rattly knocking noise from mid to top end on a G60

[Gman 0]

If it came in thur the valve surly it would have damaged the valve a bit. there is not a lot of time for that to drop thur

[Scruffythefirst 0]

Just had another look at the pics, that's small enough to get through the valve i'm sure. It also looks like it's got a lock washer still attached, which doesnt bode well from where ever it came from. Plus if you think of the speed of the airflow through a valve as its opening, it doesnt need a lot of time to drop through, it'll get sucked through pretty quick.

[Kevin Bacon 5]

I can't see a bolt that big (although it's comparitively small) getting through the inlet valve. They only open a few mm, you'd need a good 10mm lift to get that fcuker through the valve opening, and at 5000+ rpm? The valve would trap the bolt and it's game over.

 

Good theory though :lol:

 

It looks to me like it's been dropped in and stuck to the head after the initial compression stroke but the bolt would have to have been hot to compress so easily, as opposed to burying itself in the piston.

[G60Jet 1]

kevhaywire, thats the way im going as above

[Gman 0]

But surly after each ignition stroke the bolt would come lose.

[Scruffythefirst 0]

How do you know there isn't damage to the valve yet? Have you taken them out? If it hasn't come in through the valve, how on earth did you manage to run the engine for more than 10 seconds without hearing it?

[Henny 0]

I actually think that this may well have come in through a valve... I'm gonna have a play tomorrow and see if it'll go through or not... 8)

[Scruffythefirst 0]

but the bolt would have to have been hot to compress so easily

 

It will only have taken one combustion stroke to heat that bolt up red hot - volume to SA ratio and all that.

[Kevin Bacon 5]

Well let's wait for Dr Forensic Henderson to suss it out......

 

We eagerly await the post mortem results :wink:

[Gman 0]

Ok so the bolt will heat up very quickly but on every stroke i would have thought that it would do something different. It wouldnt have welded its self to the head would it?

[Kevin Bacon 5]

but the bolt would have to have been hot to compress so easily

 

It will only have taken one combustion stroke to heat that bolt up red hot - volume to SA ratio and all that.

 

Nah. It would take a good few combustion cycles to heat a steel bolt red hot.

 

Look at the burning around the bolt in the pic and how did it get in that tight space? Looks like it's been there a while.

 

I hate to say it but it has all the hall marks of being nipped up under the head from day one :? And then the piston's constant beating against the bolt perhaps prematurely wore out the big end?

 

Look at the bolt too.... it's flat and clean. It shows signs of one big compression and also on the piston. Just one mark.

 

Edit:- Not saying I'm right tho, just going by what I can see in the pics

[Henny 0]

Well let's wait for Dr Forensic Henderson to suss it out......

 

WHO?!? :?

 

I have a theory on what happened with this, but I need to check out a few things first... but I'm going to bed now, so I'll leave this alone until tomorrow now... 8)

[Supercharged 2]

I have a theory on what happened with this

 

Hmmmm :roll:

[Gman 0]

Tis a novel way to increase the compression ratio

[stevemac 0]

No. The only way it could get on top of the piston is if it was put there deliberately through the plug hole (vandalism) or, perish the thought, pixxies.

 

Could have fallen in through the sparkplug hole while Ian was rebuilding the engine ??

 

Even at TDC there should be just enough room for the bolt to sit on top of the piston.

[Gman 0]

that is a long time for it to be in there with out it making a noise.

What ever the case i think it is safe to say that he has been very lucky this time round

[scruffydubbers 0]

wow that pretty strange.

 

its not one of the little bolts which hold the wedge in place on one of the throttle flaps, or is it bigger than that.

 

surpose it could have been lodged in the intercooler somewhere :?

[Jim 1]

Jinkeys.. overnight thread explosion.

 

Well i'm glad you know what it is now Henny, but all it does is open up a thousand more questions! :(

 

I hope you manage to get J DUB put back together with minimal expense and fuss mate!!

[dr_mat 0]

Jinkeys.. ..

 

Thank you, Daphne. Now go get Scooby and we can all go home... ;)

 

My personal theory on this is that the bolt actually formed from the bits of swarf generated in the piston bore, in a complete fluke of trans-meta-morphisation-ism. Or something. It grew, like a crystal.. :)

[LJ 0]

Bizare. Very lucky more damage wasn't done!

I'd go with ...

I hate to say it but it has all the hall marks of being nipped up under the head from day one :? And then the piston's constant beating against the bolt perhaps prematurely wore out the big end?

If somehow it managed to get through the inlet valve:!: is it worth checking the I/C...

 

I reakon you need to get the Gremlin exterminators to look at your garage.

[dazzyvr6 0]

ummmm maybe a magpie flew over and dropped the bolt down a plug hole while your back was turned....seriously though its well weired :?

[Jim 1]

Bizare. Very lucky more damage wasn't done!

I'd go with ...

 

If somehow it managed to get through the inlet valve:!: is it worth checking the I/C...

 

I reakon you need to get the Gremlin exterminators to look at your garage.

 

Along those lines, is it possible that a foreign body entered the system whilst you were fitting your new boost pipes / hoses Henny?

[Supercharged 2]

Thank you, Daphne. Now go get Scooby and we can all go home...

 

My personal theory on this is that the bolt actually formed from the bits of swarf generated in the piston bore, in a complete fluke of trans-meta-morphisation-ism. Or something. It grew, like a crystal..

 

:lol:

[Henny 0]

I've been thinking about this overnight... (as you would if it were your engine ;) )

 

I am now 100% certain that this bolt HAS come in through a valve... it's the only way. It DEFINATELY wasn't there when I bolted the head back on last time (I took photos of the block, so I can tell! ;) ) and it's not a bolt from my engine... which leaves 4 options...

 

1) Sabotage... not likely at all... I've not annoyed anyone in a long while and the alarm would have told me if anyone had messed with the enginebay

2) The bolt got into the new pipework when I fitted it the saturday before and then got sucked into the engine as I was driving... Again, unlikely 'cos it's not a bolt from this engine, so wouldn't have been lying around in the enginebay/my garage to fall in, and the pipes were all cleaned through with a towel to get all of the polystyrene packing out of them...

3) The bolt was in the intercooler and has finally worked its way through into the head during the group thrash at Bruntingthorpe the day before... Possible, but seriously unlikely seeing as the car had done 7,000 miles with that intercooler on including 2 rolling road sessions, 4 1/4mile runs and several laps of Curborough...

4) The bolt got in the head while it got machined at a local engineering shop when the headgasket went and has been floating around in there since... it's just finally dropped in through the valve and could have done it at any time...

 

4 is the theory on where the bolt came from I'm going with... It explains everything including why the bolt is not from this engine, where it came from, how it got there and why I'd not seen it before... It also explains the swarf in the sump as I don't think the workshop blew the head out properly with an air-line once they'd machined it as the guy did it as a rush job... :roll:

 

I'm gonna be stripping the valves out in the next couple of nights to check for damage which will prove that it's come in that way...

 

All in all, I think I've got away VERY lightly with this, as if the bolt had of hit one of the valves I could be looking at a new head, pistons, rods etc etc etc... :| As it is, I'm pretty certain that I can re-use the head as it is (Gonna get it checked this weekend anyway) and also re-use the piston too! :D Just need to re-shell the bottom end which I think needed doing anyway from when the water got into the oil 'cos of the headgasket going... 8)

[olly elworthy 0]

hope you get this bizzare problem sorted mate,, good job you thought to stop the motor and strip it down straight away, that bolt would have done untold amounts of damage should it have been in there for a while longer!!