Engine Replacement & Reassembly on my ‘97 A3

garciapiano

Veteran Member
Joined
Feb 12, 2018
Location
Southern California
TDI
1997 Jetta TDI (1Z)
Hi guys,

I’m in the process of replacing my worn-out 1Z. This was prompted by the original engine having signs of low oil pressure, blow-by and the beginnings of turbo seal failure from 450,000 miles of hard usage, 60,000 of which was under a stage 2 tune. I’d say at this point, it doesn’t owe me anything.

After pulling the original engine and disassembling it, I found that it was remarkably clean inside. The rod bearings actually looked ok, but some were worn through the second or third layer. The intermediate shaft bearing showed moderate wear. The piston skirts had some wear and the cylinders had some wear, although much of the factory crosshatching was still visible. The crank looked pretty much perfect. I’m not sure what was causing the low oil pressure, but I’m going to guess that it was worn bearings throughout the whole engine, and the turbo.

After contacting multiple local machine shops here in SoCal, they either don’t work with TDIs or have several months-long waiting lists, which didn’t give me much confidence that I would achieve a rebuild in a timely or cost-effective manner. I also didn’t want to buy the several hundred dollars of machinist tools to check their work properly.

So, used engine it is. I worked with a local engine importer to secure a “low-mile” 1Z bare long block and picked it up yesterday, cleaned it up and disassembled it to check the bearing clearances. Supposedly it has less than 80,000 miles. The engine looks mostly fine on the inside, zero rust in the block and head, which is nice. Examining the bearings, there is a bit of IMS bearing wear and some wear on the #4 rod. Mains and crank journals look good. Just to be safe I have a set of stock sized rod/main bearings, and intermediate bearings ready to go in. All will be checked with plastigage.

I have a couple questions that I can’t seem to find the answer to:

1. When measuring the main bearings with plastigage, do I need to use brand-new stretch bolts for the measurement and toss them afterwards? Oddly, the Bentley lists a “checking” measurement spec for the rod caps (original torque spec without the extra 1/4” turn) but doesn’t list one for the mains. Maybe I’m splitting hairs here, but what have you guys done? Seems like a waste of bolts to just use them for a single measurement, but then again I'm not really sweating $30 worth of bolts.

2. I received the engine without a timing belt, and it was not at TDC. I turned the crank so the pistons were at mid-deck then rotated the cam to cam TDC. Bringing cylinder 1 to TDC results in interference before the piston gets all the way up, maybe 5 degrees before TDC judging from looking at the crank. Which doesn’t seem normal. I’m going to guess that I’m fine, since I can’t actually check proper TDC till the trans is back on, but am I doing something totally wrong here?

3. Is there a torque sequence for the main bearing cap bolts? E.g. start at the center and move outwards. I don't see one in the Bentlet but that is was what I plan to do.

4. I cannot find a part number for the crank position sensor o-ring. The sensor itself appears to be similar to the ABA and AAA engines but nowhere can I confirm that 021906445 is actually the right part.

Thanks again for all the help.
 
Last edited:

garciapiano

Veteran Member
Joined
Feb 12, 2018
Location
Southern California
TDI
1997 Jetta TDI (1Z)
2. Loosen the cam bolts to allow the cam to float, then spin crank to TDC without interference. Then put cam at TDC, then tighten cam bolts.
I suppose it's worth a try, but then I risk bending a valve when torquing the cam back down, which would be a worse situation. Someone in another forum said to rotate back over counterclockwise if I get interference... which I actually did not try, so I'll try that next time.
 

turbodieseldyke

Veteran Member
Joined
Jun 6, 2010
Location
Free Mustache Rides
TDI
98 jetta
If they're both at TDC, there won't be contact. You just need to free the cam so they can be spun independently to get them both at TDC.

If you rotate CCW, you'll get the same interference as CW.
 

garciapiano

Veteran Member
Joined
Feb 12, 2018
Location
Southern California
TDI
1997 Jetta TDI (1Z)
I am trying to plastigage the main bearings and the caps are basically impossible to get on with the bearings and crank in situ. It was hard to get the caps off, took a lot of wiggling and pulling. How does one do this without damaging the crank?
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
Tap them on with a plastic or wood mallet. You could probably use metal and be fine, but just light taps. Or use a piece of wood, between the metal face and main cap.

-Todd
 
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