M42 Sump Bolts

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As many of you know, M42 oil sumps hang awfully low and they tend to get bashed a bit by all the "spirited driving" 318iS get up to. Those perpetual knocks, thumps and vibrations take their toll, leading to an oil sump that can rattle loose from its proper location. When this happens, you're risking imminent engine death. Read on to find out how to avoid it.

Contents

Overview

When BMW designed the M42, they made the oil pickup bolt to the oil sump, which then 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 sump can slide forward, allowing the pump to suck in air. 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! It is easily achieved with basic hand tools.

Diagnosis

First thing to do is drain your oil. (17mm) Jack up the car, making sure to block the tires, and use stands or ramps, not just a jack. With a 10mm socket, remove the lower oil pan. If you are lucky you will not be missing any bolts.

With a torch, 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, which doesn't seem to be a particularly clever design.

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, four bolts were missing, and another one was finger tight. If you look closely at 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.

Repair

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. The official torque setting specifies tightening to 10Nm, although you may consider going up to 12Nm if using stronger bolts.

Note: There are 2 bolts at the very rear of the upper pan, they are not immediately accessible without removing the gearbox. However, two holes do exist to access these bolts through the bellhousing.

For the curious, here is a shot of the block as you see it without the upper sump and gasket installed.

Adapted from an original article on m42club.com