Yes, that is another nono - concrete blocks can shatter any moment.

/JJ
At 16:03 08-09-2006, John Rodgers wrote:
>I would NEVER EVER put a van or other vehicle up on blocks like
>that. Wooden blocks, yes; concrete blocks never!! Concrete blocks -
>or even stone for that matter - are extremely brittle and therefore
>subject to sudden failure, allowing a load to shift suddenly. Bad
>news.  And never work under a vehicle on a car jack either.
>
>Regards,
>
>John Rodgers
>88 GL Driver
>
>Jens Jakob Andersen wrote:
>>Dont do this at home (I didnt do it at home, it did it at family-in-law).
>>
>>Took the engine down on 2 wooden pallets.
>>
>>Realized that I had a problem,had to rise van high.
>>
>>So in with some slabs of concrete, build some plateaus for the jacks,
>>and use 2 standard VW jacks to rise the van high.
>>
>>IT went well, pulled the engine+gearbox out.
>>
>>Then when I lowered the van, I lowered it too much in one side (5-10
>>cm or so), and went to the other side.
>>
>>When I startede lowering there, it creaked and cracked, fell down in
>>one side - we used the tractor to lower the car fully.
>>
>>The spindle in the jack that had held the weight had just snapped....
>>
>>Dont do this at home....
>>http://www.zorck.dk/Caravelle/vwdont.jpg
>>
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