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.
 
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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
 

garciapiano

Veteran Member
Joined
Feb 12, 2018
Location
Southern California
TDI
1997 Jetta TDI (1Z)
Whelp, after sourcing a used engine (and turbo) from europe and rebuilding it with new bearings, and rings, (and getting the head rebuilt with new lifters, guides and a cam) it runs great... still breaking it in and it just passed 1000 miles, but hooked up the oil pressure gauge today and I have the same low oil pressure issue! Startup pressures are fine, 90PSI+ but the pressure bleeds down gradually to be seemingly too low as the oil heats up. It's giving me 30 PSI at 2000 RPM hot, and around 8-10 PSI at idle (measured from filter flange) which is just mind-boggling given there are brand-new bearings all around. Main, rod and intermediate shaft bearings.

The oil buzzer is not coming on like before, so the pressures are definitely better than before but I'm scratching my head. Clearances were all good with plastigage before it went together. But I feel like I shouldn't be getting such low pressures with "in-spec" clearances and bearings.

The only part I re-used from the old engine was the vacuum pump. I replaced the rubber seal at the end of its shaft but that's it. It has over 400,000 miles on it but my understanding is that the pressure was created at the oil pump shaft, not at the vacuum pump. Mileage aside, the vacuum pump is functioning normally.

Is it possible to lose that much oil pressure from a worn vacuum pump? As for the oil pump, I just reused the one from the new engine, figuring it was good but didn't check the gear clearance.... Oil pumps were all out of stock while I was doing the rebuild. I guess it could be out of spec but I want to try the easy stuff first.

Heartbreaking, knowing the thousands of dollars and hours of work that went into putting the engine together. Not really sure what to do next.
 
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Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
I don't see why those oil pressures are bad!
8 to 15 is normal for hot oil on a 1z and ahu. A true tell tale sign of worn internals is low oil pressure when cold. My ahu had 45 to 60 at idle when cold. You have 90. A bit high but not abnormal and a sign that things are good.
Usually journal turbos let a Lot of oil though them at operating temps. That's why tdis usually see less oil pressure when hot. I would like to see more like 15 when hot at idle. Does it build up as revs go up when hot?
As for the vacuum pump... I dont know for sure but it can be a place I'd investigate further.
 
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ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
I’d think the o-rings in the vacuum pump are just seals to keep oil/vacuum in/out.

I prefer the pressure gauge reading from the head. If oil can’t get there, the engine will be toast.

Are you using a mechanical or electric gauge?
What weight oil?

-Todd
 

garciapiano

Veteran Member
Joined
Feb 12, 2018
Location
Southern California
TDI
1997 Jetta TDI (1Z)
Yes, the pressure isn’t terrible but it’s way less than I would expect. I am using an electronic gauge from New South performance wired in. It is reasonably accurate within a couple PSI of my harbor freight mechanical gauge but I haven’t hooked up the mechanical gauge. I can check head pressures at some point this week.

Pressure builds healthily at higher RPMs but… yeah. The way it slowly slides down is indicative or some clearance being too big.

15w40 is in the engine right now but I planned on moving over to 5W40 when supplies are better.

Anyways I hit up Frank06 and he says that it could very well be wear at the cam bearing journals. There’s also a modified oil pump he recommends. I guess I’ll have to try the easy stuff first.
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
Your oil weight will only affect cold starts. I’d expect you see lower pressure when cold, once you switch weight.

Just drove around for some errands… 92° ambient… at idle:
Dead cold start.… 50psi.
Hot… just above 20psi.

My readings are taken from the head with a VDO gauge. No clue how accurate it is.
I have just under 224K on the clock.

-Todd
 

garciapiano

Veteran Member
Joined
Feb 12, 2018
Location
Southern California
TDI
1997 Jetta TDI (1Z)
Nice, would love to have 20PSI idle on a hot day. My guess is that there may be multiple loose clearances that are compounding to create the low pressure scenario. I also have no idea how worn the turbo is. It’s a used OEM stock turbo from Europe. Didn’t have any abnormal shaft play and is spooling fine with no smoke now. How much pressure drop could be caused by a worn turbo?

Turbo, the head, and the oil pump are my suspects. Franko6 says the Chinese oil pumps with the taller gearing could help, but their quality is suspect (due to not being German-made), but I suppose it is worth a shot. I am trying not to buy another turbo…
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
How much pressure drop could be caused by a worn turbo?
Brandnew gt2052 had my oil pressure at a lowest of about 20ish. when she had the runaway failure it was at 8 at idle but 15 at 1200 rpms and normal after that.
 
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