Thermostats between heat exchanger and banana tubes

[eagle]

How do the two thermostats operate please.? One has a smaller tube going into it. These are the two round bell mouths secured by three screws under the rear seat bodywork.

[purplepeter]

It (They) mix cold air from the fanhousing via the tubes under the Cylinder Head tinware in with the (excessively) Hot air from the heat exchangers. On top of the thermostat (inside the bell shaped housing) theres a disc of steel that forms a valve- when heat gets Hot, thermostat expands, opening valve & allowing cold air in to the airflow.

[eagle]

Are they liable to rust up and therefore not work? Is the replacement the same as a beetle thermostat?

[purplepeter]

I can't say for certain on either
the system functions perfectly well enough if You detach the elbow carrying cold air at the top & undo the bolt/screw holding the metal disc in & remove the disc.
I'd guess yes to it being the same as a bug thermostat, but you'd really need to check the parts book ( someone will pop up & tell You the correct operating range of the thermostat)

[eagle]

Had a look at them. The tube that is attached to the plate was rusty but still opened up. They didn't work with the OH hairdryer but worked with the heat gun needing to be quite hot to open up. The elbow is held on by a single pozi head screw. You can undo the top, you'll probably find the plate and tube come off together. Then undo the grub nut (13mm) and the thermostat should twist off but you'll probably find its siezed. As it's two flats on the bottom it can be quite hard to get off, I'm off to look for an s spanner or may cut a spanner up. A good soaking in plus gas will help as well. I've cleaned the tube off. Under the disc is a type of heat proof fibre washer gasket There's also a similar one between the body and this tube. The thermostat has a male threaded top on it so different to a beetle one.

[Editor]

The engine thermostat is the same as Bug (111 part number), but the heat exchanger/mixer thermostats are Type 3 parts, and aren't the same as a Bug - they're similar, but not sure how different. I've not heard of them being adaptable either, and they are much more common than the original engine thermostats.