E36 coolant level--I say looks good, car says otherwise!: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Aug. 27, 2010 8:15 a.m. 1988RedT2 Reader

On the return leg of her 40-mile commute, my wife says the on-board display on her '97 328iC advised "check coolant level" or something to that effect. Temp gauge did not go above normal, which is exactly half-way on the gauge.

Today, I'm looking in the reservoir and the level is maybe an inch above the "cold" mark. When I unscrewed the cap, I heard a slight hissing, which would indicate to me that there aren't any significant leaks. All the hose connections and the rad itself appear to be in excellent condition. The PO had the water pump and thermostat replaced shortly before we got the car. I checked the oil, and all appears fine there.

So what's the deal? Bad sensor? Or do I have air in the system somehow?
Aug. 27, 2010 8:19 a.m. Giant Purple Snorklewacker SuperDork

Those sensors do go bad - they are pretty cheap too.
Aug. 27, 2010 8:28 a.m. 1slowcrx HalfDork

Giant Purple Snorklewacker wrote:

Those sensors do go bad - they are pretty cheap too.

yup, and yup....
Aug. 27, 2010 8:44 a.m. 1988RedT2 Reader

Hmmm. That wouldn't happen to be the sensor on the radiator just below and in front of the cap on the overflow, would it? That would be too easy!
Aug. 27, 2010 8:46 a.m. Giant Purple Snorklewacker SuperDork

1988RedT2 wrote:

Hmmm. That wouldn't happen to be the sensor on the radiator just below and in front of the cap on the overflow, would it? That would be too easy!

No, bottom of the overflow bottle. The one on the side is the axillary fan temp switch.
Aug. 27, 2010 8:48 a.m. stuart in mn SuperDork

Yeah, those BMW sensors in the overflow bottles can get flakey. Sometimes taking it out, cleaning it up and putting it back in can help. Also make sure the electrical connector is making a good connection.
Aug. 27, 2010 10:15 a.m. Ian F Dork

Yep. I replaced that sensor on the '97 M3 we had.

Imagine my joy when I found out the E30 version is just as prone to failure (the one in my car acts flakey). There times when I really think Bosch is worse than Lucas ever was...
Aug. 27, 2010 11:25 a.m. 1988RedT2 Reader

Figures. None of the parts houses around here have it in stock, and my Pelican Parts order shows up on my porch an hour ago.

That kind of brings me to my next task: Anybody know how these convertible top flap struts attach at the top? The bottom snaps on. Naturally, I can't see either end. Gonna be fun.
Aug. 27, 2010 11:33 a.m. novaderrik Reader

what happens if you just unplug it?
Aug. 27, 2010 11:46 a.m. Giant Purple Snorklewacker SuperDork

novaderrik wrote:

what happens if you just unplug it?

The warning stays lit. It needs a resistor across it to shut up.
Aug. 27, 2010 12:25 p.m. stuart in mn SuperDork

A jumper wire would work as well as a resistor, assuming it's the same sort of thing the older cars had; the sensor is just a float switch, so all you have to do is simulate a closed connection.
Aug. 27, 2010 12:58 p.m. 81gtv6 HalfDork

The same thing happened to my 9-3. I got 3 out of the local PnP for $1 and 2 of the three were good.
Aug. 27, 2010 1:01 p.m. motomoron Reader

It's only a float switch. The one on my M3 hangs up regularly, and that's 'cause the switch is in a swanky Zionsville aluminum expansion tank. Gently agitating the tank w/ a fist usually fixes the problem.
Aug. 27, 2010 1:03 p.m. 1988RedT2 Reader

I usually spring for new when it comes to sensors, but I might consider a picked part. Anybody know what years are the same as for my '97? I'm guessing any E36? Most likely I'll just wait and add it to my next order.

I'd rather not jumper it, since my wife drives the car and I think it's a good thing to have in case the coolant starts to disappear.

I got the convertible lid strut on just now. Not easy, by any stretch, but the next one will be a lot easier! Top works great now too!
Aug. 27, 2010 1:19 p.m. Ian F Dork

1988RedT2 wrote: I'd rather not jumper it, since my wife drives the car and I think it's a good thing to have in case the coolant starts to disappear.

Considering the aging plastic parts of the radiator, that's probably a prudent course of action.

One of the more annoying parts is having to drain the coolant from the tank to replace the sensor. At least on the E30, the sensor mounts on top.
Aug. 27, 2010 2:53 p.m. Otto_Maddox Reader

In reply to 1988RedT2:

Are you absolutely sure you have enough coolant in there at all times? I had a '98 323ic that would sometimes require just a splash of coolant to turn off the check coolant light.
Aug. 27, 2010 3:09 p.m. 1988RedT2 Reader

Otto_Maddox wrote:

In reply to 1988RedT2:

Are you absolutely sure you have enough coolant in there at all times? I had a '98 323ic that would sometimes require just a splash of coolant to turn off the check coolant light.

Pretty darn sure. The level when cold is at least an inch above the "cold" line on the overflow.