Low coolant light, but radiator's full?

[Silver Bullet]

Tonight on my way to work, the low coolant light came on and stayed on the whole time I drove. The check engine light joined it for about 2 seconds, and then shut off. When parked... The idle was jumping up a little too, and bouncing around before settling down. I let the car sit for 1/2 hour and then checked the radiator. It was 100% full...

Why would I get a "Low coolant" light when the radiator's full?

<small>[ January 31, 2004, 11:22 PM: Message edited by: Silver Bullet ]</small>

 

[Zap]

Did you check the overflow canister? There is an electrical sensor in there that will cause the light to come on if it drops below a certain level. The radiator can still be full even if the bottle is empty.

 

[Shoman594]

also that same sensor can become corroded, if so clean the terminals and you should be good to go.

 

[gosho89]

Do yourself a favor and unplug the sensor until you get a new one to replace it. The '93 models have a wiring issue related to that curcuit. Don't screw around or it will pop one of the mini fuses in your fuse box this will leave you stranded without a fuel pump or spark.

Don't ask me how I know, lets just say I spent a 3-day fourth of July weekend discovering all this back about 6 years ago when I had a '93 in the stable. I discussed this issue with Doug Lewis at the time and he said that he had reported it to the engineers at ford which corrected this problem for the 94-95 model year. headbang

 

[Catastrophe]

Mine did the same thing, and the radiator was full. I looked at the overflow canister, and it was indeed empty. I just added some coolant to it, and the light stopped coming on...

<small>[ February 01, 2004, 12:15 AM: Message edited by: Clitaurus ]</small>

 

[Dr. Tweak]

Shoman594:
also that same sensor can become corroded, if so clean the terminals and you should be good to go.

I cleaned mine up good and it's still comes on frown

 

[fricker66]

JDLangevin:

Shoman594:
also that same sensor can become corroded, if so clean the terminals and you should be good to go.

I cleaned mine up good and it's still comes on

A new sensor is available still and could possibly be the fix for your idiot light.

 

[Dr. Tweak]

fricker66:

JDLangevin:

Shoman594:
also that same sensor can become corroded, if so clean the terminals and you should be good to go.

I cleaned mine up good and it's still comes on

A new sensor is available still and could possibly be the fix for your idiot light.

Yeah... well there's a lot more I have to fix first! For now I can keep an eye on my temp guage and I just unplugged it... temporary fix...

 

[Venom SHO s7]

WARNING: Long Explanation.

Since you cleaned the sensor,you probably have the same problem i had, its this here:

Inside the clear coolant reservoir tank is a small circular black tube that is held in place a gray cap that also holds the sensor plug.Inside this black tube there is a floater (like the one in your toilet) with a metal piece attached (like a dip stick).
How It Works: When there is enough coolant in the tank, the floater will obviously float high enough to make contact with the metal connector at the top of the tank (the one being held by the gray cap). If there is not enough coolant, the floater will not float high enough to make contact therefor making the low coolant light go on.

Keep in mind :The purpose of the small 'black tube' is to keep the 'floater' from dropping to the bottom of the reservoir tank when there is no coolant, and to guide the the metal stick of the floater into the connector at the top of the tank.
THE PROBLEM: This black tube is actually split in two pieces, and when the bottom piece comes lose from the cap, it will drop to the bottom of the reservoir tank and therefor will not be able to guide the metal floater to the connector, or keep the floater from dropping to the bottom too.
WHY ADDING COOLANT WILL NOT WORK: When you do add coolant the floater will go back up to the top of the reservoir tank, but since the black tank is not there to guide it into the connector anymore, it will not make contact with the metal connector at the top and thats why it will not make the low coolant light go off.
EASY SOLUTION: Unplug sensor from the tank, and the hose that goes from the tadiator to the reservoir tank. Take off 3 10mm(i think) bolts that hold the reservoir tank bracket in place and pull out the whole tank. Now pull out the gray cap, if you look at it from the top it looks like this. (I). With that out, you should be able to see the 'black tube' and the floater piece sitting at the bottom of the reservoir tank. Take them out and simply snap the black plastic tube to the gray cap, BUT make sure you put the floater piece inside the tube first. Make sure its on tight enough as to not fall off easily. Put it back together, add coolant, and you should see that light go off immidiately.

Sorry for the long post. But maybe this post will stop all the "low coolant light" threads.
(i did this on my 89, so hopefully the genIIs are the same way)

 

[projectSHO89]

Venom

Nice explanation for how the original SHO overflow tank works.

However, Bob has a 93 ATX that uses a different techniquie and hardware. It is fender mounted and uses a sensor with pair of electrodes that pass current through the coolant inside the tank. When the fluid drops below the sensor or the electrodes become contaminated, the current stops flowing and the LOW COOLANT light is illuminated.

Follow gosho89's advice to prevent getting stranded. You can later clean or replace the sensor as needed. Just periodically check the coolant level in the tank to make sure it doesn't go low/dry. My 89 has been running with no sensor since I got it over two years ago. It's just a matter of kkeping an eye on it and your temp guage to prevent overheating, just like in the days before they installed such idiot lights.

Glad to see the "Silver Bullet" is back on the road.

Steve

 

[MyFirstSHO]

VenomSHO, You always come through. I've had my overflow tank out 4 times trying to **** that freakin low coolant light in my 89. I didnt know you could pull that inside thing out, I thought it was all 1 piece.

Would you mind telling how that inside piece comes out? Does it just pull out or do you have to turn it first then pull?

 

[gosho89]

projectSHO89:
Venom

Nice explanation for how the original SHO overflow tank works.

However, Bob has a 93 ATX that uses a different techniquie and hardware. It is fender mounted and uses a sensor with pair of electrodes that pass current through the coolant inside the tank. When the fluid drops below the sensor or the electrodes become contaminated, the current stops flowing and the LOW COOLANT light is illuminated.

Follow gosho89's advice to prevent getting stranded. You can later clean or replace the sensor as needed. Just periodically check the coolant level in the tank to make sure it doesn't go low/dry. My 89 has been running with no sensor since I got it over two years ago. It's just a matter of kkeping an eye on it and your temp guage to prevent overheating, just like in the days before they installed such idiot lights.

Glad to see the "Silver Bullet" is back on the road.

Steve

Thanks Steve, Like I mentioned earlier in a post this is a serious issue with only the '93 model year. I've been correct on this issue several times. If action isn't taken the coolant level sensor will short circuit, smoke will be rolling out of the overflow tank and your SHO will be disabled (no fuel pump, no spark) really wierd. I had Ford tech's swear the sensor could not case such a failure, but the wiring schematic on the '93 shows differently. Again Silverbullet unplug or replace the sensor unit also for insurance '93 owners should add some extra 10amp mini fuses to your glove box inventory.

Look for this failure if your '93 dies while driving an then will not restart. All the electric components will work radio, lights etc....First look for possible signs of smoke inside the recovery bottle, unplug the coolant sensor, look inside the under hood fuse box, replace both the 10amp mini fuses. Engine should restart. wink

<small>[ February 02, 2004, 11:27 PM: Message edited by: gosho89 ]</small>

 

[Dr. Tweak]

Venom SHO s7:
WARNING: Long Explanation.

Since you cleaned the sensor,you probably have the same problem i had, its this here:

Inside the clear coolant reservoir tank is a small circular black tube that is held in place a gray cap that also holds the sensor plug.Inside this black tube there is a floater (like the one in your toilet) with a metal piece attached (like a dip stick).
How It Works: When there is enough coolant in the tank, the floater will obviously float high enough to make contact with the metal connector at the top of the tank (the one being held by the gray cap). If there is not enough coolant, the floater will not float high enough to make contact therefor making the low coolant light go on.

Keep in mind :The purpose of the small 'black tube' is to keep the 'floater' from dropping to the bottom of the reservoir tank when there is no coolant, and to guide the the metal stick of the floater into the connector at the top of the tank.
THE PROBLEM: This black tube is actually split in two pieces, and when the bottom piece comes lose from the cap, it will drop to the bottom of the reservoir tank and therefor will not be able to guide the metal floater to the connector, or keep the floater from dropping to the bottom too.
WHY ADDING COOLANT WILL NOT WORK: When you do add coolant the floater will go back up to the top of the reservoir tank, but since the black tank is not there to guide it into the connector anymore, it will not make contact with the metal connector at the top and thats why it will not make the low coolant light go off.
EASY SOLUTION: Unplug sensor from the tank, and the hose that goes from the tadiator to the reservoir tank. Take off 3 10mm(i think) bolts that hold the reservoir tank bracket in place and pull out the whole tank. Now pull out the gray cap, if you look at it from the top it looks like this. (I). With that out, you should be able to see the 'black tube' and the floater piece sitting at the bottom of the reservoir tank. Take them out and simply snap the black plastic tube to the gray cap, BUT make sure you put the floater piece inside the tube first. Make sure its on tight enough as to not fall off easily. Put it back together, add coolant, and you should see that light go off immidiately.

Sorry for the long post. But maybe this post will stop all the "low coolant light" threads.
(i did this on my 89, so hopefully the genIIs are the same way)

Thanks for the great info, but as pointed out, only the '89 has the float type mechanism. Additionally, I removed my overflow tank when I cleaned the sensor and also cleaned that out, it had about 2 inches of crud in it! eek!

 

[Venom SHO s7]

MyFirstSHO,
From what i can remember, the gray cap can just be pulled off. But even if im wrong, i remember its very easy to get off though. thumb

My bad, i didnt notice you had a genII, but I hope i was able to help someone.

 

[gurucomputers]

gosho89:
I discussed this issue with Doug Lewis at the time and he said that he had reported it to the engineers at ford which corrected this problem for the 94-95 model year. headbang

I just bought a 1994 SHO ATX. When I brought it home and started looking under the hood, I noticed that the coolant sensor was unpluged. So, doing what a normal person would do, I pluged it back in. Went to leave a while later and got about 1 block away and the SHO died. It would crank but no start. Being I had it only a few hours I was furious. I went to the forum here and started looking around and found your article. Great news, I replaced the fuse and the SHO was revived. So it must be common to the 94s as well. Great article

 

[projectSHO89]

According to the 93, 94, and 95 EVTMs, there is no change bewteen any of the years.

A shorted sensor in the overflow bottle will blow the 10A fuse marked IGN COIL in the engine compartment fuse box.

Steve

 

[gosho89]

gurucomputers:

gosho89:
I discussed this issue with Doug Lewis at the time and he said that he had reported it to the engineers at ford which corrected this problem for the 94-95 model year. headbang

I just bought a 1994 SHO ATX. When I brought it home and started looking under the hood, I noticed that the coolant sensor was unpluged. So, doing what a normal person would do, I pluged it back in. Went to leave a while later and got about 1 block away and the SHO died. It would crank but no start. Being I had it only a few hours I was furious. I went to the forum here and started looking around and found your article. Great news, I replaced the fuse and the SHO was revived. So it must be common to the 94s as well. Great article

gurucomputers, glad this helped you out, are you member of NWSHOC? were mostly based out of Portland but have gatherings around the N/W. You can join our club at http://autos.groups.yahoo.com/group/sholist/?yguid=65982936

<small>[ February 07, 2004, 01:23 AM: Message edited by: gosho89 ]</small>