Low Coolant Sensor
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Coolant Leak
Joined: Aug 2005
Posts: 490
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From: Dallas, TX
Low Coolant Sensor
Ok guys heres the history of this issue. When i first bought the car a few weeks ago, everything seemed fine.. then it started leaking coolant like crazy, and i determined it was the gasket on the water pump. I replaced the water pump and everything seemed fine for about a week and 1/2 then the add coolant buzzer went off. So i opened the hood added some coolant and searched around for a leak and couldnt really find one... Then as time went by about a week into that the alarm was going off more and more frequently until i started noticing drip spots under my car and a puddle of coolant on the lower shroud. So i took the upper fan shroud off and looked for leaks, i noticed as the car was running there was a constant drip from the bottom of the radiator, the lower radiator hose and the drain plug were both solid, so... i replace the radiator with a fluidyne (not a bad excuse to upgrade 
Well now the alarm keeps going off, usually when i come to a stop, but once i start moving it stops.. I check the fluid level in the radiator and its usually pretty good, a little lower then topped off, but i see no coolant in the lower shroud or anywhere else... any ideas?
Also the sensor on the radiator is brand new, replaced it with the radiator, is it possible there is a short in the wiring going to the sensor? Any ideas on how i would check that and troubleshoot it?
I know it was a long post but thanks for any help you can provide
Well now the alarm keeps going off, usually when i come to a stop, but once i start moving it stops.. I check the fluid level in the radiator and its usually pretty good, a little lower then topped off, but i see no coolant in the lower shroud or anywhere else... any ideas?
Also the sensor on the radiator is brand new, replaced it with the radiator, is it possible there is a short in the wiring going to the sensor? Any ideas on how i would check that and troubleshoot it?
I know it was a long post but thanks for any help you can provide
Joined: Apr 2005
Posts: 3,785
Likes: 30
From: And the horse he rode in on...
Ok guys heres the history of this issue. When i first bought the car a few weeks ago, everything seemed fine.. then it started leaking coolant like crazy, and i determined it was the gasket on the water pump. I replaced the water pump and everything seemed fine for about a week and 1/2 then the add coolant buzzer went off. So i opened the hood added some coolant and searched around for a leak and couldnt really find one... Then as time went by about a week into that the alarm was going off more and more frequently until i started noticing drip spots under my car and a puddle of coolant on the lower shroud. So i took the upper fan shroud off and looked for leaks, i noticed as the car was running there was a constant drip from the bottom of the radiator, the lower radiator hose and the drain plug were both solid, so... i replace the radiator with a fluidyne (not a bad excuse to upgrade
Well now the alarm keeps going off, usually when i come to a stop, but once i start moving it stops.. I check the fluid level in the radiator and its usually pretty good, a little lower then topped off, but i see no coolant in the lower shroud or anywhere else... any ideas?
Also the sensor on the radiator is brand new, replaced it with the radiator, is it possible there is a short in the wiring going to the sensor? Any ideas on how i would check that and troubleshoot it?
I know it was a long post but thanks for any help you can provide
Well now the alarm keeps going off, usually when i come to a stop, but once i start moving it stops.. I check the fluid level in the radiator and its usually pretty good, a little lower then topped off, but i see no coolant in the lower shroud or anywhere else... any ideas?
Also the sensor on the radiator is brand new, replaced it with the radiator, is it possible there is a short in the wiring going to the sensor? Any ideas on how i would check that and troubleshoot it?
I know it was a long post but thanks for any help you can provide
Pump up the pressure to about 20-25 psi. Normal is 13 psi. Any leaks you have will show right away as a hiss or spray of coolant. Don't go over 25 psi.
Another thought. Have you checked your overflow tank? Is it gradually gaining volume? That tank will hold a gallon of coolant. Your cooling system only holds 2 gallons of coolant if N/A and 9 qts (2gal+1qt.) if turbo. Fully half of your coolant can 'disappear' into the overflow tank and you think it's missing. It's not missing, it's just in the wrong place.
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From: rialto
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Joined: Apr 2005
Posts: 167
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From: Sydney Australia
dont ground it.. it is a good tool to have. its letting you know there is a problem rather than letting your engine get hot..
i dont know why you would remove the negative to "reset the ecu" as the sensor has nothing to do with your ecu at all.
check ya radiator cap is ok. if the coolant heats up expands to the overflow then when the engine cools it should suck the coolant back in.
if the seal on the radiator cap is gone this can effect it.
also definetly do the pressure test
since you have a new low level sensor wouldnt hurt to test it as well. as there is no garenty its ok cause its new..
a very good way to "burp the system" is get a 2 litre bottle of coke. cut the bum off the bottle (make cut about 2cm from bottom bottom).
put screw fitting of bottle into filler point and tape it with electrical tape from the spout up the bottle a bit and back down a couple of times so coolant wont leak around the connection.
then add coolant into the bottle until its between 1/4 to 1/2 full.
then start the car and let it get up to temp.
then do an occasional rev ever now and again to move the coolant faster around..
soon the bubbles will stop then its a matter of removing left over coolant and removing coke bottle. i usually do it a couple of times in a couple of days if ive emptied the cooling system to make sure its right..
ps if you keep getting bubbles it could be another leak somewhere or more serious like a water seal.
getting a co2 test on the coolant will let you know if a water seal is gone..
i dont know why you would remove the negative to "reset the ecu" as the sensor has nothing to do with your ecu at all.
check ya radiator cap is ok. if the coolant heats up expands to the overflow then when the engine cools it should suck the coolant back in.
if the seal on the radiator cap is gone this can effect it.
also definetly do the pressure test
since you have a new low level sensor wouldnt hurt to test it as well. as there is no garenty its ok cause its new..
a very good way to "burp the system" is get a 2 litre bottle of coke. cut the bum off the bottle (make cut about 2cm from bottom bottom).
put screw fitting of bottle into filler point and tape it with electrical tape from the spout up the bottle a bit and back down a couple of times so coolant wont leak around the connection.
then add coolant into the bottle until its between 1/4 to 1/2 full.
then start the car and let it get up to temp.
then do an occasional rev ever now and again to move the coolant faster around..
soon the bubbles will stop then its a matter of removing left over coolant and removing coke bottle. i usually do it a couple of times in a couple of days if ive emptied the cooling system to make sure its right..
ps if you keep getting bubbles it could be another leak somewhere or more serious like a water seal.
getting a co2 test on the coolant will let you know if a water seal is gone..
Last edited by sim_rx3; Nov 10, 2008 at 09:23 PM.
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Joined: Apr 2005
Posts: 167
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From: Sydney Australia
id rather hear the buzzer and let me know there is a problem and be able to fix the problem at home.
rather than be on the side of the road somewhere with the bonnet up waiting for it to cool down due to lack of coolant..
Joined: Apr 2005
Posts: 3,785
Likes: 30
From: And the horse he rode in on...
Get the pressure test. If it passes, get a new MAZDA radiator cap.
Before you start to rebuild the engine, try everything else first.
Does the coolant expand into the tank as the engine warms up? Then does it correctly pull back into the radiator when the engine cools? You can have a vacuum leak between the cap and the overflow tube that allows air to be sucked into the radiator when the engine cools. Then some of the coolant stays in the overflow. Next time you run the car the process repeats.. Eventually you are low on coolant. At this point when you run the car, the hot air and steam is bubbling into the tank and the car acts exactly like it has a blown coolant seal, only it doesn't. At this moment, you will be in very great danger of overheating your engine.
I had this exact problem with my 90 Vert N/A. I tested everything, compression, cooling system pressure test. I replaced my rad cap, my tstat with oem. The problem still existed. When the overflow tank got full or when the low coolant buzzer went off, I poured the overflow tank back into the radiator. I found I wasn't losing coolant, just moving it one-way into the overflow tank. I didn't know to test the overflow tube for a leak, so I lived with it like this for months. I then eventually changed the cooling system over to Evans NPG+ and went the nonpressurized route. It works great for me, but I don't recommend it for anyone unless they have thoroughly sorted out the cooling system and are very sure that EVERTYTHING is in perfect operating order.
Good luck.
Before you start to rebuild the engine, try everything else first.
Does the coolant expand into the tank as the engine warms up? Then does it correctly pull back into the radiator when the engine cools? You can have a vacuum leak between the cap and the overflow tube that allows air to be sucked into the radiator when the engine cools. Then some of the coolant stays in the overflow. Next time you run the car the process repeats.. Eventually you are low on coolant. At this point when you run the car, the hot air and steam is bubbling into the tank and the car acts exactly like it has a blown coolant seal, only it doesn't. At this moment, you will be in very great danger of overheating your engine.
I had this exact problem with my 90 Vert N/A. I tested everything, compression, cooling system pressure test. I replaced my rad cap, my tstat with oem. The problem still existed. When the overflow tank got full or when the low coolant buzzer went off, I poured the overflow tank back into the radiator. I found I wasn't losing coolant, just moving it one-way into the overflow tank. I didn't know to test the overflow tube for a leak, so I lived with it like this for months. I then eventually changed the cooling system over to Evans NPG+ and went the nonpressurized route. It works great for me, but I don't recommend it for anyone unless they have thoroughly sorted out the cooling system and are very sure that EVERTYTHING is in perfect operating order.
Good luck.
My leak ended up being a very small crack in the thermostat neck. One day it burst explosively. I replaced it with a new one and my trouble was over.
Good Luck
