Coolant "Failure"

[elerner61]

The overheat->warped head->toasted engine phenomenon of BMW engines necessitating the 80K mile coolant system replacement (radiator, expansion tank, hoses, pump) has been something always on my mind with this, my first BMW.

The scenario below (from a recent Bimmerfest thread) struck me as proof positive that the coolant system replacement is an absolute "must do". Anyone out there feel differently?

I could see the a failure of an expansion tank having greater probability of being caught and not really causing a loss of fluid and engine damage.

The coolant temp sensor has to be immersed in coolant to give a reading of the coolant temp. I have an acquaintance who had a similar event to your Peugeot on his E36. The radiator failure happened at night just a couple blocks from his house so the coolant temp indicator never got a chance to start moving toward the red. He lost about half the coolant in the system overnight, and it had rained during the night so his driveway was already wet when he headed out for work in the morning so there was no way to see the coolant that had leaked out. When his engine quit about 15 miles down the road the first thing he looked at was the coolant temp indicator and not only was it not showing an overheat, it was actually showing the engine was still cold, but the engine was blazing hot. He'd lost so much coolant that the temp sensor was in air, not coolant, and it was getting no heat transferred into it. Completely toasted the motor.

[XMetal]

This isn't anything new on maintenance in general. Minus the radiator and expansion tank, I've always swap out everything else on the cooling system on all my past (non-BMW) cars at around the 80K/100K or 8 years range. The X5 is my only car that I had to also do the expansion tank at around 80K as I saw some seepage. Still on the original radiator at 12yr+/111k+ miles.

I'm about to do all the coolant hoses in a month or so on the ///M due to time more than mileage. Will leave everything as is for now.

[GuidoK]

The coolant temp sensor has to be immersed in coolant to give a reading of the coolant temp.

I dont think your z4m has a coolant temp readout? I think it's oil temp?

He lost about half the coolant in the system overnight, and it had rained during the night so his driveway was already wet when he headed out for work in the morning so there was no way to see the coolant that had leaked out.

First of all it must rain pretty hard to wash that much coolant away, and secondly your z4m has afaik a coolant level sensor, so you must look pretty hard the other way not to see that yellow light that has never lit before

Those are my thoughts on the technical aspect of that story in relation to a z4m.

But in the end it never hurts to swap out parts on a car if done correctly.
Maybe also take on the vanos, timing chain, camshafts plus bearings, valves and springs, oil pump, sump, timing chain tensioner, timing chain guides, crank seals, etc etc.
Can all fail with disastrous consequences.

I think replacing parts (at least these parts) prematurely is more a case of if they fail it may be on a bad moment (with all the hassle). Maybe if you have zero technical skills and never look at your instruments it's another story, but then you shouldnt be driving an 8 year old car. For some parts it's indeed somewhat a question of when (like the expension reservoir or a water pump), but the whole cooling system? Expensive exercise, the fan alone is $500 or so. (so I'm guessing $2k+ in parts or so?)

[dc_wright]

Originally Posted by GuidoK

I dont think your z4m has a coolant temp readout? I think it's oil temp?


First of all it must rain pretty hard to wash that much coolant away, and secondly your z4m has afaik a coolant level sensor, so you must look pretty hard the other way not to see that yellow light that has never lit before

Those are my thoughts on the technical aspect of that story in relation to a z4m.

But in the end it never hurts to swap out parts on a car if done correctly.
Maybe also take on the vanos, timing chain, camshafts plus bearings, valves and springs, oil pump, sump, timing chain tensioner, timing chain guides, crank seals, etc etc.
Can all fail with disastrous consequences.

I think replacing parts (at least these parts) prematurely is more a case of if they fail it may be on a bad moment (with all the hassle). Maybe if you have zero technical skills and never look at your instruments it's another story, but then you shouldnt be driving an 8 year old car. For some parts it's indeed somewhat a question of when (like the expension reservoir or a water pump), but the whole cooling system? Expensive exercise, the fan alone is $500 or so. (so I'm guessing $2k+ in parts or so?)

We're in Florida, so yes, it rained pretty hard LOL. During the Summer it's not unusual for us to get rain storms that drop a couple inches per hour. The hose connections on the radiator are probably the biggest risk. When the plastic gets brittle from age, micro cracks form at the base and initially they just seep/weep[ a bit of coolant. Then at some point one breaks off spontaneously and you lose a large amount of coolant in just a very short time.

[chickdr]

With the Z4M being the first car I have kept for 10yrs I am starting to think about this issue as well. My car is still under 20k and garaged at all times. Do I still replace the hoses and expansion tank? I have had the coolant changed every 2-3 yrs.

[XMetal]

Originally Posted by chickdr

With the Z4M being the first car I have kept for 10yrs I am starting to think about this issue as well. My car is still under 20k and garaged at all times. Do I still replace the hoses and expansion tank? I have had the coolant changed every 2-3 yrs.

Hoses for sure. Expansion tank can wait until you see some seepage or small leaks

[GuidoK]

I think the tank is also a well known failure point. That black glass fiber reinforced plastic is a bad materials choice imho.
It usually only leaks under pressure (haircrack between the fibers), so when you see that the engine has leaked (coolant on the plastic undertray), but cant find where it's coming from, look with a hot running engine.

[pokeybritches]

If you're concerned, you can always add a P3Cars vent gauge and pull the coolant temp from the OBD2 readout. You can add a cylinder head temp sender or additional coolant temp sensor. The P3Cars gauge has three 0-5V inputs that can be programmed and scaled.