M52B28 Overheating and Coolant system issues

[ThatSoftwareGuy]

Hi guys,

Unfortunately I guess I am not the first one , but I am having overheating issues with my E30 M52B28 swap.

My engine becomes too hot when idling, coolant starts leaking after some time out of the radiator expansion tank cap and the electrical fan doesn't kick in... I am distraught at the moment and hope someone can help me. Below my setup and things I already tested to solve the problem.

- Stock E36 328i coolant hoses
- Donor car E36 328i radiator with expansiont tank included
- Donor car E36 328i pusher fan
- New waterpump
- New thermostat
- New double temperature sensor switch 81/89 degrees
- Mechanical driven fan delete

In short, I used most parts from the car the engine came from and replaced the waterpump and thermostat for new ones. I wired the E36 electric fan through the E30 power distribution box which works fine. Next things I already tested to be sure there are no big other issues.

1) Carried out head gasket leaking test with fluid (no carbondioxide in coolant system, only O2) -> so no head gasket leakage
2) Tested the electrical fan circuit with the temperature switch in external boiling water, switches on and off at right temperatures

For me it is strange how it is possible that after some time the engine became hot and started leaking coolant out of the radiator cap. I replaced it for my old E30 one which was always fine and it still starts leaking after some time. The system is not pressurized so how could it start leaking here?

Also after removing the double temperature switch in the upper right corner of the radiator, it doesn't start leaking coolant here which means there is no coolant water in that place. This could be the reason the electrical fan doesn't kick in as well while idling. Is my radiator clogged or is there still too much air in the system?

The last thing that could be occuring problems I think, is the mechanical driven fan delete. I thought that an engine normally does have an electrical fan or a mechanical one. However, I was suprised by realoem the donor E36 328i does have both and the reseller of the swap also confirmed this. Unfortuntately this will be a really hard fit and maybe only a 2-3 mm clearance between radiator and fan will be possible.

Hope anyone takes the time to ready my above story and could help me where to start. Thanks in advance guys!

[roguetoaster]

Once the system leaks some amount of coolant, or if the system is slightly low, the switch no longer triggers the fan. I suggest setting the fan to always run on high, maybe with a quick jumper wire at the switch connector and see if your issue persists.

Also make sure both of your rad hoses get hot, and check if water flows past the thermostat by removing hoses and running water.

If that sorts it, either keep the fan on, add a switch in the cabin, or convert to a probe style switch. Alternately, upgrade your pusher fan with some sort of kit. There is also a radiator that has the switch at the bottom, which would be vastly superior, but I don't recall which cars had them presently.

[ThatSoftwareGuy]

Once the system leaks some amount of coolant, or if the system is slightly low, the switch no longer triggers the fan. I suggest setting the fan to always run on high, maybe with a quick jumper wire at the switch connector and see if your issue persists.

Also make sure both of your rad hoses get hot, and check if water flows past the thermostat by removing hoses and running water.

If that sorts it, either keep the fan on, add a switch in the cabin, or convert to a probe style switch. Alternately, upgrade your pusher fan with some sort of kit. There is also a radiator that has the switch at the bottom, which would be vastly superior, but I don't recall which cars had them presently.

Thanks, I understand the fan switch will not be triggered when there is no coolant enough. But how could it be that it starts leaking and fhe radiator expansion tank cap?

Both rad hoses get hot.

With fan on permanent high it will hold it, but I am not really happy with such a solution.

A switch at the bottom or at the lower rad pipe would also be a solution.

However, my setup will never work or are there any running such a setup as I have?

[moatilliatta]

How tight is your fan sealed to the radiator?

Does it get hot on the highway?

[ThatSoftwareGuy]

How tight is your fan sealed to the radiator?

Does it get hot on the highway?

There is no mechanical driven visco fan on the engine yet.

The electrical fan is between the front of the car and the radiator, but don't kick in / starts spinning. Altough temperature is +/- 90 degrees. Distance fan - radiator should be about 10 cm.

Didn't drive that much with it after finishing swap since it became really hot after starting. First time there was air in the system I guess since now it takes really longer before it starts overheating.

[moatilliatta]

Do your have heat, usually a sign if it’s bled?

The fan, electric, sound be seat tight. Air, water, current, people usually take the path of least resistance.

[ThatSoftwareGuy]

Do your have heat, usually a sign if it’s bled?

The fan, electric, sound be seat tight. Air, water, current, people usually take the path of least resistance.

Thanks again for your response.

Yes I have heated air ini my E30 and turned the heat switch to completely red during bleeding.

You mean the radiator or the electric fan sounds to be seat tight? The electrical fan is succesfully tested with external heated water.

For some reason the radiator will not be fully filled in the upper right.

[roguetoaster]

He means is the fan mounted directly on the rad with no real gap between them, which I assume it it. If not, change where your fan mounts.

If leaving the fan set to high works then you have found your issue, your fan does not flow enough air on a setting other than continual/high, so it's time to upgrade.

As to no coolant reaching the switch at any time that probably indicates a blockage in the radiator, so either try to flush it with a garden hose/pressure washer/chemical solution, or replace it. Alternately you could have some ridiculous air pocket in the system, but it seems unlikely if coolant flow rate is good (possible WP issue, check for flow rate).

Since it wasn't addressed, many cars have two fans from the factory, one primary, and one auxiliary to add air flow at low speeds/assist if the primary fan is degraded/fails/improve AC efficiency.

[moatilliatta]

I guess you could put a known good mechanical STOCK clutch fan on it rule out any fan issues.

[ThatSoftwareGuy]

He means is the fan mounted directly on the rad with no real gap between them, which I assume it it. If not, change where your fan mounts.

If leaving the fan set to high works then you have found your issue, your fan does not flow enough air on a setting other than continual/high, so it's time to upgrade.

As to no coolant reaching the switch at any time that probably indicates a blockage in the radiator, so either try to flush it with a garden hose/pressure washer/chemical solution, or replace it. Alternately you could have some ridiculous air pocket in the system, but it seems unlikely if coolant flow rate is good (possible WP issue, check for flow rate).

Since it wasn't addressed, many cars have two fans from the factory, one primary, and one auxiliary to add air flow at low speeds/assist if the primary fan is degraded/fails/improve AC efficiency.

The problem is that the fan doesn't kick in which assumes to me the radiator is clogged or there is still too much air.. The electrical fan circuit is tested with external water and works!

I will try to flush the radiator and will also try to mount the primary one which is mountend on the water pump pully. However, this will be a hard fit..

[pazi88]

The 81/89 degrees temperature switch at radiator has too high switching temperature to be used WITHOUT MECHANICAL FAN. Without it, you need temp switch at radiator that operates about 50-60 degrees C. Otherwise you will have those overheating issues when standing still

[ThatSoftwareGuy]

The 81/89 degrees temperature switch at radiator has too high switching temperature to be used WITHOUT MECHANICAL FAN. Without it, you need temp switch at radiator that operates about 50-60 degrees C. Otherwise you will have those overheating issues when standing still

Again thanks for your helpfull and experience answers!

Will check first if all will stay okay while idling and driving with the electrical fan jumped too high speed. If that is, I will order a 50/60 degree switch, do you have a part number for me?

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)?

[roguetoaster]

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.

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.

[ThatSoftwareGuy]

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.

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.

Did some testing with jumper wires on idle. With the low speed and high feed fan on it cools the engine on idle. It don't even reach 90 degree operate temp. However, here in the Netherlands it is right now about 5 - 10 degrees.

I guess I will search for a 50/60 degree fan switch as pazi88 adviced. For me it doesn't matter if the low speed fan is always on and the high one only mid summer when the car is idling. The 81/89 degree switch simply don't work for me since it also takes some time for the themocouple notice this temperature and then it's again too late.

[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.