24v swap finally done... bouncing temp gauge

[87e30]

I have drive the car for the last couple days and the temp gauge has been fine. So I embarked on the long (35 minute) drive out to school. On the freeway (first 10-15 minutes) the temp gauge was fine, sitting right in the middle. When I pulled off the temp gauge started bouncing, so I turned on the electric fan. The temp gauge continued to bounce around, sometimes bouncing up and pegging red, rarely coming back down to middle. When I got on it the temp gauge stayed at middle, then went back to hot. Pulled over a couple times, tried to never let it stay at hot. On oddity, brake pedal lost all assist at one point, let the car sit for 10 minutes and it was fine after. (yes, vac line is hooked up to booster, I checked)

Now I found one guy claiming that a weird vac leak was causing his gauge to go crazy. I do have a vac leak (at the moment) from the crank case vent tube.

I have bled the coolant several times (driven, cooled, opened, filled, repeat) but it could still have air in the system.

The gauge itself could need the ground nut tightened.

Any other input? Really hope the car isn't actually over heating and the gauge is to blame - non bled system seems likely as does a loose ground but looking for opinions.

[MattM]

was the engine actually getting hotter? or was it just the guage, 2 totally seperate things.

if the engine was indeed going into the red zone your coolant would be boiling and you would be able to hear it doing so when you turn the engine off.

if this is the case, i would start with a new thermostat, yours may be sticky.

If its just the guage, go over all your wiring, check all grounds, and if it comes to it replace the temp sensor.... lol

[87e30]

was the engine actually getting hotter? or was it just the guage, 2 totally seperate things.

if the engine was indeed going into the red zone your coolant would be boiling and you would be able to hear it doing so when you turn the engine off.

if this is the case, i would start with a new thermostat, yours may be sticky.

If its just the guage, go over all your wiring, check all grounds, and if it comes to it replace the temp sensor.... lol

I don't know if the engine was actually over heating. It started doing weird things, like it was harder to start and it almost died once, but I think that was A) lights/fan were on so starting was harder and B) 2.5 chip learning to run a 2.8.

I didn't notice boiling coolant or the like, but tried to keep it out of the danger zone to the best of my ability.

Thermostat and water pump are new. Just checked the coolant level and it seems fine, as does the ground nut on the cluster. Also, didn't notice any air leaving the system when I took the cap off. (engine was relatively cool but not cold)

Still seemed to over heat though, drove it home about 5 minutes from the alignment shop and as I was parallel parking noticed the gauge go up to 3/4. It was also still bouncing around as it warmed up, but seemed a bit calmer this time around.

[hoveringuy]

When I did my m54 stuff I had to mount the sensor in a non-standard place. It now has it's own ground wire and if that wire gets loose I get the bouncing gauge symptoms.

I used one of those infrared thermometers to measure the temperature of the thermostat housing directly, that might be helpful to you in this case to make sure it's a wiring issue and not an actual overheating issue.

I would't take chances until you know fer sure.

[RedStar240]

new thermostat? I know for an m20 i don't know much about the 24 v yet but im learning.

[87e30]

I have a new thermostat and water pump.

Exactly, I don't want to take chances but my car is now out here at school away from my house so I gotta drive it a bit to get somewhere I can work. I think I'm going to have the cooling system pressure tested from my buddy to check that, but that's a 35 minute drive.

I've heard it could be the SI board or the gauge. e30 gauge clusters SUCK.

(Oh, PS my temp sensor is tapped into the head - so ground is good)

[Adrian_Visser]

How long did the car sit for during the swap? It is highly possible that the SI batteries died and leaked out onto the board during the long down time during the swap. Do the SI lights work?

[87e30]

How long did the car sit for during the swap? It is highly possible that the SI batteries died and leaked out onto the board during the long down time during the swap. Do the SI lights work?

The SI lights work (the green row of lights, right?). The tach works but it's ALWAYS been funky, doing the whole bounce to 0 then back to 2k deal.

This is a new cluster but the same SI board I had before. IN my old cluster (with the same SI board) the temp gauge never moved, so I'm assuming the sensor was bad. Perhaps this SI board never liked the temp gauge...)

The car did sit for maybe 9 months with some test drives in there. I will pull the cluster out and look around. The timing just seemed weird to me, as soon as I pulled off the freeway it started bouncing around. Maybe the rough city road jiggled something loose.

[87e30]

I have the cluster all the way apart. The SI board looks the same as the way that I left it, dont know why it wouldn't working. But it's always a possibility.

Any ideas on checking the gauge?


Here is something I just noticed. The speedo/tach needles when physically moved up, will pretty quickly and smoothly fall back to 0. My gas gauge will smoothly and slowly return to "0". (Which is actually F'd up, it falls all the way down and around way past empty, thus it never reaches the F when actually full)

The temp gauge on the other hand abruptly falls down and has no smoothness or resistance when falling down to it's "0" (cold) position. Normal?

[joshuaaa]

not trying to bump a dead thread, but you ever get any resolution to this problem. me cars temp gauge has been bouncin too. started after replacing all the top end gaskets and stuff.