VWDiesel.net The IDI, TDI, and mTDI source.
General Information => General => Topic started by: Quantum TD on February 06, 2008, 09:45:19 pm
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I've got this same question posted on TDIclub (yeah, I know...). But I need to get some insight soon because I want to finish this job. So, any insight is appreciated.
So, I've got a 1998 Jetta TDI with an AHU motor. The head gasket was leaking compression into the cylinders. So, I pulled the head and had it reworked by a trustworthy shop (Kiwi Engineering in CT). He did a really nice job on the resurface (took off about .006), recut the valve seats to proper projection, and ground the valve tips to account for the resurface grind down.
So, I finally got to putting it back together. The head gasket was a Reinz 2 notch (good brand), and I had 10 new Febi TTY head bolts (German brand, but who knows where they're made these days).
I cleaned the head up, chased the threads in the head with a chaser (the threads were really clean), flushed out the holes with brake cleaner twice, and blew out the excess until dry.
Following the advise of Frank (head man who advertises here on TDI) and Jack at VWdieselparts, I lubed up the headbolts in order to get proper torque (the bolts were dry to begin with). I used some 10W/30 oil I had (synthetic, not sure if that matters), and I lubed them, and let all the excess oil drain off. So, the bolts just had a thin film on them for the install.
I set the head on the gasket with locating studs, installed the bolts, removed the centering studs, installed the last 2 bolts and began the torque process in sequence.
Stage I: 40 Nm no problems there
Stage II: 60 Nm, no problems there
Stage III: 90 degress turn in sequence, no problems there
Stage IV: another 90 degress rotation: When I torqued the #1 bolt in the sequence, it seemed a bit soft towards the end, but nothing major so I ignored it. But, when I got down to the #7 bolt in sequence, after I got thru about 80 degrees of rotation, I could feel the bolt start to yield slightly. It wasn't terrible, but it was notable.
Now, perhaps I'm being neurotic and this is normal. Perhaps not. I've just never experienced this on a head install before.
I just did a head on a 1984 Rabbit 1.6 D with the same head bolts and procedure (chase threads, blow out with brake cleaner, blow out with air), but in that case I used some 15w/40 Rotella dino-oil to lube the bolts. It was tough to torque, and none of the bolts started to yield. Granted, it had a fiber head gasket, so maybe it gives more than the metal HG used on the TDI.
The only time I've ever felt the TTY bolts yield on the head was when I tried to re-torque a fiber head gasket after it had already been completely torqued to proper specs.
So, is this normal? If it's not, the only things I can think of are:
1) The oil reduced the thread friction so much that I overtorqued the bolt.
2) The bolts are crap, and somehow Febi (a good german brand) is now producing the bolts in China or some crap. This would explain why only 1 (maybe 2) bolts seemed to yeild, while all others seemed fine.
I'm 99.9999999999999 % certain that the block is fine (i.e. not cracked in the threads) since the head was held on fine before, I cleaned the threads just until the chaser stopped (which was about 1/2 inch more than I guess I needed to go), and there was not enough oil on the bolts to cause hydrolock, since I let all the oil drain before I installed the bolts: there was only a miniscule amount that might have collected in the final 1/2 inch of the thread: not enough to crack the block. I can't see any external cracks on the block, and I didn't notice anything when I was cleaning the threads/deck.
At this point, I've just installed the head and none of the other components until I get a satisfactory answer on the matter. I'd rather just pull the head and put on a new gasket and bolts (only costs me $35), rather than have to pull all this crap apart again after putting it all back together.
Thoughts?
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1) The oil reduced the thread friction so much that I overtorqued the bolt.
This seems to be the most likely. I am not familiar with the torquing procedure outlined in the bentley for the TDI though
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I second #1. Synthetic reduces friction over conventional oil, why you don't break an engine in on it.
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I third #1. There's a table I saw once that states what to do with the factory torque specs if you lube (the factory specs almost always refer to "dry") and as I recall, depending on the lube, it's in the order of 15-25%. Same with anti-seize... which I believe is something like 15%.
The last bag of Febi headbolts I bought (for my AAZ) came with torquing instructions...and including a picture of a can of oil with a line thru it. Probably doesn't mean you can't oil them, more likely "these instructions assume no lube".
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Yeah, but alot of those complete set head-bolt kits from Febi (in boxes too) usually have a light coat of oil on them. When I used to get the complete box sets from Febi, they always had a thin coat of oil on them, and I'm sure your set did too if they were in a sealed bag.
The ones I used here were in individual bags and were bone dry. I really couldn't justify putting them in dry, when two reputable sources (who only work on TDIs and IDIs: Frank from Franks TDIs in MO, and Jack at VWDieselparts), both told me to lube the bolts. Now, they didn't specify to NOT use synthetic. Maybe that's the difference? I really can't see how.
Also, check out this thread:
http://www.clubgti.com/forum/showthread.php?t=121766
As a side note, I looked at a bagful of new Febi bolts I had lying around that I had set aside for an IDI job. The batch is from 2004, and the tops of the bolts say "Germany" in clear lettering on the top of the head. The set I used on this TDI were from Nov 2007 and do NOT say Germany on them. There's just the letter 'f' as in: "You're F***-ed".
I'm getting ready to pull the head, but I'll be super pissed if it turns out that Febi is using their German name heritage to make *** bolts in China, and I have to buy new bolts and HG.
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Yeah, but alot of those complete set head-bolt kits from Febi (in boxes too) usually have a light coat of oil on them. When I used to get the complete box sets from Febi, they always had a thin coat of oil on them, and I'm sure your set did too if they were in a sealed bag.
Nope, actually, bone dry.
Rod bolts and crank saddle bolts were the same... in a plastic bag and bone dry.
The rod bolts and crank bolts I got for my gasser a year ago were in a light oil... they were German but I don't remember if they were Febi.
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There was someone selling ARP's on TDI Club. Then you wouldn't have to worry about it ever again.
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Jeez, I'm starting to sound like a Raceware sales rep...
The Racreware instruction state specifically to lube the nuts and studs with non-synthetic motor oil.
Its been my observation that most torque specs are for bone dry squeeky clean fasteners. And many times these specs are within a few % of fastener failure.
Lube makes a significant reduction in sliding friction, and therefore drastically changes torque values.
The differences between dyno oil and synthetic oil are also enough to make a difference.
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I just spoke with Jack at VWdieselparts who's personally rebuilt about 150 TDI motors and hundreds of IDI motors, and he claims that this is normal (feeling the bolt yield). I told him the whole story, and he was not concerned about the type of oil used to lube the bolts. His word were; "let her rip."
I'm gonna talk to a few others and see what they think.
The thing that is strange is that the final torque values are between 80-90 ft/lbs. Basically, I set my torque wrench to a low value (84 ft/lbs) to see if the thing would click. On most of them, the bolt moved a fraction, and then clicked. So, 80-90 is about what all the bolts final torque values are. On the old fiber gaskets on the diesels, the final value was usually over 90 ft/lbs after the reheat and torque. The TDI uses the same bolts as the old IDI. So, I'm under the final value for most of the bolts (8-9 out of 10), but one wants to yield. The only way I can explain it is that the metal gasket does not give once it is compressed, and it forces the bolt to yield once it is fully compressed. The lube may have made me reach that yield value sooner than expected.
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For an example for how lube affects torque, ARP says to torque to 80 ft/lbs with their lube or 120 ft/lbs with 10w30. A BIG difference there. If Jack didn't concern himself with the type of lube used, I wouldn't listen to a word of his advice myself.
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For an example for how lube affects torque, ARP says to torque to 80 ft/lbs with their lube or 120 ft/lbs with 10w30. A BIG difference there. If Jack didn't concern himself with the type of lube used, I wouldn't listen to a word of his advice myself.
From what I understand, ARP's lube is more like a grease than an oil. I'm talking about the difference between 10w30 dino oil, or 10w/30 synth oil. I also spoke with Frank from Franks TDIs in MO. He rebuilds these TDI heads exclusively. He wasn't too concerned about the differnece in synth either.
Unfortunately, Bentley makes no stipulation as to whether a bolt should be lubed or not. So, were' left guessing as to whether their specs are based on dry bolts or wet bolts, or are we supposed to trust the myriad bolt manufacturers out there when and if they decide to lube a bolt before it's packaged. If Bentley clearly stated how the bolts should be, then I'd happily put them in dry, but everyone who I trust on the matter says to oil the threads in order to get a correct torque reading.
So which is it? It seems to be a point of contentions among everyone whose ever woked on a motor: dry or wet? Personally, I think wet. But then again, who knows.
I just pulled the head to see if the bolt hole was cracked or something. There was no oil build-up in the thread pockets, and everything looks fine (no cracks). So, I'm down to:
1) Lube was too slick and the bolt reached it's yield point too fast.
2) My torque wrench is wrong, but I just had it calibrated 3 months ago
3) Bolts are too long somehow (they don't look it, but maybe).
4) This is absolutely normal
5) The bolts are ***/were made in China/I got a bad batch
I should have a new HG tomorrow. I think I'll just spray the bolts threads with WD40, put some oil on the washers. Or maybe just leave them dry and just lube the washers.
Inspecting the bolts, they obviously stretched (I compared to a new bolt I had). My issue is at what torque did the one bolt start to yield. Even if my torque readings were a little high because of the synth oil on the bolts, these bolts should handle about 110-120 ft/lbs of torque. When I went back over the bolts with my wrench set to 84 ft/lbs, some bolts wanted to turn a fraction and then the wrench clicked. That happened on all but the 2 bolts that yielded, which wanted to kept turning.
The only thing I can think of, is that those 2 somehow hit their braking point quick, and after that there was no turning back. Trying to torque them all to the same setting (lets say 100 ft/lbs) was not going to happen. I had this happen once while installing a tensioner on a 1.8T. The book I was using was for a newer 1.8T motor, but I was working on an early Passat 1.8T. The torque spec was 15 n/m, and so I tried to torque it to that. Unfortunately, the bolt was only rated at 12 n/m. So, I felt the bolt stretch under the torque wrench, and realized the spec might be off. So, I tried to back it down to 11 Nm, and it wouldn't take that either: it just kept stretching until it broke. I'm wondering if the same didn't just happen to me with these head bolts.
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check this article out (http://code541.gsfc.nasa.gov/documents/materials_tips_PDFs/TIP%20067R.pdf)
This is the best one I could find illustrating the difference between dry and wet bolts
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Thanks for this, and I get it. But, unfortunately, it still does not answer the question as to whether the Bentley specs are for dry or wet bolts. That then leaves it to the manufacturer to decide, or the mechanic.
Like I said before, when I used to buy Febi bolts in box kits, they were always oiled with a thin lubricant (like WD40). I would always just drop them in and go. I never had a problem with those. Now when I buy the bolts, they're always sold individiually and come dry as a bone. So, what's a girl to do?
With so many aftermarket manufacturers making these bolts, and varying methods, there really is not unifrom answer to the question.
Some people has suggested buying bolts from the dealer to see what they look like. I'm hip with that, but don't want to go buy them only to find that they sell the same FEBI bolts I'm using now, just with a skim coat of oil and getting charged 4-5x as much.
I think the best thing to do on the matter is to clean out the bolt holes, leave them dry, and spray a skim coat of a thin oil (WD40) on the bolt threads and go from there.
Thoughts?
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Why are you screwing around with the strech bolt Scheiße?
There are two choices from people who focus solely on fastening solutions. (ARP & Raceware)
I've torqued enough of those damned things and listened to the pops, pings and groans. What a way to instill confidence in a repaire job. I'll never use them again.
And you just did it as close to "the book" as possible, and it failed. I mean for gosh sakes "the book" is non specific and your hoping for repeatable results.
I suspect these torque to failure bolts were chosen for automated manufactureing, and durability took second place. At the factory, the holes were fresh and clean, the bolts were fresh and clean, and we wonder why we get horse patuty result after theses holes are corroded, pitted, or exposed to antifreeze.
Why repeat failure? Get something that works.
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If this car were a keeper, I'd splurge and spend the money, but I'm just gonna sell the car. I just want some piece of mind when I sell it. Granted, it wont' come with a warranty, but I want to do it right as best I can, without having to spend some $70-100 on head bolts.
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When in doubt with the vagarities of the Bentley I usually assume their instructions are to be taken literally, for better or worse.
Sometimes they say "use anti seize and tighten to blah" so I assume they have taken lubrication into the mix.
Sometimes they say "apply a light coat of oil".
In the case of the headbolts, for the MK2 at least, they say nothing... so I assume the torque value is for dry.
Of course, when you ASS U ME something...
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Of course, when you ASS U ME something...
Hmmm. Theres the rub. I wish those twats at Bentley were a bit more explicit, especially on something this critical. Crap, I thought Haynes sucked a wad...
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My Haynes states all it's torque values are for dry threads. The funny thing is it doesn't have torque specs for the head bolts that I've ever found.
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Here's what I believe is the main reason VW went to strech bolts. Multispindle screw insetion/torqueing machines. Brand new, squeeky clean holes and screws. Works great, lasts along time. The only time a human touches these screws is if one falls out of the hopper.
And that may explain why the manuals are vague about the 'by hand' procedure.
(http://i192.photobucket.com/albums/z236/dieselkraftstoff/10KappPS2.jpg)
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I guess it can't be so simple... What was everyone else doing? Wet intall or dry then?
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Saurkraut- you've solved it! all we need to do is each of us get one of them multispindle factory tools and more stretch bolts! We'd git-er-done in a jiffy!
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Don't forget the VW lube!
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so yes lube or none? on my arp's or racewear when I make my mind up which ones im getting?
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Lube on ARP, not sure what Raceware specs. ARP has specs for either their moly lube or 10w30, whichever you use.
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does anyone know what ARP's 11mm bolts cost?
Can't you get them at multipul places in the states?
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Update. I just got a new set of head bolts (also FEBI) from another supplier. They came as a set (in a plastic bag) and are all coated in oil. What do I do now? Wash it off and go dry? Use the oil on there? Wash it off and use another type of oil?
F**king Bentley a#*holes.
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F**king Bentley a#*holes
2nd that!
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I use them as is. Whenever I get head bolts, they always have had that light oil you speak of