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Installing a TYPE I (Upright, or Beetle Style) Thermostat Bellows on a Type IV engine (page 1)

Written by German Supply Staff

The following information is to be used for reference only. is not responsible for any modifications made to your vehicle. Please do your research and consult a professional before performing any modifications.

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Thermostat Bellows Type 1
Part Number: 111 119 159 A

We have a small supply of original thermostats in stock. These are original Wahler bellows type thermostats, genuine VW. Buy two while they are still available! Correct for upright engines. This thermostat can be used in a type IV (pancake) engine with a simple modification.

Our price: CDN$ 107.00

Why do you need a thermostat on your VW?

The thermostat on an air-cooled VW controls the air cooling flaps. On a late bus, or Type IV style engine with so-called “pancake” cooling system, the thermostat flaps also route air to the oil cooler. For this important reason, running a Type IV engine without the thermostat or cooling flaps is not recommended. It does not matter where you live or what your climate, we say the flaps are still mandatory.


If your thermostat is expanded when the engine is cool, like the one in the photo to the left, it is bad. The thermostat is designed to control the position of the air flaps by expanding as it warms up. At full expansion, the air flaps are completely open, allowing maximum airflow to the cylinders, and also to the oil cooler on a Type IV. The thermostat fails in the “flaps open” position, which means if your t-stat is bad, you will have maximum cooling airflow at all times. This might sound good, but it is not ideal for warm-up, where the flaps are designed to limit cooling air flow. This allows the engine to warm up quickly, a beneficial effect.


The original Type IV bellows style thermostat is no longer being manufactured. But the bellows used in air-cooled upright engines is available, VW part number is 111 119 159 A, is still available. Adapting the Beetle part for a Type IV engine is simple and can be done by any mechanic with basic tools and skills. Read on to find out how this simple modification is done.


The Type I thermostat bellows is very similar in design to the Type IV part. In the photograph you can see the Type IV thermostat has a different mounting nipple. The Type I part attaches to a threaded rod, the Type IV to a cable.


The only bellows thermostat currently available has a lower opening temperature than the original Type IV part. This means the cooling flaps will open a bit sooner. All other significant design details of the part are identical between the two parts.



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