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Discussion Starter · #1 · (Edited)
I think I am due for a new thermostat. Over the past two weeks, I've gotten an SES light about 3 times. All pulled a 69 on the Peake. I checked the temp through the menu function and it was around 75-76F. Seems like most dont have success until replacing the actual thermostat. I have an early '00 w/ about 83k on it. Am I on the right track here?

EDIT: the code was "Engine Coolant Temperature, Plausability"
 

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Discussion Starter · #3 ·
I replaced my thermostat along with the water pump at 135K miles - no problems or symptoms, just wanted to do it as a preventive measure. I would think your beast could use the same treatment.
I think this is what I am getting to. I probably won't be DIY'ing due to my lack of facilities (and patience grrrrrrr). If so, would it be worthwhile to replace the water pump while they are in there?
 

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Never seen a waterpump go on these badboys
Mine went at 140k and took the pulley with it,it all started when i noticed the coolant level needed topping every morning,on the third day on the way home from work the pump gave way!had to replace it together with the pulley,at least now my cooling system is almost completely new,installed a new radiator,water pump,pulley,thermostat and fan belt,wats left are the radiator hoses and the expansion tank,next on the list is new oil pump and rod bearings,i want to make this engine fail proof for another 100k.
 
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Definitely change out the water pump and the serpentine belt and the stat all at once. While it is true that the pump rarely goes out, bear in mind that when it goes, it loses the fan and the fan goes hammering into the rad, taking the rad out too, and possibly damaging other items as well (rad shroud, a/c condenser, etc etc). No need to take a chance!
 

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Never seen a waterpump go on these badboys
But they do go :)

Mine went after a weekend of fun in the Autobahn and the Ring. Seems that it didn't enjoy the extra work.

It scared me to hell though, since it sounded like a bag of marbles was inside the engine. After pinpointing the origin of the sound to the waterpump made me more relaxed.


As for the Thermostat... I replaced mine this weekend at Frits and it is great to have the beast warming up faster and maininting temperatures while on the highway of 80C/79C, instead of the 75C/76C that I was seeing.
 
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Never seen a waterpump go on these badboys
They do unfortunately :

So I had some work done recently by CPC, which stemmed around replacing my water pump that started making some horific noises/vibrations on Thursday.

Water Pump :

My old water pump was shot and full credit to Phil Crouch who pointed out to me back in June 08 that the bearing on the pump was not great, after I proudly showed him my shiny new Viscous Coupling (Fan Clutch) that I got installed ! Nearly 2 years on and KAPUT !






Interesting corrosion (tide marks) Phil reckons alot of water pumps he has seen have this effect. He reckons if you horizontally exrapoloate this mark it coincides exactly where teh coolant level would be at with an S62 with cylinder heads removed, so his theory is a lot of these cars have had there heads of at some point, and sitting around waiting for the work to finish..... :







Shiny new one :





Plastic Water Pump Pulley, with rust dust on it and cracks (cracks not visible in these pics)...I also noticed metal shavings on the water pump housing below the T Stat housing, and basically the water pump/bearing/shaft was grinding itself to a slow but would be catostrophic end.... :



 
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Discussion Starter · #11 ·
Thanks, gentlemen. Real world feedback is what makes this place great. It is worth doing at 83k? I based this on my previous cars and the "Old School Maintenance Guide" @ 60k (however, it doesn't mention the S62).

I have some limited service records up to around 2007, which don't show it being done. Although, they did replace the thermostat at 27k (this will be #2). Is there a way to tell if it has been replaced? (Doubtful, I know.)
 

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FLGatorM5, if you are getting yourself in there to replace the thermostat and the coolant and you want to do a bit of preventive maintenance (and you can afford to do so), then yes, I would think its worth it to replace it at the same time :)
 
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It is kind of amazing how many thermostats are in need of replacing on the M5. I am about to take on this project starting tonight. All the items arrived today (just got the UPS confirm on that) from two different sources. I priced out Bimmerzone, AutohausAZ, and Tischers. Some things were cheaper and some were more at each place so I mixed and matched. It appears as if the thermostat is a weak point on the car. Luckily it is not all that expensive for the parts but if you pay someone to do it then the repair would be more irritating. Gives me an excuse to explore the engine a little and take off the plenum to see what things look like under there. I also plan on replacing the lower oil separator hoses while Im doing the thermostat. The hoses were only $6 each.
 

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I replaced my stat and nearby hoses over the weekend. Glad of the rich information on the forum in preparation. Getting the housing out was the hardest part (needed a pry bar). I did find a leak due to a sheared O-ring on the first try at putting everything back together, but having done it once it took only 30 mins or so to unbolt everything, get the housing out again and re-inserted properly. Didn't bother with the plenum cover, because if you put the three pipes into the engine first there is plenty of visibility.

Cue massive sense of satisfaction seeing the KTEMP at a steady 79-82 degrees.

Beware of the lower oil separator return hoses though - the crimps holding them on at the bottom are a real pain, particularly the left-hand one as there is very limited space to work. A good pair of tin snips is what is needed - unfortunately I didn't have a set handy and the shops were closed, so I only managed to prise off the right-hand crimp with pliers and screwdriver and had to leave the other one for another day.
 

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A key issue for thermostat replacement that I found it to install the short coolant pipes in the engine, not the thermostat housing, make sure the thermostat U frame is in line with the front axle, not in line with the length of the car. Kind of hard to explain, but you will understand that if the thermostat frame is parallel to the front axle, you have more room to insert the thermostat, pull it back toward the front of the car to then properly align the coolant pipes (not on an angle) and slide the coolant pipes in without catching an o-ring. You should plan on having at least 1 large spare O-rings on hand as these are easy to break. They usually do not leak quickly, until the engine gets up to operating temp and starts to build some cooling system pressure.

If you do not have at least 6 O-ring, 4 larger, 2 smaller and fatter, you do not have all the O-rings you need. You should also plan on replacing the thermostat seal inside the thermostat housing. It looks like a wheel bearing seal. I actually used a wheel bearing seal puller to remove the old one and a wheel bearing race/seal installation tool to install the new seal. Worked out really well.

At the end of the day, the thermostat is very easy on this car, it just needs to be done a very specific way. I also had to use a pry bar to actually pull the thermostat housing away from the short coolant pipes, this was tough, use a block of wood and do not put too much stress on the intake box!

I did not get a chance to change the oil return line behind the stat, will need to do that later, however, I did find one of the crank case vent hoses very soft, 1 had been recently replaced, so I replaced the other soft hose. I did not get a chance to check and clean the oil separators either, this will be a Spring time job.
 
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