I killed my AAZ - How strong is the bottom end?? PIC HEAVY

[Shaggy]

Hi Guys.

Ive suffered from the dreaded bottom pulley failure. Here is the broken crank pulley on the bench:





So I whipped the head off to discover the pistons don't look that bad. There are marks from the valves but these only seem to be very slight. The marks appeared to be mainly in the carbon. I cleaned them up and took some photos:










So the head appeared to be not that bad. I took the valves out and started cleaning it up and discovered cracks in between every inlet & exhaust!!









So I have to buy a new cylinder head - no choice there?? I'm wondering if I should tear the bottom end down and rebuild with new shells?? I don't know how many miles this engine has done. I'm also wondering how hard it is to grind the flat on to make the TDI pulley fit??

Thanks in advanced for all your advice.

Shaggy

[theman53]

I am NO expert, but I would have the head checked out new valve job and run it. The head I have on my 1.6 has worse cracks than that and my machinist said it was fine.
The crank key way looked ok though...looked more like the sprocket teeth very odd.

[8v-of-fury]

those cracks in the head are fine. I dare you to find a used diesel head that doesn't have cracks there lol

How odd that the pulley grenaded like that!

[Shaggy]

WOW - I really thought the head was fit for the bin with those cracks in it.

All the exhaust valves are visibly bent, except maybe 1. The inlets appear to be fine but Ill need to check 'em.

Here is a pic of the keyway. It looks pretty good to me?? I might take that high spot off it with an oil stone and fit an original type keyway pulley - with a new type bolt & thread seal. There appeared to be no thread seal on the bolt I took out!!





Thanks again, Shaggy.

[Vincent Waldon]

There appeared to be no thread seal on the bolt I took out!!

Actually that's fine... the bolt is designed to be installed dry.


Yeah, I don't get the broken teeth either... the keyway and groove both look like they have *some* meat on em.  

Pistons look fine to me... as do the cracks in the head.

Any ideas on how the teeth got shredded?

[Shaggy]

Hi Vince.

Thanks for your answers.

It seems the bolt wound out then eventually snapped. I guess the pulley rattled around and this cracked the teeth off. Do you think this head will be OK to wind up the boost and fueling on? I'm running a K03 and so don't think it can develop that much boost anyway. Im not going for massive power - just more low down torque would be nice.

Because the exhaust valves that were removed were bent do you think the guides could be damaged??

Thx, Shaggy.

[rallydiesel]

I'd definitely change the guides.

[smutts]

You might need a M8? helicoil kit for the cam cap studs as they might well have pulled their threads in the head alloy.

[wolf_walker]

Not real up on the AAZ, but that crank snout and key looks just like the ME code motor's don't it?
I remember noticing it was quite different than the early stuff I have been used to dealing with.
Mine still had the original non-stretch bolt and I re-used it with a healthy dose of lock tight.

[burn_your_money]

You look to be extremely lucky. That key was probably about to spin. While you have everything apart, now is the time to upgrade the crank nose. Pull the crank and bring it to a machine shop. It shouldn't cost a lot, certainly less then a new head. If there is someone local that can do it in car you can go that route too, it's usually not as expensive but may not be as accurate.

Did you find the other pieces of the crank gear? If not I would speculate that someone tried to use a 2 foot puller to remove the gear and snapped the edges off and then for some silly reason reused it.

[Rabbit on Roids]

another thing, if you re build that head, put new pre cups in it. they look cracked.

[theman53]

I couldn't tell  the head is dirty, looked good from what I can see...but I would inspect it and then if you need to replace.

[Shaggy]

Hi chaps and thanks for all your comments. Ive cleaned the bottom of the head up and taken these pics - starting at the right of the head and working left. I think it looks good apart from the cracks between the inlet and exhaust and the pre - chambers look good too - should I leave them??:



















As for the threads in the head for the cam cap bolts - they are fine and I DTIed the cam on rotation with the caps off and there is no bend in it.

The guides are good too so Ill leave them for now.

I think I'm going to leave the crank nose as it is. I'm not going to change it for a TDi one (and when it goes again I'll get a barrage of  ). Ive looked at the end of the crank and it seems very good to me. As 'burn_your_money' says "Ive been extremely lucky". I'm going to clean it thoroughly and then oil stone the high spots off it and get the keyway type crank wheel bolted on properly (torqued up correctly) before the head goes on. This can be a test to see if the original design works when the correct torque is applied on assembly.

Ive been told that the reason the pulleys come loose is because mechanics buzz gun the bolt off and then buzz gun it back on to save time when doing the cam belt - that way they don't need to remove the bottom pulley cover or undo the 4 allen headed bolts that hold the ribbed belt pulley on. Seems to add up to me??

I changed the cam belt about 15k miles ago and the bottom pulley was fine. It wasn't loose (didn't wobble) and dint have any bits missing. I wish I'd know at the time about the issues with this nose wheel. I was more interested lowering the car, getting it driving straight and sorting the stereo at the time - rather than researching the engine. The nose wheel pulley must have smashed as it came off. Ill take some pics of the bolt and post em up - it seems it would quite a way out before it snapped!!

Two more questions:

I'm going to fit an EGT gauge at some point and was wondering what size to tap the exhaust manifold - I can fit a bolt for now - but at least its done. Are all the probes the same?? Or can anyone recommend I buy just the probe and wiring in the UK??

Also if Im going to wind up the boost on the K03 will I need to get ARP head bolts or will the standard (brand new) ones be OK??

Chaps - thanks again for all the advice and comments. Even if I don't appear to be taking all of it onboard I am - Ill try and justify my reasons and document / photo them. It makes a nice change to be on a forum where people are into the engineering and not the look   


Shaggy
 

[Dakotakid]

"Visually bent exhaust valves" and a decision to go with the existing guides. Well, I hope your stores have a sale on oil!
Can't wait to hear these justifications...........

[burn_your_money]

If you have a K03 there is no need for head studs. You can't (shouldn't) be able to turn the boost up high enough to need them. It's just a wee little guy.

Your head appears to have been welded and rebuilt before. The area between the valves is ground down on stock heads.

Here is a picture. I've only provided the link because it is huge
http://img.photobucket.com/albums/v603/burnyourmoney/DSC07745.jpg

Since you aren't doing the TDI crank mod when you get a new pulley make sure that it has ZERO play on the crank nose. Loctite or JBWeld are not a good solution. I also would not put loctite on the bolt.