Ground Issue??

[anthonymax007]

So I replaced the temperature sensors on my M42. Now the temp gauge reads all the way to the left when the car is on, and when the key is turned to the ACC position the gauge reads all the way to the right. The oil light is on now too. It wasn't on before I replaced the sensors. Did I fry some electrical stuff? Maybe bump a ground? I'm 99% sure I plugged everything in correctly. Kinda stumped as this was a pretty routine maintenance job. Either way I'm not overly confident with anything electrical so I'm a bit nervous. Any ideas?

[bmwman91]

You probably swapped the oil pressure sender and temp sender plugs. I did that once myself.

[Jaxx_]

The oil light sensor turns on when the sensor grounds--the light goes out when you have like 5psi of pressure when the sensor opens(idle oil pressure). I'm not 100% sure on the coolant gauge, but I believe that ground is "cold."

It sounds like some weird floating ground issue, only because of the issue in ACC position. It's the cheapest and simplest thing to check and fix, though. You can temporarily ground the motor with some jumper cables from the negative terminal to something like the intake manifold(I hope it's obvious to not touch 12V from the battery or junction point to the motor or the body). If the symptoms improve you've found your issue.

You probably swapped the oil pressure sender and temp sender plugs. I did that once myself.

I like this idea too

[anthonymax007]

The sensors were swapped. Good call guys. The oil pressure light is no longer on, and the temp sensor is now operational when the car is started. Now on to my next problem...The car is overheating.

Before I changed the sensors the car would run hot at the stop lights. The gauge would start to creep to the 3/4 mark. I figured the sensors needed to be replaced, since they hadn't been replaced since my 3 years of owning the car. While I was replacing the sensors, I also changed the plastic coolant pipe while I was in there. I'm glad I did, it was corroded and falling apart. I put everything back together and bled the system.

This morning, after swapping the sensors I let the car get to temperature, and then went for a test drive. The needle is now showing that the car is overheating after I drive it for a bit.

I followed these directions to bleed the system:

http://www.esatclear.ie/~bpurcell/318ismaintenance.html#bleed

It seemed pretty fool proof. Now I'm more frustrated than anything.

[squidmaster]

When does your auxiliary fan come on?

[anthonymax007]

When does your auxiliary fan come on?

The PO had it set to always be on. I have not changed it at all.

[squidmaster]

Check under your oil cap for an opaque gunk.

[anthonymax007]

Here's a couple pictures. Engine is cold now though, FYI.

[squidmaster]

Just making sure no coolant was mixing with your oil.
Give it a try bleeding it again then.

[anthonymax007]

Just making sure no coolant was mixing with your oil.
Give it a try bleeding it again then.

Will do. Thanks again for the input and help fellas!

[anthonymax007]

Would you guys recommend running a compression check even though it doesn't look like there isn't a coolant/oil mixture under the oil cap?

[squidmaster]

Never hurts. I have a tester if you want to use it

[anthonymax007]

Ground Issue??

Never hurts. I have a tester if you want to use it

Thanks Jesse. I may text you this week.

On another note. I tried bleeding the coolant again this morning. I think I've officially given up haha. I'm sure I'm not following the instructions correctly. With the engine cold I make sure the coolant level is at the cold mark. Start the engine (no need to turn on the heat since my heater core is bypassed) and wait for the engine to come to temperature. As the top radiator hose gets warm, the level of coolant in the expansion tank rises. It rises nearly to the top. Is that normal? The level started at the "cold" line and gradually increases almost to the top. Also, I'm not noticing anything coming out of the bleed screw when I start to unscrew it. I unscrewed it probably about 5 turns or so, it was pretty loose.

Any ideas? I know the topic of bleeding the M42 coolant has been discussed many times, but I'm annoyed. Are the instructions linked in my first post incorrect? I feel like I shouldn't be leaving the cap off of the expansion tank. Wouldn't the system need to be closed for the air to successfully bleed out? The instructions don't mention replacing the cap until the end.

[romeomike]

If it hasn't been done already, consider changing the thermostat.