I have only replaced 3 of them. Once with the Behr and went around chasing my tail trying to find my fuel problem, then later caught the culprit. Afterwards I have used 2 of the Wahler stats and never had a problem with either of them,,both holding right at 94C from checking the OBC test 7. Almost 300k miles on the car now and never had an inkling (knock on wood) from an over heat.
Do you know DME opens fup tstat when driving at 60-70mph?? So when driving it's ok to have 89c Test when idling without heater. Behr is 94-96 very steady, plus upper limit can be calibrated unlike Wahler. If you look at Wahler you can see it's much cheaper than behr. Behr has solid metal wax motor design and similar to V8 design unlike plastic behr. Don't forget 90% cooling failures are bc of high pressure and the higher the temp the more likely you'll get famous radiator cracks and cooling tank cracks along with other leaks. I always install lower pressure rad caps and in one car cooling system lasted 150kmls since last colony system overhaul. Pretty impressive. Look most of the Wahler failures are due to rubber getting old and tstat plate isn't sealed well, Behr has metal plate without any cheapy rubber, which shrinks with age just like any rubber part and leaks coolant.
Let's put it this way:
How many behr failures vs Wahler on m54??
Wahler fails every 50-70k due to that plate not sealing. Behr only fails if bearing goes bad
Last edited by s14b23; 08-17-2014 at 06:35 PM.
All you have to do is use a lower temperature thermostat and an electric fan. The E31 840Ci uses a cooler 95C thermostat that is a direct bolt in. There is also a guy on ebay selling 80,87C thermostats for 540i's. Then lastly you will need to connect the heater element wires to a 12 ohm 100watt resistor to avoid any codes being set.
Function of the characteristic map thermostat
The characteristic map thermostat is tuned such that it opens at a coolant temperature at the thermostat of 103oC from the engine inlet without intervention of the integrated heating facility. Due to the coolant being heated in the engine, the temperature at the engine outlet (place of installation for the coolant temperature sensor for DME and instrument cluster display) is approx. 110o C at this point in operation. On reaching this engine operating temperature the characteristic map thermostat begins to open without control intervention.
In the event of control intervention by the DME control unit, power (12 V) is applied to the heating element integrated in the thermostat. Heating the expansion element means that the thermostat opens at lower coolant temperatures (thermostat control range: approx. 80oC - 103oC).
no, the map thermostat sucks. Everyone knows that. Most of the time you are not at the hot 103C, it keeps you at 105-108 on most 540is which is way too hot. The way to go is the 95C thermostat and an electric fan. There are may other benefits to this including , no exploding fan, a much cooler running engine and increased water pump life.
Electric Fan conversion, 840Ci thermostat, Dinan style CAI,de-screened MAF, Dinan transmission chip, 255lph LS1 fuel pump, drilled slotted rotors, 3.15 differential, Bel rx65 radar (hard-wired). Hemi Killer!
Hello Jim: I am also located in Huntsville, AL. I would love to have you look at my car if you would be willing to do so. I have a 2001 740i. I have a few issues to resolve in my cars...Please email me at dannywolfe@knology.net for info on how to contact you to set something up. I do have some questions for you...thanks very much!
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