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pldubs

2006 325i bad temp readings

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Right so like a few weeks ago my car came up red over heating, I stopped checked all the normal things found nothing but some water ejected from the overflow. So I let it cool, topped it up and carried on driving worry free for the rest of the day. The next day it shows hot after 10 mins driving, so I turn it off and on and carry on with no problems. I proceed to battle this every time I drive it.

so today I get the temp gauge going and notice it rises up to 120c, warning comes on, I stop turn it off and on drive off and watch the temp reading drop from 118c to 89 in a split second and continue from there to drive with no worries. 

 

Can anyone tell me what the f**k is going on? I really don’t wanna fork out $800 for a new water pump haha

Edited by pldubs

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I’ll add that I’ve tried to start the self bleed system and nothing happens 

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It will cost more than$800 to sort that out properly

 

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What type of temp gauge and more importantly, where are you measuring the 118 - 89 degree drop?

Sounds like a sticky thermostat to me but depends where you're taking the measurements

 

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On 4/2/2018 at 2:09 PM, *Glenn* said:

It will cost more than$800 to sort that out properly

 

Thanks for the completely unhelpful reply Two N Glenn.

 

2 hours ago, M3AN said:

What type of temp gauge and more importantly, where are you measuring the 118 - 89 degree drop?

Sounds like a sticky thermostat to me but depends where you're taking the measurements

 

The temp gauge in the OBC menu, unsure where the factory sensor is located sorry, but yeah I thought it would be the Tstat. 

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51 minutes ago, pldubs said:

The temp gauge in the OBC menu, unsure where the factory sensor is located sorry, but yeah I thought it would be the Tstat. 

That's engine temp sensor (as opposed to radiator) so yeah, I think it's a stuck thermostat.

What appears to be happening:

  • Thermostat closed (resting position)
  • Engine coolant temps rise 
  • Thermostat doesn't open at ~90*c (or ~98*c)
  • Engine coolant temps continue to rise (no coolant going to rad)
  • Thermostat unsticks or "pops" at >110*c
  • Coolant flows through rad, rapidly decreases in temp
  • New, cooler coolant flows past engine temp sensor
  • Engine temp sensor drops rapidly reflecting lower coolant temps

And yes, a sticky thermostat will most likely exhibit the same symptoms time and time again from a cold start. Once it's open it may also stay open whilst hot which is why the problem may not reoccur on a drive.

I'd start there unless there are codes that tell you to do otherwise.

 

Edited by M3AN

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21 hours ago, M3AN said:

That's engine temp sensor (as opposed to radiator) so yeah, I think it's a stuck thermostat.

What appears to be happening:

  • Thermostat closed (resting position)
  • Engine coolant temps rise 
  • Thermostat doesn't open at ~90*c (or ~98*c)
  • Engine coolant temps continue to rise (no coolant going to rad)
  • Thermostat unsticks or "pops" at >110*c
  • Coolant flows through rad, rapidly decreases in temp
  • New, cooler coolant flows past engine temp sensor
  • Engine temp sensor drops rapidly reflecting lower coolant temps

And yes, a sticky thermostat will most likely exhibit the same symptoms time and time again from a cold start. Once it's open it may also stay open whilst hot which is why the problem may not reoccur on a drive.

I'd start there unless there are codes that tell you to do otherwise.

 

Thank you so much for taking the time to reply man! Super helpful,

I’ll change the thermostat and hopefully it cures it. 

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As you have the N52B25 engine, it is most likely the electric water pump.    You can certainly start with the thermostat...

12 years old, prime time for a cooling system overhaul.  As Glenn indicates, it's unlikely to be cheap.  Still, good luck with the thermostat.. 

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1 hour ago, Olaf said:

As you have the N52B25 engine, it is most likely the electric water pump.    You can certainly start with the thermostat...

12 years old, prime time for a cooling system overhaul.  As Glenn indicates, it's unlikely to be cheap.  Still, good luck with the thermostat.. 

I’ll continue to stick my head in the sand I think. 

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I actually agree with Olaf - if you're attacking any part of a BMW cooling system it probably pays to do the whole lot whilst you're in there.

I don't know if the N52B25 water pump is reliable or not but the older mechanical ones BMW used are guaranteed to fail at some point. An intermittently failing water pump could cause the same symptoms.

But that pump is expensive and if it's failing it should be throwing codes. From BMW:

Quote

SI B12 04 05
Engine Electrical Systems October 2008
Technical Service 
This Service Information bulletin supersedes SI B12 04 05 July 2007.

[NEW] designates changes to this revision

SUBJECT 
Check Engine Lamp Illuminated and/or Vehicle Overheats MODEL 
[NEW] E83 (X3) with N52K engine 
[NEW] E85 and E86 (Z4) with N52 engine
[NEW] E70 (X5) with N52K engine
[NEW] E90, E91, E92 and E93 (3 Series) with N51, N52 and N52K engines
[NEW] E60 and E61 (5 Series) with N52 and N52K engine
[NEW] All models above produced up to December 31st, 2006

SITUATION 
The customer complains that the Check Engine lamp is illuminated and/or that the vehicle overheated. One or more of the following fault codes is stored in the DME: 

FC 2E81 Electric coolant pump, speed deviation, speed outside the tolerance
FC 2E82 Electric coolant pump cutoff, over-current
FC 2E83 Electric coolant pump, power-reduced operation, dry run
FC 2E84 Electric coolant pump, communication
FC 2E85 Electric coolant pump, communication, no voltage at emergency operation input of pump

CAUSE 
One of the following can be the cause: 
- Insufficient power supply 
- Insufficient grounding 
- BSD signal not present 
- Defective electric coolant water pump 
- Electric coolant pump water pump processor disturbance 
 

PROCEDURE A 
This procedure only applies to vehicles produced after September 1, 2005. Both faults must be stored; if any other combination of the faults is stored, refer to procedure B. - FC 2E81 Electric coolant pump, speed deviation, speed outside the tolerance 
- FC 2E85 Electric coolant pump, communication, no voltage at emergency operation input of pump 
1. Remove both battery cables from the battery for 15 minutes . 
2. After reconnecting the battery cables, clear the vehicle fault memory and ensure that the electric coolant pump operates using the bleeding procedure, described at the end of this bulletin. 
 

PROCEDURE B 
This procedure applies to all vehicles with any combination of faults listed below. 

FC 2E81 Electric coolant pump, speed deviation, speed outside the tolerance
FC 2E82 Electric coolant pump cutoff, over-current
FC 2E83 Electric coolant pump, power-reduced operation, dry run
FC 2E84 Electric coolant pump, communication
FC 2E85 Electric coolant pump, communication, no voltage at emergency operation input of pump

NOTE: All measurements should be performed with the battery charger connected to the vehicle. 1. Measure the following at connector X6035 on the electric coolant water pump: - E90 and E91 - Pin 1 (fuse F09) and Pin 4 ground (X6455) = 12 volts 
- E60 and E61 - Pin 1 (fuse F23 and Pin 4 ground (X6455) = 12 volts 
- Pin 2 (fuse F02) and Pin 4 ground (X6455) = 12 volts 
- Pin 3 BSD signal (DME Pin 26) and Pin 4 ground (X6455) = 7.5 - 8.5 volts - If any of the above measurements are incorrect, continue troubleshooting using the DIS Plus or GT1 to determine the source of the problem. 
- If all of the above measurements are correct, proceed to step 2. 

2. Replace the electric coolant water pump (PN 11 51 7 546 994) in accordance with Repair Instruction RA 11 51 000. 
3. After performing any service work requiring draining of the coolant, the system must be bled to ensure that there are no air pockets present. The system can be bled using the DISplus/GT-1 or by following a special procedure. To bleed the system, follow the procedure described at the end of this bulletin. 

BLEEDING (VENTING) THE COOLING SYSTEM 

NOTE: BMW recommends filling the cooling system for protection against freezing down to -34 degrees F (-37 degrees C) ; this is an antifreeze ratio of 50% antifreeze and 50% water. In severely cold areas, the antifreeze can be increased to 60%, which provides freezing protection down to -62 degrees F (-52 degrees C) . Do not exceed a 60% ratio of antifreeze. 
The specified antifreeze ratio is important, since an insufficient amount would impair antifreezing and corrosion-inhibiting protection. An excessive amount would not improve freezing protection, but would instead reduce freezing protection. At all times, the antifreeze and water should be premixed before pouring into the engine. If premixing is not performed, damage will occur to the water pump assembly.

NOTE: Always connect a battery charger while performing the bleeding process. 1. Fill the system with coolant via the expansion tank (AGB). Top up the coolant level to the lower edge of the expansion tank. 
2. Close the expansion tank. 
3. Switch on the ignition. 
4. Set heating to the maximum (temperature); switch on the blower (lowest stage). 
5. Press the accelerator pedal module to the floor for at least 10 seconds . The engine must NOT be started. 
6. Bleeding via EWP takes approximately 12 minutes . Then check the coolant level in the expansion tank; top up to the MAX marking if necessary. 
7. Check the cooling circuit and drain the plugs for leaks. 
8. If the procedure needs to be repeated several times, allow the DME to completely de-energize (remove the ignition key for approx. 3 minutes ) and then repeat the procedure, starting from item 3. 

 

Edited by M3AN
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Regardless of what it is you'd be stupid not to replace both at the same time on these motors (im assuming there is no record of work done)

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I got the whole shibang, peirburg oem pump, down to the ali bolts and bmw coolants for like $500 from ECS in a kit.

Youd be crazy to just change the thermostat, its nearly the same amount of work as changing the pump as well.

Edited by Jacko
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I have done an electric pump on a car at work. Intermittent fault code but could watch the erratic operation of the pump on current data.

Have only done the one but i understand they are a fairly common failure.

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Just replaced my original one today (at 236k, so not exactly unreliable and it hasnt actually died yet, spat out one canbus error a month ago)

Its pretty simple job, bit tight, took about 3 hours (learning how to do it on the way), theyre not worth anywhere near the amount of "scare" associated with it online.

Longest part was trying to find the ali bolt torques online (10Nm + 90 degrees!)

 

 

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Edited by Jacko

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could be wrong, but when the pump fails (and the ECU realises) doesn't the AC fan come on full tit ?

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