Eccentric Shaft Sensor Seal

fotontom · 08-18-2021, 03:26 PM

Trying to figure out how/why this happened, so please read on if you have the time.

I work for a chain of transmission repair shops. Most of our guys are general-repair savvy, some have extensive experience in our cars. I had them do a general cooling system rebuild recently-water pump, thermostat, radiator, overflow tank, all hoses, lines, clamps, new bolts, OFHG while it was torn apart. All OEM. Why? Because the car has 108K on it and while nothing was bad, it would not be long before these things began to fail. Preventative maintenance.

About a month later, I see a pool of oil under the car. Down a quart after 1000 miles. I check it out, and I can see visible oil behind the oil filter housing, so I am thinking the gasket somehow failed, and I took it back in. Our tech then sees a head bolt top is sheared off and recommends taking it to a good local BMW indie.

They extract and replace the head bolt, and tell me the eccentric shaft sensor gasket is creating the leak.

I ask about how it could have happened, and the shop tells me this is known to happen on N52's, and they do see it somewhat regularly. It just seems to be an odd coincidence, but I would like to hear any comments or advice.

NorthernDancer · 08-19-2021, 02:14 PM

Two years ago, my BMW indy recommended a VCG replacement. I could see "sweating" on the lower engine side but no great leak at all so I was skeptical.
So I removed the engine cover and immediately could see oil in some of the recesses on the engine head. Since this was up high, it was not leaking from the VCG per se but from the ESS gasket. If I had let it go, in a year or two, the oil would be leaking down into the spark plug recesses.

Thunderguts · 08-26-2021, 10:32 AM

At 108k miles, I can definitely see your valve cover and ESS gasket failing, but I'm not sure how that affects your other problems.

The ESS gasket wouldn't cause a pool of oil anywhere. It's internal to the valve cover. If the gasket leaks, you just get oil in your sensor and it fails. It doesn't leak outside the valve cover unless you include a *tiny* pool of oil in the plug itself.

Your pool of oil was almost certainly caused by that sheared head bolt and/or cracked valve cover and gasket. How the hell did the bolt shear off? I'd say the mechanic botched the job and hoped no one would notice.

08-18-2021, 03:26 PM	#1
fotontom Second Lieutenant 178 Rep 262 Posts Drives: BMW 128i E82 M-Sport, 528i F10 Join Date: Jul 2020 Location: SoCal iTrader: (1)	Eccentric Shaft Sensor Seal Trying to figure out how/why this happened, so please read on if you have the time. I work for a chain of transmission repair shops. Most of our guys are general-repair savvy, some have extensive experience in our cars. I had them do a general cooling system rebuild recently-water pump, thermostat, radiator, overflow tank, all hoses, lines, clamps, new bolts, OFHG while it was torn apart. All OEM. Why? Because the car has 108K on it and while nothing was bad, it would not be long before these things began to fail. Preventative maintenance. About a month later, I see a pool of oil under the car. Down a quart after 1000 miles. I check it out, and I can see visible oil behind the oil filter housing, so I am thinking the gasket somehow failed, and I took it back in. Our tech then sees a head bolt top is sheared off and recommends taking it to a good local BMW indie. They extract and replace the head bolt, and tell me the eccentric shaft sensor gasket is creating the leak. I ask about how it could have happened, and the shop tells me this is known to happen on N52's, and they do see it somewhat regularly. It just seems to be an odd coincidence, but I would like to hear any comments or advice.
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08-19-2021, 02:14 PM	#2
NorthernDancer Colonel 848 Rep 2,276 Posts Drives: 08 Sedona 128 & 06 330xiT 6MT Join Date: Apr 2011 Location: Ottawa On Canada iTrader: (3)	Two years ago, my BMW indy recommended a VCG replacement. I could see "sweating" on the lower engine side but no great leak at all so I was skeptical. So I removed the engine cover and immediately could see oil in some of the recesses on the engine head. Since this was up high, it was not leaking from the VCG per se but from the ESS gasket. If I had let it go, in a year or two, the oil would be leaking down into the spark plug recesses.
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08-26-2021, 10:32 AM	#3
Thunderguts Captain 776 Rep 992 Posts Drives: 2009 128i Sport MT Join Date: Jul 2018 Location: DFW iTrader: (0)	At 108k miles, I can definitely see your valve cover and ESS gasket failing, but I'm not sure how that affects your other problems. The ESS gasket wouldn't cause a pool of oil anywhere. It's internal to the valve cover. If the gasket leaks, you just get oil in your sensor and it fails. It doesn't leak outside the valve cover unless you include a tiny pool of oil in the plug itself. Your pool of oil was almost certainly caused by that sheared head bolt and/or cracked valve cover and gasket. How the hell did the bolt shear off? I'd say the mechanic botched the job and hoped no one would notice. __________________ Official BMWP Whore - BMWP suspension kit w/ M3 arms, BMWP big brake kit, BMWP intake w/Mishimoto tube, BMWP exhaust, BMWP carbon strut brace, BMWP short shifter, and BMWP carbon spoiler. OZ Leggera HLT w/ 245 square setup.
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