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25 November 2008

Coils & Plugs at 50,000 Miles

As part of my 50,000-mile service last month, I replaced the plugs and coils again. The last replacement was at 25,000 miles (instructions).

The coils are one revision newer - the last ones I installed were the "C" part number, these are 07K 905 715 D.

One of these things is not like the other.... (the coils):
1     -     2     -     3     -     4

The coil I pulled from cylinder 4 had a lot of corrosion near the sparkplug end:

The NGK BKR7EIX plugs with 25,000 miles of usage:

Plug 1

Plug 2

Plug 3

Plug 4

Notice the corrosion around the back of Plug 4, corresponding to the corrosion on the coilpack:

When I posted pictures of these in the 2.0T forum, I was accused of negligently getting water in the plug recess due to pressure-washing the engine. The fact is that I have never pressure-washed the top of the valve cover, nor caused any water to get around the coils that would cause this.

Looking at each of of the plug recesses, you can see some degree of corrosion around the top of 1, 2 and 3, but significant corrosion down in 4. I'm going to keep an eye on the new coil in the No. 4 spot to see if it starts developing corrosion, too. This is probably just a cosmetic problem, since it didn't make it past the threads of the plug nor did it interfere with the functioning of the coil.

The plugs were purchased from an eBay vendor for $37.00, and the coils were obtained from World Impex.

As I experienced before, installing the new plugs and coils had an immediate improvement in idle smoothness. After nearly 2000 miles of driving on the new parts, the idle is still smoother than it was prior to the change.

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Group 48 Battery

Last week was pretty cold. When I left work on Friday evening, I tried to start the car and it turned over once.... paused...... lights dim.... then turned over again and caught. I hoped the battery wasn't really dying, but I tried it Saturday morning after it sat overnight and the same thing happened, then again while I was out running errands. OK, time to replace the battery. This one had lasted 3 years and 50,000 miles, which is OK for an original battery. The one in my old GTI died completely after only 6 months. I replaced it with an Optima Red Top, which lasted the next 6 years.

Car batteries are referred to by their "group" number, which denotes the dimensions (length, width, height), terminal type, and terminal orientation (left/right). Here is a table that shows the measurements for different battery groups.

The battery that comes in the A3 from the factory is a Group 47 size. It has recessed terminal posts, and reversed terminals (viewing the long side when the terminals are closest to you, positive is on the right and negative is on the left). It has a heat-insulating blanket around it that must be re-used.

If you want a little better performance, you can install a Group 48 battery. The only difference between the Group 47 and Group 48 is the length, and the larger one will just barely fit in the A3's battery box. The original battery is only 480CA/280CCA capacity.

I wanted to put in an Optima battery, but they don't specifically make a Group 47/48 style. (I later learned that an Optima 75/35 can be made to fit.) Batteries are sold under several brand names which are all made by Johnson Controls. "Interstate", "Duralast" and "BOSCH" are three of those brands.

I chose a BOSCH Group 48 battery that cost $90.00.

It has a 850CA/690CCA capacity, 36-month free replacement & 96-month pro-rated replacement warranty, and came with a roadside assistance card for free jumpstarts for the first 36 months.

Remove the top cover from the battery box. Completely remove the battery hold-down bolt/plate with a 13mm tool.

Remove the battery cables, loosening the connectors with a 10mm tool. ALWAYS LOOSEN & REMOVE THE NEGATIVE SIDE FIRST! Also, INSTALL and TIGHTEN the NEGATIVE side LAST! I have 3rd-degree burn scars from doing it wrong years ago.

When you pull out the old battery, the insulating blanket will come with it. Slide the blanket off the battery. If you're installing a Group 47 battery, you can just slide it onto the new one. If you're installing a Group 48 battery, you'll need to look for the tab where the blanket is attached to itself, and undo it. It will wrap around a Group 48 battery, but with no overlap, so it's a little harder to get it back into the battery box if you're doing this by yourself. It does fit, though.

Re-attach the cables (see note above) and the hold-down, making sure it's actually holding the battery down securely.

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Jack Pads

Here's a little enhancement that I've been meaning to do for a while. These inexpensive rubber pieces provide a good place to raise the car using a hydraulic floor jack, or a 4-point lift (like when having tires installed, for example).

Each pad is composed of two pieces. You position them together, then use a jack to press them into the correct points on the underside of the car. They lock together and lock into place on the car.

Back in 2005 "SwiftA4" posted instructions for doing this on the A3 Forum. The instructions and pictures are excellent, so I'm just going to link to them here. Part numbers are included. (If for some reason that thread on the forum becomes unavailable, I have a copy saved that I can post here.)

In addition to the 4 pad assemblies, I also got a special metal disk from ECS Tuning that fits into the pad when using a hydraulic floor jack. This gives a very stable lifting point. The disk has a bump on the top that fits into the bottom of the jack pad to keep it from sliding.

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