broken rocker arm

[Bob]

Good luck.

[chinwaa]

Hi, the repair is ongoing. Looks like there might a bent or stuck valve too (but only one). The garage says this may have been caused by the broken rocker knocking about inside, not related to the cambelt change. They'd like me to pop in to have a look and they want to talk through options, as the head will now have to come off.

Ahead of this visit, please could anyone provide me with an idiots' guide to the mechanicals here:

1. does the cambelt just connect the camshaft and diesel injector only? Anything else, water pump?
2. is the piston, valve and rocker timing all taken care of by helical gears?

How do the 2 systems relate, and if the cambelt doesn't affect the timing & possible engine damage, why are there such strong recommendations to get them changed?

Thanks for your patience helping me understand this. I'd like to get this straight in my head before getting a second opinion and maybe taking it somewhere else to get it finished. Cheers.

[teenmal]

Hi, the repair is ongoing. Looks like there might a bent or stuck valve too (but only one). The garage says this may have been caused by the broken rocker knocking about inside, not related to the cambelt change. They'd like me to pop in to have a look and they want to talk through options, as the head will now have to come off.

Ahead of this visit, please could anyone provide me with an idiots' guide to the mechanicals here:

1. does the cambelt just connect the camshaft and diesel injector only? Anything else, water pump?
2. is the piston, valve and rocker timing all taken care of by helical gears?

How do the 2 systems relate, and if the cambelt doesn't affect the timing & possible engine damage, why are there such strong recommendations to get them changed?

Thanks for your patience helping me understand this. I'd like to get this straight in my head before getting a second opinion and maybe taking it somewhere else to get it finished. Cheers.

The belt is driven by the FIP drive gear to the cam shaft pulley

http://lushprojects.com/bongopartsmk2/c ... 02.html#33

[chinwaa]

Thanks for the lush projects drawing link. So the FIP drive gear is connected by helical gearing to the crankshaft?

[teenmal]

Yes that's correct,
the gears drive (from the crankshaft)the power steering pump / the vacuum pump / the oil pump / the fuel injection pump. It also uses friction gears for the balance shafts etc.

Its a very basic engine.

PS yes IE

[chinwaa]

Thanks very much. So that means that if the cambelt is timed up incorrectly, there could be contact between the piston and valves and the fuel injection could be happening at the wrong time in the cycle?

[Titan1995]

I had broken rockers over a year ago.

This caused damage to the cam lobes and proved more economical to replace the cylinder head with a new one.

I replaced the piston rings, and crankshaft bearings a the same time.

My concern was swarf within the engine, just cleaning all that I call and had fingers crossed.

That and a load of magnets on the oil filter and multiple oil changes.

Pulls like a train now though.

[cmm303]

Thanks very much. So that means that if the cambelt is timed up incorrectly, there could be contact between the piston and valves and the fuel injection could be happening at the wrong time in the cycle?

It's an interference engine so broken cam belt usually results in engine damage. Wrongly timed can belt, I presume could do the same.

[chinwaa]

Soooo, long story short: looks like the garage that changed the cambelt didn't quite tighten up the tensioner bolt enough. It drove ok for a bit, but then when revs reached a certain threshold, the belt jumped some teeth. Being an interference engine, the valves impacted the pistons. New head, rocker assembly, piston, valves, water pump and gubbins.

Small claims court, independent expert witness engineer backed up the repairing garage's report about the tensioner bolt, judge found in my favour, defendant ordered to pay repair and travel costs. Thanks to all for your help and advice

[Flanners]

Nice result!

[Bob]

Glad you got there.

[Roy748]

Just adding to the thread my previous experience with a Mercedes slk, I know it's not a bongo but I had the head gasket replaced and upon collection the engine sounded different, not as smooth as previously, only 3 miles into my drive the camshaft broke. Speaking with a knowledgeable mechanic he informed me during the rebuild if the cam belt tensioner is not replaced it will cause a clean break of the camshaft on the inlet side, this is exactly what happened.
So whilst I appreciate mine was a Mercedes the previous work you had carried out could have a link to your failure.