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A week ago I drove my 1998 V70 a few miles to run some errands and meet a friend for lunch. The car ran fine on the way there, sat for a few hours, and I drove back with no signs of problems. When I got home I opened the hood on a whim and saw three very alarming things:
– Coolant expansion tank empty
– upper radiator hose nearly detached with broken hose clamp
– coolant dripping onto the driveway[IMG]http://i.imgur.com/M2LEbFA.png[/IMG]
The temp gauge had never deviated from where it normally sits and there was no sign or smell of boiling coolant while driving. Luckily the block and radiator were still full and only the upper hose had some air in it. The hose held with a new clamp but leaked slightly, and the car still ran fine.
What concerned me most was how the the coolant warning light hadn’t come on, even though the expansion tank was empty. The lamp itself still worked when the ignition was turned on, the tank was a bit dirty inside but the float worked, and there was system voltage at the sensor connection when the engine was running.
[IMG]http://i.imgur.com/OeM8Gjb.png[/IMG]
That little $25 magnetic switch had failed stuck in the open position sometime since the tank was assembled in late 1996, going unnoticed since my parents and I have been very careful about checking fluids and maintenance. Those thousands of hours sitting at boiling temperatures likely cooked it. Similar results would come from a loose connection or damaged wiring.
[IMG]http://i.imgur.com/20wtYyj.png[/IMG]
This is a good example of how failure of a small, inexpensive component can hide the presence of a failure of a critical subsystem, which itself fails because of a small inexpensive component. A crack in the clamp allowed it to corrode unnoticed until the remaining metal gave out with no warning. A very slow leak from the old hose could have contributed.
The “test” when the ignition is turned on only verifies the warning lamp works, not the failure detection system. In order to test the switch at startup, there would need to be a small electromagnet coil in the same package, an extra wire to power it, and possibly a way for the ECU to check for proper switch function. All of this costs extra for a part that hopefully lasts the expected service life of the vehicle.
I have no idea if other cars could have a similar problem, but simple parts like that can make the difference between getting there in one piece and getting stranded. I replaced the hose with an OEM part and two new clamps because it was old and never quite stopped leaking after I clamped it. I’ll also be checking operation of the brake fluid sensor the next chance I get, as it appears to be a very similar magnetic switch and float assembly.
Thoughts on this kind of insidious failure? Similar stories?
I’m interested to hear what you think.
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Thoughts on this kind of insidious failure? Similar stories?
I’m interested to hear what you think.Pretty scary failure. Those stainless hose clamps are usually pretty durable parts. Glad you were able to catch the low coolant condition before it matured into something more serious.
On my 1997 Mercury Cougar beater, I have the opposite problem. The low coolant sensor also doesn’t work, or works intermittently in the false positive mode; the dash always reads “low coolant”. I think it is a purely electrical sensor, it appears to work by measuring the resistance between two terminals. However, it seems that Ford didn’t count on Ethylene Glycol vapors to eat away at their weatherproof sensor seal, exposing the circuit components (resistors, capacitors, integrated circuits..etc). Also, it seems that the old green ethylene glycol antifreeze polymerizes into oily goo over the years and coated the overflow reservoir, probably also causing incorrect resistance readings. At least Ford managed to design it to fail in a active manner. I’d replace it if it was easily available.
Anyways, it turned out recently that my thermostat housing decided to randomly wanted leak because the thermostat bolts began rusting out (steel bolts on an aluminum block + 17 years = fail!). So same outcome…inoperable sensor and low coolant.
Interesting that the Cougar uses a more complex electronic level sensor, and good that it failed positive. At least you now know to check often, though a problem like mine may go undetected for enough time to cause damage.
I’m not familiar with the way it sends a signal to the dashboard to turn on the warning light, but there might be a way for you to retrofit a different expansion tank/overflow tank with a working sensor. If you’re electrically inclined it would make for a cool project to see if that would be possible.
Good luck keeping it on the road 🙂
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