Potential waxstat solution

[Nevadan]

While working on a solution to my air to oil cooler thermostat problem on my 2.0TD QSW conversioin I came across this:



Clockwise from top left: Valve in my 2.0TD oil distributor, thermostat (or waxstat) from the innards of that valve, internal portion of thermostat from an old 1.6TD, a complete 1.6TD thermostat.

A waxstat is just the control mechanism for a thermostat.

The 1.6 internal piece fits nicely into my valve and it may just solve the problem, it doesn't fit perfectly tight but it doesn't need to since there's spring pressure holding it in place. The bad/old one taken out was stamped 100 Celsius so I'll see if I can find one close to that temperature, for now I'm experimenting with a 90 Celsius unit.

There has to be a similar solution to the waxstat at the injection pump and I will be looking into this in the next few weeks when I install a new waxstat I purchased from Amazon UK.

[ngoma]

For the cold start waxstat, isn't the actuating pin removable? Can't you pull out the pin and refill it with antifreeze, reinsert the pin, test, and----- (if luck is with you that morning...) there you go!

[Nevadan]

It's filled with something else, wax maybe, hence the name, I'm not real sure what but it's not antifreeze.

Excellent idea on interchanging the pins. On mine the pin diameter is a little different so I'll need to look at some other thermostats to find one that matches.

I've done further testing and will do more today.

Heating the thermostats in oil rather than water allows me to keep the temperature more consistent and have a longer working time.

In the above photo the original "waxstat" from my oil diverter valve will open at around 220-230 but doesn't retain enough resistance to overcome the force of the return spring; I can just push it back closed with pliers, so it's not working.

The innards of the 1.6 thermostat work perfectly, it opens at a little cooler temp than I want for the oil cooler but I may use it anyway. I think it would work excellent for the IP waxstat.

More to come

[ngoma]

My old Alfa mechanic rebuilt them (being NLA) for those SPICA mechanical IP. Similar, they were called "Thermostatic Actuator." He used antifreeze, which surprised me as well. I had thought they were filled w/ brake fluid? Worked!

[Nevadan]

So here's a photo showing, top to bottom:
1. Waxtstat/thermostat from my 2.0TD oil cooler diverter.
2. Waxstat/thermostat from another Audi oil cooler diverter.
3. Waxstat from an '85 Jetta TD thermostat, just the center portion of the thermostat. 83 degrees C.
4. Waxstat from a '85 Volvo 2.4TD thermostat, just the center portion of the thermostat. 87 degrees C.


There appears to be two different sized removable pins that can just be pulled (thanks Ngoma) from the non-working waxstats and pushed into the working waxstats, the pins having different tops depending on the application.

I called my local Bosch shop and they said the actual waxtstat for the IP advance (Bosch PN 1467202302) is no longer available.

There's an excellent description of how a thermostat works on Wikipedia here, it explains how the wax works inside a thermostat:
https://en.wikipedia.org/wiki/Wax_th...ve_thermostats

I'll need to select a thermostat with the correct temperature rating for each application, a hot one, above 190 degrees, for the oil cooler circuit and a colder one, around 160 degrees, for the IP timing advance.