aheinlein

I have a 2000 model A6 2.7t with an automatic transmission. Recently one of the turbos failed so I pulled the engine and sent the turbos out for overhaul. Since the car has just under 200,000 miles, I purchased a new first run long block and swapped all of the components from the old engine to the new long block. Unfortunately, I made one big mistake in the process of swapping components. I ended up unbolting the flexplate from the old engine without first installing the TDC locking pin and marking the position of the flexplate relative to the crankshaft sensor/TDC. I have inspected the flexplate and reluctor and find no alignment marks of any kind inscribed on the flexplate. The only feature that is at all different is one larger gap in the reluctor section of the flexplate. I am guessing that this larger gap may hold a clue to the flexplate/crankshaft sensor alignment mystery.

It is my understanding that the engine won't run if the flexplate is installed improperly relative to the crankshaft sensor. At this point, I have the locking pin installed at TDC on the new long block. I would sure appreciate if someone could provide instructions on the proper way to install the flexplate so that the reluctor is properly aligned with the crankshaft sensor. Thanks for your help.

4Driver4

Doesn't it only bolt on one way?
Have you tried to line up the bolt holes yet?

aheinlein

Interestingly, I did attempt to turn the flexplate to determine whether it can be mounted in different positions or whether it only bolts up one way. The flexplate will actually line up so that the bolts can be started in several different positions. Alternatively, some of the positions are so far off that the bolts won't start at all. Since there are a few different locations that line up it doesn't give me much confidence about just installing the engine in the car. It is too much risk that the car won't start after assembly requiring that the engine be removed again.

I spoke with a local mechanic about my situation. He admitted that he actually had this problem on a customer car and had to remove the engine to realign the flexpate. It was not an Audi so he stated that he wouldn't be much help on my A6.

I think the answer might come from VW only manuals that I don't have access to. I have a Bentley manual for the A6. It indicates that marks should be made on the flexplate and shims relative to the block prior to removal. However, the technician at the factory didn't have marks to rely on at assembly so there must be some reasonable explanation on how align the flexplate. Thanks for your question.

seishuku

From an engine management (ECU) point of view, the sensor will typically be 90 degrees BTDC from the missing tooth(s) (the large gap). Though the actual angle can differ.

I do seem to recall that the flex plate/reluctor will only bolt on one way, but I could be wrong.
The manual also says to note the position of the cam sensor reluctors as well, but those will only go on one way as well.

aheinlein

Thanks for your comments. I would have thought that the sensor being a magnetic pickup would be triggered by a gap in the reluctor at TDC. I never would have thought that the gap would be positioned as much as 90 degrees before TDC. In any case, it sure would have been helpful for VW to put some kind of mark on the block to use in lining up the flex plate. As stated earlier, the flex plate will bolt on in several positions. I will try to turn the flex plate to see if it will bolt up anywhere within 90 degrees before TDC. If so, that is probably the correct alignment. However, I don't want to be wrong about this requiring the engine to be pulled out of the car again. Do you feel that I am on the right track here? If not, how should I get to the bottom line with regard to the correct alignment? Thanks again!

seishuku

Well, I'm not saying that it is 90, that's just an example. It really could be aligned anywhere and as long as the ECU is programmed for it, it'll work.

But just doing some searching, I can't seem to find any good info on it... I find it hard to believe that they didn't put some kind of alignment mark on it...

Prospeeder

Dude, rotate the thing until all the holes can have a bolt threaded in. It doesnt need a mark because its designed to be installed only one way. It can only bolt on one way. Just bolt it on. Iv had them off of 2.8 and 2.7 cars, its like wtf some spinning rotating, looking just like all go in but 2, then take it off and try another position.

aheinlein

Thanks for your comment on how the flex plate can only be installed one way. I will give it a try and report back. However, there are other comments with regard to the 2.7 engine that I have read about people that have been able to bolt the flex plate on is such a position (obviously incorrectly) that the car won't start. I'm just trying to save myself an incredible amount of work and time by making sure up front that the flex plate is installed in the proper position. As you know, removal and installation of an A6 engine is a difficult task. Thanks again for your comments.

aheinlein

As promised, I am sending additional information as a follow up to my last comments. I have very carefully removed the flex plate spacer between the crankshaft flange and the flex plate. The first step was to turn the spacer to attempt to find the best alignment of the holes in the spacer and the bolt pattern in the crankshaft. I did find that it is possible to bolt the spacer to the crankshaft in a two or three positions. However, there is one position that appears to line up better than others. The next step was to install the flex plate and rotate it on the spacer to find the best alignment. Once again, there are two or three positions that would allow bolts to be inserted. However, there is only one position that seems to be in perfect alignment. At that position, the "window" in the reluctor ring on the flex plate seems to align with the mounting position of the crankshaft sensor on the bell housing.

I am making a big assumption that utilizing what appears to be the correct alignment between the holes in the flex plate, spacer and crankshaft will result in proper alignment with the crankshaft sensor. If I'm wrong then this will require removal of the engine. Given that no one has a better solution, I am prepared to try the alignment listed above knowing that this technique may not work. In the future, I will be sure to lock the crankshaft at TDC and mark the flex plate and spacer carefully before removal. I will follow up with a status report as to whether this plan turns out to be successful. Thanks for your comments.

jcman

Or you can read this to get an idea what the sensor is looking for.