Crank Pulley Fell Off? How Much Damage?

[teekay523]

Was doing about 50mph last night and my lightened crank pulley came off (obviously i pulled over to one side straight away). spent 3 hours towing the FU***** thing back home. how much damage u reckon that would've caused?

TK

[grass777]

Was doing about 50mph last night and my lightened crank pulley came off (obviously i pulled over to one side straight away). spent 3 hours towing the FU***** thing back home. how much damage u reckon that would've caused?

TK

well i would say valves bent possible damage to the top of piston's.Not good really.

Why did it come off has thread lock been used? or just not tight enough...........

[Matty]

Perfect excuse for a Glanza or 3SGTE conversion.

[teekay523]

Probably not tight enough. damn stupid garage. gonna mash em up later. also i noticed that my crank pulley now has been spinning a little bit erratically? should i be really concerned about this?

Was doing about 50mph last night and my lightened crank pulley came off (obviously i pulled over to one side straight away). spent 3 hours towing the FU***** thing back home. how much damage u reckon that would've caused?

TK

well i would say valves bent possible damage to the top of piston's.Not good really.

Why did it come off has thread lock been used? or just not tight enough...........

[Gnome]

If the part was fitted by a shop, give them hell.

How many miles have you done since it was fitted?

It's not gonna be pretty, as without looking, you don't know how much damage can have been done....

[armoredfist2002]

I thought the crank pulley was on the outside of the engine, so I wouldn't have thought there would be much damage.

[Benno_uk]

Well yeah the crank pully is on the outside of the engine but the crank bolt also holds on the bottom timing chain sprocket!! So, it all depends on how lucky he`s been. Worst case timing chain sprocket jumps, valve timing goes t*ts up, and valves hit pistons. Best case is if timing chain sprocket stayed on and chain stayed put. Then just replace pully & bolt.

[teekay523]

well the good news is that no damage was done but the crank pulley is spinning erratically. is this something to worry about? it seems fine once i step on the gas then the aliignment is back to normal just when its running on idle?

[grass777]

well the good news is that no damage was done but the crank pulley is spinning erratically. is this something to worry about? it seems fine once i step on the gas then the aliignment is back to normal just when its running on idle?

Well the pully should be true and inline with all the other pullys at every speed if it is tight and on properly.

I would take the pully off and put it alongside the original an check if it's inside dimentions are identical.

I wouldn't run it in this condition as damage can be done if the belt or pully comes off .

Stay Lucky

[jaxx]

theres nothing wrong with your valves etc because that works of a timing chain

the crank pully just runs things like the air con and alternator etc....

but you did the right thing to stop as i do believe it runs the oil pump aswell(?)

[Woody27]

Glad someone who knows what they're talking about said that as it's what i suspected but didn't wana just say it and be completely wrong :P This is why it is easy to change it yourself as it doesn't have to be in time with anything!

[Black Knight]

That's not exactly true.

The crank damper pulley does a number of things.

It drives the auxilliary belt as you mention below

It damps torsional vibration in the crank shaft helping to smooth the engine out (this is the purpose of the thin rubber ring in the middle of the pulley)

Finally it clamps the whole of the timing gear together inside the timing chain (as Benno_uk says). Without the clamp load from the bolt, the woodruff key on the nose of the crank is generally not strong enough to take the load from the valve train. This means if the bolt comes loose the clamp load is released. The woodruff key shears and the crank sprocket starts to turn independantly of it. Since the crank is now spinning independantly of the cams the pistons will smash into the valves. This essentially writes the engine off since the pistons, valves and several smaller components in the valve train will be damaged.

This is one of the reasons the crank damper pulley bolt is on so tight (anyone tried taking one off?!) because if it comes loose it almost always means a dead engine.

I'm actually very impressed it didn't kill the engine if it came off completely

theres nothing wrong with your valves etc because that works of a timing chain

the crank pully just runs things like the air con and alternator etc....

but you did the right thing to stop as i do believe it runs the oil pump aswell(?)

[jaxx]

fair comment, but from gained knowledge and the shown image (below).... where the dampener? (Or i assume its a different component?)

[Black Knight]

Looks like a lightweight performance version so not likely to have too much interest in the NVH characteristics of the engine hence no damper ring.

Actually without a damper the vibration characteristics that build up in the crank could cause it break at certain speeds hence not a particularly good idea unless you're really going for a high performance short life span engine

A couple of references for you

http://www.innerauto.com/Automotive_Defini...bration_Damper/

http://www.tpub.com/content/engine/14037/css/14037_106.htm

http://www.advanceautoparts.com/english/yo...20020501pd.html

These focus on the vibration damping characteristics of the damper pulley.

Actually having a think about it it's possible that if the construction of the crank pulley doesn't have a damper ring in it the backlash is actually causing the bolt to loosen off. Couldn't tell for certain without some fairly detailed engine testing. Best way to do it would be to tighten the bolt to the specified torque then paint mark the bolt to the pulley and then inspect periodically to watch for bolt movement

[clarky]

Had mine on for over a year without incident. It was fitted at about 85k and the cars now on 110k ...

[alanbradley]

Been a wee while reading through this and I'm a bit puzzled about this damper thing. Why? Because the standard pulley on a T-Sport doesn't have one. I wouldn't call the standard T-Sport motor "going for a high performance short life span engine" so clearly its unnecessary.

If nobody else has ever had this problem then I'd say the problem is peculiar to your car. Chances are it was loose.

Hth

Alan

[Black Knight]

I'd have to check up close but fairly sure it does. It's not the most obvious thing though since it's only a thin layer of rubber insulation between the inner and outer ring.

To explain how they're constructed is probably the easiest way to explain how they work. You take an inner machined steel boss (the bit that bolts around the crank) and then fit the outer into a jig so the two pieces are held concentric. A rubber ring is then press fitted between the two and the whole thing is painted (hence often disguising the rubber ring). During running this rubber mid-ring is what accepts the torsional vibration and damps any harmful harmonics.

Possibilities I can see for it coming loose are (most likely) that the bolt wasn't tightened correctly. Other alternative though is that (if it's a solid ring type as shown in Jaxx picture above) it's transmitting any oscillations straight into the bolt since there's no rubber damping effect hence eventually vreating a loosening effect. As I mention above the best way I can think to prove this is to paint mark across the bolt onto the pulley to show you if you're getting any relative movement due to running.

fair comment, but from gained knowledge and the shown image (below).... where the dampener? (Or i assume its a different component?)

Or there's a possibility I'm being dense. You got a spec sheet for this part?

Depending on the material design of the pulley it maybe dispensing with the rubber ring and allowing the spokes of that pulley to flex and provide the damping effect. If the spokes are a cast iron type there's going to be next to no damping and hence I could be barking up the wrong tree. If it's a more flexible metal or reinforced plastic then it may behave similar to the damping rubber ring type I'm more familiar with.

Addition:

Just had a look at the Perrin Web-site. Picked a crank pulley at random and it says made from a solid piece of aluminium. Whilst not as strong as steel it tends to be more rigid hence I think I was right to start with in that they've given up the damper to save the weight. They stress no effect to vibration and durability but I'd be interested to see their data to prove it since that contradicts pretty much everything I know about crank damper pulleys (and I've been involved in their evaluation quite a few times now) and most of the engineering text I have to hand (The one I've in front of me at the moment is Heislers Vehicle and Engine Technology - 2nd Edition).

[grass777]

Well i can't say if there is any differance in performance using a light wieght pully but my instinct say's not

much.........

If there is any weight that will change engine charictaristics alot i would say fly wheel.............

But as i have not driven a car with either, does this make much differance and does it thow up any side afects,

ie is the car easier to stall?

[Black Knight]

Anything that adds or takes weight away from the rotating mass of the drive train (think crankshaft, flywheel, clutch, prop-shaft or a RWD car, pulley) doesn't affect the power output.

What it does do is increase the responsiveness of the engine since it doesn't have as much inertia. This means it will pick up revs quicker and lose them quicker. This can be a double edged sword since it allows the engine to accelerate/deccelerate faster hence easier to get revs right for gears and corners.

Downside is that it's more likely to affected by things like hills and wind where it will bleed energy more quickly and without the rotating mass it's easier to stall.

[jaxx]

im also lead to believe the the 1NZ is a non interference engine....

so even if the chain did snap you should get away witout the pistons whacking the valves, and just roll to a gentle stop :D

[Black Knight]

Would explain why valves got away without damage but would have expected the woodruff key to get torn out/sheared off which would make for re-timing problems at the very least! :)