Overheating Issue

[Salvo1]

I finally got my temp gauge working, the guy before mixed up the oil pressure sensor and the temp sensor plugs. Car ran a little above the middle which I thought was normal since I put the upgraded thermostat in. But randomly it would just start creeping up to the red but never get to the red. I realized my radiator cap gaskets had cuts so I bought a new one. Car ran a tad above the middle for a couple weeks then one day it started creeping again. Now everytime I drive it, it will get to the line between middle and red. MY question is what do you guys think it is? Possibility the gauge is just screwed up or what? Car has a new thermostat, just replaced the sensor in the block, did all the coolant hoses under the manifold, new OE replacement radiator.
And I thought it was odd when I shut the car off the gauge will drop to the middle instantly then start going down to where it sits when the car is off.

[Gerta]

Did you check to see if your mechanical fan clutch is working correctly? Is the belt to the water pump loose? Was the car coolant bled properly?

[vpilarrt]

I assume you know there are 2 temp sensors - 1 for the DME and 1 for the gauge. There rear one is for the gauge.

[Salvo1]

Forgot to mention the car has an electric fan, that thing guy before me wired to always be on high. So it's definitely pushing enough air. I have not checked the belt though. And sorry, yes I did replace both the temp sensors.

[Gerta]

If the belt is fine I would recommend rebleeding the system. Search the M42 thread for a recommended bleeding process.

[jntar]

This is going to sound stupid, but when it's creeped up close to red, smack the dash a few times just above the gauge. See if it jumps back to the middle.

[d_elson0]

^not dumb. My needle jumps around sometimes

[Salvo1]

I have bled the system numerous times, with the car on an incline and with the hear on full blast. I will try smacking the dash though because on a occasion it will jump around a little

[oldmann]

You need to find out what temp. of coolant actually is.

Thermometer works well for this, may not have an overheat issue at all.

[vivalegreg]

i tell you what my m42 temp gauge defffff acts funny most all e30s do...i replaced my thermostat, cleaned the corrosion out of the aluminium housing, changed the radiator with a brand new oem unit, and used bmw coolant (btw i have mess under intake mod done, very few coolant lines on my setup) and my gauge would be great for like a week or two, then it started to climb the more i drove the car (car had sat for two years before i bought it)

ive driven the car to tenneseee, 14 hours, and to montreal, 10 hours, never overheated, never had an issue, temp gauge danced like a fairy, i get mad, smack the shit out of cluster, it goes back to normal, then begins to dance again. time to take cluster out and check those connections

[isamemon]

sounds like a ground issue if it is jumping around.

my temp gauge reads high...at first was concerned. then compared to a friends m42 using a thermo gun on several engine locations and temps was same as his...or within a few degrees

[romeomike]

The fuel and temp gauges should have a 7mm brass nut on them. If that's missing or loose, that may very well be your issue (it certainly was with my dancing temp gauge). Unfortunately, you have to remove the instrument cluster to get at them.

[Salvo1]

Thank you everyone for the replies! Of course right after I made this the gauge stopped acting up. It did it tonight though and I smacked the cluster and the needle would hop around but never dropped back to normal. I'm sure I was freaking out over nothing. My cluster is still very easily accessible since I just had it out so I will make sure the ground on the back is tight before putting everything back together.