Needle in the Red, No Overheat

[EatsHondas]

I recently swapped heads on my 325i that broke a timing belt about a month ago. I filled her with coolant, bled the system, and the car drove great for a week.

Tonight when I was coming home from work, I noticed the temp needle was really wobbly and climbing towards the red. I tapped the cluster at a stoplight and the gauge suddenly went back to the exact middle. 500 feet down the road later, the needle made its way back into the red zone. Freaking the hell out, I pulled over, blasted the heat, and let her idle for a minute or two so she wouldn't heatsoak.

A minute or two later, I shut her off and set my hand on the valve cover. Toasty, but by no means scalding. Coolant hoses were warm to the touch, but again, not scalding. No steam or smoke anywhere in the engine bay, and nothing else seems out of the ordinary. I also slowly pulled the coolant cap off maybe 5 minutes after I turned the car off, and it came off willingly (no boiling, no steam, no hissing, nothing). I couldn't see the coolant level through the yellowed plastic, but my finger could feel warm coolant about an inch below the filler neck. I checked the oil and found... oil (no coolant-y milkshake).

Anyone else ever experience anything like this? How likely is it that this is a temp sender/gauge problem over an actual overheating problem?

I'll check the coolant level tomorrow, but I'm pretty sure I'm not low.

[bmw325csi]

First thing I would do is check the grounding nut on the back of the temp gauge. If its loose it will cause the gauge to act up.

[ButtJuice]

What he said^


If that doesn't work you should replace the gauge itself. I had similar issues until I swapped out gauges.

[EatsHondas]

What he said^


If that doesn't work you should replace the gauge itself. I had similar issues until I swapped out gauges.

Did you spring for a new one or did you just find one from a donor car/cluster?

First thing I would do is check the grounding nut on the back of the temp gauge. If its loose it will cause the gauge to act up.

I pulled the cluster about a month ago and it was snug. I have a bulb to replace in there now anyway, so I'll pull the nut off and clean it up.

[SlamedIAm]

I had an issue with intermittent coolant temp gauge wonkiness (technical term) that seems to have been cured after replacing the ground from the oil pan to chassis.

[dnguyen1963]

How old are your SI batteries? Your gauge might be ok, but the SI board/batteries might be shot.

[EatsHondas]

I had an issue with intermittent coolant temp gauge wonkiness (technical term) that seems to have been cured after replacing the ground from the oil pan to chassis.

Funny you should say that. Mine was so bad that the insulation was totally gone and the copper wire was covered in road grime. I found a brand-new (looking) one in a junkyard and quickly replaced it. This was before I had any gauge issues though.

How old are your SI batteries? Your gauge might be ok, but the SI board/batteries might be shot.

Pretty sure they're factory. You have to melt the solder holding them in and resolder the new ones in place, right?

[dnguyen1963]

Contact Gregs///M for batteries replace. If your SI board has no corrosion and you have Batteries Plus near you then they can replace the batteries for about $10. Gregs///M can also reflow your board and he is trusted by many users.

[SlamedIAm]

+1 for Gregs///M. Got my ground cables from him as well as a refurbished SI board I'm about to install with a George Graves voltmeter.

[redlightpete]

Check the electrical connector under the throttle body. When mine went bad I also was getting false high temp readings. The signal from the temp sender goes through that connector.

[EatsHondas]

Thanks for the heads up guys, I'll definitely send Greg a PM. My left turn signal arrow in the cluster doesn't light up because there's no continuity in the circuit, so that'd probably get fixed too.

Check the electrical connector under the throttle body. When mine went bad I also was getting false high temp readings. The signal from the temp sender goes through that connector.

I know exactly what you're talking about. The hose part is really loose on the intake, at least one of my intake/vacuum leaks is probably coming from there.

[EatsHondas]

Hooray new symptoms!

I installed a brand new Graf water pump (quality rated as 'excellent' by Pelican Parts) two weeks ago along with a new Contitech timing belt. For last few days (and NOT AT ALL the week before), there has been a fresh puddle of coolant underneath the car about 9 inches in diamater.

The most interesting part: Yesterday I topped off the coolant, drove to work, then parked her for ~2.5 hours. When I came back outside to leave, there wasn't a single drop of coolant on the ground. The spot I normally park in school is angled up ~10-15 degrees (front end sits higher than the trunk). The spot that I parked in at work is perfectly flat. Would this have anything to do with the leak? Or would it make more sense that the leak starts after the car cools all the way back down?

I squeezed all the hoses with the cap both on and off, but it didn't speed up the leak rate. The coolant will drip right before your eyes, but very slowly (a single drop every minute or so). I made damn sure that there wasn't a single spec of old gasket on the block before bolting up the new pump. It came with a paper gasket that I installed with no sealant or torque wrench, but I tightened the bolts a little at a time until all were rock solid (are we supposed to use sealant on the bolt threads?). I also checked multiple times to make sure the gasket wasn't getting pinched.

I can't take a more in-depth look at the leak until Sunday. It really is one thing after another with this car...

The gauge problem hasn't happened again, but the needle will move about a needle's-width toward hot if I'm idling for more than a minute or two. I'm assuming that means my fan clutch is on its way out, my new, quality water pump is toast already, or I have a really tiny air bubble.

[e30Rooster]

Hooray new symptoms!

I installed a brand new Graf water pump (quality rated as 'excellent' by Pelican Parts) two weeks ago along with a new Contitech timing belt. For last few days (and NOT AT ALL the week before), there has been a fresh puddle of coolant underneath the car about 9 inches in diamater.

The most interesting part: Yesterday I topped off the coolant, drove to work, then parked her for ~2.5 hours. When I came back outside to leave, there wasn't a single drop of coolant on the ground. The spot I normally park in school is angled up ~10-15 degrees (front end sits higher than the trunk). The spot that I parked in at work is perfectly flat. Would this have anything to do with the leak? Or would it make more sense that the leak starts after the car cools all the way back down?

I squeezed all the hoses with the cap both on and off, but it didn't speed up the leak rate. The coolant will drip right before your eyes, but very slowly (a single drop every minute or so). I made damn sure that there wasn't a single spec of old gasket on the block before bolting up the new pump. It came with a paper gasket that I installed with no sealant or torque wrench, but I tightened the bolts a little at a time until all were rock solid (are we supposed to use sealant on the bolt threads?). I also checked multiple times to make sure the gasket wasn't getting pinched.

I can't take a more in-depth look at the leak until Sunday. It really is one thing after another with this car...

The gauge problem hasn't happened again, but the needle will move about a needle's-width toward hot if I'm idling for more than a minute or two. I'm assuming that means my fan clutch is on its way out, my new, quality water pump is toast already, or I have a really tiny air bubble.

I hate having cooling system issues. I've been in your shoes as I'm sure most have. I use the silver colored rtv made for water pumps and thermostats. Fuck that paper gasket bullshit. Just go buy some more coolant (I know it fkin sucks) pull the timing covers off again, take the water pump off pull off the crappy paper gasket put some good silver rtv get it good and tight and have a beer. I love having a car that doesn't leak all over the road/ driveway.
How old is your radiator? I would replace it with a new one.

PS: order from blunttech. pelican parts is over priced and slow as fuck blunt will have your shit there super fast with ground shipping. Most things are there next day.

[EatsHondas]

I hate having cooling system issues. I've been in your shoes as I'm sure most have. I use the silver colored rtv made for water pumps and thermostats. Fuck that paper gasket bullshit. Just go buy some more coolant (I know it fkin sucks) pull the timing covers off again, take the water pump off pull off the crappy paper gasket put some good silver rtv get it good and tight and have a beer. I love having a car that doesn't leak all over the road/ driveway.
How old is your radiator? I would replace it with a new one.

PS: order from blunttech. pelican parts is over priced and slow as fuck blunt will have your shit there super fast with ground shipping. Most things are there next day.

The same symptoms happened to me yesterday driving 20 miles from school to home: needle all over the place, but no apparent overheat. I pulled my cluster, removed both the fuel and temp ground nuts, cleaned 'em, and put 'em back on nice and tight. Now my temp needle is steadier than a Navy SEAL sniper and actually hangs out about a millimeter to the cool side. Hell yeah! I'll have to see if it stays that way.

On a side note, I fixed a vacuum leak and replaced my coolant temp sensor today. I wasn't expecting any difference, but I could've sworn she took less time to crank, has a slightly steadier idle, and actually pulls harder. I thought that the coolant temp sensor is only doing work when the car is trying to reach operating temp. Apparently not?