Cooling system, impending failure?

J

Jalfrezi

Member
 Bristol
Hi all,

I spend quite a couple of hours in heavy traffic yesterday, towards the end the temperature guage was up a to 3/4. Is this normal in hot conditions, and when not moving, or do I need to work on my cooling system?
 
I was driving with the roof up, and A/C on. As the engine got hotter, the A/C switched off, I'm guessing to help the engine cooling.

It didn't get to boiling, and when I got home, I put the heater on full, and the temperature quickly returned to normal. The A/C and everything else appear fine today. Just wondering if this could be a water pump on it's way out.

However, I could also imagine that this is all normal, and OK :)
 
The stock gauge is heavily damped so if it’s getting up to 3/4 I would say you have a problem somewhere as the temp should remain in the middle. I have seen temps of 105 but the gauge never moves from the middle.
There is enough cooling capacity of the radiator and volume of coolant to cope easily with hot weather providing everything is ok.

It does have proper coolant in not just water ? I’m guessing it does.

Faulty rad tank cap not venting properly, fan not coming on fast enough or slow pumping water pump due to impellers braking off.
 
mr nurburgring said:
The stock gauge is heavily damped so if it’s getting up to 3/4 I would say you have a problem somewhere as the temp should remain in the middle. I have seen temps of 105 but the gauge never moves from the middle.
There is enough cooling capacity of the radiator and volume of coolant to cope easily with hot weather providing everything is ok.

It does have proper coolant in not just water ? I’m guessing it does.

Faulty rad tank cap not venting properly, fan not coming on fast enough or slow pumping water pump due to impellers braking off.
Click to expand...

+1 on this, the gauges are designed to sit dead centre in the 'normal' (about 80 and 110 deg C) over that is outside normal operating range and the gauge will rise to the next step which equates to over-hot running.

Overheating is pretty much the only way to kill an M54 engine so I'd avoid driving personally. Micro leaks from the plastic header tank are a common cause of pressure and water loss both of which can lead to hot running and eventually a blown head gasket / cooked engine.
 
As your car is 16 yrs old there is also a good chance the radiator is gunked up with rust and silt...kind of depends if the coolant changes have been done on schedule and the right amount of antifreeze added. They are often neglected as people don’t see it as an important maintenance issue.
 
Just checked the coolant, it's red and appears clean as you'd expect. Level was halfway between full/low, so will top it up. I think I'll just give the whole system a going over, new pump & belts, fresh coolant, and the radiator... thinking of back flushing it, but is this the rightway to get it cleaned out?
 
Just a thought before you go to town on it....... I'd check that the temp sensor, gauge and fan are working correctly. Is the reading correct? Is the fan kicking in at the right temp? (check TIS for the value but I'm guessing about 98 dec C)
There is a way to get a temp reading via a hidden menu in the dash setting or you can connect an app like Torque pro via the OBD2 port.

Hidden menu - you want function 7
https://z4-forum.com/forum/viewtopic.php?t=15176
 
Change the expansion tank whilst you're in there. It will fail sooner or later anyway.
 
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