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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old April 11th, 2008, 18:34   #1
Herm TDI
 
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Default TDI Piston info needed

I have been searching through ETKA on the topic of TDI pistons

Tring to sort out what pistions are interchangeable and what is not.
Here is what I'm finding:
1999
1999 AHU (A-3) engine # 101808 and above
Cyl 1 & 2 038-107-065-AA (MAHLE)
Cyl 3 & 4 038-107-065-AB (MAHLE)

1999 AHU / 1Z (A-3 & B-4) engine # 101807 and lower
Cyl 1 & 2 038-107-065-D
Cyl 3 & 4 038-107-065-E

1999 AHU engine # 101808 and above
Cyl 1 & 2 028-107-065-BK (ALCAN)
Cyl 3 & 4 028-107-065-BN (ALCAN)

1998
1998 AHU / 1Z (A-3 & B-4) engine # 101807 and lower
Cyl 1 & 2 038-107-065-D
Cyl 3 & 4 038-107-065-E

1998 AHU engine # 101808 and higher
Cyl 1 & 2 028-107-065-BK (ALCAN)
Cyl 3 & 4 028-107-065-BN (ALCAN)

1998 AHU (A-3) engine # 101808 and higher
Cyl 1 & 2 038-107-065-AA (MAHLE)
Cyl 3 & 4 038-107-065-AB (MAHLE)

1997
1997 1Z / AHU engine # 101807 and lower
Cyl 1 & 2 038-107-065-D
Cyl 3 & 4 038-107-065-E

1997 AHU (A-3) engine # 101808 and higher
Cyl 1 & 2 038-107-065-AA (MAHLE)
Cyl 3 & 4 038-107-065-AB (MAHLE)

1997 AHU (A-3) engine # 101808 and higher
Cyl 1 & 2 028-107-065-BK (ALCAN)
Cyl 3 & 4 028-107-065-BN (ALCAN)

1996 1Z engine # 101807 and lower
Cyl 1 & 2 038-107-065-D
Cyl 3 & 4 038-107-065-E
1996 engine # 101808 and higher
Cyl 1 & 2 038-107-065-AA (MAHLE)
Cyl 3 & 4 038-107-065-AB (MAHLE)


A-4 ALH engine
A-4 ALH series 1999.9 thru 2003
Cyl 1 & 2 038-107-065-AA (MAHLE)
Cyl 3 & 4 038-107-065-AB (MAHLE)

Now here is where I'm a bit confounded:
The AHU and 1Z engines both have the same block (028-100-090-TX)
Both engines use the same crank (028-105-101-L)
Both engines use the same rods (028-198-401-F)

The only thing I see different between these engines (1Z / AHU) are the pistons.
Early: AHU / 1Z (A-3 & B-4) engine # 101807 and lower
Cyl 1 & 2 038-107-065-D
Cyl 3 & 4 038-107-065-E
Late:
Cyl 1 & 2 038-107-065-AA
Cyl 3 & 4 038-107-065-AB


The A-4 ALH engine uses the same connecting rods (028-198-401-F)


My questions are:
Ques. #1
Are these pistons the same but only different manufactures?
1998 AHU engine # 101808 and higher
Cyl 1 & 2 028-107-065-BK (ALCAN)
Cyl 3 & 4 028-107-065-BN (ALCAN)

1998 AHU (A-3) engine # 101808 and higher
Cyl 1 & 2 038-107-065-AA (MAHLE)
Cyl 3 & 4 038-107-065-AB (MAHLE)


Ques. #2
Are the pistons for the higher # series (101808 & higher) the same design but different manufactures? ALCAN ~V~MAHLE ? In other words are these pistons interchangeable?
Cyl 1 & 2 028-107-065-BK (ALCAN)
Cyl 3 & 4 028-107-065-BN (ALCAN)
Cyl 1 & 2 038-107-065-AA (MAHLE)
Cyl 3 & 4 038-107-065-AB (MAHLE)

Ques. #3

If you were rebuilding a 1Z or AHU of any series # (high or low)
What is the reason you could not use the A-4 pistons (as long as you used all 4 of the same P/N AA & AB)?
Cyl 1 & 2 038-107-065-AA (MAHLE)
Cyl 3 & 4 038-107-065-AB (MAHLE)

I know this is long winded but it would let me sleep tonight if I have some good solid answers.
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Old April 13th, 2008, 11:32   #2
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Here are a few pics comparing a 1z piston to the Nural ALH piston. I put the Nural piston in every 1z/ahu/alh block I rebuild.








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Old April 13th, 2008, 13:10   #3
Herm TDI
 
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In the above photos the piston on the right is:
Cyl 1 & 2 038-107-065-D
Cyl 3 & 4 038-107-065-E

The piston on the left is:
Cyl 1 & 2 038-107-065-AA
Cyl 3 & 4 038-107-065-AB

The main differances being the placement of the top compression ring and the longer skirt on the early version.

This answers my question of interchangeablity (Thank you).

Now the question about "BK" & "BN" pistons...are these the same as the "AB & "AA" ?

But I thank you for posting the great photos.
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Old December 31st, 2008, 14:18   #4
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Has the BEW engine have the same piston as ALH?

Last edited by Tad1; December 31st, 2008 at 14:31.
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Old December 31st, 2008, 14:28   #5
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Quote:
Originally Posted by Tad1
Has the BEW engine have same piston as ALH?
No.

The later AHU/1Z pistons are an improvement over the older ones, as you can see in the excellent photos above, with regards to ring placement. That is really the only difference.

So long as they are all weighed the same, just replace them in sets. And yes, ALH pistons in the older engines would be an improvement, and is why I think the ALH engines seem to generally have less oil use than its older cousins.
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Old December 11th, 2010, 18:32   #6
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I have a question. I have my head off my 1998 AHU with 175k miles and I plan to rering and have the head rebuilt. I have access to a set of ALH pistons and rods. Should I rering the block with the ALH or the AHU parts?

I'll be able to a bare minimum take a comparison picture for anybody that might need it in the future. The block is not coming out of the car but I will be checking the bores to make certain they aren't egged out.
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Old December 12th, 2010, 18:36   #7
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I bet you find the bores are cherry, G60ing,

The ALH pistons are lighter and the ring placement is higher than in the AHU's. If you do make the swap to the ALH's, I would be sure to hone the top of the bore to make sure that you don't have any problems with a wear land. They don't usually have much wear to speak of at that mileage. Instead, there is a little burn ring. But I would hone until it's straightened out.

Also, as for the rods, they are the same in the AHU's as the ALH... no difference. However, I've found up to 3 gr of difference in a set of rods coming out of a vehicle. Same is true about pistons, to a lesser extent.

Unless you are going to put in something more exotic for rods, leave the rods with the block that were in there to begin with. There is a length issue you might run into.

Nindee-gold-tdi: that new piston you show next to a AHU is a ASV piston, not an ALH. The dead giveaway is the smaller reliefs by the wrist pin and the oil chamber holes in the bottom of the piston. The ALH has no oil chambered piston head; it is domed.

Also, the ASV is shorter from the wrist pin to the top of the piston to allow for machining the block. Your picture exaggerates the difference because the skirt is longer, but if you push the wrist pin to fit across both pistons, you'll see about an .008" variation. If building with that piston, that should be taken into account, and the block should be decked. That is SOP for oversize or replacement pistons.

Last point on the ASV's and that would include several chambered pistons... you have to re-aim the oil squirts in order for them to work correctly.

Herm: As for interchangability, although the pistons have the same numbers, you can bet the weights are different and the overall sizes can vary around .06mm (that's .0018"). I would not recommend installing pistons in anything but matched sets. If putting a replacement piston into a set, try to match the measurement on the top of the piston. For example, 79.44 or 79.46mm are common.

Some pistons are engraved with the piston size. I think most of the pistons have been laser etched with that diameter number. If you use even a Scotch Brite pad on the piston, you will erase that number. I use an acetylene torch with oxygen, lightly passing it over the widest flat area on the piston top and the number comes up like magic.

That's packing in the information...
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Last edited by Franko6; December 12th, 2010 at 18:48.
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Old December 12th, 2010, 19:05   #8
G60ING
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You are right the bores look better then any gas engine with this many miles which I chalk up to the lower RPM range and synthetic oil.

Thanks for the details. I think I'll just use the OEM pistons as you have a good point with the wear heights from the different pistons.
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Old October 8th, 2012, 19:23   #9
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Hi All,

Let me bump this up with some more questions:

Q1: What is the difference between #1-#2 and #3-#4? If it is a balance/weight issue, then why not pair them as #1-#4 and #2-#3?
Is there a visual telltale differentiating these pairs?

Q2: Did most ALH engines receive an original Mahle piston or were there other manufacturers?

Q3: What are all those numbers stamped and etched in the bottom and sides of Mahle pistons?

Q4: somewhere on this forum someone identified a Mahle piston to be 79.44mm just based on the casting code: 79L46. As far as I see, there are 8 different Mahle pistons with that casting code and none of them have that exact measurement.
( http://catalog.mahle-aftermarket.com...ilterId=973418 )

Q5: it seems that the new piston in the pictures is not an ALH piston,correct?
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Old October 8th, 2012, 20:06   #10
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Quote:
Originally Posted by GregZ View Post
Hi All,

Let me bump this up with some more questions:

Q1: What is the difference between #1-#2 and #3-#4? If it is a balance/weight issue, then why not pair them as #1-#4 and #2-#3?
Is there a visual telltale differentiating these pairs?

Q2: Did most ALH engines receive an original Mahle piston or were there other manufacturers?

Q3: What are all those numbers stamped and etched in the bottom and sides of Mahle pistons?

Q4: somewhere on this forum someone identified a Mahle piston to be 79.44mm just based on the casting code: 79L46. As far as I see, there are 8 different Mahle pistons with that casting code and none of them have that exact measurement.
( http://catalog.mahle-aftermarket.com...ilterId=973418 )

Q5: it seems that the new piston in the pictures is not an ALH piston,correct?
Question #1: It's all about the valve pockets on the head of the piston. Intake valve is bigger than the exhaust valve and their orientation is reversed from #1#2 to #3#4.
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Old October 9th, 2012, 20:44   #11
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Makes sense for Q1. Thanks!
Any other takers for Q2-Q5?
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Old November 5th, 2014, 18:06   #12
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Default clarify 1z and AHU piston interchangeable

Hi, quick question. Are 1Z and AHU pistons interchangeable in complete sets? Thanks Artie
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