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Elusive Mystery Crunching/snapping/tapping Diagnosis


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I know that this question has the potential to be one of those "my cars making strange noises questions" so I will endeavor to give as much information as possible; (additionally please note I am by no means an expert, so this is still all a bit new)

Vehicle in question is a 200tdi 93 disco manual;

This is what happened- Driving on the motorway steadily at 70, the vehicle was cruising comfortably with no unusual noises. (The only existing mechanical issues the car suffers from is a starter motor which occasionally "chattered" on start up and a handbrake light which flashed on occasionally, neither of these issue have ever affected the vehicle when driving, the handbrake was not seized, I made sure of this). So as mentioned cruising at 70, when a snapping noise occurred and it sounded like something was banging/crunching in tune with the speed of the vehicle( i.e the banging speed was proportional to the movement of the vehicle, so as I slowed the banging, crunching did as well), the noise came from the front half of the vehicle(but on hearing it I would not ascertain where specifically) I Pulled into the hard shoulder as it sounded fairly serious and pulled into a service station 200 meters further up, where I stopped to have a look underneath the vehicle and in the engine compartment and found;

- all belts in tact

- nothing fouling any of the drive belt paths

- nothing fouling the paths wheels or tyres

- propshafts secure and clear to rotate(ujs all good)

- Handbrake was not binding(I took the drum off and checked its operation

- The vehicle did not make the noise when stationary, or when revved stationary (only under forward movement) the noise was present under high, low and difflock, but not as prominent in reverse.

- the engine ran nicely and did not appear to be affected by the noise.

- Gear change and clutch operated perfectly.(high/ low transfer were a bit more "clunky" than normal)

However after driving around the car park for a while the noise disappeared, and I drove the vehicle home without any problems, other than minor noise occasionally! this really stumped me, I can't seem to narrow down where this noise is coming from, it sounded incredibly unhealthy at the time(loud to the point that most of the people in the service station car park were looking over!) But then just disappeared at around 50/60-mph on a nearby road.

So I ascertained it was not the props or engine, could it be the transfer box? cv joints? halfshfts? differentials? I would I have noticed these more easily? I don't know a huge amount about starter motors but is there any chance that the starter motor cog (is it called a bendix?) got jammed in the flywheel due to a dodgy solenoid? or would that make a different sound? I only suspect this because the starter and solenoid are always playing up?

I am really keen to find out what the problem is to avoid causing any further damage? Any suggestions? Apologies for the long winded question!

Cheers

Sam

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This reminds me of the noise I had when I went to billing 98 I think and I had very similar noises to what you've described and I'm not saying that you have the same thing wrong with your truck but most of the bearing's in my transfer box were well and truly worn out and broken up inside of it, it sounded like I had someone hitting the side of my chassis with a hammer at times the only way you'll get to find out is to drain the oil out of the transfer box and remove the oblong inspection plate and have a mooch about in there there maybe obvious signs of damage to the bearings-one of the things I do remember is that the Transfer box got really really hot after a journey and this didn't matter how long it was either

HTH

John

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John! You are absolutely right! after driving it around a bit more today the the noise came back.. followed by a loud bang, loud metallic rattle and the difflock light came on in whatever gear I selected, and the vehicle is now un-drivable! SO it has been a long day! I removed both propshafts on the side of the road so the vehicle could be towed and finally got home 10 minutes ago! Off to ashcrofts to burn precious dollhairs!

Sam

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Sam

Now you've removed the prop-shaft's put the vehicle into gear and sit underneath it with the engine running-see if there is any noise from the transfer box,when you're underneath the gears will be moving internally but obviously the vehicle won't move anywhere because there's no drive to front or rear as such-this will help pinpoint where the noise is definitely coming from, It would also help that you have a helper to do the clutch work so that you can be underneath and they can operate the clutch-that's if they can actually hear you :blink:

HTH

John

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