Coolant Light Issue M5

[TroyArboc]

Been dealing with a coolant light issue on my M5 for a couple weeks. I first noticed some coolant residue on my expansion tank, it was likely an original part so we were hesitant to do a pressure test. We replaced it with a new tank, new tank cap and coolant level sensor, as well as any hose that ran to the tank. No luck. Still getting the coolant light and still notice coolant residue on the new tank. It's never fully drained the tank but has lowered the level a bit after some long drives, but I can't figure out where the coolant is leaking from. There's no obvious areas, when I run the engine with a close eye on the hoses.

Could the tank be bubbling over due to air in the system? That's my only theory left. Any help is welcomed. The car doesn't overheat, in fact the temp gauge doesn't move past the middle but that little red light taunts me everyday.

[Mike W.]

Do you have the right sensor? There are at least two different ones, similar except for length. Have you bench tested it? As far as the coolant residue, does the nut for the sensor screw on tight? Many times the replacements have had nuts with too few threads and while the kind of feel ok, crank on them hard, just by hand, no tools, they slip and consequently do not hold pressure. The solution is to just reuse the old nut with the new sensor.

[austin8753]

i've been dealing with this for the last couple years. the true solution is to use an e30 coolant level sensor, with the round 2.5mm pins, and change the body side connector to the round pins. no matter what you do, the flat pin coolant level sensors don't seal and always leak and i'm sick of it. the e30 sensor is a great fit and works excellent.

[TroyArboc]

i've been dealing with this for the last couple years. the true solution is to use an e30 coolant level sensor, with the round 2.5mm pins, and change the body side connector to the round pins. no matter what you do, the flat pin coolant level sensors don't seal and always leak and i'm sick of it. the e30 sensor is a great fit and works excellent.

Thanks Austin, I'm going to give it a try. Just ordered an e30 (2.5 pin) sensor to test it out.

[milarsky]

Is this the e30 part you referenced?

https://www.pelicanparts.com/More_Info/ ... cGEALw_wcB

[jhh925]

I might be misunderstanding your original post, but it sounds like the "Coolant Level" light in your "Active Check Panel" up above the rear view mirror is staying on even after you fill up enough coolant into the expansion tank?

The switch in the level sensor should be open when the float is up (coolant level is full) and closed when the float is down (low coolant level). If the switch closes (low level), that completes a circuit from the check panel to ground through the coolant level switch. See page 6212-2 from the ETM for the 87/88 535/M5.

If you've confirmed that the switch is actually working as it's supposed to, then you most likely have a short to ground somewhere between the switch and the Active Check Panel.

Also, I'm not sure how the solid state electronics work in that unit for the coolant level light, but those circuit boards are infamous for developing bad solder joins. I'm not sure whether or how a bad solder joint could trip that light, but you might also try re-flowing all the solder joints on that printed circuit board.

[austin8753]

Is this the e30 part you referenced?

https://www.pelicanparts.com/More_Info/ ... cGEALw_wcB

yes, Jeff, that is the one!

[Foonfer]

I'd like to revive this thread, mostly to find out if OP swapped the stock part with the recommended part No.61311378320 (OEM calls it "Levelling Switch Radiator"), and if said part did the job.

My car is not an M5, it's a M30B35-swapped 528e which I have owned for 10 years now (swap is 2 years old). Within the past month or so, every time I drive the car, the "coolant" light on the display near the rearview mirror lights up as soon as the car has warmed up. But the coolant is topped off, the car doesn't overheat, and there don't seem to be any leaks.

I'm tempted to get the $18 part with the round prongs to test it out (mine has the blade prongs, one horizontal one vertical). Also, does anyone know the part number for the harness-side plug that attaches to the round prongs of Part 61311378320? Because... it's kinda necessary knowledge...

any feedback is appreciated - thanks

[Aldo525]

I'd like to revive this thread, mostly to find out if OP swapped the stock part with the recommended part No.61311378320 (OEM calls it "Levelling Switch Radiator"), and if said part did the job.

My car is not an M5, it's a M30B35-swapped 528e which I have owned for 10 years now (swap is 2 years old). Within the past month or so, every time I drive the car, the "coolant" light on the display near the rearview mirror lights up as soon as the car has warmed up. But the coolant is topped off, the car doesn't overheat, and there don't seem to be any leaks.

I'm tempted to get the $18 part with the round prongs to test it out (mine has the blade prongs, one horizontal one vertical). Also, does anyone know the part number for the harness-side plug that attaches to the round prongs of Part 61311378320? Because... it's kinda necessary knowledge...

any feedback is appreciated - thanks

Check this web. I'm using my cell phone so I can't add the link properly....sorry.
Plug is 61 13 1 378 408

https://e30journey.blogspot.com/2017/06 ... d.html?m=1

[Foonfer]

Plug is 61 13 1 378 408

https://e30journey.blogspot.com/2017/06 ... d.html?m=1

This is a step in the right direction, thanks. However, Part 61131378408 appears to be just a housing for the connectors. The wires need to terminate at a piece or pieces with cylindrical holes, so the cylindrical plugs of the E30 sensor (Part 61311378320) go into them. These pieces are what goes inside the connector housing. The question now is, what's the part number for those connectors? (is there a part number, or are they standard "torpedo" terminals the likes of which you get at Autozone or any generic store? I'd be surprised if that's the case...)

[Aldo525]

Plug is 61 13 1 378 408

https://e30journey.blogspot.com/2017/06 ... d.html?m=1

This is a step in the right direction, thanks. However, Part 61131378408 appears to be just a housing for the connectors. The wires need to terminate at a piece or pieces with cylindrical holes, so the cylindrical plugs of the E30 sensor (Part 61311378320) go into them. These pieces are what goes inside the connector housing. The question now is, what's the part number for those connectors? (is there a part number, or are they standard "torpedo" terminals the likes of which you get at Autozone or any generic store? I'd be surprised if that's the case...)

Still just in my phone....check RealOem an Euro e28 520i model year 03/83 "Vehicle electric".....inthere there are a lot of electric round connectors.....one of these is the right one. (Choose that model because the coolant sensor is used in that e28...)

[Foonfer]

I would imagine it is No.3 or No.7 in this diagram,

https://www.realoem.com/bmw/enUS/showpa ... Id=61_2861

(this diagram is the same across many many models in RealOEM)

[Aldo525]

I would imagine it is No.3 or No.7 in this diagram,

https://www.realoem.com/bmw/enUS/showpa ... Id=61_2861

(this diagram is the same across many many models in RealOEM)

No, that is a e34 diagram.

I mean this:
https://www.realoem.com/bmw/enUS/showpa ... Id=61_1806

I have a sensor 61311378320 and their plugs are about 2.1 mm, so #1 or #5 are the options.
[/img]

[Foonfer]

Hey Aldo- Thanks for taking the time of measuring the diameter of those prongs, that really is one of the most useful pieces of information in this thread.

Now, I don't want to seem I'm contradicting you, but the reason I included the link to that RealOEM page (from the E34) showing miscellaneous connector bits and pieces was... because RealOEM shows that that specific E34 model (535i) uses the same Part 61311378320 coolant level sensor as your 528i.

I'm inclined to think that your 2.1mmØ parts (for the E28 528i) are probably the best fit, but the E34 parts listed as 2.0mmØ are probably workable as well. That, or we just found a gap in RealOEM.com, which wouldn't be the first time...

will report back when my order comes in. Thanks again

[Aldo525]

Hey Aldo- Thanks for taking the time of measuring the diameter of those prongs, that really is one of the most useful pieces of information in this thread.

Now, I don't want to seem I'm contradicting you, but the reason I included the link to that RealOEM page (from the E34) showing miscellaneous connector bits and pieces was... because RealOEM shows that that specific E34 model (535i) uses the same Part 61311378320 coolant level sensor as your 528i.

I'm inclined to think that your 2.1mmØ parts (for the E28 528i) are probably the best fit, but the E34 parts listed as 2.0mmØ are probably workable as well. That, or we just found a gap in RealOEM.com, which wouldn't be the first time...

will report back when my order comes in. Thanks again

Hello, don't worry, you didn't contradicting me....this is why e28 forum exist!!...I'm learning a lot in this forum so my contribution:

Original connector (NLA): 83300492946 short body, superseded by: 61131378408 long body
Plug: 61130007441 plastic covered, cable included, fit into 61131378408 ....very rare and expensive. Alternative: 61130007449, seem to be the same but without plastic cover, cable included.

Plugs info:
https://www.realoem.com/bmw/enUS/showpa ... Id=61_2865

Connector 61131378408 view with plugs inside (plastic covered plugs....like 61130007441)


Plug 61130007441


Alternative plug 61130007449

[Foonfer]

OK, my Febi Bilstein unit is in, and the measurement is about the same position in the Vernier caliper as Aldo's - 2.38mm-2.40mm. Now I need to get myself some terminals...