daja1975

If you mean the smaller pipe that goes into the top of the tank through the smaller hole, then yes the coolant comes through there. I left the coolant at the min though. If i was to go out to the car now (being cold) to bleed the system what would you suggest how i start the process? Ive done many cars over the years but this one has left me scratching my head.

daja1975

Would also like to add that once the Thermostat had been replaced, i was still getting the code P0599. Also numerous O2 codes.

daja1975

Just found this. Could someone comfirm if this is right?

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.
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.

sanjsanj

It might take a few drives of it NOT seeing the fault before it doesn't throw up the code. I wouldn't worry about it too much though, being a petrol engine.

Here's another post saying the same this: http://forums.bimmerforums.com/forum....php?t=1595876

By all means try it, you'll know if it works because pressing the accelerator for 10 secs, you'll see the water flowing. Remember to set the centre vents through the iDrive to HOT as well.

When you did you initial test, are you sure you had connected the fan up properly? It sounds like you were testing it with the engine idling and the car standing still (in which case, if the fan wasn't working, it can easily overheat, where as driving around wouldn't have let it overheat). BUT touch the pipes and upper and lower bits of the radiator to check if there is an airlock or not! also check the OBC temp readout!

daja1975

Like i said previously, i dont think my pump is electrical i thought it was pulley driven? Correct me if im wrong. Also nothing was disconnected when i installed the thermostat so i see no reason why the fan wouldnt be working. Check the OBC readout? ive heard of secret menu!! how do you access this?

My understanding is that when the cap is off and with the heater on and the car on idle, the heater would open the thermostat. This would then circulate the water around the engine and any air would come out? But after leaving the car a while like this, i turn the heater to cold and the expansion tank boils over.

Ive never had any trouble whatsoever with overheating, so this really is frustrating. Im going to drive the car to work today as i need to, The heater will be on hot to stop it over heating so i will have to try something later when i get home from work.

Thanks in advance to all who have taken time to reply.

sanjsanj

I don't know if its electrical or mechanical.

when you saw it boil over, wasn't the fan on? It's pretty hard to miss, it's quite noisy.

Did you get a warning on the idrive that it's overheating?

http://lmgtfy.com/?q=obc+menu

Boiling over without the cap is normal though, it's supposed to be a pressurised system which increases its boiling point. Sounds like your thermostat might not be opening properly... so check the pipes and top and bottom of the radiator for warmth, to check circulation!

jgt

This was the bleeding procedure I was referring to in my original post. I used it to bleed the air out of my N52 engine (electric pump) when I replaced the radiator and was receiving a similar overheating engine warning. I noticed you have the M54 engine though which has the mechanical water pump so this doesn't even apply to you but I still think there might be air in the cooling system. That or you just have a bad thermostat and/or pump. Good luck.

daja1975

Update: Possibly my old thermostat was faulty and stuck open. This i believe to be electrical? I tried again to bleed the system with the new thermostat still on the car, again boiled over. Top hose red hot bottom hose cold so i think that the the new thermostat wasnt faulty but not opening. What i did was use the old thermostat housing and removed the thermostat, this allowing a full open circuit creating a stuck open thermostat situation that probably i had in the first place? The car now doesnt overheat but will obviously take longer to warm up the heater than normal. At least i can carry on using the car until i work out what the problem is. I will order a new part and fit and see if the problem happens again.

Will keep you updated.

Thanks for all the response.

AchtungE60

When the thermostats (at least for M52/54) fail they fail open.

sanjsanj

I thought they failed closed too? That's why they all have a small bypass valve that allows some coolant flow even if it's jammed shut...