e39 520i M52TU Cooling Issues - Bimmerfest - BMW Forums



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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 12-29-2019, 09:49 AM
Guerciotti Guerciotti is offline
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e39 520i M52TU Cooling Issues

Hi all,
I have a 2001 520i post facelift with the M52 2.0 TU engine (my car is Portuguese and they carried on with the M52 TU even after other European markets went to the M54 2.2 for the 520i model).

I bought the car about a month or so ago and didn't experience any cooling issues. I had the valve cover gasket off and there was no 'mayonnaise' on the cover indicating head gasket issues.

I then took it to Spain for the holidays. Then after getting stuck in a traffic jam for about 5 mins the car overheated with steam coming from the front. I immediately shut down the engine, waited a little while for it to cool before driving for another 5 mins to get to my destination. Before driving home I checked the expansion tank and it was low so I filled it with half a litre of water. No obvious leaks. The car was well behaved on the way home (about half an hour) although no traffic. I checked it again the next morning and it used another half a litre so I topped it up, set the digital temp readout on the dash (test 7) before starting the drive home watching the temp gauge like a hawk with lots of spare water bottles in the car.

Some cooling related observations:

1) The main fan comes on from even when the car is started from cold
2) The aux fan does not come on when the A/C is turned on (which implies an issue with the aux fan from what I have read)
3) The digital temp gauge can be very erratic. On the highway it will stick around mid nineties for a while, drop when going up a hill to the mid-eighties. Sometimes when going down a hill or slowing down it will go right up to 105 before dropping to 90 in literally 5 seconds. Given that there may be an issue with the aux fan this rapid cooling doesn't feel right and implies an issue with the temp sensor.
4) It feels the the top radiator hose is leaking as it makes a hissing noise when the engine is warm.

I would appreciate any help on the above. I'm guessing I will need a new aux fan relay / switch and a complete cooling system refresh (thermostat, temp sensors, hoses etc) but would appreciate any help.

Thanks in advance !
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  #2  
Old 12-29-2019, 10:17 AM
E39Hoon E39Hoon is offline
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1) The main fan is always on. The fan clutch engages when it gets hot as it expands thus turning faster.
2) You are correct. I've read it could be the resistor pack. Do some electrical testing.
3) Maybe an air bubble due to a leak
4)Top off the system, bleed, and check for leaks.
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Old 12-29-2019, 10:59 AM
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bmw blue bmw blue is offline
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Sounds to me like your fan clutch is not working and your auxiliary fan is not working.

There are no resistor packs for your auxiliary fan on the TU motors, the electric fan is controlled by the ECU and the lower radiator hose temperature sensor.

Sounds like it's time for a complete refresh of the cooling system and that means pretty much everything minus the heater core if you want your car to survive.
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  #4  
Old 01-01-2020, 02:02 PM
Guerciotti Guerciotti is offline
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Quote:
Originally Posted by bmw blue View Post
Sounds to me like your fan clutch is not working and your auxiliary fan is not working.

There are no resistor packs for your auxiliary fan on the TU motors, the electric fan is controlled by the ECU and the lower radiator hose temperature sensor.

Sounds like it's time for a complete refresh of the cooling system and that means pretty much everything minus the heater core if you want your car to survive.
Thanks for your feedback. Apologies but could I just confirm why you believe that there is an issue with the fan clutch? I thought that it should be on when the engine is turning.

Thank you very much.
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Old 01-02-2020, 06:03 PM
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the fan clutch is a temperature controlled unit, the clutch is either engaged, or allowed to slip dependent on the temp in the engine compartment. its fluid coupled, and after the engine sits off for a bit, the fluid settles and the clutch will be engaged til the fluid redistributes. it never stops fully as long as the engine is rotating, but may not be rotating at the speed it should (slip vs engagement) with a hot engine compartment.. look up "fan clutch magazine test" on youtube as for how to check for proper operation.
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Old 01-05-2020, 12:13 AM
Guerciotti Guerciotti is offline
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Thanks for the suggestion. I did the test and the fan clutch passed so that's some good news...

Thank you again for all of the help.
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Old 01-28-2020, 10:18 AM
Guerciotti Guerciotti is offline
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Hi all,
After waiting on some parts I'm still working on renewing the cooling system...

Since there was a small leak from the upper radiator hose I replaced it with a new one (the previous one was dated 2001 !)

It went on easily enough however after re-filling the car with coolant the car is visibly dripping from the bottom of the radiator (driver's side on a LHD car). I've put my hand under the hose and water is definately leaking from the hose. I've taken it on and off three times now and it looks as if it is on correctly (see photos).

[IMG] photo Top Radiator Hose 1_zpsw3xyrclh.jpg[/IMG]



Does anyone have any ideas? The top of the radiator seems in decent condition with no obvious cracks.

Last edited by Guerciotti; 01-28-2020 at 10:30 AM. Reason: Photo link
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Old 01-28-2020, 10:31 AM
528iAut 528iAut is online now
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Never seen the hose being attached like that but I guess my car is just too old for fancy stuff.
By the way, mayo under the oil filling cap can also just indicate short drives where engine does not get properly warmed up, I had that on our e46.
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Old 01-28-2020, 10:33 AM
Guerciotti Guerciotti is offline
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Yes the top radiator hose on my car is the same as the M54 cars I think which has the metal clips you can see rather than being attached by a jubilee clip
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Old 01-28-2020, 01:13 PM
effduration effduration is offline
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Any chance a previous owner used any "stop leak" type product in your engine ? Sounds to me like you have some obstruction in your cooling system or a bad water pump that is not pushing coolant around like it should. Stop leak is not good for these engines because it hardens in places throughout the cooling system and tends to clog things up.

It also sounds like you have a leak, which may be due to this hose. But it sounded like it was somewhere else before you replaced the hose. Once you figure out this hose, I would either do yourself, or find someone to do a pressure test on your cooling system looking for leaks.

Last edited by effduration; 01-28-2020 at 01:14 PM.
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Old 01-28-2020, 01:20 PM
Guerciotti Guerciotti is offline
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Thanks. I have a pressure test kit so I could have a go with this tomorrow.

The car was a one owner car before me so I could ask if he used any Stop Leak type product
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Old 02-17-2020, 08:58 AM
Guerciotti Guerciotti is offline
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Just to give you all an update I decided to perform an (almost) full cooling system refresh and changed the following:

- New radiator
- New upper and lower hoses
- New expansion tank
- New water pump
- New serpentine belt
- New lower hose temp sender
I realise I am missing a new thermostat but the shop didn't have a suitable one at the time. Is on the list to do.

After performing the work I bled and refilled the system 3 times (although there were still bubbles coming out of the bleeder screw by the expansion tank even on the third bleed cycle)
The leak described earlier in the thread between the upper hose and radiator has now gone (upon inspecting the original radiator it was damaged here). The car drives well, there is no white smoke from the exhaust (I had head gasket worries after the overheat) and the aux fan comes on when it should when the AC is on.

Although the temp gauge sits resolutely at the vertical position, the digital readout on instrument panel is very erratic (between 85 and 108 C) and as per my original post point 3. The movement between the extremes is very rapid which is making me think that the temp gauge in the block might be faulty or there is air still in the system despite bleeding it 3 times.

Any ideas?

Thanks
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  #13  
Old 02-17-2020, 12:30 PM
effduration effduration is offline
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You can replace the dual temp sensor, but I don't think that's your pblm.

To replace the temp sensor - the easiest way is to buy a cheap 22mm open end wrench, and cut it in half. That way the open end will fit in the tight space you have. You don't need much force to remove / reinstall the sensor.

If the sensor was bad (and they don't go bad often), you would have much wider temp swings. Like 108 to zero, or you would have a zero reading on the gauge and not the cluster or vice-versa

I think you have some obstruction or an air bubble. You can try to bleed it again (raise the front of the car during bleeding). You might also backflush the heater core using the hoses in the engine bay.
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Old 02-18-2020, 04:55 AM
Guerciotti Guerciotti is offline
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Thanks for your comments and suggestions.

I re-bled the cooling system using a different method and it worked - the temp displayed is now rock-solid between 92-96 degrees.

Here is the link to the method I used: https://www.bimmerfest.com/forums/sh...d.php?t=558386

My suggestion is to watch the video in the first post - it's great. There are other methods out there (such as the one I used originally) but this one worked very well for my car.
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