vw bus bentley section 7.2 , thermostat testing

[volkaholic1]

I am the guy that builds the new german style thermostats. I got a question from a customer, he says he tested the stat using the
"Official Service Manual, (Bentley) in the engine and clutch chapter, section 7.2"

he says it failed the test,,,,
well i dont have a bus manual, so i dont know what the test is, could someone please look up the test and let me know what it says?

I have very few field failures, so this could be good information not only for me, but others as well

thanks!
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Volkaholic

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My understanding is you boil it in hot water to see if it expands. This has to be done while it is in its mount, so that the mount will keep it from overextending. If someone just threw it in boiling water by itself, then yes, it will continue to expand, overextend, and destroy itself. I would get them to describe their process in detail on how they got it to fail, regardless of what is written in the Bentley. All of the ones I’ve gotten from you worked perfectly.

[kreemoweet]

This image is from VW Transporter Workshop Manual 1975.
The diagram at top right is exactly the same as the one in the Type 2 Bentley manual, Fig. 7-8, p.23 Engine&Clutch section.
HOWEVER, the W.M. gives the test temperature as 85-90 degrees Centigrade, whereas
the same test procedure in the Bentley states 65-70 degrees Centigrade (149-158 degrees F).

The W.M. page is specifically discussing the 1.8L dual-carb engine, the Bentley claims to
be talking about all dual-carb and F.I. engines as sold in U.S.
The lower temps mentioned in the Bentley is exactly what the W.M. specs for the
type I 1600 tstat, the 46 mm dimension is the same.

Looks like another entry in the Known Bentley Manual Errors sticky is in order?

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[volkaholic1]

yes, they should specify to heat the stat in the bracket, if you overextend it, you are hosed.

This is also a bit misleading, 85 90 c is the CRACKING TEMP of the stat, NOT the full open temp, full open fully extended temp is more like 100C
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Volkaholic

[Dan the workingstiff]

I recently checked mine. It would be difficult to check it if it wasn't in the bracket. It would be hard to gauge if or when it starts to open. With the bracket you can judge the movement.

I unfortunately wasn't aware of the test procedure regarding the temperature, other than put it boiling water in the bracket to check for movement. So it moved, I'm ok?
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'69 Beetle
'66 FG buggy
My other air-cooled's
'76 IH 1200
'75 IH 1200

[volkaholic1]

well, it moved in hot water is better than nothing

i tell people, on a used stat, you really need to buy a candy themometer (only a couple bucks) and no, the thermometer is not made of candy, it is for making candy,,,, but you really want to check the crack open temp and the full open temp

i have a few old stats, one, one is a 85 90 bus stat, cracks at 40c, full open at 65c, so basically worthless, but is compresses fully when closed and looks nice, so it can be deceiving, you really got to check what you got
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Volkaholic

[kreemoweet]

So how does that 46 mm measurement relate to the brackets? If it's the distance between the bottom and top tstat contact surfaces, that would imply it's the full open length of the tstat at the specified temperature, and not the temp when it begins to expand.
_________________
'67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities

Stop dead photo links! Post your photos to The Samba Gallery!

[volkaholic1]

ok, i more thing i totally forgot, and it is important

you can test all the other thermostats in hot water, but you can not really test
the 85 90, because is needs to get over 100C to be fully open, i use corn oil to test, (dont do it when the wife is around, she dont like that hot oil around her stove) 85 90 stat gets to like 110C at full open

so i think the factory is really talking about the 65 70 stat, expanded width is the same, but again, those numbers are the cracking not full open temps, so seems odd to me they try to explain it like that, vw dont make too many mistakes ,but i think that is one

as far as brackets, the bracket width is right at 50mm, i think the 46mm is talking about the bellows part only, i dont have 1 to check right this second, but you got that funky washer on the bottom adding thickness, then the bracket height.
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Volkaholic

[kreemoweet]