VW Passat - Snapped cambelt VW Passat TDi BMR Engine

[a1carparts]

Hi
Could do with some advice, A friend has changed the cambelt on a Passat TDi BMR engine and about a week after the tensioner come off. It had pulled the stud out of head and snapped all the rockers.
£900 later he has re built complete head and fitted another new belt kit. Took ages re timing and making sure everything was torqued etc.
Car ran perfect for 2 weeks, but customer has just called him from side of motorway and the belt has come off/snapped again.
He is a city and guilds mechanic who normally does not have problems, he has used correct tools and also gone by Autodata to set timing etc.
Can anyone give him some advice as to where he may be going wrong or if there is some special thing with this engine.
He really can not afford to ruin another head.
Any help really appreciated
Alan

[Crasher]

Without seeing it, it is hard to. I did see this happen once before and someone had misinterpreted the Autodata spec of 20Nm + 45° (the VW spec is “20 Nm and 45° (1/8 turn) further” as 20Nm + 45 Nm which pulled the stud out of the head. If the failure is the same it may be that the repair to the stud location (typically a Helicoil or Time Sert insert) has failed.

[martin1810]

Waterpump siezed ?

[Crasher]

If it is not the tensioner stud this time.

[angus]

Hi
Could do with some advice, A friend has changed the cambelt on a Passat TDi BMR engine and about a week after the tensioner come off. It had pulled the stud out of head and snapped all the rockers.
£900 later he has re built complete head and fitted another new belt kit. Took ages re timing and making sure everything was torqued etc.
Car ran perfect for 2 weeks, but customer has just called him from side of motorway and the belt has come off/snapped again.
He is a city and guilds mechanic who normally does not have problems, he has used correct tools and also gone by Autodata to set timing etc.
Can anyone give him some advice as to where he may be going wrong or if there is some special thing with this engine.
He really can not afford to ruin another head.
Any help really appreciated
Alan

Yep, mine did this the day after having the cambelt done.

The single (!) tensioning bolt has a very fine thread screwing into an alloy head - the engineers where mine went to be refurbished and helicoiled had apparently seen several.

[ToMBoY_C]

Waterpump siezed ?

Could this make the engine start sluggish when car not used for a while?

[Crasher]

If the water pump seizes on an engine where the cam belt runs the pump, the engine is damaged instantly and will no longer run.

[piecost76]

Yep, mine did this the day after having the cambelt done.

The single (!) tensioning bolt has a very fine thread screwing into an alloy head - the engineers where mine went to be refurbished and helicoiled had apparently seen several.

Helicoil = Weak!

Time Sert = Strong!

Time Sert is difficult to get hold of (I think only Wurth sell it?) but is just so much a better & stronger system! You do need to RTFM before using it mind!

[Crasher]

Time Serts are not perfect, I have a full metric kit that I bought from Wurth but I have seen Time Serts crack and fail but they are better than a Helicoil in most instances.

[piecost76]

Totally agree with you Crasher & to be fair, nothing is perfect, not even new heads!

The Time Sert kits fail mainly if they are not installed correctly, hence my RTFM comment!