Thermostat reliability

[80stech]

Yes, I ordered the Hepu water pump awhile back (not installed yet) looks good and has "made in Germany" all over it

[srmmmm]

I just had to replace the thermostat for the second time in the last 60,000 miles. I'm thinking the dealer had a bad batch of OEM parts maybe?

Here's my repair and maintenance recap including cooling system service intervals for your reference:

On a regular basis:

> Rotate tires, inspect pads & Rotors, CV boots, general lookover every 5000 miles
> Oil / Filter change every 8000 miles
> Brake fluid flush every 30,000 miles
> Replace belts and clean CCV every 100,000 miles
> Replace differential and transfer case fluid every 100,000 miles
> Replace sparkplugs every 120,000 miles
> Replace expansion tank, coolant and hoses every 150,000 miles
> Replace bake pads every 163,000 miles (Akebono ceramics)
> Replace rotors??? (237,000 miles on current Brembos)

My unplanned repairs have included:

> Front axles at 60,000 miles (Prior owner didn't maintain CV boots)
> FSR at 78,000 miles
> Two sparkplug coils at 124,000 miles
> Alternator at 126,000 miles
> Front driveshaft at 136,000 (used a salvage transfer case for cost savings)
> FSR (again) at 159,000 miles
> Thermostat at 176,000 miles
> Rear differential seal at 200,000 miles
> Secondary air pump at 224,000 miles
> Rear suspension bushings and upper control arms at 242,000 miles
> Thermostat (again) at 245,000 miles - at least it was warranty this time
> Steering column double U-Joint shaft at 245,000 miles
> Valve cover gasket at 245,000 miles
> Both fuel tank sending units, fuel pump and canister at 245,000 miles
> Aux fan when the harness got chewed up in the mechanical fan and shorted out at 259,000 miles
> Pre-cat O2 sensors at 260,400 miles
> Water pump at 262,800 miles
> DISA Valve and MAF at 263,800 miles
> Thermostat (again) at 299,00 miles (don’t know what’s going on with these)

The "Expected" replacements have been:

> All four window regulators
> Driver door handle carrier
> Front axle outer CV boots (each side one time)
> Front tension struts

All in all, except for the front driveshaft job that cost $4200, I have really been happy with the vehicle. It doesn't get babied, but I do monitor and maintain it. I think a lot of my good fortune is due to four things: I live in Texas with short winters so I don't have a lot of the CCV condensation problems, my daily commute is 60 miles so the engine oil always reaches full operating temperature, I run the "M" series viscosity engine oil from May through September when I my driving includes 3000 miles of towing a 1400 pound Waverunner and trailer, and I stick with Shell gasoline.

Additionally, I don't change the transmission fluid! I'm a firm believer in leaving it alone and simply installing a full re-manufactured transmission if it ever becomes necessary.

With that, I'm off towards 500,000 miles!

2002 X5 3.0 300,600 miles
2014 428i 17,400 miles

2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles

[80stech]

Thanks, that's some really good info! A bit scary about the thermostat though especially since I ordered a OE BMW one thinking that I didn't want to be replacing a good factory one with a cheaper aftermarket one that might fail sooner than if I left the old one in. Hopefully that doesn't backfire on me! Really good to hear from someone who has some big miles on

[bcredliner]

Originally Posted by bmw540san

While it's theoretically ingenious idea to vary opening temp through DME, I don't like potential issue behind it when heater fails or leaks and coolant makes its way up through the wiring and cause havoc.
Yes, it's rare and only happens with M62TU thermostat, but M54 thermostat is not that much different when it comes to that feature.
Therefore, I went backward in technology and installed 95 C thermostat found on E31 840ci with M62 non vanos engines.
With a simple radiator hose modification and along with Spal fan (fan clutch delete) my X5 runs around 95-97 C with Spal coming on at 102 C if needed as a back up:
http://www.xoutpost.com/bmw-sav-foru...ch-delete.html

Since the clutch fan is the primary fan, when I went to an electric fan I set the electric fan to come on just prior to when the aux fan kicks on. I also wired it so it continues to cool after the ignition has been turned off. The controller I have is adjustable so I can set it anywhere from constant on to not a good idea.