those missing them.
With a flashlight, look up into your pan. Laying on your back, you should see something like this:
Inside there should be 6 bolts.
The thee bolts closest to the dipstick along the front are the 3 most important ones we are looking for, however you obviously want all of them. Blue designates a pan bolt.
Pink designates the hole for the dipstick.
If you were to remove the upper pan, this is what you would see with an
overlay of the gasket.
Here you can see the little extra piece that goes around the oil pump pickup. As you can see, there is really nothing to hold it in place other than those front bolts (terrible design in my opinion).
Here is what happens when those bolts fall out.
The pan gasket shifts forward, allowing the pump to suck air from the oil pan.
On this engine, you could actually see a small tab of the gasket hanging out in front of the block.
This is what the gasket looked like when the pan was removed.
When we removed the lower pan, all of the bolts were tight.
The upper pan however, was extremely loose. Some bolts came out with our fingers! When we got inside, 4 bolts were missing, one was finger tight. If you look real close in the pictures with the pump pickup, you can actually see threads pounded into the pickup. The pan would drop down, a bolt would get just underneath, and then the pan would get hit, imprinting the pickup with its threads.
RepairMy advice is to tighten as many upper pan bolts as you can reach, which is not many. You may even want to consider pulling them one by one, and adding Locktite (blue). Then remove the lower pan, and find all of your bolts (odds are at least one will be sitting in the pan) and add some Locktite to all of them before re-installing the lower pan. I will try to acquire the pan bolt torque specs, I reccomend 10-20% increase on that number, which is what I was recomended to do.
If you think your motor is not like this, I did a quick check today on the
outer upper pan bolts I could see from outside and I have at least one upper pan bolt missing. My lower comes off this week for a complete check, and I am contemplating jacking up the engine to re-torque/replace all of the upper pan bolts. my motor only has 140k miles.
Note* There are 2 bolts at the very rear of the upper pan, they are not accessible without removing the trans, nice one BMW! (dumbasses). The good news is that both were as tight as the day they left BMW. Which is another reason why I suspect bumping the pan, (along with engine vibration, particulaarly from teh timing chain and oil pump) is the cause of all of this.
Update: apparently there is 2 access holes to allow you to access these bolts through the bellhousing.
Bolt torque specs:Bolt torque depends on quality of the bolts.
Stock bolts the proper torque is: 10 nm (89 in-lb)Better high end bolts (higher grade) can go 12nm (9ft-lb) *Note the change to foot pounds.
Jim at Metric Mechanic recommends adding about 10-20%, but that is your call.
Thank Eurospec for finding those.
For the curious, here is a shot of the block as you see it without the upper
pan and gasket installed.
