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I drive my '80 e12 to work every day and it's been running very well for several years. Yesterday the temp gauge barely raised off cold. I've pulled the connector and reseated it on the sender but no change. Any advice about the cause for this? I can't find info anywhere about what the resistance of the sender should be for hot or cold conditions. I'd like to test it before I order a replacement just so I have some idea that I'm on the right path.
Thanks,
John

The more I think of it, the more I imagine I've probably got a stuck thermostat. I'll drain the coolant down and replace it. thanks.

Can you see the coolant circulating in the reservoir ? Also check grounds

I've found a lot of times they get tired and what starts out as an 80 after a few years will be maybe a 70. I'm not sure of the mechanics of why, just that they often do. Not always, but often.

Thanks for the comments. I apologize for not replying sooner. The thermostat was failed catastrophically. The frame that wraps the thermal mechanism had split and bent back so it couldn't close at all. While I was at it I discovered that the water pump bearing was badly worn, so I dodged a bullet there. Got all new hoses while I was at it. Just got the hoses in last night but haven't filled it yet.

I have another question. When I installed the thermostat, I didn't notice if there was an arrow or mark on it and just stuck it in there. I've since seen comments that it should be oriented correctly. What's the issue with this? Have to decide whether I need to open it up and reinstall or if it's ok as is.

Thanks,
John

nerdorama wrote:Thanks for the comments. I apologize for not replying sooner. The thermostat was failed catastrophically. The frame that wraps the thermal mechanism had split and bent back so it couldn't close at all. While I was at it I discovered that the water pump bearing was badly worn, so I dodged a bullet there. Got all new hoses while I was at it. Just got the hoses in last night but haven't filled it yet.

I have another question. When I installed the thermostat, I didn't notice if there was an arrow or mark on it and just stuck it in there. I've since seen comments that it should be oriented correctly. What's the issue with this? Have to decide whether I need to open it up and reinstall or if it's ok as is.

Thanks,
John

Good to hear that you figured it out.

As for the orientation, I think there is a little hole in the separation plate that is intended to be at the top. I think it helps in bleeding the system. You know about bleeding it right? If I remember correctly, some thermostats don't have this hole. Hopefully someone can confirm what I am posting, as I am just going by memory.

Thanks Blaise,

I've heard of drilling your own small hole and placing it at the top to help with bleeding, but I didn't notice any hole in my new stat. Another guy that is highly experienced with cars says that it really doesn't matter as long as it isn't installed backwards. This, of course, assumes that it doesn't have the little hole for bleeding. Probably should have drilled my own small hole but I'm fighting the weather since I'm working in the driveway and just want to get it running again at this point.

Good think I bought another BMW a couple of weeks ago so I have something to get me to work. Got a '92 E34 wagon. I think it's going to be a nice car.

Thanks again,
John

It isn't just a hole. It's a threaded hole with a male threaded small bolt which is a bleeder plug. It should be on top.
Warm your car up real good, watching the temp. guage after filling with coolant.
Put your rear wheels at the lowest point in between your driveway & the street, which makes the front of your car higher than the rear.
Add coolant to the remote resevoir til it seeps outta the hole. Close it with the the bleeder bolt. Never go too tight. Run your motor til nice & warm; shut it down; loosen the bleeder til you hear air coming out. Add coolant til it seeps outta the hole again. Repeat. Just loosen the bleeder bolt, don't remove it. If you don't hear air, just pretend.
When nothing but coolant slowly seeps out, it's bled properly.
If this isn't done, it will eventually over-heat. Ask me how I know!
I got this from this forum. If I'm missing something, please interject.
Greg

Greg, all you said is true and correct, unfortunately they were talking about the thermostat itself having a hole on top and not the thermostat HOUSING that has the bleeder bolt on top.

DUHHH? DERRR!
Back under my small shadetree I go!
Thanx for keeping things straight. Maybe English really isn't my first language!
On another topic; are you going on the Vintage run?
It was fun hangin' with you & your family at whatever the name of that park is.

Greg, I was planning to go there but I am presently in the Philippines and wont be back for at least 2 months. Hope you guys meet up there and have a nice time. Yeah, we had a good time last year alright, I think it was Woodley Park and the kids still have the tennis balls you gave them.