Thermostat and housing differences

[Mike Goble]

I had a failure of my thermostat recently, it didn't close at the right temperature resulting in lower than normal engine operating temperatures. I use a later housing with multiple threaded ports for my fan control and mechanical thermometer, and the thermostat is the lower one in the picture. My original E3 housing with the single threaded port uses a thermostat like the upper one, and side-by-side comparison shows that the recirc valve seating surface is recessed further in the old housing. RealOEM shows the same thermostat part numbers interchangeable for all years, so I installed the long thermometer in my short housing. It did take a while longer to warm up, but a 40 mile test drive shows that it does work.
Any clues as to when the housings changed the depth?

 

[sfdon]

I believe it was September or October of 1985.

Part Number: 1153125104180
Notes: thru 08/85
Part fits: 1985 BMW 535i Base Sedan E28 3.5L L6

 

[sfdon]

The updated t-stat housing is clearly marked with an embossed "A" on it
Attempting to install an early t-stat in a "A" housing is a fail.
Opposite for late T-stat in an early housing- fail.

 

[mosearch]

related info found here:
https://e9coupe.com/forum/threads/thermostat-housing.22476/

 

[mosearch]

I gather this photo is the "early T-stat housing"...which is what I have in my e3. So...which t-stat is the proper one? Part number?

 

[Mike Goble]

I went to the boneyard and got a 180° thermostat out of an 86 E28 528e, looks like it will fit right in.

 

[Mike Goble]

I gather this photo is the "early T-stat housing"...which is what I have in my e3. So...which t-stat is the proper one? Part number?

The early housings use the long thermostat, the upper one in the initial picture. Don listed one of the part numbers.

 

[mosearch]

I couldn't find part # 1153125104180 on Realoem...but it does seem to be offered from many vendors as fitting our cars...just a bit unclear whether that aprt# is for the early or later housing...

 

[Mike Goble]

The last 2 digits of Don's number represent the opening point in degrees C. The part number is 11531251041.

 

[sfdon]

Let's meet at dipsea and we will work this out.
Saturday or Sunday?

 

[sfdon]

11 53 1 710 953
That's the later tstat

 

[mosearch]

Sorry Don...missed you note until just now. Could meet at Dipsea Cafe about 9:15 (Sunday 8/27)...text me at 415-717-9995 if you can still make it.
-Mose

 

[sfdon]

See you there- 9:15