M52B28 Overheating and Coolant system issues

[ThatSoftwareGuy]

Yes, coolant should come out, even when cold. Anything below the fill reservoir should be full of coolant.

EDIT: Removed temp sensor and coolant was coming out. So that's good since there should be no air in.

Re installed my wiring to the temp sensor and YES FINALLY! The slow speed turned on when the coolant temp in the instrument cluster was just before 90 degrees. Awesome!

In short, it looks like there still was air in always and now after some really good driving (+ 100km) with fan always on at low speed all air left the coolant system.

Will thanks you all guys for helping me!

[AndrewBird]

Yes, coolant should come out, even when cold. Anything below the fill reservoir should be full of coolant.

[ThatSoftwareGuy]

If you can pull out the temp sensor and no coolant comes out, you have air in the system. Jack up the front driver side of the car and run the engine with the cap off, adding coolant as needed.

FYI, I've been running the M50 in my E34 with no mechanical fan for years. The stock auxillary fan only comes on occasionally in 90° weather with the AC on and in traffic. I'm using the 80/88 degree switch from an M42.

Hi Andrew,

Even with a cold engine turned off there should come coolant out if I remove the temp sensor?

This looks like to be the same setup as me. I also reemoved the mechanical fan and am using the stock auxillary electric fan with 80/88 degree temp switch.

[AndrewBird]

If you can pull out the temp sensor and no coolant comes out, you have air in the system. Jack up the front driver side of the car and run the engine with the cap off, adding coolant as needed.

FYI, I've been running the M50 in my E34 with no mechanical fan for years. The stock auxillary fan only comes on occasionally in 90° weather with the AC on and in traffic. I'm using the 80/88 degree switch from an M42.

[ThatSoftwareGuy]

I'm glad you found at least a temporary solution... I ll send you the pn tomorrow morning since i left my car at my workplace for the weekend!

Thanks for your info. Sorry for my late response.

You did also removed the viscious fan from the engine? So only an electric pusher fan?

And radiator with temp switch in the upper right corner of the radiator.

In that case my 81/89 temp switch (even lower) shouldn't give no problems.. But it did.

[PshlosE30]

So i found it, https://m.onlinecarparts.co.uk/facet-2180787.html .... I think it has different temperatures that original... It has 91-86 and 99-94... I'm using the first one and it works as it should,needle stays exactly at 2/4..
RealOEM pn is 61311378073

[roguetoaster]

I also choosed for the 80/88 switch based on E30 wiki information. Maybe we have some differences while it is working for you and for me unfortunately not at all.

Wha engine are you running? Radiator? Waterpump?

M42, M42, and stock.

[PshlosE30]

I'm glad you found at least a temporary solution... I ll send you the pn tomorrow morning since i left my car at my workplace for the weekend!

[ThatSoftwareGuy]

Mate did you find a solution? I had similar problems with you...I used a pusher fan,tight on the front side of radiator and used a temp switch from an air conditioned E36 (i can find the part number if u are interested,don't remember exactly the temperatures) Also made another electrical circuit and installed a button in cabin,so i can have it always on! I'm using a 88c tstat and a radiator from M42 with the expansion tank on it. BUT i had also similar problems to my VW transporter too (was overheating and fan wouldn't turn on, boiling water was leaking out of expansion tank) so i flow tested the radiator and it was blocked... Bought another radiator and everything is fine. So i suggest you,to just flow test on a shop the radiator...Also replace the expansion tank cap!

Hi PshlosE30 ,

Thanks for your response. I still didn't totally fix the problem, since I hadn't much time lately and it is really hard to find a usable 70 - 80 degree temp switch. For now I jumped wire the low speed mode of the electric fan. Cooling system is working really properly and is able to cool down the engine enough (it doesn't even reach 90 degrees anymore while normal driving...) So it looks like the radiator is all fine.

As far as I know a E36 air conditioned temp switch is about 91/99 degree so even higher compared to the 81/88 degree I was using, but I could be wrong. If you would like to share the part number with me I can do the research myself.

[PshlosE30]

Mate did you find a solution? I had similar problems with you...I used a pusher fan,tight on the front side of radiator and used a temp switch from an air conditioned E36 (i can find the part number if u are interested,don't remember exactly the temperatures) Also made another electrical circuit and installed a button in cabin,so i can have it always on! I'm using a 88c tstat and a radiator from M42 with the expansion tank on it. BUT i had also similar problems to my VW transporter too (was overheating and fan wouldn't turn on, boiling water was leaking out of expansion tank) so i flow tested the radiator and it was blocked... Bought another radiator and everything is fine. So i suggest you,to just flow test on a shop the radiator...Also replace the expansion tank cap!

[ThatSoftwareGuy]

Here's what doesn't quite follow with such a low temp switch for me, having very recently switched over from a clutch fan to an M44 e fan and used an 80/88 deg switch, which seems to function perfectly. Agree that the switch is on the outlet side, but it is in the top 1/4 of the outlet side tank, and I doubt that these rads are more that simple crossflow units. So, I really don't see how coolant would achieve a 40ish dehree C drop before it hits the switch, and so it would seem that a switch substantially lower than the factory unit would simply be always on.

I also choosed for the 80/88 switch based on E30 wiki information. Maybe we have some differences while it is working for you and for me unfortunately not at all.

Wha engine are you running? Radiator? Waterpump?

[ThatSoftwareGuy]

You need to go universal one. Unfortunately I don't have part number for you. I run the fans controlled by ecu that has extra temp sensor installed where the temps switch normally is. And e36 fan should be fine. Stock BMW fans normally flow way more air that aftermarket fans do. Like those cheap spal fans that people normally use that think that those are better than oem.

pazi88 thanks again for your helpfull answers! Makes all sense and will do some more research. Up to know I only found M22 temp switches for these range instead of M14. Should be something like a 60 - 70 degree switch what I need.

Your fan is probably controlled by a function within your stand alone ECU? One of my future dreams to put a turbo on it later. Love to watch your videos.

Agree about it, on full speed the electrical fan sounds that loud and I already tested this (however it was quite cold outside).

[roguetoaster]

Clearly wrote the wrong one for some reason, whichever fan in in the engine bay is the primary.

Here's what doesn't quite follow with such a low temp switch for me, having very recently switched over from a clutch fan to an M44 e fan and used an 80/88 deg switch, which seems to function perfectly. Agree that the switch is on the outlet side, but it is in the top 1/4 of the outlet side tank, and I doubt that these rads are more that simple crossflow units. So, I really don't see how coolant would achieve a 40ish dehree C drop before it hits the switch, and so it would seem that a switch substantially lower than the factory unit would simply be always on.

Now I want to chop a used radiator open to see if there's anything beyond assumptions going on with coolant flow in the radiator.

[pazi88]

I guess this should be an universal one or does BMW OEM also have these 50/60 degree switches? And do you know if the stock E36 electrical fan should be capable for delivering enough air without the mechanical one installed (will know after my test)?

You need to go universal one. Unfortunately I don't have part number for you. I run the fans controlled by ecu that has extra temp sensor installed where the temps switch normally is. And e36 fan should be fine. Stock BMW fans normally flow way more air that aftermarket fans do. Like those cheap spal fans that people normally use that think that those are better than oem.

[pazi88]

The stock E36 mechanical fan is an AUXILIARY unit, not a primary. That said, it would work perfectly in Siberia, not so much in the Sahara at mid day, but it all depends on where/how you drive.

Wrong. The mechanical fan is the primary one in m5x engines. If you have car without AC those only have mechanical fan. No electric one at all. Electric fan is mainly to just cool down the AC condenser and the temp switch for electric fan in radiator is just backup if something goes wrong. These engines are designed to work with the mechanical fan and if you take it away, you will need to do changes to the cooling system, or you are going to have problems.

I don't know for certain, but a 50/60 degree C fan switch sounds to me as if the fan would run continually once the car is even up to temp, as I seriously doubt that water temps can realistically be maintained below 100 degrees F. IIRC, M42s use an 80 something degree switch when converting to electric fans.

The point is that the radiator temperature switch is at the radiator outlet side. So it senses the coolant temperature going back inside the engine. Not the coolant temperature in the engine. If the coolant temp going inside engine is already 80 degrees or higher, it's way too high temp to cool down the engine which has normal operating temp at 90-100 degree range. The coolant temperature going inside engine needs to be way lower than that. The 50/60 degrees is at the ballpark but the actual value bit depends on the setup and the cars owner preferences. I have PWM controlled fan and it starts gently blowing at 50 degrees. And it's at full blast at 70 degrees. In practice it means that the fan never runs when driving normally. But when sitting at traffic lights it starts blowing little bit to keep engine temps normal. And only gets higher if I do burnouts etc. and no cooling problems.