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Old 08-25-2016, 01:27 AM   #1
BaronVonDrewsuf
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M10 Strangely Overheating

Just purchased a 85 318i e30 with the m10 engine. Beautiful candy apple red with the chrome bumper. In amazing shape and only 90,000km. Few things I plan on doing but for the most part it's all good.

Unfortunately after having it for a week I noticed something odd. It was slightly overheating. Original owner said he replaced the water pump and fan before selling. And he never noticed it overheating. The thing is it only slightly overheats in very specific circumstances.

Driving on city roads stop and go for over 20 minutes, doesn't overheat. On the motorway it doesn't overheat, in fact stays just slightly cold. But when I get off the motorway after driving for about 10 minutes it starts to creep up to the 3/4 mark. Then as I get going it goes back down. And then just jumps between 1/2 and 3/4 until I get home. However if the heat is on (always hot, never cold) it will always stay dead center.

Thought maybe just some maintenance would fix it. Changed the oil and had the radiator flushed. the guy who flushed it said it all looked good. Yet didn't make a difference.

Thought the thermostat was bad so I replaced that, topped up my coolant and bled the system by running it with the cap off for about half an hour. Yet still the same thing was happening.

Finally thought I'd bring it to a BMW specialist and he ran some tests and looked it over. He did a CO test to check for cracks in the gasket, came back fine. He replaced the fan clutch as he said it was sticking, and replaced the thermostat as well. After that he ran some tests and said it was all good and stopped overheating. Took it home and on the way home did the same thing, overheating! Still getting up to that 3/4 mark.

I am at a loss, any ideas? Spent too much money already and nothing makes sense. Could it be the temperature sensor? Or the gauge? Or is this normal for this car? The only other thing I've done so far was change the stereo. I feel like I'm going crazy, sorry about the long post, just in need of some help. Thanks.
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Old 08-26-2016, 04:49 AM   #2
packratbimmer
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fan clutch
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Old 08-27-2016, 11:40 PM   #3
TobyB
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Well, you replaced everything I'd try.
Test the fan clutch- look up the 'rolled up newspaper' test.
Also, do you have a shroud around the fan? Those help a LOT, and sometimes get pulled off and not replaced.

It really does sound like it's not getting enough airflow/cooling at idle.

I guess it COULD be the radiator's silted/clogged/coated up enough it's not
cooling well enough.
Get one of those infrared heat guns, and try shooting the lower hose. If it's getting hot
(over 60c) then either you don't have enough air, or enough radiator.
If it stays cool, you might have a waterpump problem. Maybe a crappy cheap one,
or the wrong one?
You can also shoot the thermostat, but it's probably going to be 'all hot'.

Hmmm...

t
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Old 08-31-2016, 12:12 AM   #4
kevinxu19950601
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Quote:
Originally Posted by BaronVonDrewsuf View Post
Just purchased a 85 318i e30 with the m10 engine. Beautiful candy apple red with the chrome bumper. In amazing shape and only 90,000km. Few things I plan on doing but for the most part it's all good.

Unfortunately after having it for a week I noticed something odd. It was slightly overheating. Original owner said he replaced the water pump and fan before selling. And he never noticed it overheating. The thing is it only slightly overheats in very specific circumstances.

Driving on city roads stop and go for over 20 minutes, doesn't overheat. On the motorway it doesn't overheat, in fact stays just slightly cold. But when I get off the motorway after driving for about 10 minutes it starts to creep up to the 3/4 mark. Then as I get going it goes back down. And then just jumps between 1/2 and 3/4 until I get home. However if the heat is on (always hot, never cold) it will always stay dead center.

Thought maybe just some maintenance would fix it. Changed the oil and had the radiator flushed. the guy who flushed it said it all looked good. Yet didn't make a difference.

Thought the thermostat was bad so I replaced that, topped up my coolant and bled the system by running it with the cap off for about half an hour. Yet still the same thing was happening.

Finally thought I'd bring it to a BMW specialist and he ran some tests and looked it over. He did a CO test to check for cracks in the gasket, came back fine. He replaced the fan clutch as he said it was sticking, and replaced the thermostat as well. After that he ran some tests and said it was all good and stopped overheating. Took it home and on the way home did the same thing, overheating! Still getting up to that 3/4 mark.

I am at a loss, any ideas? Spent too much money already and nothing makes sense. Could it be the temperature sensor? Or the gauge? Or is this normal for this car? The only other thing I've done so far was change the stereo. I feel like I'm going crazy, sorry about the long post, just in need of some help. Thanks.
hi is it possible if you put up a picture of your engine bay? also what is your spark plug order on the ccw or cw rotor cap?
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Old 09-02-2016, 02:20 AM   #5
BaronVonDrewsuf
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Well brought the car back to my mechanic. He looked at it for another week. Replaced fan clutch again as well as looked at waterp pump and thermostat and everything else. Did a pressure test which came back good. And... Still doing the same thing. Overheating after driving on the motorway. I'll post a picture of my engine bay tomorrow.
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Old 09-03-2016, 11:23 AM   #6
TobyB
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It sure reads like the thermostat- I've had a few bad ones, but 2 in a row seems unlikely.

I vote radiator, as a wild- assed internet guess.

But checking the lower radiator hose temp would tell you yeah or nay on that.

t
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Old 09-06-2016, 09:58 PM   #7
BaronVonDrewsuf
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Well, it's been resolved. Thanks for your help everyone. Found an awesome mechanic, German guy who specifically works ok older BMWs, talked about my problems and at first he thought it may have been my gauge cluster, he took it apart, replaced some bulbs while he was at it, and found out that wasn't the problem, but it was actually my radiator. Small blockage that was causing the occasional overheat. Took him 30 minutes to figure it out.
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Old 09-12-2016, 11:52 PM   #8
TobyB
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Called it!

hee

t
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