After saying I seem to be having a good run in another thread it seems I spoke too soon. A couple of nights ago driving home (app 50kmph) not thrashing and the engine died with a big CLUNK. Popped the bonnet to check for obvious things. busted belts, oil pouring out, anything obvious out of place and found nothing although it was 10pm at night with less than adequate lighting, I got in and decided if it was dead it was dead but nothing like a shot on the ignition, tried it once for long enough to know it was not firing (about as long as it takes to turn the key to start and back again no sustained cranking, I heard no sounds of cam chain destruction, hoping beyond hope they had not already done this figured the cam belt has failed (new belt however has had complete 100 k service.) rang the wife and got the car transported home. Today while it was light popped the bonnet again and now see the top idle pulley busted through the top of the cam covers, pulled the hard pipes etc and yes the stud that holds this pulley has snapped right at the manifold. Questions Is this common? I have a spare intake and while it looks like another plenum pull (did a complete bypass etc only 3 months ago crapppppp) can the stud be removed? if so how? I can not get the other out using both an easyout and heat. nor can I budge the one on my other manifold. I do realise the chance of internal damage here is quite high but the engine was not reving hard at the time and the cams have settled on their own in the neutral position where all valves are as closed as possible, not going to hold my breath but not discounting a stroke of extreme fortune here either.
Doesn't sound good. I would guess that maybe the idler pulley stud has sheared off . There are 2 and i just replaced mine with Heavy Duty ones from Coz as a local member had his go recently and bent the valves ( he said he was doing 5000 r.p.m from memory ) so that may have made the damage worse. I have heard reports that when you change a timing belt you should replace the studs. That said i feel that if you use a torque wrench on every bolt and nut on a motor you will never have a bolt break or nut shear off. I was taught this years ago and to this day i always use a torque wrench and have never broken a bolt. I feel it takes bugger all to set a torque wrench and you have to tighten them up somehow.Back to your question you just lock 2 nuts up on the stud then undo , of course if it is shear you may need vise grips or worst case have to drill and tap it out. Any way get the Heavy Duty ones from Coz $25 us pluss postage. They trick is to look them up under both the performance and the normal section as although they are the same product one was cheeper ( must be a mistake on there web site but hey our win ). Cheers Dave
@ Blackbeast picking the valves etc are bent but have 2 complete spare sets of heads so this is not really a problem just a pain in the arse. I do also know that there is a spot where the cams can sit stationary and all the valves are closed or as close that it does not matter, again 2 spare assembled sets of heads I ams certain of this as this is how both these heads are sitting at the moment, I know there is a chance I also know it is so miniscule that if this has happened no point in buying any lotto tickets ever again as I will have used all my luck I am due in a lifetime or 2. @ TwinTerror Tried both visegrips and locking 2 nuts to this one and tried with heat can not budge it. on the busted one am in th process of drilling have some star shaped easyouts they have just gutted the bolt (again wiht heat) my thought here is that I know I have to p[ull the plenum to check the valver train but if I can avoid pulling the rest I will especially for the sake of one BS stud.
My top one was a pain in the but to remove. Even with 2 nuts locked on it just spun the nuts. I heated up then cooled with water a couple of times then heated again and let sit over night. When i tried the next day the dam thing just came undone as easy as (didn't think it would come out that easy ? ). Worst comes to worse just drill it out and tap a new thread maybe. You never know with the valves could be real lucky and there o.k. Cheers Dave
yeah in the process of drilling and tapping, As for the valves the only reason I am even considering that they may be ok is the fact I have heard engines smashing valve trains anmd this did no sour noises at all except the initial sound of the tensioner going, Irealize this is going to be faster than a speeding bullet but when a valve train gets smashed the sound goes on for more than a single clunk. This all being said my plans always have been to build a new engine it just may be sooner than anticipated. and as stated before I have 2 spare sets of assembled heads and a long block waiting to be pulled down from what I believe was a case of too much boost not enough fuel with the PO's of my car.
this really sucks, not a common problem, i would be quite sure you have bent valves. leak down test will be the go here
old stud is drilled out and removed. new high tensile bolt is now fitted and engine has been turned by hand to ensure nothing is contacting anything else. I do not have access to a leakdown setup so I bit the bullet and pulled all the plugs disconnected the PTU and did a normal comp test (stone cold engine and not really enough battery app 11 volts.) 1-4 test at 155-160 psi 5&6 come in at 125-130 this is a cold engine no use of the throttle so I know its not an accurate test but I am happy enough with those readings from my $400 engine (again thanks go to Awgazm) Time to reassemble and try the engine I think. If this goes right then I guess there is no point ever buying a lotto ticket I will have used up all my luck. Do remember I would have been lucky to be doing 2500 rpm when this happened
Just to close this off, after a fair bit of standardized Z work (knuckle dusting etc) I have had the cam covers off to have a physical look, there was no sign of any damage, I still have no leakdown kit, sio I reassembled and tried. Car started first turn of the key, no nasty sounds and I even found a boost leak in the process. (the cap had come off the passenger side nipple for the original boost control). All in all am very happy with this result although still very worried as to the cause of this failure. there are no signs of prolonged failure, it appears to have snapped off completely in 1 single motion. AS nan aside I now need to replace the recirc valves, upon fixing the boost leak I have a lovely case of goose honk.
You are very lucky stumagoo, I knew of a Z years ago with the same luck as yours. Even Joe Imbesi the Z mechanic who worked on it, put a new timing belt on & said he was very lucky not sustain any damage.
The reason a lot of pulley studs break is that the required clearance 4mm in the tensioner jaws isnt there. IF the tensioner isnt constantly able to keep the strain on the belt during revving under control. The weakest point is the studs and eventually they flex enough to snap. Always follow instructions and check the tensioner jaw clearance is correct.
