bizzare temp gauge needle

[bingobill]

Problem with my 89 325 i convertible. Sometimes my temp gauge needle acts like its connected to the accelerator pedal. I press down and it goes right, let off and it returns to slightly above center. It will peg to the red hot side, or occasionly wiggle between center and right. If I hit a bump it wiggles. One day it remained dead center for the entire drive. At idle it remains at the 3/4 position, twitching slightly. The engine is not overheating, no fluids are lost, it seems fine.

Today something truly bizzare happened. It was staying far right, and pegging hot when I sped up. I had slightly less than a half tank of gas, so I pulled into a station and filled up. When I started back up the needle went slightly past dead center, stayed there, never moved, never twitched, and never wiggled when I hit a bump. Does anybody know what up with this? I would sincerely appeciate help. The engines not hot, but watching the needle is unnerving.

Thanks, Bill

[Jared at Pelican Parts]

Hmm, Im having this same problem right now. So far I have checked the following...

-Coolant temp sensor replaced
-Checked leads to sensor for continuity, they were fine

I noticed that if i hit the dash with my hand, it causes the needle to jump to the right position and stay there for a little bit, so i am not suspecting a loose ground somewhere, mostlikely on the gauge itself inside the cluster. The mounitng holes for the gauge also act as a ground, so it may simply be loose. I'll let you know what I find out...

[Dub-Dub]

I too had a similar jumpy gauge. I am assuming Jared just mis-typed when he said "... I am not suspecting a loose ground". My thought would be that it IS a loose ground.

Bingobill, does your's react to tapping on it?

[Jared at Pelican Parts]

oops, typo, sorry, I did meant to say i suspect a loose ground.

[Dub-Dub]

I too had a similar jumpy gauge. I am assuming Jared just mis-typed when he said "... I am not suspecting a loose ground". My thought would be that it IS a loose ground.

Bingobill, does your's react to tapping on it?

[bingobill]

Thanks for idea, I hoped a Louisiana tool kit, (fist, ball peen & 8lb sludge), would solve it or aid diagnosis. Nope , I tapped the gauge, slapped the dash, slapped on the expansion tank, no change. If it is a ground problem where do I chase that down?

[bm318ist]

if your temp guage moves like its possessed,unfortunately the problem is your dash cluster!It is a very common problem!Best bet is junkyard!!!!!

[Jared at Pelican Parts]

funny, I re-tightened the mounting nut on the gauge on the back of the cluster (it was loose) and the problem is now solved...

[bingobill]

If tightening worked for Jared, I'll try that this weekend. That solution would be less painful than a junkyard dash cluster. I liked the word choice "possessed", that fits fits the needle perfectly.

[Jared at Pelican Parts]

I think my car is at the very least a neutral possed spirit. I've owned cars in the past that i swear were out to go straight to the boneyard

[bingobill]

I may have been barking up the wrong tree. The temp guage was not loose at any connection, and the car actually is running hot. I discovered that putting the heater on brought the needle down to slightly above dead center, and it stays there. This is truly miserable in South Louisiana. I'm losing no fluid, and I placed cardboard under the car over night finding no drips. Since I have heat, do you suppose my problem is as simple as a new thermostat.

Bill '89 325i conv

[Jared at Pelican Parts]

It could be. i would replace the thermostat, and see if it makes any difference. On my 89, even in 100+ temps with the AC on, it never goes past 1/4 on the gauge.

[bingobill]

Appreciate the quick reply, and I did think of one other thing. I noticed fluid had come out of the plastic tank from the plastic hex nut that holds in the device with the float. It came out between the nut and the flat top piece, making me wonder if an "O" ring was missing. I'm giving a visual description, as I can't name the part, but it must be a coolant level sensor. This escape would tell me that my pressure is not being maintained. How important is this leak on the tank.

Bill

[Jared at Pelican Parts]

What tank?

[bingobill]

I agree, my descriptions are weak. Its the coolant reservoir (expansion tank), the device with the float is at the opposite end off the pressure cap. The leak occurs in the top of this float device where a plastic nut presses down upon a circular top piece. The nut presses down as it is turned. This is where I wonder if I should see an "O" ring, because if I really try to firm it, it slips and becomes loose. I think it hits the top of the tank and can go no farther down and jumps back up one thread.

Thanks

Bill

[Jared at Pelican Parts]

There is no O-ring on that nut. Sounds like you may have stripped the threads on either the tank or the nut. This might be responsible for bringing air into the system. Have you bled the sytem? Im startign to think you need to replace the thermostat.