P4N Lotus Posted January 27, 2012 Posted January 27, 2012 "loose crank bolt " Thought this may be of interest... Monday - I noticed , engine pitch had changed, sounded to me like alternator was on its way out, couldn't see anything, informed mechanics at my place couldn't see anything. Tuesday - on way to work, noticed noise was more pronounced, like alternator was about to fail, eventually slight rattle, heard the sound reverberating off cars as I passed, knew it was mine . I was in queuing traffic, rattle became louder, then battery warning light came on, eventually sounded like my exhaust had dropped off and rattling, at this point I cut the engine off, fortunately I rolled into a junction to a halt. Had a look in engine bay smelled slight like burnt plastic, noticed one of the pulley cogs looked like it was at an angle, AA man came checked it out had a feel, said he thought it was idler pully collapse, bu it was a loose crank bolt which had caused pulley to collapse. So decided to take it to the garage...seconds away from the end here's what we found... Fortunately the engine is safe, it was seconds away from being destroyed a very close call. From what I understand here is what happened. Bare in mind I had my cambelt changed about 18months ago by Peter Smith Lotus during a costly C-service. As you can see it appears the bolt hasn't had any lock tight put onto it during the timing belt change (very worrying, considering this was done by a "former" Lotus Garage). It appears because no lock tight was put on it, its allowed the bolt to come out over 18months, this has forced out causing the key to shear off, pushing out causing the pulley to slack, causing the alternator to fail (no power being charged to battery so light comes on), then pulley completely collapses (loud noise), forcing the cam belt to edge out, which slices the bottom cam cover in half and forces it off completely till I turned engine off with only a few mm left of the cam belt still on. Fortunately the timing mechanism was affected and this was a very close call... its good to be paranoid about sounds and if in doubt, kill the engine. Thankfully its all repaired, I have to thank mike at MGW racing for getting me back onto the road quick as its my day to day car. Very lucky, really really angry though with the fact my last Cservice with PS lotus appears to have been a cowboy job, feel free to comment.
Martin R Posted January 27, 2012 Posted January 27, 2012 Lucky escape. Its hard to tell from the pics what come loose first ? If its was the crank pulley IIRC Rover do not recommend you put loctite on it. Although i do. I also check mine on a yearly winter check as a precaution, i have mentioned it on here a couple of occasions. Its a common fault on K series cars. It also has to be done up very tight. 220 nm rings a bell. Trust me this is tight and not that easy to do on your back with the car on ramps. If it was the tensioner pulley this should not come undone either if torqued correctly. Glad you escaped reletivley unharmed though. Edit, ive looked at the pics again and it looks like it was the crank pulley that came loose. A timely warning to all K series owners. Check it every year and you should not have a problem IMO. You have to stop the crank from turning when tightening it. Jam a great big flat bladed screwdriver in the ring gear. This is on the drivers side by where the drive shaft enters the gearbox. You will also need a cut down 22mm socket as the bolt head is close to the engine mount.
dobbo Posted January 27, 2012 Posted January 27, 2012 Paul - I saw those bits at Mike's when I dropped mine off tonight. Lucky indeed ! At least you took notice of the noises and avoided an engine disaster. Edit - "Idler/pulley collapse" is a slightly mis-leading thread title (in case any one is searching in future). It's the loose crank bolt that has allowed the pulleys and their keys to fret away that's caused it, rather than the collapse of either pulley. It might be worth changing the title slightly if you can ? Martin - if you Loctite the crank bolt but then do an annual check on the tightness, surely you risk breaking the Loctite ??? If so, I assume you then remove it, clean it and re-Loctite it. How do you check it ? 220Nm to tighten it, or 220Nm to check it doesn't undo ? Also, (you probably already take this into account) - it's worth "warming" up the torque wrench before going for the full 220Nm as they're usually a little tight when they've not been used for a bit, and will be inaccurate. I do (eg) wheel nuts to 80Nm first for the warm-up, then go to 100Nm. I also get mine checked at work every year - if I put it on at 80Nm, it often initially reads ~90 for the first few clicks, falling to 80 as it frees up. If I'd put it on at 100Nm straight away, I'd have over-tightened the wheel nuts. If you go straight for 220Nm for your check, you're probably putting 240Nm into it, which is likely to break the Loctite. //All this is b*llocks if you're using the torque wrench regularly (but is good practice if there's any doubt).
Martin R Posted January 28, 2012 Posted January 28, 2012 Chris, i always leave my torque wrench unwound to zero as recommended. I set the torque wrench to the appropriate setting and try to retighten the bolt. You can feel if it moves and breaks the loctite seal. If it does i remove clean, loctite again and retighten. As i say a lot of the "experts " Say you should not need loctite at all on the crank pulley bolt.
lummo Posted January 29, 2012 Posted January 29, 2012 I had my cambelt changed a couple of services ago by Top Gear Automotive. When I picked the car up, Kevin said he'd got a great big breaker-bar out to undo the bolt, only to find it needed hardly any force at all. Seems like mine was well on the way to working loose. A lucky escape for me too it seems. A common problem it would appear.
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