g60 crank bolt...why do they snap?

[steveo29 0]

i seem to be reading alot that the g60 crank bolt can snap. is it just random bad luck? does having a modded engine cause it..anything i can do to prevent mine snaping?...does it usually go when its been disturbed??

[beavis 0]

Crank bolts on the PG engine are stretch bolts. They are single use bolts. On occasion people remove, then refit without realising this resulting in them failing. Being a stretch bolt they are also under tension, this weakerns the Grain of the metal making them more prone to snapping. Perhaps not scientifically to the book, but you get my drift.

 

Replace with a early DX engine crank bolt fitted with a bit of threadlock, you want the old style bolt, not the so called VW 'revised bolt'. They are all of 2 quid from VAG.

[steveo29 0]

so if mine is original untouched it "should" be okay?....and if i disturb it use a new dx bolt

 

i dread the day i have to loosen that bolt.. :oops:

[Banana Man 0]

Mine was original and hadn't been touched and mine wasn't ok!!!To be on the safe side change it whats £2 when it can cost you a new set of valves and pistons whic will cost in excess of £600????

[CaiosG60 PWR 0]

When one went on my car. I was told by the part suplier that the bolts sold now have a higher tensil strengh than the original ones.

 

I would recomend that everyone changes to this bolt. If it goes it can be a complete disaster! I was very lucky!

[steveo29 0]

can you tell by if its a 6 or 12 point weather its the good un

[beavis 0]

can you tell by if its a 6 or 12 point weather its the good un

 

12 = late

6 = DX strong = :D

[steveo29 0]

so how come other cars like 16v and 8v gti dont seem to suffer?

 

if ive got the 6 should i leave it?...and to those that changed em,how the hell did you loosen it?

 

i was under the impresion that they failed due to movement on the keyway? and that however strong the bolt is if there slack in the key way then it would fail..and what the hell do you use to remove the remaining bolt?

[Henny 0]

The late model 8V MKII golf GTIs have a similar problem with this bolt... On MKII 8Vs (late ones only, for some reason!) the bolt works loose. This damages the keyway and key meaning that there is no drive to the cambelt as the pulley is free to spin on the crank! :shock: I've seen this on several MKII golfs, it starts off as the engine not running right, normally it starts to pink a lot and be a sod to tune up. This is because the sprocket is wearing the key away and turning slightly on the crank so throwing the cam timing out gradually... Not good... :?

 

I think (and this is just my engineering thoughts on it after mine sheared off) that the reason that the G60 suffers from the bolt shearing more than any of the other VWs is the size and width of the pulleys attached to the crank. On a 16V, for example, you've got the same number of pulleys attached to the sprocket, (2!) but both of them are just V belts to drive the P/S and alternator/waterpump respectively. They're both really quite narrow and to don't exert a huge amount of twist onto the bolt. By twist I mean pulling the pulleys towards the front of the car, which will exert all of the pressure on the hinge point which is the part of the bolt where it is no longer in the threaded part of the crank. Now look at the 2 pulleys on a G60 engine and you'll see that the Supercharger belt is a LOT wider than a V belt and under a hell of a lot more tension than a normal V belt. Then you've still got the normal tension on the P/S pump belt, but this is now 2 or 3 times further away from the hinge point on the bolt.

 

As "torque = force x distance " you can clearly see that there is a hell of a lot more torque exerted on this point of the bolt in a G60 engine.

 

Now here comes the interesting bit...

 

This bolt is a stretch bolt was designed to stretch a small amount only and you're now exerting quite a significant torque SIDEWAYS across this bolt which is continuously changing direction due to the engine turning. This is basically introducing a wobble to the equation which will weaken the bolt even more as it's not under a constant force (which it would take) but is under a varying force (basically acting in all directions) which the designers probably never even thought about. This causes it to stretch slightly more than it's tollerance and eventually shear off flush with the end of the thread in the crank which is where the hinge point it. (I'll put money on that banana man's bolt sheared in EXACTLY the same place as mine on the bolt.)

 

To sum it up, it's a crap design! :roll: :? Putting a hardened, non-stretch bolt in will make this problem disappear for a LONG while, but even that bolt may well suffer the same failure... however not within the life of the engine! :)

 

 

Jees, that went on a bit didn't it... Sorry! :oops:

[steveo29 0]

so how did you fix it?...new/used crank or reuse the old one

[Henny 0]

so how did you fix it?...new/used crank or reuse the old one

 

Depends what the damage is... I was lucky in that the pistons didn't touch the valves (as far as I can tell at the moment!) but I know that Banana Man's bent a couple of valves when it came off... :?

 

Some people have been able to get the bolt out with a reverse tap (basically a drillbit that turns the other way and is tapered so it should turn the bolt out as it bites into the bolt) I decided that seeing as my engine had 250K miles on anyway, it was time for a rebuild! :lol:

 

Have a look in my galary section (Henny's J-Dub) for more info... 8)

 

If you can't get the bolt out with the engine in the car, then you're stuck with having to get the engine out and taking it to an engineering workshop who can drill it out on a lathe and re-tap the thread afterwards, or a new crank... :shock:

 

Either way, it's not good! :? :(

[G60JAY 0]

Something else, is the supercharger it`s self is putting a lot of stress on the bolt and key with the 20 something hp to turn it.

[h100vw 0]

Steve, I like the sound of Hennys explanation. My bolt is the original as far as I know. Then I think back and when I changed my big ends 2 years ago at 90K someone had been here already. So who knows for sure????

 

Thing is if your car starts displaying the symptoms Henny describes, pinking, difficult to setup etc. Check the cam timing and ign timing. They will start getting further from the TDC reference. Thats when you need to change that bolt and the possibly the woodruff key and pulley.

 

A mate of mine had a similar problem on a MK2 16V he bought. It had a 2litre engine in it. It would pull like mad on small throttle openings but if you went a little too far then it would pink badly. Luckily for Kev it sprung an oil leak from the seal behind the bottom pulley. While we were checking it out, we discovered the seal had been damaged by the woodruff key ripping into it.

 

The Woodruff key and the bolt were replaced and its still running like a train today, 4 years later. His engine had been apart and I think the bolt had been reused and thats why it had become slack and allowed the cambelt pulley to chew the woodruff key.

 

Kev got a 6 point bolt from VW, after hearing from C&R it was a good idea.

 

On VWVortex there is a a guy who machines the end of the crank and the cambelt pulley so that you can have a couple of pegs fitted. That way the pulley cannot rotate except with the crank. His name is Fastbunny I think.

 

Like Henny says you should be able to get the remainder of the bolt out if it snaps off. Without any tension on it the bit in the crank would come out with an easyout. Snap On do one that you drill into the crank and knock in a splined rod.

 

Me I wouldn't worry. If it goes big time the crank in a G60 is the same as an 8/16 Valve. I have a brand new one in my garage, along with a brand new set of G60 rods. I ummmed and arrrd about giving the lad £30 for the lot, NOT!..

 

Later

 

Gavin

[Henny 0]

G60JAY I thought about this too, but driving the S/C belt is a force which is exerted mainly in the wrong direction (actually it's the wrong plane, if I'm going to be technically correct!) for snapping the bolt... If driving the S/C were the main problem, then the key on the cam belt sprocket would shear off and cause the whole lot to stop spinning, not to shear the head of the bolt off... :?

 

H100VW, The pinking and other symptoms only happen with the 8V GTI engine... With the G60 there is no warning symptoms that I've heard about, the engine just stops running like you'd stalled it... :shock: :? My G60 was running the best I'd ever had her 'cos I'd just put a new, gas flowed and ported head on about 5 days before the bolt sheared... :shock: :cry:

[G60Jet 1]

I changed mine the other week just to be sure

[Henny 0]

I changed mine the other week just to be sure

 

Wish I had... :roll:

[Supercharged 2]

Anyone have a part number for this?

[Banana Man 0]

The part number for the 12 point corrado stretch bolt is N 903-208-02

[steveo29 0]

i thought the old 6 pointer was best?

[Henny 0]

DX engine 6 sided bolt : Part number: VN 040 106 4

 

This is IMHO a better bolt, just don't forget to put some thread locking compound on it when you fit it!

 

Oh, and, steveo29, you've just managed to upset me... I've just looked at my receipt and it's only 77p + VAT! :cry: :cry: :cry:

[Toby 0]

To those that have changed this as a preventative measure - is it easy to undo. I have a horrible vision of going to replace mine and in undoing the old one - sheering it off ?!?!!?

[Henny 0]

Toby yup, that is a worry. :shock: The bolt is in there somewhat tightly. You're best of getting a garage with an airgun to remove it and fit the new one as you are unlikely to be able to undo it with a bar unless you can get the car well up in the air while being on all 4 wheels. The best way (I've been told) to undo the bolt with a bar is to put the car in gear with someone sat in the car with the brakes on HARD and chocks under all of the wheels to make sure that it can't move off the 4 post ramps... :shock:

 

An airgun does just sound a hell of a lot easier! :roll: :lol:

 

At least if the bolt DOES shear off when you are trying to get it out you haven't damaged any of the internals of the engine ('cos it's not running!) and you know that it probably would have snapped off soon anyway! :shock: You've also then got it in a place you can work on it and will probably be able to get the broken bit out with a set of reverse taps. 8) Banana Man's probably a better person to ask about removing this broken bit as I just cheated and have had the block rebuilt! It's someone else's problem then! :lol: :wink:

 

Good luck to anyone who tries to do this, please put up a comment on how you did it and how it went here so that people can gauge how likely theirs is to snap and how is best to do it! 8)

[Joe M 0]

I did see a trick for removing the crankshaft pulley bolt on the vwvortex (they were talking about vr's though.)

Get the bar in place, in the right position so that you can lower the car down so the bar is touching the ground, remove the fuel pump relay then turn the engine over for a split second and the starter motor will loosen the bolt for you.

[Henny 0]

I did see a trick for removing the crankshaft pulley bolt on the vwvortex (they were talking about vr's though.)

Get the bar in place, in the right position so that you can lower the car down so the bar is touching the ground, remove the fuel pump relay then turn the engine over for a split second and the starter motor will loosen the bolt for you.

 

...or shear the bolt's head off and bend some valves as the sprocket comes off... :? :shock:

 

I've seen that trick mentioned before too and, IMHO, it's too risky as you are turning the engine while stressing a bolt that's potentially going to snap even more. This is putting you in a similar situation as I was when mine sheared at idle... :?

 

This trick does work, I will add that, but I personally wouldn't try it just in case the bolt sheared... :?

[Joe M 0]

Fair enough, I suppose its a lot safer on the vr as the belt the pulley runs only runs the water pump and alternator, dunno what else but nothing that would cause that damage.