sporadic overheating

[arucano]

The shop I use was asked to go through the cooling system before I went to O'fest at Laguna Seca. The following items were replaced in several phases, paying several times for some of the same work:
replaced Radiator, Fan, Fan Clutch, Electric (condenser) fan, radiator shroud, thermostat, expansion tank, water pump. Cooling system was pressure tested.
The car does not overheat if started and left to idle. I drove the car home and it got hot as I reached home (10 miles).
The 4 days I drove the car and checked the coolant level every morning and have not lost any coolant. Yesterday, it started to "overheat" again. i have been monitoring the coolant temperature with the OBDII scanner (I use a C110). The radiator outlet temperature remains fairly constant and the OBDII temp swings between 190 and 225 when driving slow and to a lesser degree on the highway. When it goes bonkers, it swings up to 235/240 and will drop down to 180 at times.

just performed some further checks. The radiator outlet temperature increases to 200F when the engine run too hot. The electric fan is running at full speed when it gets that high. I cant find my remote temp gun to verify these temperatures however.

EDIT: 2003 530I sport standard with 225000 miles


I am out of ideas and am seeking your wisdom.

Chet

[Dmitry at Pelican Parts]

What year and model is your 5-series? It'll be easier to point you in the right direction with that info.


-Dmitry

[arucano]

Originally Posted by Dmitry at Pelican Parts

What year and model is your 5-series? It'll be easier to point you in the right direction with that info.

-Dmitry

Sorry i missed that. It's 2003 530I standards sport.

Chet

[CPC]

These cars have quite finicky cooling systems to say the least.
1) Are you getting heat consistently in the car?
2) Any noisy or worn out belts?
3) Is your outside temperature probe reading temparture correctly? The outside temp has a feedback impact on coooling/heating system (ECM).
It is possible that you have an airlock in the cooling system. If your system is registering transiant over-heating but there is no coolant leak (which occurs through the overflow when coolant becomes over pressuraised or overfilled). This can still show coolant levels OK etc. The bleeding can be tricky in these cars. I found the best is to bleed air out when car is cold. loosen the bleed valve on top of expension tank. Open expension tank and fill premixed coolant until you see coolant coming out of bleed valve without bubbles. Then close the bleed valve, then the cap. Run car with heater on max until car reaches operating temprature.
Also, as the car has an electric thermostat, check that the electrical plug on the thermostat is well seated. It is possible (remote chance) that you have a faulty thermostat. Good luck!

[arucano]

It is possible that you have an airlock in the cooling system. If your system is registering transiant over-heating but there is no coolant leak (which occurs through the overflow when coolant becomes over pressuraised or overfilled). This can still show coolant levels OK etc. The bleeding can be tricky in these cars. I found the best is to bleed air out when car is cold. loosen the bleed valve on top of expension tank. Open expension tank and fill premixed coolant until you see coolant coming out of bleed valve without bubbles. Then close the bleed valve, then the cap. Run car with heater on max until car reaches operating temprature.
Also, as the car has an electric thermostat, check that the electrical plug on the thermostat is well seated. It is possible (remote chance) that you have a faulty thermostat. Good luck![/QUOTE]

1 If I turn the heater on, the heat is consistent
2 The belts and tensioners have been changed and are in good condition
3 The outside temperature indication is correct.
I have checked the electrical connection to the thermostat and it is seated correctly. I will try bleeding the system as you recommend. I have also bought an IR temperature gauge to do a temperature scan. I will update the results later today.

Thanks

[arucano]

After thoroughly bleeding the system the temperature appears to have stabilized. I drove it 50 miles to work this morning monitoring the temperature via the OBDII port.
The coolant is clean, so I hope that confirms that I do not have a head gasket problem. I did not see any bubbles in the coolant after driving about 10 miles yesterday.
Next test is the 50 mile commute home.

[Dmitry at Pelican Parts]

Originally Posted by arucano

After thoroughly bleeding the system the temperature appears to have stabilized. I drove it 50 miles to work this morning monitoring the temperature via the OBDII port.
The coolant is clean, so I hope that confirms that I do not have a head gasket problem. I did not see any bubbles in the coolant after driving about 10 miles yesterday.
Next test is the 50 mile commute home.

Let us know how it goes and if any of the issues come back. For reference, I've included a link to our tech articles on the E39 in case you need to research anything else.

BMW 5-Series E39 (1996-2003) DIY Technical Articles - Pelican Parts


-Dmitry

[arucano]

Bleeding the system resolved the problem. The temperature is stable within a few degrees. I mistakenly ass-u-me-d that the shop had done that correctly. The plus side is that my cooling system should be good for the next few miles... Thanks for the input and feedback

[CPC]

Happy it worked out for you without complication (or additional cost).