xoeightx

Hey Everyone,

After getting my car's SES light code read, it came out to be P0128, Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature). After doing some research I believe my thermostat is stuck open, which seems to be a common problem. I confirmed this after checking the temperature through the instrument cluster hidden options and saw that its running about 85 degrees instead of the 97 degrees it should be operating at.

I just purchased a new OEM replacement thermostat and want to tackle the job myself. I've done some searching on and google and couldn't find any DIY on this particular job for the N52 Engine (06 530i). If anyone has done this or know where I can find a DIY on this please send it this way.

Thank you in advance for your help!

Danny

crewzer

I don't have a DIY. However, these drawings (1 and 2) suggest the thermostat is located just above the electric coolant pump, and the Bentley Manual instructions for the N52 thermostat R&R (page 170-15) are just over 1/2 page in length, which, although you'll need to drain the coolant, otherwise suggests it's not a huge job.

I'll probably regret that last comment... .

HTH,
Jim / crewzer

pcy

Raise the vehicle, get under the vehicle, remove the splash guard.
Remove the cap on the coolant expansion tank/reservoir,
Drain coolant by opening the coolant drain plug at the bottom of radiator,
Release hose clamps on 4 hoses that are connected to the thermostat, detach all those 4 hoses from thermostat,
Disconnect electrical connector to the thermostat,
Remove the 2 screws that attach thermostat to the water pump,
remove thermostat,
put the new thermostat and put back the screws, reattach the electrical connector, reattach 4 hoses, attach hose clamps,
tighten the drain plug on the bottom of the radiator,
pour new coolant in to the expansion tank,
Next, you will need to vent the cooling system (that procedure is already posted, please search).

Only difficult part of this job is accessing all those 4 hose clamps, releasing those clamps, and then releasing those 4 hoses. They may be stuck.

Good Luck!

balbs

Is your car under warranty? My car is an 06 as well and just had mine replaced under warranty.

txag_530i

Don't forget to bleed the cooling system once you've put everything back together.

Here's a link to a thread that shows pictures: Coolant Drain and Flush

xoeightx

Thank you pcy for this quick detailed write up and the picture guide. Sounds fairly easy enough. I will try to tackle this job this weekend using this Coolant Drain and Flush guide as a reference to the steps you provided. I just have a few questions about this guide and with your steps:
1.under the draining coolant in the Coolant Drain and Flush guide it says to "Remove reinforcement plate and remove engine block drain plug from left side of engine and drain coolant." is this only for the N62 engine or is this even necessary at all b/c you didn't mention to do this?2. How much coolant and distilled water will I need? The Coolant Drain and Flush guide shows (2) 1 gallon coolant and 1 gallon distilled water.

xoeightx

unfortunately my car is not under warranty anymore. My car isn't a CPO so it ended in 2010 but i'm still under 60K. I wish I could get this covered warranty still!

xoeightx

Thank you for posting this link. I found this DIY before I made this thread but just wanted to make sure I wasn't missing anything since it's for a different engine. I found 2 videos on Youtube of this procedure. Which one would you recommend is the most proper way of doing this. I believe video would be or video ?

crewzer

Neither of the two videos are correct.

The N52 engine in the 06 530i uses its electric coolant pump to perform the bleeding procedure. The procedure is described on pages 170-10 and -11 in the 5 Series (E60/E61) Bentley manual.

Total cooling system capacity varies according to your car's transmission. Bentley reads 11.2 US qts for the MT, and 10.6 qts for the AT. However, an online VIN decoder reads the other way 'round.

I drained and refilled my 6MT-equipped '06 a few weeks ago and it took exactly 8 qts (one gallon of BMW antifreeze and one gallon distilled water) to do the job.

HTH,
Jim / crewzer

xoeightx

I'm glad you chimed in to tell me those 2 videos are wrong b/c I would've used them as a reference and would probably screwed everything up. After doing some more research I found this:

Cooling, draining and filling procedures:
1. Remove splash shield from under the engine. Unscrew fasteners (8 screws) and lower rear of cover and pull out of bumper cover.
2. Remove cap from radiator expansion tank.
3. Place 5-gallon pail underneath radiator.
4. Loosen drain plug on peacock at bottom of radiator and allow coolant to drain.
5. Place 5-gallon pail underneath engine block coolant drain plug.
6. Remove engine block coolant drain plug and drain coolant. The engine drain plug is located on right side of engine block near cylinder 2 (If you are sitting in the driver seat and looking at the windshield, cylinder 1 is at the front of the engine). See page 120-2 of the Bentley Service Manual. (DOES ANYONE HAVE A DIAGRAM OF THIS?)

Before refilling radiator:
1. Switch ignition on. Do not start engine.
2. Set temperature controls to full warm.
3. Set blower control to low.

Using a coolant mixture of 50% antifreeze and 50% distilled water, fill expansion tank ?slowly?. Continue until coolant emerges from bleed screw. For the N52 engine with automatic transmission, the capacity is 2.6417 gallons (10 liters).

Cooling System, bleeding (N52 engine) procedures: Whenever the coolant is drained and filled, bleed the cooling system.

Close cap on coolant expansion tank and perform the following steps:
1. Connect vehicle to power supply (I guess this procedure prevents the battery from draining when the car engine is not running for 12 minutes during the process).
2. Switch ignition on.
3. Set heater to MAX temperature and turn on fan to lowest speed.
4. Press accelerator pedal to floor for 10 seconds.
5. Bleeding procedure begins when accelerator pedal is pressed and takes approximately 12 minutes. (Electrical coolant pump turns ON and OFF automatically after approximately 12 minutes).
6. CAUTION: Do not open expansion tank cap while electrical coolant pump is ON.
7. Fill coolant expansion tank 100 ml above MAX (dimension A).
8. Check coolant system for leaks.
9. If leaks are found, remove ignition key and wait approximately 3 minutes before repeating cooling bleeding procedure.
10. When bleeding procedure is complete, close coolant expansion tank cap until marks on cap and tank line up.

and I also found this on bleeding the N52 electric pump. I believe this is the right one. Can you please verify.


I believe what you read on the Bentley manual is correct b/c this one also says the N52 AT takes 2.6417 gallons (10 liters) (maybe this is from the Bentley Manual?). In that case would I be okay using 1 gallon (4 qts) of antifreeze and the the rest distilled water (2.6 qts), living in Cali or should I buy 2 gallons of antifreeze just to be safe and go 50/50.

Thank you again for your help!