Please HELP Overheating - BMW Forum

e46323 · 06-12-2011, 01:26 AM

I have a overheating issue with a 2000 323i. All started after driving a 60 mile trip, was at the rest stop and noticed the gauage was in the red, I immediately powered off the car. I let the engine cool and topped of the coolant. I was able to get home with no issues. Over the next couple of day I noticed the car temp would rise if idle. I bled the system and had no problems other than no heat which told me a bac thermostat. I drove the car with no issues with the ts not generating heat. A week or so later the car started to heat up again, check under the hood and noticed the expansion tank was leaking. So I ordered a ts and expansion tank. Replaced both and after blleding the system the car ran fine at idle for 20+ minutes or so. Took the car for a test drive and noticed the temp gauage rising. Bled the system several more times. Still heating up and I noticed the top hose from the ts to the expansion tank has alot of pressure and very hot. Drained the radiator and expansion tank fluids and refilled with a good bleed. Took the car for a drive and the pressure built up and the hose blew off the ts. I am going to replace the hose and the expansion tank cap. I am wondering if the cap is causing the top hose pressure. Just to add, the bottom hose to the radiator is warm and not rock hard like the top hose. Not sure whats going on with this crazy car, any advise would be greately appreciated.

Forgot to add: there is no heat coming from the heater. No water in the oil or oil in the water. No smoking from the exhaust.

Thanks

drz · 06-12-2011, 01:52 AM

Is the electrical fan running at all? You can check really quickly in your garage/driveway by simply turning on the car and running the A/C. The electric fan should run whenever the A/C is running. If the fan is not running, then go ahead and check the fuse. If the fuse is fine, you may need a new fan. I forget, but I believe your car should also have the mechanical fan (let me know if it doesn't) that runs off the engine with a viscous clutch. If so, has that fan been replaced recently? Try giving it a little push -- it should spin with some resistance. If it spins freely, you need a new fan clutch.

e46323 · 06-12-2011, 02:04 AM

The fan is electric. I did check and after running idle for a few minutes the fan starts. I can take a rolled up piece of paper and stick in the fan and that confirms it was spinning. And my car does not have a fan clutch.

brettski · 06-12-2011, 04:06 AM

Welcome to the Werkz.

How long have you had the car for?
Was any work done prior to this issue arising?
Check that the small hose that runs between the radiator and the expansion tank isn't kinked or pinched at all. Park your car with the front elevated (on ramp or similar) and put the heater on flat out, start the car and let it idle in this position to see if you can purge any trapped air from the system. Is the water pump housing heating up fairly quickly?
I have heard of the water pump impeller separating from the shaft once it heats up and expands, and contracting back onto it when it cools down, not sure on you model though.

Jack Dabsy · 06-12-2011, 06:27 AM

As Brett says....
Lift the front of the car as high as you dare ! This will help to flush through the heater matrix which may have either an air-lock or even a slight blockage...
Other causes - faulty thermostat !
Is the lower hose noticeably cooler than the top hose?
DAZ

e46323 · 06-12-2011, 01:10 PM

Quote:

Originally Posted by Dabsy

As Brett says....
Lift the front of the car as high as you dare ! This will help to flush through the heater matrix which may have either an air-lock or even a slight blockage...
Other causes - faulty thermostat !
Is the lower hose noticeably cooler than the top hose?
DAZ

Dabsy,

The lower hose coming from the radiator is much cooler than the top hose and doesnt have near the amount of heat and pressure as the top hose.

e46323 · 06-12-2011, 01:13 PM

Quote:

Originally Posted by brettski

Welcome to the Werkz.

How long have you had the car for?
Was any work done prior to this issue arising?
Check that the small hose that runs between the radiator and the expansion tank isn't kinked or pinched at all. Park your car with the front elevated (on ramp or similar) and put the heater on flat out, start the car and let it idle in this position to see if you can purge any trapped air from the system. Is the water pump housing heating up fairly quickly?
I have heard of the water pump impeller separating from the shaft once it heats up and expands, and contracting back onto it when it cools down, not sure on you model though.

Brett,

I have owned the car for about 6 months. The previous owner had replaced the radiator, and t-stat along with various other parts that were due to be replaced. The previous owner was a mechanic and the car ran great for the past 6 months.

I have the car on some ramps when trying to bleed. I hope its just air, that top hose is hard as a rock and makes me wonder if my new t-stat is letting coolant flow.

brettski · 06-12-2011, 06:18 PM

Can you feel the waterpump & thermostat housings to see if they heat up reasonably quickly?
If you have a large airlock which effectively isolates the thermostat from the coolant it may cause this issue, some people go the the extent of drilling a small hole in the thermostat body (not mechanism) so that trapped air can be purged through by the water pump.