AHU Rebuild - First timer -- Looking for advice :)

[festethejeste]

Hey guys,

Rebuilding my first ahu, originally had 350k km in a passat that ran from Rob mcgill. Rebuilt motor going in a diesel t3 replacing an aaz, giles pump, k03 hybrid, intercooler, rear geared tranny 3rd and 4th.

Here's a video, cause why not! with some prelim questions.

https://youtu.be/tfo6V42X65A

1. Wondering about quality of aftermarket piston rings, main bearings, rod bearings. Should I go for vw genuine do they really last longer? crazy prices for these but I don't mind paying if they are better quality.

2. Waldo mentioned in another post if the mains and rod bearings are in spec leave them in, as new ones could wear down the crank.

3. Should I get the valves done? I've never done it before, and don't know where to start or what the price would be -- if not should, is it hard to just clean it up, decarb etc and redo the seals on the valves. Is there anything else i should do when servicing the head?

I'm most def going to have more questions so stay tuned, follow along and feel free to roast my ignorance

[Zeitgeist 13]

I'll leave it to Waldo and the others with more TDI internal experience to provide advice about the specifics, but that engine looked pretty darn good all things considered. It probably would've been easier to pull the injectors when the head was still on the block. My ALH head had 204k miles on it, and I just measured the valve seat margins and guide wear, and went ahead and hand lapped them in place. I also ported/polished the head, but you don't need to do that. These are super tough engines.
_________________
Casey--

'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
'01 Weekender --> full camper
y u rune klassik?

[?Waldo?]

I would have plastigaged mains and rods during disassembly. You'll have a bit of backtracking to do. There are three areas of spec; new parts, used parts, wear limit. When doing a rebuild, if any of the bearings are out of spec for new parts, then they should be replaced. The mains never seem to wear (unless the engine is run with dirty oil or low oil pressure) and I've seen very high mileage with them still within spec for new parts. If the mains are out of spec for new parts, then the crank is probably out of spec also. Mic the journals if plastigage shows the clearances out of spec for new parts. The upper rod bearings tend to get worn and at 350,000 km I'd probably replace those if the outer white metal has worn to the yellow metal even if they still plastigage within spec for new parts. Mahle or Kolbenschmidt are fine for bearings. There is typically no need to replace the thrust bearings either. Center the cap by moving the crank each direction, then tighten, then check for endplay with a dial indicator. Odds are good it is within spec.

I would hone cylinders before purchasing rings. You'll find out fairly quickly how much wear there is at the top of the cylinders. At 350,000 kms bores might be out of spec and need to be bored oversize with new pistons. The TDI blocks seem to wear very slowly, though, compared to the earlier IDI engines so they might still be good. New ASV pistons are available at 0.5mm OS and work fine. If you need to have the cylinders bored, then wait to get the head gasket surface trimmed until you test fit the rods/pistons and measure piston protrusion so you can be sure to remain in spec for one of the three head gasket sizes.

If the bores clean up with honing/deglazing, I'd recommend using Goetze rings which is what they came with originally. Right now Autohaus has them in standard size for a great deal - $12.50 per piston.

Elring or VictorReinz are both fine for head gaskets.

Yes, slide hammer works great for pulling the injectors. I got a coupling nut that fit one of my slide hammers and welded a nut onto it that fits the injectors. It works a treat! I wouldn't bother with trying to turn the injectors with a wrench, and especially not in the direction that could loosen the two halves of the injectors. Just go right for the slide hammer.

You can mic the piston skirts although if the skirts look decent they are most likely still within spec. If reusing the pistons, clean the piston ring grooves of all carbon. An old broken ring works well. Thoroughly clean the carbon off the tops so you can get a decent protrusion reading.

The cam is probably fine if there isn't any obvious wear at the lobes. They tend to last without issue.

I would replace the lifters, guides, valves. Have the head skimmed or hand-lap on an actual flat surface - skill/technique required.

Replace the intermediate shaft bearings - special tools required.

You will lose more than you gain from the electronic engine management of the 1Z/AHU vs. a decent quality mTDI pump. If you sell the harness and stock pump and purchase a quality pump, you will be ahead on install time, performance, and reliability. The cost of an mTDI pump is also similar to what you can sell a similar condition eTDI pump for. In other words, if you get a used LR pump you can likely sell your eTDI pump for a similar amount. A new or rebuilt mTDI pump will also be similar in cost to a new or rebuilt eTDI pump.

[festethejeste]

Thanks for info waldo, such a treat to have info like this and so quickly i might add Cheers,

[valvecovergasket]

[festethejeste]

Waldo,

Can I ask why you replace the actual valves. Yep probably newb question but wouldn't the head be the first to wear out? needing a valve job?

I've found some valves from autohaus. I've never ripped apart the head of a diesel before is there anything to worry about? Do you have to adjust the new valves once they are in?

[/quote]

[?Waldo?]

[?Waldo?]

Some things worth mentioning:
The main bearing bolts and rod bolts are single-use. Plastigage clearances with the torque prior to the angular torque (48 ft-lbs for mains and 22 for rods). Do the final angular torque only after you know everything is correct (clearances and piston protrusion).

If you're going to have the block bored oversize, then get it magnafluxed. I have had several blocks with cracks and even though it is not common and very disappointing to find out, it is a lot less disappointing to find out early than it is to find out during or after a full build due to a failure.

It is a good idea to replace the freeze plugs (36.6mm) and the oil galley plugs (12mm). The two galley plugs are located one at each end of the block. One is by the intermediate shaft seal carrier and the other matches that position at the flywheel end of the block. If the block is tanked, then it is no longer a suggestion, the freeze plugs and galley plugs must be replaced.

The Mk3 Bentley is WRONG for the torque spec on the 'oil spray nozzles' and say that the AAZ, 1Z, and AHU should all be torqued to 89 inch-pounds. This is NOT correct. There are two styles of oil jets that were used on the Mk3 diesel engines and the torque spec required depends on which style is fitted to your particular engine. AHU probably has the later 18 ft-lb version.

If you use 89 inch-pounds on the larger bolts (as the Mk3 Bentley suggests) you run a serious risk of having them fall out from vibration. If you use 18 ft-lbs on the earlier version you will snap the bolts off in the block.

Here are the semi-homemade tools I use for installing the intermediate shaft bearings. The two dies I had made by a local machinist. The rest of it, I assembled. Basically I pull the old bearings out, and then pull the new bearings in afterward. Alignment of the hole in the bearing with the oiling hole is important and there is a small oil channel cut into the inner bearing that aims a jet of oil at the intermediate shaft/vac pump gear interface. It has to face the right way. You can get the pre-sized bearings for fairly cheap and they work fine. Federal Mogul 1926M is an interchange part number for the pre-sized bearings and will be called "cam bearings" but are the correct intermediate shaft bearings.

Use a very light spray of hylomar (in the spray can) on both sides of the head gasket and on the block and head surfaces for the head gasket. That does a great job of eliminating the pesky oil leaks that can occur at the oil drains or at the high pressure oil channel through the head gasket (front of block between 3+4).

Glyco are another fine brand of bearings and the typical brand for replacement non-integral thrust bearings. Do NOT use the integral thrust bearings. They have a habit of chewing up the crankshaft thrust surface.

[Vanagon Nut]

Wow. Great info! Nice use of Vanagon wheel nuts on those tools! Dies are steel?

The machine shop installed the intermediate shaft bearings on my Mk3 gas I4. Thinking now, especially since their first attempt of bearing install failed, I should've checked oiling hole alignment.

Will re using old bolts to get Plasti Gauge readings on new bearings, clean parts etc., provide inaccurate measurements?

Neil.
_________________
1981 Westy DIY 15º ABA
(VW Gas I4)

1988 Westy DIY 50º ABA

VE7TBN

[?Waldo?]

It's fine to use either the old or new bolts for the checking clearances or piston protrusion. The important point is to use the ft-lb torque spec without the extra 1/4 turns during checks and save the 1/4 turns for the new bolts when you are sure everything is all set. The ft-lb spec without additional 1/4 turn can be repeated as many times as necessary on the new bolts without needing to replace them. Once you do the additional 1/4 turn on the bolts, if you loosen them again afterward, they should be replaced.

Yup, those are repurposed Vanagon lugs welded onto the threaded rods for counter-holding. The dies are aluminum. They are a little loose for the bearings (and that's a good thing). When going to install the bearings, I use layers of scotch tape stuck onto the dies 180° apart. I add layers until the bearings slide onto the tap snugly and are held in position (usually 2 or 3 layers each side of the die). I mark a line onto the tape and line up the oiling hole of the bearing with the line on the tape. I then look through the oiling hole and center that line on the oiling hole when pulling the bearing into place. The final alignment does not need to be perfect between the hole in the bearing and the hole in the case, but you need it relatively unobstructed. The bearing ID will shrink a little when the bearing is pulled into place. The scotch tape absorbs that compression nicely rather than having the bearing and die mar each other if they were a snug fit without the tape.

[Vanagon Nut]