Coolant Temp. sensor

Post your E12 technical questions and comments here. Please, no off-topic posts.

Moderators: Mike W., Pierre

User avatar
Mike W.
Posts: 2447
Joined: Wed Aug 30, 2006 12:12 am
Location: Sonoma County

Re: Coolant Temp. sensor

Post by Mike W. » Wed Apr 18, 2018 11:48 am

528i-1981 wrote:
Tue Apr 17, 2018 7:36 pm
Thanks guys.

As it turned out, I needed $4 worth of knurled nuts for the taillight covers in the trunk. They have them at bavauto.com, but I needed to spend $99 for the free shipping. It turns out that adding the thermostat cover and the temperature sensor brought me right to that free shipping. I can now tell my wife how thrifty I'm being.

Do you think a dab of antiseize on the bleed screw will do any good?
Absolutely. I always put anti seize on it, the thermostat cover bolts and the water pump bolts. It doesn't take much of a drip off a 40 year old casting to start rust.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter

User avatar
maybeillbuyit
Posts: 200
Joined: Mon Feb 17, 2014 12:26 am
Location: Vancouver BC

Re: Coolant Temp. sensor

Post by maybeillbuyit » Wed Apr 18, 2018 7:24 pm

OK thx Mike, I'm going to do that to the new cover I just installed.
1977 530i another project
1979 635csi Euro "project"
1987 635csi

User avatar
Lock
Posts: 355
Joined: Sun Oct 04, 2015 1:51 pm
Location: Washington state
Contact:

Re: Coolant Temp. sensor

Post by Lock » Sat Apr 21, 2018 2:47 pm

I got the new style bolt, I don't use anti-seize but I found it doesn't need to be done up very tight especially as it's seating to aluminum. I tighten mine to a little more than finger tight and it doesn't leak. Feels like it would break easy.
Last edited by Lock on Tue Apr 24, 2018 1:04 am, edited 2 times in total.
1979 528i 5-speed conversion G260/6, Motronic 1.3 179
1980 Honda CX-500

User avatar
528i-1981
Posts: 276
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: Coolant Temp. sensor

Post by 528i-1981 » Sun Apr 22, 2018 6:51 pm

If you ever order a new OEM cover again, order the bleed screw as well because the cover doesn't include the screw.
(oo=00=oo) Eric
1981 528i Manual

User avatar
maybeillbuyit
Posts: 200
Joined: Mon Feb 17, 2014 12:26 am
Location: Vancouver BC

Re: Coolant Temp. sensor

Post by maybeillbuyit » Mon Apr 23, 2018 11:37 am

528i-1981 wrote:
Sun Apr 22, 2018 6:51 pm
If you ever order a new OEM cover again, order the bleed screw as well because the cover doesn't include the screw.
^^ Right, I commented earlier that the bleed screw was included but I remember now the screw was purchased separately and I put them together and put the cover back in the box. A year later when I pulled it out I assumed it was a package deal.
1977 530i another project
1979 635csi Euro "project"
1987 635csi

User avatar
528i-1981
Posts: 276
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: Coolant Temp. sensor

Post by 528i-1981 » Tue Apr 24, 2018 4:49 am

Amazon Prime has a lot of BMW OEM stuff, and the shipping is always free, at least in the US. For one-off parts like a bleed screw, it's been a good resource.
(oo=00=oo) Eric
1981 528i Manual

User avatar
528i-1981
Posts: 276
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: Coolant Temp. sensor

Post by 528i-1981 » Sat Apr 28, 2018 8:05 am

Any recommendations on gasket sealant for the thermostat cover? Haynes refers to it as "jointing compound," which back in the day might be Indian Head or shellac, but Permatex 2 or even the spray-on might work OK.
(oo=00=oo) Eric
1981 528i Manual

User avatar
Lock
Posts: 355
Joined: Sun Oct 04, 2015 1:51 pm
Location: Washington state
Contact:

Re: Coolant Temp. sensor

Post by Lock » Sat Apr 28, 2018 2:29 pm

I used Elring Dirko Grey Sealing +300°C, I believe it's the recommended stuff, and less is more. When I took the thermostat cover and timing case off, PO had used so much that it was difficult to pull apart, tore the gaskets (inc. the head gasket) and took forever to clean, let alone the pieces that probably fell into the sump.
When I assembled, just the tiniest bead will seal fine. Don't understand why people pour it on joins like they're making a sandwich, it all just gets squeezed out the sides anyway.
1979 528i 5-speed conversion G260/6, Motronic 1.3 179
1980 Honda CX-500

User avatar
528i-1981
Posts: 276
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: Coolant Temp. sensor

Post by 528i-1981 » Sat Apr 28, 2018 7:10 pm

OK, great - thank you for the product and the advice. A dab'll do ya. I'm wondering what I'm going to find when I pull the cover off of mine. Do you know what's a good solvent for this stuff when dried? It's an RTV silicone-based product - have you tried a silicone dissolver like Permatex's?
(oo=00=oo) Eric
1981 528i Manual

User avatar
Mike W.
Posts: 2447
Joined: Wed Aug 30, 2006 12:12 am
Location: Sonoma County

Re: Coolant Temp. sensor

Post by Mike W. » Sun Apr 29, 2018 11:28 am

I like Permatex #3, Aviation as a light sealant. It's not going to fill big gaps, but helps prevent weepage and actually makes it easier to disassemble if need be later. Avoid RTV at all costs, it does work quite well, but only in very limited applications and not as a gasket dressing. Removing it? No great solutions, just time energy and much cursing at whomever applied it.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter

User avatar
maybeillbuyit
Posts: 200
Joined: Mon Feb 17, 2014 12:26 am
Location: Vancouver BC

Re: Coolant Temp. sensor

Post by maybeillbuyit » Sun Apr 29, 2018 12:19 pm

When I disassembled another BMW engine someone had used some sort of green sealer. It seemed like an epoxy. I used acetone and lacquer thinner and scotchbrite pads to scrub it off. It still took forever.

Mike when I installed my thermostat housing and cover I just used the BMW paper caskets. Would the Permatex #3 be better? Maybe I'll wait to see if it starts to weep.
1977 530i another project
1979 635csi Euro "project"
1987 635csi

User avatar
Mike W.
Posts: 2447
Joined: Wed Aug 30, 2006 12:12 am
Location: Sonoma County

Re: Coolant Temp. sensor

Post by Mike W. » Mon Apr 30, 2018 11:41 am

If it's installed and not leaking don't worry about it.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter

User avatar
528i-1981
Posts: 276
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: Coolant Temp. sensor

Post by 528i-1981 » Sat May 19, 2018 5:35 pm

Hello gents: replaced the thermostat, thermostat cover and temp sensor for the dash gauge today. Draining the radiator was a little worrisome, the coolant is very dark in color. I really don't know how long it's been since the last flush, so I'll need to keep an eye on the coolant after it's changed. The reservoir coolant looks normal, so perhaps there was just some buildup in the rad or maybe the core is oxidizing. Or, yeah, a head gasket or a cracked head or block but I'm not going there.

Question about the drain plug on the block - it's on there pretty good. I had a breaker bar and couldn't budge it. Will a hose flushing get it cleaned out good enough, or is it essential that I get the plug out to get any goo out of there?
(oo=00=oo) Eric
1981 528i Manual

User avatar
Mike W.
Posts: 2447
Joined: Wed Aug 30, 2006 12:12 am
Location: Sonoma County

Re: Coolant Temp. sensor

Post by Mike W. » Sun May 20, 2018 12:50 pm

I've always been able to get it out without too much trouble, excepting for the location of course. I have had more trouble digging thru the sediment to get it to drain. If it's that tough you might be better off not breaking it off, that would be a real problem.

No, it's not essential to get it out for a flush. Nice to do, but do the best you can and it'll be fine.
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter

User avatar
528i-1981
Posts: 276
Joined: Wed Feb 07, 2018 5:50 am
Location: Boston North Shore, MA

Re: Coolant Temp. sensor

Post by 528i-1981 » Sun May 20, 2018 8:18 pm

Thanks Mike, that's what I ended up doing. The thought of breaking that thing off made me err on the side of caution. She's all buttoned up and happy. It's nice having a working temp gauge and a functioning bleed screw with a hex head.

The engine's running great, and I swear it's smoother. I don't know why. Perhaps it was running too hot before the flush but I never knew because of the bad coolant temperature sensor. I guess I'll never know, but today the German Car Gods have been merciful.
(oo=00=oo) Eric
1981 528i Manual

Post Reply