Weird overheating issue

[slavik1988]

Hey guys, so I am nursing a weird overheating issue on my M3. Just some background, I have a 02 M3 with 59k miles. About 10k miles ago I did complete cooling system refresh. Parts that were replaced:

-OE BMW Radiator
-Geba metal impeller water pump
-OEM hoses
-OEM coolant reservoir
-50/50 BMW Coolant
-OE BMW Fan Clutch and URO blades
-OEM Thermostat

With the old system, I did two track weekends in the summer at Road Atlanta without any overheating issues.

Last year I went on track again (July 20-21st) with the cooling system refreshed and I start overheating on the back straight at 110mph. My thoughts were that the fan clutch is blocking the air from cooling the engine so I remove it. A few weeks ago, I took a short morning drive (Temps in the mid-60s). If I don't rev the engine out, the temperatures stay in check. Once I go for a hard uphill run (2nd and 3rd gear), the temperatures start to climb. Since that drive, I installed the fan clutch again and bled the system three times of the course of three days. It is still doing the same thing.

Drained the system yesterday and the coolant is clean. Also checked the engine oil and it is good and no signs of water as well so I don't think it's the head gasket.

I can install an aftermarket radiator that has more coolant capacity to rectify this issue possibly, but I want to have the stock system running as efficiently as it is supposed to, prior to going that route. Has anyone checked how much water do the aftermarket water pumps move? That is currently my only suspicion.

[Obioban]

I’d also be suspicious of the water pump.

That said, did you change any of the front end ducting that goes into the rad?

[SteelGreyM]

My vote is for water pump or faulty thermostat. I had an OEM thermostat that was bad from the factory. If I had to choose I’d say water pump. If you saved your old one and it works fine swap them out and see how it goes.

[sapote]

either Tstat or water pump, but I'm more to Tstat since I have not seen a water pump with the turbine fell off yet.

Do this: cold engine and running until operating temperature. Reach down and hold on the lower radiator hose: hot or luke warm? You should not be able to hold it for more than a minute without tears on your face.

[slavik1988]

I’d also be suspicious of the water pump.

That said, did you change any of the front end ducting that goes into the rad?

None of the ducting was removed or altered. Everything is like it came from the factory.

My vote is for water pump or faulty thermostat. I had an OEM thermostat that was bad from the factory. If I had to choose I’d say water pump. If you saved your old one and it works fine swap them out and see how it goes.

I have the OE water pump lying around. Going to do that tomorrow.

either Tstat or water pump, but I'm more to Tstat since I have not seen a water pump with the turbine fell off yet.

Do this: cold engine and running until operating temperature. Reach down and hold on the lower radiator hose: hot or luke warm? You should not be able to hold it for more than a minute without tears on your face.

I actually went ahead and removed the T-stat. Did a test on it in the kitchen. I threw it in a pot and with a thermometer waited to see when it opened up. It started to open up at 177 degrees F. It is when it should so that isn't the issue. Looked at my aftermarket unit and it seems fine and doesn't look like it failed. My only suspicion is that it doesn't move enough water when the engine is at full chat.

[Casa de Mesa]

Are all your belts clean? Almost sounds like it could be slipping on the water pump pulley.

Shooting from the hip here...

Also when my H2O pump took a nap, it was weeping for quite a while. You should see white residue if so.

Shooting from the other hip...

[slavik1988]

Are all your belts clean? Almost sounds like it could be slipping on the water pump pulley.

Shooting from the hip here...

Also when my H2O pump took a nap, it was weeping for quite a while. You should see white residue if so.

Shooting from the other hip...

Forgot to mention that the belts and tensioners were also replaced.

I removed the water pump and there is no weepage. Just looking at the how the fins are designed on both the OE BMW and the Geba, I think that it just inferior and doesn't push as much water as the BMW unit. Will take a picture and post it tomorrow.

The BMW pump temporarily will go in and I will do a test this weekend.

[slavik1988]

Here are a couple of up close pictures of the OE BMW pump and the Geba unit. The fins on the aftermarket ones doesn't look like they will flow more water. Also, the water channels look smaller because of the thickness of the steel.



OE BMW:


Geba:


I had the used water pump installed today. Will be going for a test drive either tomorrow or Saturday. Hopefully it fixes the issue.

[Johnvu]

Here are a couple of up close pictures of the OE BMW pump and the Geba unit. The fins on the aftermarket ones doesn't look like they will flow more water. Also, the water channels look smaller because of the thickness of the steel.



OE BMW:


Geba:


I had the used water pump installed today. Will be going for a test drive either tomorrow or Saturday. Hopefully it fixes the issue.

Please keep us posted! This is my next maintenance item, so it will be good to know this information. Thanks!