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Old 04-17-2012, 11:12 AM   #1
acroll80
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Default Phantom Overheating M20?

Hello to all E30 patrons! I Have been frustrated for some time now with a possible overheating issue with my e30. Let me give a quick background of my situation. I have a 1989 325i coup that I have owned for seven years now. This thing is a trooper to say the least, I bought it with a spun rod bearing and basically did an entire lower end rebuild at that time. I have done all repairs and maintenance myself. I just finished a timing belt replacement a few weeks ago. Ever since then my temperature gauge creeps up to 3/4 in any driving situation unless Im hauling ass on the freeway, or if my heat is on full blast, or if I jump the high speed aux fan. It will stay at the 1/2 mark doing those things. So let me say that I have replaced the fan clutch, water pump, t-stat, v-belt, coolant cap, cleaned the radiator inside and out.
The system holds pressure, it heats up at a normal pace, heat works as it should. Ive bled the system many times over with no sign of air left in the system. There is no traces of oil in the coolant, no coolant in the oil, no loss of coolant, the exhaust appears normal (no coolant burning).
All my replacement parts are from OEM suppliers so Im not assuming that they are faulty. the only thing I can think of now is that the gauge is lying to me, and or sensor is bad, but Ive never seen or heard of that happening.
Thanks to all that read this post and any help or suggestions would be greatly appreciated.
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Old 04-17-2012, 11:25 AM   #2
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you probably replaced it with a higher temp Tstat. Get a real temp gauge and take a look at what it's doing. If it's stable, you're fine. Stock gauges aren't linear FYI.
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Old 04-17-2012, 12:40 PM   #3
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I put in a 75 deg. t-stat, the previous was 80 deg. so if I monitor with another temp gauge what should the average temp be reading at normal operating conditions?
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Old 04-17-2012, 12:53 PM   #4
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usually I see cars sit anywhere from 180 to 190. Anything over 200 would be concerning. 210+ is dangerous. 250 is bad news bears. I've hit that a few times lol.
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Old 04-17-2012, 01:10 PM   #5
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Thanks for the insight! I will give that a try. I might change out the temp sensor and gauge as well just for good measure. I have a ton of them laying around.
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Old 04-18-2012, 10:25 PM   #6
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Try tightening hose clamps maybe there is a little leak getting in. Happened to me once. But got a lot hotter.
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Old 04-18-2012, 10:34 PM   #7
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My old 84 323i and Mum's E34 520i both had a similar ailment; the earth on the temp gauge itself. They both would flick from a regular half way point on the gauge to 3/4. I chased this phantom overheating in my 84 for ages until one day I saw the gauge flicking from 1/2 to 3/4 and back again.

Just sayin', make sure it REALLY is getting too hot before chasing this one. If you can, grab a laser temp temp gun and check it.
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Old 04-18-2012, 11:05 PM   #8
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^^^that
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Old 04-18-2012, 11:23 PM   #9
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make sure the pisser tube from the radiator to the tank is free flowing, when you rev it with the cap off you should be able to see a stream, if this is plugged the system won't function properly and will eventually overheat. when the gauge is above normal smack the piss out of the dash on that side of the cluster and see if it moves
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Old 04-18-2012, 11:29 PM   #10
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^^Haha, yep, Mum got the shits with hers and smacked the dash. It obediently went back to 1/2!
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