Overheating

QUA2468

MEMBER
2007 BMW 328
V6
2WD
AUTOMATIC
216 MILES

I let my car run in idle for about thirty minutes so I climb under it to check hose. First squeezing the front big hose of the thermostat while feeling the big hose on the out side of the thermostat. I noticed I could feel the coolant gush through as I squeeze but I also notice that the front hose was way cooler than the back hose, it was burning hot. Also, the fan was not coming on so I shut it off waited a while and did the same test. This time I turned the A/C on to get some fan play and I ran that car for an hour and it never overheated. Can someone tell me what I got going on? I was thinking a thermostat stuck in the open position, but would that bother my fan? Car is driving me crazy.

4 Replies

KHLOW2008

MECHANIC
41,814 POSTS

With modern vehicles, many components are computer controlled and if any sensor is not giving the correct signal, the control unit would not be commanding the required action.

Have you checked for trouble codes? A scan tool can help to understand what is functioning correctly or not as it can provide live data of engine operating conditions. This avoids time wastage wondering what could be wrong and trial and error could be expensive if you replace the wrong component without rectifying the problem.

It does not look like a stuck open thermostat as coolant would be circulating and being over-cooled, rather than overheating. Symptom indicates coolant not circulating.

It could be a faulty temperature sending unit or fan control module.

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Monday, November 20th, 2017 AT 5:47 AM

F4I_GUY

MECHANIC
3,302 POSTS

Your vehicle is notorious for faulty coolant pumps. Usually there will be a stored fault. Have the vehicle scanned, if it is a BMW based scantool you can perform a function test on the coolant pump. When you replace the pump, the thermostat must be removed, I recommend replacing both the thermostat and coolant pump together.

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Monday, November 20th, 2017 AT 11:28 AM

QUA2468

MEMBER
8 POSTS

Okay, thanks I will give it a try and let you know when done.

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Thursday, November 23rd, 2017 AT 6:27 AM

KEN L

MASTER CERTIFIED MECHANIC
47,574 POSTS

What will happen to the water pump is the impeller with become dislodged from the shaft allowing it to spin sometimes. Also when the engine is overheating do you hear the cooling fans running?

This guide can help

https://www.2carpros.com/articles/engine-overheating-or-running-hot

Here is the wiring diagrams for the cooling fans. (below)

Please let us know what you find.

Cheers, Ken

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