[NToxx]

Hi there,

My 525i E61 left me stranded on the highway yesterday. It is only 110000 km and I own it for a few months only but it already has its fair share of issues : no airbag, thermostat changed last month, rear plate light wire broken.

Yesterday I was on the highway at about 130km/h on a steep hill and it showed me an alert : "overheating, please drive slowly". I stopped as soon as I can and I plugged my Carly OBD app : no error code, fan running (albeit slowly), cooling liquid and oil temperature @120°C. The waterpump turns at about 250RPM, and it only shows deviation speed for a second when it the target speed change. I called the assistance and now the car is at home, but I am almost clueless.

For me it should be one of these issues :
- Thermostat closed, at least partially
- Bad waterpump
- Failing fan ? I have some doubts since I was driving at high speed : could the fan be needed even when there is already a fair amount of airflow?
- Failed temperature sensor
- Clogged radiator

When I changed the thermostat I was wondering if I should change the waterpump but the part being about 400***8364; I finally kept it. Thermostat change should be problem free as I had done two 650km trips with high heat (>35°C) and traffic jam without any issue (I certainly lack a temperature jauge, but I had no alert :dunno.

This morning the cooling liquid level is perfect (no drop since the thermostat change), and I tried succesfully to cycle the waterpump (with this procedure with the contact on: heater on, minimum blower speed and accelerator pedal down for ten seconds). No suspect noise (I think so, it just does some typical electric motor noise...). Water pump is known to fail on the N52, but for me it looks like it is working...

I tested the fan with ISTA and it works perfectly. It was quite loud with a lot of airflow, which was not the case when I stopped on the highway.

Concerning the sensors, the car is stopped from about half a day and without the engine on I thought that I should have all the same readings. The ambient temperature shows at 24°C (OK), almost like the coolant temperature (engine, 26°C). But the engine oil and the intake air show respectively at 31 and 34°C. The inside DME temperature is at 40°C but I think that it is OK since electronics must work while connected to ISTA.

For the clogged radiator I have no clue how to test that...

Do you guys have any ideas of additional tests, ISTA procedure or preventive maintenance I should do?

I was thinking to change the waterpump and maybe cleaning the radiator (disconnecting it and flushing it with tap water). If it is not the problem it the 400***8364; waterpump will be preventive maintenance but it won't help me much :dunno:.

Thanks a lot!

 

[pshovest]

I would repeat the bleed with expansion tank cap removed. Make sure you see bubble free flow in the visible stream.
Confirm electrical connection on pump is secure and terminals are clean.
Radiator won't clog that quickly. You had two trips w/o problems.
You can unlock the cluster, go to test 7 and monitor coolant temp while you drive.
250 rpm is low, but the exact circumstances when this was measured aren't clear. Pump is capable of >6000 rpm. You likely need a water pump. Many of these pumps have failed with less than 110kkm.

 

[scottalexander]

I changed my N52k water pump and thermostat and hoses at 50,000 miles (but that's because I'm paranoid and have read countless posts like yours).

It could be as simple as the temp sensor malfunction, but these water pumps have a long history of failing at any time.

I talked to Pierburg in Germany (who makes our pumps) a few months ago. They told me the pumps break due to the wrong coolant, low coolant, electronics overheating).

Their new version of our water pump is much better.

What you don't know is if the prior owner put stop leak in the radiator and now its restricted.

This is the challenge with a used vehicle.

My philosophy is always to invest in quality parts and do preventive maintenance to make the vehicle stable.

 

[twh]

Classic water pump failure. Change the water pump.

 

[Burning2nd]

water pump..

From the cold start..

Idle the vehicle until the thermostat opens, and the fan cycles OR it overheats..

You'll find in about 16 min your car will be telling you to shut down,

 

[NToxx]

Hi there !
Waterpump changed, with most of the hoses while everything was removed.

I have only been able to a short trip in town while looking at the temperature on the dashboard ("motor temperature").

It fluctuates between 98 and 108°C (205-227°F) which seems a tad high. But I don't know if it is an oil temperature or coolant.

Does it seems OK for you?

What are the usual temperature range?

Thanks!

 

[twh]

Hi there !
Waterpump changed, with most of the hoses while everything was removed.

I have only been able to a short trip in town while looking at the temperature on the dashboard ("motor temperature").

It fluctuates between 98 and 108°C (205-227°F) which seems a tad high. But I don't know if it is an oil temperature or coolant.

Does it seems OK for you?

What are the usual temperature range?

Thanks!

that is coolant and that is normal

 

[tstiglich]

Scott: "Their new version of our water pump is much better." Not doubting you, but what did you hear / where did you read this / in what way is it better? If I recall, the mean time before failure which they quoted you seemed surprisingly low.

 

[scottalexander]

In a earlier discussion (about 3 months or so) ago I took it upon myself to reach out to Pierburg in Germany.

The reason for this is there was debate about the mtbf and why the pumps go bad.

I decided I would go to Pierburg in Germany and have a discussion with the water pump product manager. It took me a while to find him.

I put all the learnings in that earlier post.

Here's the answer to your questions:

You say, Their new version of our water pump is much better."

Yes, this is what the Pierburg product manager told me. They made refinements.


You say, what did you hear

I need to find that earlier post where I put all the learnings. In short, he told me the pumps go bad due to:

- the wrong coolant
- low coolant levels
- the pump should last the duration of the car ( I told him he was insane as they fail at anytime)
- I told him the electronics fail and he told me he never gets old pumps where his group can do a post mortem analysis on the electronics


You say, in what way is it better?

Pierburg claims the duration of the pump will last longer

In short, Pierburg has an over rated view of their water pump and believes it dies due to owner mis-treatments.

They have a point, there are people that don't use Pentosin Pentofrost NF or equiv

 

[tstiglich]

Thanks Scott. I remember your earlier post, and you contacting them. I must have missed their response.

 

[dharmabmw]

In a earlier discussion .........there was debate about the mtbf and why the pumps go bad.

I decided I would go to Pierburg in Germany and have a discussion with the water pump product manager. It took me a while to find him.
..............
- the pump should last the duration of the car ( I told him he was insane as they fail at anytime)
- I told him the electronics fail and he told me he never gets old pumps where his group can do a post mortem analysis on the electronics...,..........

I'll send him mine, if they pay for shipping.......

 

[tstiglich]

Just reread your post "he never gets old pumps where his group can do a post mortem analysis on the electronics". That is just crazy. How can one make improvements when one does not know the failure modes?

 

[Annolago]

Would be interesting to see the technical documentation on the pumps. Any product have an expected life span. The question is what they expect the car lifespan to be....?
We all know that BMW thinks that no oil service is needed on the transmission even though ZF claims otherwise. Maybe the designed lifespan from BMW to it***8217;s suppliers is 100K an no more. After that the buyer is on his own..
However I fail to see the importance of the type of coolant being used. If there is no corrosion then why? I guess extreme difference in viscosity could affect the cooling of the bearings. I would be more concerned about the pressure being the main reason for gaskets failing and what ever havoc that will create.

 

[NToxx]

Just out of curiosity, do you know what part fail?
On my previous pump the rotating speed looked fine (250RPM seems to be the maximum speed), the impeller seems to be okay too.
I will dismount mine but they say that the pump must remain in coolant so I may find a lot of corrosion.

 

[Burning2nd]

Its a electric water pump...

9/10 the winding's burn
if its not that

its a physical failure which is like a impeller or bearing

such a bad design, Id consider a mod/fabricated part with a longer belt and a some added pullys and brackets

anything to get away from a electric pump (*its like they let someone from the race division make a decision )

 

[tstiglich]

More than likely they went with an electric for an improvement in gas mileage. I would have to imagine that any improvement in fuel economy would be minimal.

 

[scottalexander]

Some of the research shows they went with an electric pump:

- so when the car is idling in high heat, the pump can pull high rpms and cool the engine better (unlike conventional pumps that are spinning at idle rpm)
- when the engine is turned off and the engine gets hotter after shut down, now the pump can continue to run with the engine off and bring the engine heat index lower

 

[NToxx]

Hi there!

Bad news

I was on the highway few hours ago, and the warning came back : Overheating, please drive carefully.

Now I follow my temperature on the dashboard and by driving slowly I managed to go home (few miles away). At about 90 km/h (~55mph) my temperature (KTMP) oscillates between 115 and 120°C (~240 and 245°F).

I don't understand : I tested it at idle without any problem, and I made two test trips with a far more spirited driving, and I never got above 108°C (~227°F).

And it is almost the same problem as before : I see no dead component, my cooling system seems to work (no error codes, water pump rotates) but it is not enough even on light loads (even if it is quite hot there, about 95°F today and 104°F during my previous test).

Maybe I have still air trapped in my cooling system? I am waiting for it to cool and I will perform another bleeding procedure (Found in the TIS).

I will also explore ISTA in order to see what I can find... But do you have any idea?

Thanks!

 

[fred530xi]

Hi there!

I will also explore ISTA in order to see what I can find... But do you have any idea?

Thanks!

Did you flush the radiator? What about the heater core? There is also a small space between the radiator and the air conditioning condenser that accumulates debris, so you might want to inspect that. I would re-check the fan and all electrical connectors for the cooling system.

Good luck,
Fred

 

[twh]

Hi there!

Bad news

I was on the highway few hours ago, and the warning came back : Overheating, please drive carefully.

Now I follow my temperature on the dashboard and by driving slowly I managed to go home (few miles away). At about 90 km/h (~55mph) my temperature (KTMP) oscillates between 115 and 120°C (~240 and 245°F).

I don't understand : I tested it at idle without any problem, and I made two test trips with a far more spirited driving, and I never got above 108°C (~227°F).

And it is almost the same problem as before : I see no dead component, my cooling system seems to work (no error codes, water pump rotates) but it is not enough even on light loads (even if it is quite hot there, about 95°F today and 104°F during my previous test).

Maybe I have still air trapped in my cooling system? I am waiting for it to cool and I will perform another bleeding procedure (Found in the TIS).

I will also explore ISTA in order to see what I can find... But do you have any idea?

Thanks!

Did you replace the pump before?