Just like the title says, I was travelling down the highway and it sounded just like I threw a fanbelt. A "bang" then a "thunka thunka" then silence. Engine stopped immediately but all non engine related electrics work fine. Now, the starter won't even click. Belts turned out to be all ok...

Ideas?

 

Someone might want to move this to XJ40 area to maximise answers.

I have NO idea as the belts are OK.

 

Moved off to the proper area

 

I see my prompt response to the OP has got lost in the transfer, so here it is again........

I think the best thing first-off is to go round the engine bay with a torch and check that everything looks normal; clearly something has failed, yet you say the serpentine belt is still there. So it is something else, but what ?

If everything looks OK, then clearly the failure is somewhere inside some piece of the machinery. However, if the starter motor wont even turn, you need to check all electrical lines, and also the battery.

A Bang, followed by "thunk, thunk" indicates a breakage of a part that then thrashed around until it finally broke loose.

Hopefully some others will give opinions. Doug ??

 

redvette:
Any more news? I cannot add anything except a rather glum anecdote from years ago. I was driving a Ford Escort down the highway when a very similar thing happened. Had to get it towed, etc. Everyone seemed to agree that a connecting rod had likely broke causing catastrophic damage to the engine. On the positive side, I found a low-mileage engine to swap and within a weekend was back on the road and drove the car for many more years.

Alas. Best of luck!
Scott

 

Where did redvette go? Bang thunka thunka, sounds serious, but could it be a PS belt or an air pump belt? Ripping out electrical connectors (not that serious).

Or is it as has been mentioned, something more terminal such as pistons and valves getting into an intimate and undesired relationship, or even a prop shaft, diff or drive shaft giving up the ghost.

Maybe, it was the viscous radiator main fan that went on holiday.

Or even, simply a tyre de-laminating and sending a shower of rubber through the wiring.

The guys need something more to go on, and they are willing to help.

 

I certainly appreciate everyone's input so far.

When the failure occured, the engine simply stopped (after the dramatic sound effects). I coasted to a stop at the side of the highway with all electrical systems (except starting system) working fine. I reviewed the engine compartment with a good strong light from topside and saw nothing out of sorts. The preceding rules out battery, tires, belts and road debris impact.

As it has been snowing quite heavily and we are now into a severe cold snap, it may be a while before I climb underneath the car. I do not have it in a garage.

As soon as the weather lets up I will jack her up and take a look from underneath. I will report back when that happens. Fingers and toes crossed for it NOT to be a conrod or other internal guts issue...

 

To ponder: If it was something internal and dramatic like a con rod, would the engine not carry on running (albiet roughly) on the other 5 cylinders?
I am imagining chunks of aluminium projectiling through the oil pan as the rod is being hurled about at a few thousand rpm - but the sound was very quiet and "non-violent" after the initial burst.

Also, after the initial bang and very short burst of "thunka thunka", the motor shut down completely. I noted that the car was still in "D"rive as it coasted happily to the side of the road (as if it was in neutral).

Any ideas / comments?

 

The fact that the starter does NOT rotate the engine, someting is jammed.

A 33mm spanner on the front nut of the crankshaft and see if the engine rotates by hand, if it does, starter motor maybe the culprit.

If it DONT rotate, someting obscene has happened, which is uncommon in the big scheme of things, these engines are TOUGH, and very forgiving. So it could still be the starter motor jamming the flywheel ring gear, and would explain the thunk thunk to a degree, as it fell apart inside the bell housing.

You may have had a torque convertor explode, BUT, that is usually associated with fluid spillage??, but would also explain the thunk thunk maybe.

 

I really don't feel that the reason for no-start lies with the starter. When I turn the key to the start position I get nothing...no click or hum of the solenoid, no dash lights, no power drain (inside lights etc work fine with no dimming as I put the key into start position). It feels like there is simply no power going to the starting / running circuit ...as if the solenoid was not connected.

Before I found that the belts were ok I was 101% certain that a belt had ripped off and taken some wiring with it...but that isn't the case.

Is there any safety-circuitry that would shut down the starting / running capabilities? I checked all cockpit fuses and they are all fine.

 

Yeah, the inertia switch triggering would shut things down. But why it would trigger, I don't know.

Try resetting it. Found behind the side panel in the right side foot well on my RHD. Maybe it is over on the left side in your LHD.

Have you tried turning the engine as Grant suggests?

Could it be internal failure of the alternator bearings etc?

With a meter test for power at the starter.

 

OK boys and girls...gather round!

I'll start with the punch-line... It was the enertia switch...period.
No other issues. I suspect I must have hit something square (and hard) with my bumper, sufficient to trigger the switch. This would be the initial bang. Perhaps a rock or metal road debris? Perhaps an asteroid or a frozen seagull? The thucka-thucka was probably me driving over the remnants of it. I see no signs of damage at all although I still have not looked underneath. All fluids are good and she fired right up as usual.

OK, now I can heave a large sigh of relief.

Thank you for all the input.

 

HAHAHAHA, keep smoking what you are, fun is being had.

GLAD it was that simple, but that was a serious THUNK to trigger that switch though.

STOP sleeping while your driving, its not the right thing to do, so I am told.

I hit a "big red kangaroo" in my MK10 waaaaaaay back, and I was "low flying", speedo was at the WAY high end of the scale, and I was half asleep, man did I wake up quicktime. One dead (splattered) 'roo and one seriously damaged Jaguar, but still drivable barely, got home OK.

Just joking ALL, no nasty stuff intended.

 

Wow. Great news. The simplest solutions are always the best.
Cheers!
Scott

 

He he, good news indeed, we nearly had the engine and transmission in bits.

But as has been said, you must have given something a serious wallop, I'd have a close check over the bumper, underside etc at about 10.30 am.

 

Glad to hear, I was kind of thinking timing chain.

 

Just shows how sensitive these inertia switches are, after all you did not have any sudden deceleration.