Philes Forum – Fall 2016
by NJ BMW CCA
By Vic Lucariello, Sr.
Hello, bimmerphiles! I am closing the 30th year of Philes’ Forum publication with a few unrelated tech tips.
Most of us know about or have patronized Harbor Freight Tools. While some tool snobs out there might pooh-pooh HF stuff, my opinion is that some of their hand tools provide good value, especially for occasional or DIY use. Hey, a set of inexpensive combination wrenches in the trunk of your Bimmer beats the heck out of no wrenches. However, according to reports on iATN [International Automobile Technicians Network], you should be wary of HF automotive fuses. These fuses, which come in an assortment, look pretty much like fuses from traditional manufacturers such as Bussman and Littelfuse.
In a recent thread, an iATN member reports testing the fuses from one HF 5-30 amp fuse assortment. He reports that they ALL held about 75 [that’s seventy-five, folks, you read it correctly] amps before blowing! Fuses have a temperature-time curve, meaning that the time to failure depends not only on the amount of current flowing through the fuse, but the amount of time the current flows. For example, a 10-amp fuse might endure 13 amps or so for a few minutes before blowing, while the same fuse should blow much more quickly at 20 amps. Regardless, a 5-amp fuse holding 75 amps for any amount of time is pretty scary.
So, while carrying an HF wrench set in your Bimmer may be a good idea, carrying their fuse assortment might not be.
After writing the foregoing I happened to see the following HF ad for a ½- inch pneumatic impact gun:
The ad claims that the HF is more powerful, lighter and quieter than a Snap-on model, at less than 1/3 the price!
Many of you change your own brake pads, and hopefully you don’t use pads from HF [kidding of course]. I’m sure you use OE [Original Equipment – from your BMW dealer] or OE-quality pads from a reputable aftermarket source, but what about that new pad-wear sensor?
I have previously written about the evolution of BMW brake-padwear sensors, so I won’t repeat my tome other than to say that recent Bimmers use sensors that actually predict how many miles remain until the pads need replacing. Older sensors simply illuminated a dash lamp when he pads wore to the replacement point. The old-style sensors could be reused if they hadn’t yet turned the lamp on, but I always replace them. On cars with the newer-style sensor and the Condition Based Service [CBS] feature, it is important that you use an OE or OE-quality new wear sensor when you replace brake pads. I have experienced difficulty, and read others’ reports to this effect, in getting the CBS brake-pad monitor to reset after the new pads and sensor have been installed, and the problem turned out to be an aftermarket pad-wear sensor that the CBS electronics didn’t “like”. An OE sensor fixed things. So, if you are buying brake parts from an aftermarket source, be sure to confirm with them beforehand that the pad-wear sensors they supply will not cause CBS-reset problems. If you inform them of problems afterwards, be prepared to be told that you don’t know how to reset the CBS. [Heck, you will probably be told this anyway.] Personally, I always use OE sensors, regardless of what brake pad I am installing.
Although the following applies to many Bimmer models, some as much as twenty or more years old, this specific account applies to an E46 325i with over 150,000 miles. A fellow had a valvecover- gasket oil leak [Imagine that!] and after replacing the valve-cover gasket he had no more oil leak but he had an illuminated “Check Engine” lamp. OBD II diagnostic trouble codes P0171 and P0174 were stored in the engine control computer [DME in BMW-speak]. WTF!?
These codes set when the DME detects a lean-running condition; the 171 code is for Engine-Cylinder Bank 1 and the 174 code is for Bank 2. Banks on an in-line six? Yes: Bank 1 is cylinders 1-3 and Bank 2 is cylinders 4-6. So the codes suggest that the whole engine is running lean. But how can a valve-cover-gasket replacement cause the engine to run lean?
First of all, whenever you remove a “plastic” valve cover from any BMW engine, especially a six, it is not unlikely that the cover will be warped. Removing the cover and replacing the gasket will NOT correct the warp situation; Indeed, it will probably make the problem worse. Don’t ask me why this is, but it is so. [Remember that on the subject E46, there were no lean-running codes stored prior to the valve-cover-gasket replacement.]
Second, BMW’s engine-crankcase-ventilation [PCV] system tries to maintain a prescribed vacuum on the engine internals. The actual vacuum spec varies from engine-to-engine, but the vacuum one should measure on a warm-idling E46 325i is about 4 inches of water column. If there is an air leak on the valve cover, either due to a bad gasket or that warped valve cover, the PCV will, in trying to maintain the engine internals at the prescribed vacuum, suck a lot of unwanted air into the intake manifold and…..BINGO…..the DME will set lean-running codes.
On the subject E46, the owner lucked out with the valve cover itself insofar as warpage, but when he checked his work, he found a piece of the original gasket had been left on the cylinder head when the valve cover was removed the first time. So the piece of old gasket created the air leak that caused the lean running codes.
That’s all for now, bimmerphiles. See you next time.
Anyone wishing to contribute to Philes’ Forum can contact me at firstname.lastname@example.org.
I’m interested in tech tips, repair / maintenance questions, repair horror stories, emissionsinspection sagas, product evaluations, etc.
© 2016; V.M. Lucariello, P.E.