[CCiCarbon335i]

Just bought an '08 335i with only 90,000 Kms a week ago. Have already done a few things as a preemptive maintenance. New plugs, oil change, cleaned vanos, lpfp sensor, inspected intake ports and intake system (had to reconnect charge pipe). Car has a new/used hpfp installed by previous owner. Unfortunately the car does not have any maintenance records so I dont know when/if items were replaced.

Everything was fine until yesterday when I was driving home for lunch in light traffic and got a yellow temp warning that went away almost immediately. Drove back to work in same conditions, stopped for a coffee and left it to idle to see if it would return, it did and then went away after about 10 secs of driving.

I looked into the cooling issues of this engine, found that these electric pumps / thermostats are problematic so I decided to park it in the garage last night to see what was going on. Coolant level is good, coolant looks good. Tested the pump using the on board bleed procedure. Pump moves coolant, however there is an odd (to me) almost grinding noise when the pump comes on during that procedure. Watched a few youtube vids and a couple seem to have the same sound. Still odd to me though.

Next I decided to see if the system would overheat again and watch if the rad fan would come on. I let the engine idle and warm up to operating temps, no fan and sure enough the coolant temp warning light came on. Upper rad hose was really hot and lower (passenger side) rad hose was also hot.
I shut it down to let it cool, also thinking the soak will kick on the rad fan. Nothing.
Then I noticed a pressurized spray of coolant coming from the bolted seam on top of the thermostat housing. Weakest link found!

I was going to jb weld that connection seam but I think I'll leave it parked until I can get a thermostat and housing.

1- Did that seam blow due to a stuck closed t-stat and thats why the fan never came on?

2- If the coolant warning came on, shouldn't the fan have kicked on?

3- Is there a way to test fan operation or the sensor that should signal it to turn on?

4- Is the water pump noise a concern?

Seems like its recommended to replace both tstat and water pump as a preventative. But damn are they pricey!!

Was looking into getting the k+Can cable and mhd? program to read any hidden codes. Will this do that?

Thanks for any advice.

[CCiCarbon335i]

I just did some further inspection from under the car without removing anything yet that the water pump is not original, it is a continental with the bmw logo/insignia removed.

[jsune]

If coolant is leaking from the bolt area it's most likely that the thermostat alone is your issue. Verify it's not trickling from the water pump though.

Continental is a manufacturer of the OE water pump, so the original owner may have changed the pump and opted for the OE pump rather than the BMW pump. They're 99% the same but the BMW stamp costs more.

You can find ISTA+ (on google) and use it to activate and test the pump and read memory faults too, if you own a K+D Can cable. The cost of labor is the primary reason why it's recommended to replace the water pump if you dont know it's history, while you're replacing the thermostat.

[CCiCarbon335i]

Thanks for replying Jsune
Ive downloaded INPA and the cable will be here tomorrow morning, tstat will be here on Thursday. There was a small crack only slightly visible on the tstat gasket.
Going to test the fan tomorrow with INPA provided I can get the connection done with relative ease.
Bought a temp sensor as well just cause. Checking resistance across the pins there is a 200 ohm difference between the new and old.

Also, didnt think to mention it earlier, but the previous owner put in a new battery. Looking at another post someone mentioned that was their problem with the fan operation. I guess the battery needs to be coded to the car as well?? Hopefully INPA can give some insight on that as well?

Thanks for the help