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E36 (1991 - 1999)
The E36 chassis 3-Series BMW was a huge hit among driving enthusiasts from the first moment the car hit the pavement. The E36 won numerous awards over the years it was produced and is still a favorite of many BMW enthusiasts to this day! -- View the E36 Wiki

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  #1  
Old 10-01-2012, 11:10 AM
Bimmer68 Bimmer68 is offline
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Help Please!!

Good morning...I have a 97 BMW 328i. Sporadically it overheats when driving mostly when I have the AC on. If I leave the heater on low the needle stays in the middle. I've checked for leakage - None -, I've checked the top hose to see if the thermostate is operating. It's warm to touch. I've checked the clutch, pump, and belts and all seem okay. Just recently, I ran the car in park w/o the air on for 15 minutes and then 10 minutes with the AC on and then turned it off for another 10 minutes. Needle stayed in the center. Also, I've bleeded the radiator correctly. It's crazy and over heats only when driven. One other thing, I've taken the cap off the radiator, started the car to see if the radator collant is ciculating. It doesn't seem to be doing anything. Calm as could be. Could this be my problem? Please help. What is causing the car to overheat only when driven?
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  #2  
Old 10-02-2012, 06:29 AM
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Sounds like you still have air in your coolant or not enough coolant in your car. Try bleeding it again and keep adding coolant until it streams out of the over flow screw.
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  #3  
Old 10-02-2012, 06:52 AM
gotrice415 gotrice415 is offline
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Just as Peels mentioned above. Make sure the coolant system is completely bled. Typically in our dealership I tell all my apprentices to open the bleeder screw on the top, add coolant mixture until water comes out. Tighten the screw and with a screw. Mistakes that most people make is top off coolant with the car running and or engine hot.

If after bleeding car still overheats with AC on. Make sure the electric fan comes on. Not all E36's came with electric fans. But if your does the fan should turn on with AC on. Then make sure that the fan clutch is operating. When engine is cold the fan clutch should have slight resistance then more resistance once the engine heats up. The oil within the clutch will get "thicker" to engage as the temp increases.

Lastly, as you may know. Water pumps are a soar spot within the cooling system. Depending on when and where the water pump was replaced, you could have a plastic impeller that has separated. To check flow open the radiator cap WHEN COLD and you should see a steady stream of coolant flowing within the tank.

Good Luck!
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Old 10-02-2012, 07:33 AM
Bimmer68 Bimmer68 is offline
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Thank you for the reply! Yes, I did bleed the coolant out of the radiator as you have instructed. The car still overheats! And yes, the electric fan does turn on but only when the AC is operating. I read somewhere that the electric fan will turn on w/o the AC being on if it reaches a certain temperature. It definetely doesn't do that so not certain if that is acccurate information or not. My next step is that I've completely drained all coolant from the block and radiator. I'm going to tackle the coolant pump. Unfortunetely, I can't get the fan nut to break seal which I've been through before. On my other car I had to completely remove the radiator then take out the pump by removing the four bolts. Once out, I put it on a vise and torch the bolt and was able to get it freed. It's a pain and I destroyed the clutch. Any other suggestions on getting this bolt off? Let me know if my next step (removing the pump) is the right direction to take. I appreciate all of your help.
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  #5  
Old 10-02-2012, 08:01 AM
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If you turn your heater on, does heat come on? I've always had to have my heater on max with the circulation button on in order to bleed my system.

Have you replaced you tstat?
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Last edited by peels'bimmer; 10-02-2012 at 08:03 AM.
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Old 10-02-2012, 08:20 AM
Bimmer68 Bimmer68 is offline
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Yes, I did have the heater on and when I was bleeding the system it overflowed out of the bleed screw and once all the bubbles were gone I closed it off. The ran the car for awhile and topped off as needed. As for the Tstat, through my research for testing purposes it says to run the car until the needle is center. Once the needle hits the center location feel the top radiator hose. If it's warm to touch the Tstat is working properly. If there's any cool spots they say the Tstat is not working properly. I dfidn't have any cool spots. Being that I'm pulling at the pump though I might as well replace the Tstat also. Any thoughts? Appreciate your help.
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Old 10-02-2012, 09:04 AM
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SOunds like you are on the right path. Have you check for any leaks? Not just on the upper and lower radiator hose. But the one that is right under the manifold. I once had a small hole in that hose and the car would over heat from time to time. The hole was so small, that coolant didn't actually come out. It was just big enough to allow air in and change the pressure. If you are replacing the water pump, I would replace the tstat as well. Personally, I would get the metal water pump. Some will say stick with the plastic oem style pump.
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Old 10-02-2012, 09:10 AM
Bimmer68 Bimmer68 is offline
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Yes, I did check for leaks but didn't look under the manifold. Thanks for the tip. I'll check that out. As for the pump with the metal rather than plastic. Absolutely, I'll go with the metal. I'll keep you posted. Let me know if you have any tips on how to get the fan bolt off. Thanks again!
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Old 10-02-2012, 09:37 AM
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I used a 32mm open wrench, a rubber mallet and a long flat head screw driver. It's be awhile since I did this, so I may be a little off on the steps. I used the driver and wedge it into the water pump so the fan won't move much. Then with the mallet, give it a nice hard hit. Remember, it is reverse thread.
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you never notice how ugly something is until you get rid of it
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That's what my first wife said.
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  #10  
Old 10-02-2012, 04:34 PM
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dc_wright dc_wright is offline
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Long handle 32mm open end wrench and a 32 oz brass hammer is what is used. The metal on metal puts some vibration into the nut that helps break it loose. Also be sure to remember the nut is LEFT HAND thread so you go clockwise to loosen it.
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Old 10-03-2012, 12:29 PM
Bimmer68 Bimmer68 is offline
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Thank you! Wish me luck....I'll tackle it tonight.
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  #12  
Old 10-04-2012, 01:36 PM
Bimmer68 Bimmer68 is offline
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Okay, update...I did get the fan bolt off by using the hammer. Took the tstat out but it was stuck so I had to pry it off with a flat head and it was broken where it connects to the round face plate. I don't know if it was already broken or I did it. Took the coolant pump out and it has the metal blades and looks perfectly okay. As for the clutch, the part that faces towards the radiator was caked with grease build up. Is this normal? Do you think I need to replace it?
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Old 10-04-2012, 01:42 PM
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ZeGerman ZeGerman is offline
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1) Sometimes t-stats just get stuck in there - it isn't that uncommon. Mine did exactly the same thing, so I had to rip it out with some pliers.

2) I'd recommend replacing the water pump with a new one while you have it opened up. Even if the impeller looks good, the bearings are known to fail between 75-100k miles. And you would definitely want a new gasket anyway.

3) Grease/grime buildup on the fan clutch is somewhat typical. I would recommend thoroughly cleaning it, and then check it for functionality afterward by performing the "newspaper test". This test if performed by lightly rolling a section of newspaper, starting the car, and gently putting the end of the newspaper onto the fan while the engine is idling. If the fan stops spinning easily, your fan clutch is worn out. If it keeps rotating despite you putting pressure on it with the newspaper, the fan clutch is still good.
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Last edited by ZeGerman; 10-04-2012 at 01:45 PM.
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  #14  
Old 10-04-2012, 01:45 PM
Bimmer68 Bimmer68 is offline
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Great...Thank you! Will do the replacement and the test. Didn't know the bearing wear out over time. It is kind of stiff when I try to spin it.
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