Cooling System

[mk43]

I'm not sure what's causing the constant low reading on my temp gauge or why the coolant light is blinking, so I did a little digging around today. I previously have washed out the coolant reservoir and slightly overfilled it to see if either of those were causing the light.

Today I took out both the ECTS and the temp gauge sender, both were the new brass design, and looked fine. The connectors also looked cleaned, but I gave them a bit of a rinse with isopropyl alcohol anyway. I also took out the temperature sensor for the (automatic) transmission, it's the old design plastic sensor, but that's not a problem from what I've heard, and it wasn't cracked anyway. That connector also looked fine, but I rinsed it for good measure. (The reason I checked this is because I heard it can set off the blinking coolant light.)

The only thing I can think of now is the thermostat. Does this make the coolant light blink if there's something wrong with it? I thought maybe it could be stuck open, since the car has 170k on it (actually something like 135k on the engine and transmission), but the fan wasn't on when the temp gauge was at 1/2 (and it rarely reads the high - usually has to be 85+ and driving in the city, today it was 72) and the car was in park. I even turned the AC on, but the fan still didn't budge. My AC doesn't actually work, though, so maybe that's why it didn't turn on? The car's got me sort of stumped at this point.

This makes no sense to me:
Temp gauge usually reads around 1/4, sometimes up to 1/2
Coolant light is blinking
I haven't seen the fan on (then again I can't watch the fan while driving)
Sensors all seem fine

Hopefully someone can enlighten me or point me in the right direction. I should mention now that the car actually runs fine, I just want to try to work out these little issues. (Only mechanical problem aside from this is a rattling idler pulley, but I have a spare and plan to replace that soon.)

[LotusLord]

It might be a good idea to replace the thermostat. I think there is a float sensor that tells the car the level of the coolant, but I'm not 100% sure about that.

[Old95SL2]

When you cleaned the coolant reservoir, could you hear the sensor move in there when you tipped the tank upside down and back. I'm not 100% sure, but I thought it rattled or sounded like it was moving up and down when I had mine out awhile back.

[madpogue]

Indeed, coolant LEVEL sensor in the reservoir should rattle when it's out of the car and empty.

[mk43]

Yes, when I cleaned the reservoir the float rattled. I'll probably end up changing out the thermostat anyway, but I'd love to hear any ideas.

[BarnOwl]

Most likely either the sensor in the coolant reservoir is shot or you don't know how full you're supposed to get it. You can pull the connector on the bottom of reservoir and jumper it. If the light goes away, you know that it can't be anything but, the sensor or the level of the coolant itself.

[DonP]

A temp gauge reading 1/4 scale or lower except when stopped for extended periods or inching along in very slow traffic is a sign of a stuck open T-stat (assuming other sensors are OK). But that should not effect the coolant level sensor.

[mk43]

I should have mentioned that I already tried jumping the connector, and that it made no difference. The light was still blinking. And when I filled the reservoir, I filled it at least half an inch past the full cold point. (I don't really remember.) The next step would probably be to dig out all the wiring to the coolant level sensor, but that would take a lot of effort. I'd like some suggestions as to what else could make the coolant light blink first.

I'll also mention that it isn't showing any codes when I jump the two terminals by the PCM.

[madpogue]

Originally Posted by mk43

I should have mentioned that I already tried jumping the connector, and that it made no difference.
....
I'll also mention that it isn't showing any codes when I jump the two terminals by the PCM.

Jumpering the connector as a test was def'ly the next thing to try. Sounds like it's the wiring between the connector on the res and the PCM. And since this function has its own light, it won't set the SES light or set a code.

Figure out (you'll need a wiring diagram) where those wires connect at the PCM, and jumper them there. If the light goes off, check the continuity of each of the two wires.

[richpin06]

Originally Posted by madpogue

Indeed, coolant LEVEL sensor in the reservoir should rattle when it's out of the car and empty.

Ever wonder what the coolant level sensor looks like.

http://i202.photobucket.com/albums/a...EVELsensor.jpg

[mk43]

Nice photo. I'm a bit busy/lazy today to try to find and interpret a wiring diagram, so if someone could help me out a bit on that it would be great! When loosening and retorquing the two nuts that are supposed to be retorqued after mounts are replaced (I should have done that months ago, didn't know), I discovered that my engine is leaking oil somewhere. It's strange to say, but I'm sort of relieved to see that, because that means it's not burning oil as hellaciously as I thought it might be. Now if I only knew where it was leaking... The bottom of the transmission is wet, and there was a wet spot where I was parked (I smelled it and it was oil). If I can't figure that out, I'll have to clean the engine so I'll be able to see.

Back to the topic: Still looking for any suggestions or help finding/interpreting a wiring diagram for the coolant level sensor.

[madpogue]

Originally Posted by richpin06

Ever wonder what the coolant level sensor looks like.

http://i202.photobucket.com/albums/a...EVELsensor.jpg

Um, that's gonna have a slight leak....

As for a wiring diagram, it depends on year and model. AutoZone's web site has _some_ diagrams in their "Repair Info" section.

[mk43]

Okay, so I swapped out the thermostat (it was the stock/OEM one), with a new Stant from Advance. Now the gauge sits right on the 1/2 mark and gets there within a few miles. Awesome.

The temp sensor wasn't wrong, the thermostat was just stuck open.

The fan never came on because the engine never got hot enough since coolant was always flowing through the radiator, and it was never THAT hot to begin with. The AC didn't make it come on because it doesn't work. (I think because it was disconnected during the swap, the lines need to be evacuated by an AC technician, then refilled.)

The only thing left to fix with the cooling system is to get that stupid light to quit blinking. The level is fine. When the two terminals on the connector for the coolant level sensor get jumped, the light continues to blink.

What I need to know: Is there ANYTHING other than the coolant level sensor that can cause this light to blink? Also, if someone could tell me where I can override the entire wiring to the sensor and just jump a couple terminals in the fusebox or something to know if the wiring is bad somewhere, that would be awesome. I'll look for the wiring diagram again, but I haven't had much luck finding one yet.

[madpogue]

Year and model?

[mk43]

Well, it's in my signature...
92 SL2, but it's a 93 engine/transmission/pcm.

[madpogue]

Originally Posted by mk43

Well, it's in my signature...
92 SL2, but it's a 93 engine/transmission/pcm.

You have to have signatures turned on to see them. Not everyone does.

Dang, the AutoZone engine schematic for the gen-2 ('96+) shows the level sensor (and what terminal on the PCM it goes to), but the schematic for gen-1 ('91-'95) doesn't show it. Grrr!

[mk43]

Ah, sorry. Didn't think about that. I looked on AutoZone's website yesterday, but as you already know it's not very helpful. I used to have access to AllData Pro, but not so much anymore. I have a Chilton's manual where I do most of my work (my dad's friend's garage), maybe that will have a diagram.

If anyone on here has one or can scan one, that would be great!

[richpin06]

This is a schematic for gen-1

http://i202.photobucket.com/albums/a...chsch.Gen1.jpg

[mk43]

Thanks! I'll try to decipher this, and I might figure it out, but in the meantime if someone who has had more experience with this could tell me how to bypass the wiring to the coolant level sensor that would be helpful!

[busterSL2]

Sounds like you have enough help in the coolant department.. However I have been dewelling on your AC. Your radiator fan should come on the moment you turn your A/C on. If it does not it could be a bad relay, fuse and worse case the fan motor it's self. It does not matter if the A/C has no charge the fan will still come on the moment the A/C button is pushed. The low refrigerant only effects the compressor cycling on. It is possible to unplug the A/C compressor and still turn the A/C on just to see if the fan works properly....