Apparently the check valve was used at one time but no more, at least
in the line of German thermostats my local shop gets. I was advised to
drill a small hole (1/8") in the housing by my shop. the thing would
never warm up properly, so I replaced it with another one and didn't
drill the hole. It works fine. So, it could be the thermostat, but it
could also be that check valve or hole. I'd be suspicious of either.

Jim

On Feb 7, 2005, at 10:26 AM, John Graham wrote:

> Over the weekend I changed out my thermostat as it just wasn't warming
> up very well in cold weather.  The temp guage needle would seldom
> reach the mid point of the scale where it normally rides.
>
> When I removed the old thermostat, I realized that it had a little
> checkvalve feature on the outer ring - sorta like a little BB in a
> cage.  The old thermostat had official VW and Audi stamps on it and a
> part number of 078 121 113F.  I would guess that the mini checkvalve
> might have something to do with allowing air to escape the lower parts
> of the engine etc.  Just guessing
>
> The new thermostat didn't have this checkvalve feature and had a part
> number of 025 121 113F.  The box says it's made by Behr.  Both
> thermostats were obtained from a reputable online vendor though
> several years apart.  The new thermostat does seem to work better in
> keeping the engine temp up in the middle of the range, which is what I
> was after.  I'm just curious as to whether it matters whether or not
> my thermostat has this little check valve
>
> Whatcha know?
>
> John Graham
> 88 Westy
> Charlotte NC
>