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Discussion Starter · #1 ·
Hey,

I have a 1987 325 BMW with two pretty simple problems with easy remedies. However, they occured within 5 minutes of one another. So I am wondering if there is some causation or something else going on.

Today, at a drive-thru my radio cut out. Like a bonehead, I decided to turn off my car and restart it to see if the radio would work. Of course, when I tried to restart it the battery was dead.

So I got a jump and went on my way to get a new battery when I notice the car is overheating. I check the fluids and while the coolant is a little low, nothing appears out of the ordinary. I also checked and the belt off the waterpump which was turning and the heat which blasted inside the car. I just replaced the thermostat and thermostat housing and both hoses coming off the thermostat are the same temp.

Is this just that my battery died and I had cooling problems within 5 minutes of each other? Or is there something about the electrical problem that would cause the cooling problem?
Thanks,
Rich
 

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D'oh, You Kids!
1984 633CSi, 1985 635CSi, 1985 325e, 1987 325is, 1993 325is, 1995 318is, 1995 M3, 2003 F150
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Is it still showing overheat with a new battery installed? The temp gauge is electronic, and will show all sorts of wonky readings when the battery is low. Same with the gas gauge.
 

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old car nut
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A running car with a faulty battery should still run the radio. I think you have an alternator problem. Better to replace its voltage regulator first unless its less than 5 years old then charge the battery overnight then test the battery and alternator on the car. If you put a volt gauge across the battery terminals you should see something above 13 volts car running and no less than 12.5 car off.
 

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Discussion Starter · #6 ·
It wasn't a problem with the gauges. When I stopped the engine was actually running hot.

Also if it's the alternator, does anybody have a good set of instructions on replacing the voltage regulator in the alternator? It's currently on the side of the road in D.C. and I need to fix this quick.

Thanks for the help!
 

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old car nut
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The voltage regulator is very simple, remove the air cleaner box: 2 nuts a clamp and 2 wiring connectors. On the back of the alternator are 2 screws holding the regulator onto the alternator case. remove 2 screws pull out regulator insert new, replace 2 screws. I would look very closely at the alternator belt for being too loose first though. A loose belt will cause the water pump pulley to slip causing the engine to run hot and it will cause low alternator output which will cause a weak, dead battery. If you can rotate the alt pulley by hand, the belt's too loose.
 

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D'oh, You Kids!
1984 633CSi, 1985 635CSi, 1985 325e, 1987 325is, 1993 325is, 1995 318is, 1995 M3, 2003 F150
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31,079 Posts
+1 to that^, but disconnect the battery first.
 

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livin large
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Its its running hot then start with the simple things. If its hot all the time, highway and city driving, then tstat. If just city, then fan clutch. Im sure the electrical issue and the heating issue are seperate

Sent from my Garminfone using Bimmer App
 

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Discussion Starter · #10 ·
I finally got around to taking a look at it today.

First, to my amazement after sitting for a couple of days the battery had accrued enough charge to turn over the engine. So the battery was fine.

After that revelation, I checked the alternator belt. It was a little lose and a little glazed and so I replaced it. After that I started it up and it drove perfectly for an hour. The electric problem was gone and it stayed safely at operating temperature the whole time. I am guessing it was just the alternator belt, but I will make sure to keep an eye on it.

Thanks for all the help with the diagnosis, it was extremely helpful.


Rich
 
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