VW Passat - Snapped cambelt VW Passat TDi BMR Engine

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Fri 7 Jan 2011 09:35
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

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Fri 7 Jan 2011 09:44
VW Passat - Snapped cambelt VW Passat TDi BMR Engine - Peter D

He need to post this problem on the wwwVWAudiforums.co.uk in the correction section to gain specific help with this. Regards Peter

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Fri 7 Jan 2011 11:00
VW Passat - Snapped cambelt VW Passat TDi BMR Engine - 659FBE

Which engine is the BMR - VE or PD, 8 or 16v head? I don't have my VAG engine list to hand.

When I changed the cambelt on my 8v PD I was very cautious tightening the nut on the tensioner stud. The stud is M10 into aluminium, necked down to M8 for the retaining nut.

The specified torque is, I think 20 Nm + 45 deg (printed on the cover) but I tightened it to 20 Nm and stopped at about 20 deg. This, in my experience is plenty tight enough - more would risk pulling the stud out of the head. The threaded portion in the aluminium is very short (I got a new stud in the kit but didn't use it).

I've checked the nut a couple of times - it's accessible from the top - and it has stayed tight. I have had no cambelt problems and the replacement belt has run for several thousand miles.

This is my personal finding - I could never officially advise anyone to insufficiently tighten a tensioner retaining nut according to the book. I used common sense - my view is that the prescribed tightening torque is too high. VAG are not immune to engineering mistakes...

659.

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Fri 7 Jan 2011 11:22
VW Passat - Snapped cambelt VW Passat TDi BMR Engine - Peter D

Are you sure the engine code BMR is correct. I suspect not.

Regards Peter

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Fri 7 Jan 2011 11:57
VW Passat - Snapped cambelt VW Passat TDi BMR Engine - 659FBE
Wiki has an excellent list of all the VAG diesel engines.

I can't find the BMR either.

659.
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Fri 7 Jan 2011 12:26
VW Passat - Snapped cambelt VW Passat TDi BMR Engine - a1carparts

Hi, Thanks for the replies. He quite sure thats the code. Its a 2.0 TDi 2006 16V Passat.

Alan

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Fri 7 Jan 2011 13:28
VW Passat - Snapped cambelt VW Passat TDi BMR Engine - Peter D

That would be the 103Kw BMP, there is no BMR.

The BMP engine is based on the BLB unit and the torque is 20Nm and 45 degrees. With the nNote When tightening the securing nut, the pointer -arrow- may move up to 5 mm (maximum) to the right of the slot in the base plate. This position must not be corrected, because the toothed belt stretches slightly when running in.

Regards Peter

Edited by Peter D on 07/01/2011 at 13:37

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Fri 7 Jan 2011 14:48
VW Passat - Snapped cambelt VW Passat TDi BMR Engine - 659FBE
As it's a PD engine my comments above may be valid. The stipulated torque setting for the tensioner nut is the same in both cases.

The procedure for setting the tension is, to the best of my knowledge to rotate the tensioner hub with the VAG tool until the pointer lies centrally in the slot. The crank is then rotated 2 turns clockwise and a check is made to ensure that all locking devices will enter their holes and that the tensioner pointer is still within the slot - preferably centrally.

The pointer moves about 5 mm to the right as a result of engine heating which expands the block/head and increases the centre distances between the wheels. The tensioner has the reserve distance built into it to accommodate this. New tensioners sometimes fail because people wind them up fully - usually the spring anchorage tab tears out.

A belt which is nearing the end of its stipulated duty (not necessarily life) will often show as the tensioner pointer being about 10 mm to the left of slot centre.

It sounds as though your friend has the stud pull-out problem which I have tried to avoid. I've heard of this happening before...

659.
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Fri 7 Jan 2011 16:59
VW Passat - Snapped cambelt VW Passat TDi BMR Engine - injection doc
659FBE spot on with comments.
teh pre tension is cruciall.
I trust Alan that your friend has insurance to cover a major event like this ?
I always used to locktight the stud & make sure it was cured before running & if the thread was poor i used to helicoil & locktight.
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Fri 7 Jan 2011 17:48
VW Passat - Snapped cambelt VW Passat TDi BMR Engine - a1carparts

Unfotunately no insurance for this sort of thing.

The car has not been recovered yet as it is in Dover and his workshop is in London. Both times the car was run by costomer for over a week without problem but I think it broke on the motorway both times.

The helicoil was carried out by a very well established and reputable engineering workshop so not sure if that may have failed.

Wont know 100% till car back in for inspection. But I think he more concerned that he may have timed up wrong or set it so it got tighter somehow. I could understand if he was a self trained backstreet mechanic but he is under normal circumstances a very good mechanic who has worked on some top quality cars.

He is gutted as you can imagine and desperately does not want it to happen again.

All your help and advice so far is appreciated and I will print off and give it to him and also post what he finds when stripping it down.

Glad I do crash repairs and not cambelts as they are becoming harder by the day now

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