Author Topic: aaz crank cap bolts, one time use? (Read 4315 times)

giulianot · « **on:** January 23, 2008, 05:13:11 pm »

Are the crank cap bolts for an AAZ motor stretch bolts? do they need to be replaced or are they reusable?

Vincent Waldon · « **Reply #1 on:** January 23, 2008, 07:03:44 pm »

Yuppers.

Somewhere here there's a thread where the bolts got reused, one broke, cap poked a hole thru the block.

QuickTD · « **Reply #2 on:** January 23, 2008, 07:38:11 pm »

Actually, it can go either way.

Some very early engines had normal bolts like the 1.6 that can be reused. These bolts have partially threaded shanks and they are torqued to 48ft/lbs.

Later engines have fully threaded bolts that are one time use stretch bolts and cannot be reused, these get torqued to 48ft/lbs plus a 1/4 turn (90º).

giulianot · « **Reply #3 on:** January 24, 2008, 04:11:43 am »

Quote

Somewhere here there's a thread where the bolts got reused, one broke, cap poked a hole thru the block.

ya well that just happened to my block :roll: :evil:

MJF · « **Reply #4 on:** January 24, 2008, 04:23:27 am »

QuickTD · « **Reply #5 on:** January 24, 2008, 06:11:18 am »

Yikes, thats messy. The bolts used above are the reusable type though.

I wonder if any of these failures are the result of the wrong torquing procedure for the bolts that were used. It's easy enough to get confused... I would think that if a reusable bolt were torqued in the same fashion as the torque to yield type bolt, it would do most of its "yielding" in the small area where the thread meets the unthreaded shank, perhaps fatally weakening it?

Vincent Waldon · « **Reply #6 on:** January 24, 2008, 07:03:55 am »

That theory makes sense to me... expecting a non-yield bolt to yield would result in a lot of stress the bolt was not designed for... and perhaps every once in a while... SNAP.

Bottom line for me is: they are important, they are under a lot of duress particularly on a diesel, and they are relatively inexpensive. I replace 'em every single time, regardless of what type they were, with the newer torque-to-yield design.

Having said that, my local VW mechanic does not... and he claims to have never had an engine come back in the thirty + years he's been rebuilding engines.

TMMV

giulianot · « **Reply #7 on:** January 24, 2008, 07:20:51 am »

here is the proof that the should be replaced EVERYTIME

not even 1000kms on a fresh rebuild and the engine builder does not want to take responsibility for it cause i never told him to replace the bolts :roll: He is supposed to be a professional engine builder!

jtanguay · « **Reply #8 on:** January 24, 2008, 07:26:30 am »

ouch! has the guy ever done any vw's??? did he tell you that he doesn't have experience with vw's??? are vw's one of the only companies that use the one time only stretch bolts?

giulianot · « **Reply #9 on:** January 24, 2008, 07:36:02 am »

the shop name is Peter's engines, they used to be located in barrie but are now located in peferlaw. I asked him about his experience before i brought the motor to him and he assured me that he is very experienced with diesels and he has rebuilt many before. i also have receipts showing all my costs of repairs and a one year warranty on parts and labour on the motor. Now he is saying that this damage is not covered under warranty. WTF? what recourse do i have other than small claims court?

jimfoo · « **Reply #10 on:** January 24, 2008, 08:13:25 am »

If he is a professional builder, he should be expected to know what gets replaced and what it gets torqued to.

burn_your_money · « **Reply #11 on:** January 24, 2008, 12:47:25 pm »

Depending on how the warranty is worded you may or may not be covered. Read it over or get a lawyer too (lawyer friends are nice) and see where you stand. I forget from your thread but you were running the engine outside of stock conditions no?

giulianot · « **Reply #12 on:** January 24, 2008, 01:08:57 pm »

I was running boost up to 18 psi but im sure that didnt cause this.
I was half way to work when this happened. The motor was at operating temp and i was accelerating from a stop MILDLY Im still in the break-in stage so i was not giviner! Surprisingly the motor still runs on all 4 cylinders i havent removed the pan yet because the engine builder want to do that himself so he can see what happened. After speaking to the engine builder some more we have come to somewhat of a resolution. On sat i will bring him the old long block and a spare block . We will first remove the pan and see the extent of the damage, take pics, and see what caused it , Even though i know what cause this he reused the main cap bolt which are torque to yield bolts. The way i figure is he owes me a GOOD bottom end , so i will request that he swap over all my parts (plus new gaskets, seal, rings) to the spare block plus machining at no cost to me off course ! I shall report back after sat and we will see if he honors his work.

burn_your_money · « **Reply #13 on:** January 24, 2008, 01:14:34 pm »

Good luck with it, I hope it works out for you

giulianot · « **Reply #14 on:** January 28, 2008, 11:59:44 am »

The engine builder is buying a used short block from the junkers and boring it out. He also needs to replace two pistons since they are cracked and .5mm over (+.035). I am also going to machine a flat on the used aaz crank to fit a tdi crank sprocket. AAZ crank noses were inherently weak and were changed to a stronger design for the TDI's. As for the cap bolts i just came to a new discovery, there is an engine serial number specific cap bolt to use, prior to AAZ 560 000 you use N 102 638 01 which is a m10x65 bolt, and after AAZ 560 001 you use N 901 300 01 which is a M10x80 bolt. I wish my engine builder new this before he did my motor. Thanks all for your responses and thats the end of my cross posting