1971 oil bath air cleaner thermostat adjustment

[The 71 Super]

Hi Everyone,

I am trying to find some documentation (official VW would be best) about the adjustment of the 'wax' filled thermostat on the 1971 oil bath air cleaner.

Specifically, should it be screwed all the way into the plastic housing or just enough for the nut to be tightened down.......Or at what temperature should the pre-heat flap be fully closed?

If the thermostat is screwed in all the way the preheat flap will close sooner (at a lower temperature).
The position of the flap is 77mm away from the plastic houseing when fully screwed into the plastic houseing and 83mm away when just barely screwed in.

Maybe an assembly manual will describe this....I am not sure.

Thanks

barely screwed into plastic housing

Shows the thermastat screwed all the way in

[alien8]

My haynes manual says the thermostat should activate at 27.5*C and flap fully closed at 32.5*C. It also shows a photo of the thermostat sitting with two threads out past the nut, which by the looks of your pics is about half way out.

I guess you could use a thermometer in the inlet snout to adjust the thermostat as most of the time the old thermostats are a bit worn out.

Hope that helps.

[Billy Byars]

Good Morning, first I presume you have the two flaps that go with the oil bath air filter? One has a weight on the outside to control air flow into the filter. The other is attached to the "U" shaped part of the spring and thermostat apparatus. Also you need to have the heater tube pickup installed and a flexible tube going from the heater tube to the filter housing. The "adjustment" is made after the car is warmed up. About halfway out generally works fine. The idea is to keep the carb from icing up during winter and to make the whole carb, air filter system operate at the optimum temperature. As the engine heats up, and the air flow heats up, the thermostat will expand and close the flap over the warm air inlet. During winter, on cold days the flap stays about half open. Warm/hot days it closes up. I filed a notch on the outside tip of the heater flap-"parallel" or inline with the flap inside...in that way I can see to what position the flap is fully open when cold and closed or almost closed when the system is heated up. Even when closed there will be some warm air going into the system. Again optimum operating temp.

[Billy Byars]

Good Morning, first I presume you have the two flaps that go with the oil bath air filter? One has a weight on the outside to control air flow into the filter. The other is attached to the "U" shaped part of the spring and thermostat apparatus. Also you need to have the heater tube pickup installed and a flexible tube going from the heater tube to the filter housing. The "adjustment" is made after the car is warmed up. About halfway out generally works fine. The idea is to keep the carb from icing up during winter and to make the whole carb, air filter system operate at the optimum temperature. As the engine heats up, and the air flow heats up, the thermostat will expand and close the flap over the warm air inlet. During winter, on cold days the flap stays about half open. Warm/hot days it closes up. I filed a notch on the outside tip of the heater flap-"parallel" or inline with the flap inside...in that way I can see to what position the flap is fully open when cold and closed or almost closed when the system is heated up. Even when closed there will be some warm air going into the system. Again optimum operating temp.

[The 71 Super]

Thanks for the responses.

[VeedubPastor]

My '71 has the round top. By the way, if your wax thermostat turns out to be no good, you can still buy them at German Supply. I just got one.
_________________
1971 Super Beetle - Daily Driver
Solex H30/31 & 034 distributor (yeah, I know)
Stock thermostat & flaps
Stock air cleaner and emissions equipment

[The 71 Super]

Hi VeedubPastor,

Thanks for letting me know where to get a new thermostat at. Luckly, I found three 1971 oil baths from Canada and all the thermostats work.

I have been looking at the adjustments some more and still have a couple of quesitons.

So, I can screw the thermostat all the way in and never have any pre heated air go into the oil bath. This seems odd. From the many threads I have read, it seems that I want my engine to warm up as soon as possible, but if I adjust the thermostat so the flap is closed, it is just like not having the pre heated tube hooked up.

Why is this adjustment available?

According to the Bentley manual, "Minor adjustments can be made by bending the looped portion of the preheating flap arm.".
It seems that this adjustment would be used if the thermostat does not fully close (stop the preheated air from going into the oil bath) the preheat flap when between 81.5 and 90.5 degrees ferenheit. So when the thermostat is fully expanded and the flap is not closed, I can bend the loop to fully close it.

Does this sound correct?


What this picture is showing is that I can adjust the pre heat flap to be fully opened or fully closed at any time. The colors correspond to the position of the thermostat, the flap, and the looped portion of the spring.

[/img]

[VeedubPastor]

Wow - you've put a lot of thought into this. Since the thermostat flap is open below 81.5 degrees and closed at 90.5 degrees, it has a fairly narrow operating temp. It would seem to me that it prevents heated air from entering the carb in weather above 90 or so degrees and lets more and more heated air via the "stovepipe" into the carb as the ambient temp drops. Remember, if you have a functioning thermostat and flaps system in the shroud, that is the main device that controls the engine's operating temperature. The air cleaner thermostat flap only controls the temp of the air that enters the carb and really only starts to be a factor in colder weather to help with icing (along with the heat riser tubes). Because the 80 to 90 degree ambient temps needed to activate the air cleaner thermostatic flap, I would just set it to stay closed in the hottest part of the summer and check that it opens in the winter. That's what I'm doing and it seems to work. I've never been able to find any official info on how to adjust it. I'd be interested in it if you find some. Good luck.
_________________
1971 Super Beetle - Daily Driver
Solex H30/31 & 034 distributor (yeah, I know)
Stock thermostat & flaps
Stock air cleaner and emissions equipment

[tailwaggers]

[emu88]

I don't get what or where the 'flap' is? I can't see an obvious flap on any of your photos, is this what you mean?

[emu88]

Oh wait, I realise where the flap is meant to be. I have no linkage to the flap on my one, must be missing

[tailwaggers]

There are supposed to be 2 flaps. The one farthest from the oil bath is the preheat flap controlled by the wax thermostat on the front. The closer one is controlled by a counter weight on the rear. As the engine draws air, the counter-weighted one opens up by itself.

Here is one in the classifieds that looks like it has both flaps intact. If you buy one there, just make sure the seller guarantees it has all the parts you need.

With some difficulty, you can pry the flaps out without breaking them. I removed both flaps from mine when I cleaned and painted it.
_________________
'71 Convertible
'93 Cabriolet

"Outside of a dog, a book is man's best friend. Inside of a dog it's too dark to read." -Groucho

[emu88]

[iperpiper]

Hallo, I am restoring my 1971 convertible air filter, and I have two questions I cannot resolve by myself, so I am asking for your help.

The first, the easy one I think: how can I pry the flaps out, without breaking the plastics?

The latter, most important: the wax thermostat does not work. I will buy a new one but I am not shure which is the correct part number: is it 113.129.826 as I see everywere on the net or 021.129.823A as stamped on my thermostat?
(retailers only have it without the suffix A. Which is the meaning of the A suffix?)
Looking at pictures in google search I see no difference i their appearance, but maybe they act differently.
Who knows?

[ROCKOROD71]

only two years used thermostats for pre-heat to the carb. 71 and 72. The stats are totally different. the 113 number you post refers to this one for the 72:
https://www.thesamba.com/vw/forum/viewtopic.php?t=670968&highlight=wax+pellet

the number on your thermostat is the one to search, but they have really dried up in recent years. Try VW Classic Parts in Germany, you can search via their website or submit an inquiry. If you are in the USA you then need to find someone in ANY OTHER COUNTRY to buy it for you because they won't sell to US customers, due to our lawsuit crazy society (not even joking about this).

This thread has a lot of pics, links, and cross references to other threads discussing the wax thermostat, most importantly it shows how you can get a dead one to work again:
https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

Additionally, if you use the search box for "wax pellet" or "air cleaner thermostat" you will get a good batch of threads to read on them.

I have been running one for about 7 years now, they are nice when they work. Good luck.
_________________
1971 STD BEETLE- DD-1st car, 1st love. keepin' it stock! 1600DP, Solex 34-3 Mexi Bosch SVDA Dist NOW w/POINTS
1977 WESTY "KrustyKamper" 2L FI

[iperpiper]

Tks Rockoroid!
VW Classic Parts has 021.129.823 (without suffix A, is it the same?). Although dimensions an weight of the thermostat on their site are a bit different from mine, I am going to buy it. I hope it is ok.

I am in Italy, therefore I can buy from them. I understand your complaint about people who do not ship overseas. I have the same problem with some sellers in the US! I am lucky my daughter lives there. The big inconvenience are shipping fees, sometimes higher then the cost of the goods.

Any help to take the flaps apart?

[ROCKOROD71]