Index

Breathing new life into your M62's leaky intake system, and fixing that nagging valley pan coolant leak.

At around 82k miles my engine was clearly showing signs of minor air leaks in the intake system: rough idle when cold, occasional miss at idle, periodic extended cranking times during starting, etc. Additionally, a BMW tech pointed out that my valley pan seal was leaking a small amount of coolant, a common occurence on these motors.

There is some good news here: these two problems, leaky intake seals/gaskets and seeping valley pan, appear to have nothing in common except, perhaps, for mileage. However, even if you're only trying to fix one, it's an easy task to take care of the other on a pre-emptive basis while you're in there. In the case of the intake manifold, the only additional work is R&R of the water manifold/plumbing and the valley pan. Total additional cost is around $50, a little more if you replace the two hoses that attach to the manifold. Conversely, if you're after the valley pan in the first place, the manifold gaskets/seals come along "for free."

I reviewed the BMW TIS documents and decided this would be a fairly straightforward procedure: no special tools required, and less than a day's work. So I headed over to the dealer with parts list in hand.

Note that a good majority of the required parts had to be special ordered, so plan your time accordingly. The entire job took me just over six hours and included taking numerous photos for this writeup and a trip to the dealer since I hadn't planned on the valley pan heat shield being too brittle to swap to the new pan. Additionally, I made several stupid mistakes (hey, I had pneumonia when I did this work, so cut me some slack, ok?) which are noted in the text by "Dork Alert!". Together these cost me at least 30-45 minutes, so I'm sure the job could be done in less than five hours if you were really in a hurry.

Just to keep things fair, I've got many years experience as a shadetree mechanic, so it's difficult to say with certainty the skill level required to complete this job. However, there are no particularly significant skills required to perform the work. Look thru the information provided here and determine if your own experience level is appropriate for the task. I followed the BMW TIS procedures verbatim, and the job went very smoothly with only minor surprises.

Valley Pan: Determining whether your valley pan is leaking or not is pretty easy. Does your car inexplicably lose small amounts of coolant over time, yet you are unable to find the source of the leak after carefully checking all the usual suspects? Simply remove the engine cover and, using a flashlight, look carefully behind the intake manifold down at the engine block. Locate the water manifold which bolts to the back of the block for reference (two heater hoses attach to it), then look forward an inch or two along the block/head interface on the passenger side until you find the valley pan, which sits about an inch deeper in the engine block. If it's leaking, you'll see a buildup of cooked coolant in the corner(s) - no matter where the pan is leaking, the coolant will settle back here over time and slowly bake from repeated heat cycles. Note that the equivalent area on the driver's side of the block contains a drainage hole and the view is blocked by the engine vent tube. You can also see the valley pan/block seam by looking down past the manifold at the front corners.

Intake System leaks: This one is a bit tougher to diagnose, unless you have a really bad leak. Rough idle on cold mornings is common, along with a subtle bog when increasing throttle setting. I was also experiencing very subtle "hiccups" usually when idling at a red light - the engine would just sort of skip a beat then resume running smoothly. Finally, my motor was starting a bit more slowly at times than normal - by this I do not mean the starter was turning the engine over slowly - but that the engine, instead of catching within one second of turning the key, would sometimes take 2 or 3. Nothing really drastic - just when it happened, it would give me pause. If you suspect a leak, you can sometimes prove one by carefully spraying appropriate liquid (Berryman's, etc.) on the suspect seal with the engine running. If you find a leak, the liquid will momentarily seal it and the RPM will increase for a short time. Note this is not a guaranteed method, and you can make a mess of your paint if you get the spray on the wrong areas.

The information provided here is supplemental and is not intended to be used as a sole guide when performing the tasks described. By providing this information I accept no responsibility whatsoever for your safety or the success of your work.

You are responsible for ensuring your safety and the proper use of all tools, jacks, supports, etc., proper care when handling flammable liquids, and for the proper installation and assembly of components. Failure to do so can result in damage to your vehicle and/or serious injury or worse to your person.