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Old 12-02-2011, 09:00 PM
robbcarlos robbcarlos is offline
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Mein Auto: 1998 Z3 Roadster 2.8
Unhappy Z3 Over heating/no heat coming through vents inside the cabin

Monday morning I turned on my car to warm up, as usual because it was a cold morning, I turned the fan on to 2 and turned the heat up all the wasy......10 minutes later I went out to leave and i noticed steam coming from the front of the hood. When I got into the car it was reading hot on the temp gauge. So I let the car cool drained the coolant and removed the parts necessary to check the thermostat. The thermostat was completely destroyed in a way that i had never seen a thermostat go bad. It had broken at its seams. Like it had blown apart. so I replaced the thermostat, installed a new water pump while i was already in there. When I put it all back together...including the coolant and bleeding according to BMW procedure, the engine continued to overheat. I then realized after inspecting the radiator that it had two cracks on the top where i could see coolant bubbling out. I removed the radiator, took it to a radiator shop to see what could be done and unfortunately it was beyond repair and was only blowing 50% of its capacity. I bought a new one....OEM exact fit.....installed it, drained and flushed the engine block until flow was clear and draining from all orifices. The first flush produced little flow.....the second flush was higher pressure and then flow was heavy from all orifices.. I then put everything back together....filled the system with coolant, bled it according to specs....Started the engine and when it got to normal operating temperature.......i turned off the car....let it cool completely and topped off coolant as specified. After a good 15 to 20 minutes the cars temperature remained at the half way mark as it did before these problems started. The problem here is that there is no heat coming from the vents inside the cabin when I have the heat at full and the fan on. This has kept me very cautious because I know that there should be heat coming from the vents when the car is warmed up to operating temperature. But there is no heat. I took it for a short drive and it maintained the temperature but was a nervous wreck that it would suddenly jump to hot. I have been working on this car since monday and before was completely secure with my z3...now..i have grown skeptical and would like the same confidence I had before.. Anyone out there with any suggestions as to what could be going on? Would really appreciate it.....close to the end of my rope and fresh out of ideas! Thanks!!
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Old 12-03-2011, 06:01 AM
dougmcintyre dougmcintyre is offline
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Location: Chapel Hill, NC
Join Date: Sep 2009
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Mein Auto: 2000 M Coupe, 1997 318ti
No heat is usually caused by air in the cooling system or a broken Bowden cable. Assuming last weekend the heat was working correctly, I'd bet there is still air in the cooling system. Just seems too unlikely the Bowden cable happened to break at the same time.

http://www.bimmerfest.com/forums/sho...t=bowden+cable covers the Bowden cable

Here's the proper bleeding procedure.
Originally Posted by aba4430 View Post
First of all, I recommend bleeding the system. Drive your car up on ramps (optional). shut it off, loosen the bleed screw, turn heater control all the way up, remove expansion tank cap, start it back up (does not necessarily have to be in this order) and see what happens. Your coolant level has to be at @ the cold mark on the expansion tank. It might take a few minutes to reflect the true level if the car is cold. As coolant level (or if it) drops, continue to add coolant to the expansion tank. At some point, you should start to see bubbles coming out of the bleeder screw. Wait till there are no more bubbles coming out, ensuring that the tank is not low. Close bleeder screw and adjust level in tank to roughly the cold mark, and place the tank cap back on. I have found that accelerating the engine to 1500 to 2000 rpms helps with the bleeding process.

Make sure you watch the temperature periodically; you do not want the car to overheat. This is possible if you have compromised the head gasket due to your "overheating" incident.

If the bleeding is satisfactory, drive around and watch the temps. Next time prior to using the car, check the coolant level, and add to the cold mark as needed. Thereafter, watch the car over the next several days for any anomalies. Good luck.

PS. Can you tell me the P/N of the hose that ruptured. I had 8 or 9 hoses, but replaced only 4 when I redid my cooling system < 3 weeks ago. Will take care of the balance at some other time. A few of them might be a pain to replace. Another issue, replace components associated with your cooling (including belt drive) system. It is cheap insurance.
Good luck. And welcome to the forum.

Last edited by dougmcintyre; 12-03-2011 at 12:33 PM.
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Old 12-03-2011, 06:46 AM
robbcarlos robbcarlos is offline
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Location: Texas
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Mein Auto: 1998 Z3 Roadster 2.8
Thanks Doug! This morning I jumped in the car to go get gas down the road and another errand....there is now heat blowing when i turn on the heater as there was not last night.......i followed the bleeding procedures that you outlined yesterday until there were no bubbles coming out of the bleed screw...It seems to be maintaining the temp fine at this point....the hoses when I touch them are warm/hot and am not able to squeeze them as easily as i could yesterday. I will most likely, once the car cools down, try and bleed the system again to make sure there are no air pockets in the system....Ill keep you posted! Thanks for the info.....REALLY appreciated!
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Old 12-03-2011, 11:36 AM
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Steamer Steamer is offline
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Mein Auto: 2011 550i, 00 M Roadster
I followed the same procedure that Doug posted. It worked well, except the first time, I never got any heat out of the heater, I kept trying to get more air out and all I got was fluid. I put it down and as soon as I started driving, heat poured from the heater. I then took it back home, let it cool down and did a system bleed again. The following day I had to add a small amount of coolant to the resevour, but nothing since and it is working as it should. My thermostat also went bad which is a bit weird for only 42K on the car..
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