Or you could heat the spring with a mini torch (one turn on both sides) to soften it up slightly so it will allow the t-stat to open sooner.

 

Can you be certain in the consistency of your heating exercise and how much you altered the spring stiffness?

 

Trial and error will determine what the temp will be. I've already heated about 3/4" of one coil on both sides of the middle coil. The spring isn't quite as stiff as before.
Putting the unmolested t-stat in boiling water didn't cause it to open which was expected. Doing the same after I heated the coil showed that the t-stat had just started to open as the water approached 98C. A digital temp meter was used to read the water temp.
I haven't put it in yet so I don't know what the final temp will be. This is on a 540 that normally runs at 108C, the t-stat is marked 105. I'm hoping it will run in the 96-98C range just to lower the internal pressure of the cooling system which can be as high as 16-17 PSI.
I'll install it this winter when she becomes a garage queen.
Just an FYI for those that don't know, the expansion tank cap doesn't control the pressure.

 

Russian research.

lol

 

LOL, Geezer, no Russian vodka was consumed while doing my kitchen stove top testing.

 

You'll run cooler,,bur sacrifice fuel mileage.

 

This thread can be cross referenced to:
What is the coolant temperature of an E39 (I6 or V8) under normal operating condition

 

I believe the Stewart WP achieves same results. I rarely see 96°C on the KTMP - and this only in heavy stop-and-go traffic, and only in the summer months. usually my KTMP since I installed the Stewart WP doesn't go higher than 94°C, and this also when it's warm outside. I also installed the TMS underdrive pulleys to slow down a bit the WP, so with the stock setup, the KTMP might go a tad lower.
In day-to-day traffic, my KTMP sits between 92° - 93°C steady.

 

since I installed the Stewart WP doesn't go higher than 94°C, and this also when it's warm outside. I also installed the TMS underdrive pulleys to slow down a bit the WP, so with the stock setup, the KTMP might go a tad lower.
In day-to-day traffic, my KTMP sits between 92° - 93°C steady.

Doris, what is your current temps these days in Cowtown?

Here is mine, checked during a brief stop on a spirited sprint up to Forget-me-not pond and back.

Ingredients:
- "cold" thermostat
- Stewart WP
- Evans coolant

 

Bob, not me, I've never used Evans.
I'm keeping the old school stuff.

 

Hah, okay, never mind. I guess I've read so many Evans threads that I can't keep everybody straight.

 

Doris?

 

Me bad. Was talking to Doru.

 

That temp (86°C) is much lower than mine. At 86°C, the needle just went to 12 O'clock (actually around 75-ish). That's too low of an inlet temp for the engine. It will never warm up properly, I believe, and the most concerning issue is not fuel economy, but rather the inability maybe to "clean out" the condensate paste (which some people refer to "mayo") during the cold months. This could be actually a kiss of death....
if I were to use the OEM pulleys with the Stewart WP, the temps I see would be another 2-3°C lower, so maybe around 90°C, which I thought to be a tad on the low side.
With your setup, maybe the Evans fluid is more suited.

 

That temp (86°C) is much lower than mine. At 86°C, the needle just went to 12 O'clock (actually around 75-ish). That's too low of an inlet temp for the engine. It will never warm up properly, I believe, and the most concerning issue is not fuel economy, but rather the inability maybe to "clean out" the condensate paste.

87-89degC does not even put it into S62 territory, for example. And all older engines (M50-52) somehow managed to survive for 100's of thousand miles running in this range - and excavate the oil vapor and condensate properly.
Not trying to sound engineer-y, as I am clearly not one, but my impression from researching the subject is that lots of problems we have with M54 and subsequent designs, stem from that excessive heat.

On the mayo thing, after each run (even on colder days we had some time ago) I have the transparent oil catch can covered with yellow foamy goo that later settles down as liquid and some sediment. So I guess it works as it should.

I cannot comment on oil consumption yet, as I only made less than 300 miles / 500 km on this setup.

 

I am glad I have a 1998 528i, I simply swap a Wahler tstat with lower temp and done with.