Running hot under load

[smahala1286]

My car has been running hot under constant load and wont rev above 6000rpm. It pulls fine up until around 5k then struggles to get up to 6k and wont go above that. If I'm cruising around on flat ground my temps stay right around 195-200°F but if I'm on a hill they will creep up to 210-215°F. I have fault code 1222 (lambda control #1) and have been trying to resolve that as well. Would a lean condition cause it to get that hot? I tested my fuel pressure and got 36psi at idle and 42psi with vacuum line removed, pinched the return line and it shot up to 50psi+. I have replaced the following parts within the past 1000miles:

Water pump
Thermostat
Coolant temp sensor
Fan clutch
Bleed the cooling system (at least 5 times)
Fuel Filter
Fuel Pressure Regulator
Spark Plugs
Distributor cap and rotor

Tonight I'm going to test the fuel pump flow, o2 sensor, and plug wires. Any advice would be helpful at this point. Thanks

[jlevie]

Check the WOT switch in the TPS. If it is bad the engine will sort of fall on it's face above 5k. A new TPS will fix that.

The 1222 code will most likely be intake leaks and/or a bad O2 sensor. The O2 sensor is a scheduled maintenance item with a replacement interval of 100k. If that applies, replace the sensor and have a smoke test run to find the leaks.

The fuel pressures lead me to believe that this is a 325i/is/ic. In which case the engine is running too hot all the time. With a stock thermostat installed and AC off the engine should stabilize (at idle or while driving) at 170-180F. You can test the thermostat to see if it is working properly, or just try a different thermostat. If no joy there, replace the radiator. Just because of the age of the also replace all the hoses, expansion tank, and cap. Then flush the cooling system. If, when changing the hoses and thermostat, I saw deposits in the passages I'd first flush with a detergent compound, and then flush with an oxalic compound.

Your statement about bleeding the car five times is a touch worrisome if you got a significant release of air each time. That would mean that the bleed procedure was flawed or that there is a head gasket leak the pumping air into the cooling system.

As an FYI: Bleed the system by:


1) Using ramps or a jack get the front of the car 1' or more higher than
the rear. That will make the radiator and bleed screw the highest point
on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of
the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max
temp and fan speed. Leaving the cap loose will prevent air that's still
in the system from causing a "coolant fountain" once the engine heats
up. Start the engine and allow it to warm up to operating temp. As it
warms up occasionally crack the bleed screw to release any air and top
up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500rpm for a few seconds
several times. Then crack the bleed until no more air is released. At
this point the heater should be throwing lots of hot air, which
indicates that the heater core is filled with coolant. You may have to
repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the
bleed for air. Over the next few days you may get very small amounts (a
few bubbles) of air out of the bleed screw.

[smahala1286]

Yes it is a 325is, do those fuel pressure readings seem low? This is my 2nd thermostat and it is opening properly. I bled the cooling system exactly the way you described at least 5 times. I'm using an autometer water temp gauge with the sending unit installed in the gauge cluster coolant temp sensor location. I have tested for vacuum leaks with carb cleaner and didn't find any although I didn't check the bitch-tube. I would like to smoke test it. I checked the TPS a little while back and it was working properly. I will check it again tonight though.

[jlevie]

The fuel pressures look right. You can have leaks at a number of places where carb cleaner won't work. Replace the O2 sensor and have a shop run a smoke test.

Are you getting air out when you bleed the system?

[smahala1286]

I will swap in a new o2 sensor and get a smoke test done. No i don't get any air out when bleeding the system, I did the first couple times but not since then. I'll report back after o2 and smoke test. Thanks for all your help Jim!