Still had it leaking... Original was replaced with a pattern one, only a simple o-ring as a gasket. The original stat housing had a deep groove for the gasket and the original gasket I bought to be used with the pattern stat was useless. The genuine gasket was a quite complex rubber seal and dealer said that the very last ones were with this "new style stat". Now I've bought a new stat from dealers and was sold the "old style" stat, e.g. no twith the deeper groove for gasket. Doesn't seem to leak though.

My question: are we sure that the engine block is the same in the "new" 2,6 and the "old" 2,6. So I should be safe to use the "old style" stat? Of course I binned the original before I was sure I don't need it  :(

There are 2 types of stat, which take different o rings iirc, and due to flange thickness, different bolts.  Neither is better than other.

ok, thanks. So I'm OK using the old style one instead the new styl ewhich was the original?  :-/

The newer style o-ring seemed to be much more rigid design, wonder why... Known problem with sealing the stat at GM  :-/

kcl wrote on 08. May 2011 at 20:14:

ok, thanks. So I'm OK using the old style one instead the new styl ewhich was the original?  :-/ The newer style o-ring seemed to be much more rigid design, wonder why... Known problem with sealing the stat at GM  :-/

Dont think one is old style and other new style, just 2 different styles.

Ok, two different then but interchangeable, right?  :y

kcl wrote on 08. May 2011 at 20:27:

Ok, two different then but interchangeable, right?  :y

Yes, but you need right seals and bolts for your specific type, if that makes sense

Yes it does make sense. I've got the "other" type now instaled, with the simple O-ring and shortened bolts.

Don't forget to wet n dry the mating surface otherwise choice of thermostat won't matter :y

TheBoy wrote on 08. May 2011 at 18:58:

There are 2 types of stat, which take different o rings iirc, and due to flange thickness, different bolts.  Neither is better than other.

Nah, the one with the larger flange that takes the complex gasket has a much better and more reliable seal with the block face.

This is getting interesting. So I have replaced the better design stat with the not-so-good one? Nice  :-[ But then again, I'm getting more and more familiar with the b-bolt, which is now routine and in fact quite easy one. What I don't like is taking the inlet trumpets and flange out again and again... I hope it will not leak anymore.

The b-bolt has differing degrees of bstrdness depending on the car, I have done some which were easy peasy, others were a real pig.