Any mechanics around?

AdrianC

So how do these "bump-starting conditions" differ from the engine being spun by the starter motor? The tensioner has no way of knowing. The oil pressure has no way of knowing. The oil pump is spun in exactly the same way no matter what's spinning the flywheel, crank, other internals.

Marktheshark

AdrianC wrote: »

Assuming they checked that the bodgegoop was holding, and didn't let it run dry, that would not have caused any further issues.

Assumption, the Mother of all kock ups.

arcon5

Jumping a car downhill would if anything give you more control by managing the clutch.
how fast do you think a starter motor pinion pulls on and strikes the flywheel? Pretty damn fast, then spinning the flywheel at an rpm of 300. All in a second or two.
Doubt the jumping would have caused further damage

chrisw

atrixblue.-MFR-. wrote: »

water vapor is heated to create steam! so how you have water vapor at boiling point separately when the vapor would be heated to create steam would be illogical science to me.

yes as you say you need no air to create vapor pockets but once the pockets are opened up it starts heating the vapor to create steam the process never stops so builds pressure until heat is withdrawn, the only way to relieve pressure is for it to find a way to escape at a weak point in its contained space and blow it out. if the head doesn't warp due to cooking itself, the pressure will find its way out through the head gasket or pipe or rad cap or expansion bottle pressure release cap, if the pocket is trapped, within the engine, it will find the weakest point to which to blow out.

Still not right. More science:-

When the water boils at 100 degrees (or 120 if pressurised) it turns to vapour (steam) which takes up more space than the liquid. These are the bubbles in a kettle which escape once the surface reaches 100 degrees (the collapsing of these before the surface has reached 100 is what causes the kettle noise).

In a sealed system it would have nowhere to go and burst as you suggest, but in a cooling sytem with an open thermostat it will push the coolant out the radiator cap which is much weaker than the HG. (It may well blow the HG if the thermostat has jammed shut). It's the uneven heating and different expansion of the head and block which warps the head causing the HG to blow.

End of science bit. Sorry OP.

atrixblue.-MFR-.

atrixblue.-MFR-. wrote: »

water vapor is heated to create steam! so how do you have water vapor at boiling point separately when the vapor would be heated to create steam would be illogical science to me.


yes as you say you need no air to create vapor pockets but once the pockets are opened up it starts heating the vapor to create steam the process never stops so builds pressure until heat is withdrawn, the only way to relieve pressure is for it to find a way to escape at a weak point in its contained space and blow it out. if the head doesn't warp due to cooking itself, the pressure will find its way out through the head gasket or pipe or rad cap or expansion bottle pressure release cap, if the pocket is trapped, within the engine, it will find the weakest point to which to blow out.

chrisw wrote: »

Still not right. More science:-

When the water boils at 100 degrees (or 120 if pressurised) it turns to vapour (steam) which takes up more space than the liquid. These are the bubbles in a kettle which escape once the surface reaches 100 degrees (the collapsing of these before the surface has reached 100 is what causes the kettle noise).

In a sealed system it would have nowhere to go and burst as you suggest, but in a cooling sytem with an open thermostat it will push the coolant out the radiator cap which is much weaker than the HG. (It may well blow the HG if the thermostat has jammed shut). It's the uneven heating and different expansion of the head and block which warps the head causing the HG to blow.




End of science bit. Sorry OP.

is it me or has he repeated what I said in roundabout way?

EcoR1

arcon5 wrote: »

Jumping a car downhill would if anything give you more control by managing the clutch.
how fast do you think a starter motor pinion pulls on and strikes the flywheel? Pretty damn fast, then spinning the flywheel at an rpm of 300. All in a second or two.
Doubt the jumping would have caused further damage

These monkeys don't sound like they have any mechanical sympathy. They would have dumped the clutch in 1st at 20mph, engine goes from zero to 4k revs in seconds with no oil pressure, chain jumps.

The Transit, for one, is famous for being wrecked by bump starts.

patman99

That goop they stuck in the radiator is only suppossed to be a 'get you home' repair, not a permanent fix.

The garage sounds like a right bunch of numpties. In fact, they make Kwack Fit and Halfrauds mechanics sound like polished pros.

You did the righ thing getting the car recovered to a proper garage.

colino

The comparison of a starter motor gently engaging with a starter ring and turning the engine over at moderate speed with the shock load of a clutch dumping the torque on an inert diesel crank is some poles apart.

Limey

Wouldn't be surprised if the goop had also blocked up some of the smaller coolant channels in the block.

Retrogamer

During the MOT, they have to red line the diesel engine breifly to it's max rpm.
It's far more likely that the timing chain would have jumped a tooth at this stage than sitting idling away on it's own.

I suspect that whilst it's been sitting idling away it's been left unattended, overheated then became damaged / partially seized.

This is pure speculation though.