Coolant Resevoir Level - Warning Light

sebastianlieken · 10-10-2013 1:09pm #1

Car is an 07 golf mk5 1.6FSI

About two weeks ago, the coolant level warning light came on the dash straight away when I started the engine one morning. I killed the engine and got out, checked the coolant; it was perfect. I drove to the bottom of the hill, pulled in and opened the bonnet again and coolant was still at level in the resevoir. I started the engine again and the warning light was gone! great!

Then Yesterday morning again the same thing. same procedure as above.

Now this morning again it came on, so i just left the car at home and got a lift in.

I'm fairly sure it's the level sensor in the resevoir that's gunked up. plan is to remove the resvoir now after work and give it a clean so that the mechanism can work freely again.

Question: Do I run any risks driving with this warning light on, even though I can visually confirm the coolant level is spot on? (I don't know will this effect engine control, the fans, etc.)

Second question: Would I be correct in assuming the resevoir level switch is probably the issue?

Third question: would it be recommended to do a coolant flush and change or would that be unnessesary?

George Dalton · 10-10-2013 1:12pm

You won't need to remove the reservoir at all. Just open the cap and look down into the tank and you will see the 2 metal probes. Give them a clean with an old toothbrush or similar and it will probably be fine. If not then new reservoirs are quite cheap off VW.

sebastianlieken · 10-10-2013 1:31pm

Hi George,

I looked in to the resevoir this morning and saw those two probes you refer to, they were a little gunky but nothing major. I thought those two probes were temperature or conductivity sensors or something? Like, I don't understand how two metal probes are measuring the fluid level? I thought there would be a mechanism with a float in there like what you have in the cistern of a toilet.

biko · 10-10-2013 1:33pm

One probably send small voltage which is picked up by the other, but only if there is fluid to conduct the electricity between them.
Just a guess of course.

sebastianlieken · 10-10-2013 1:52pm

oookay, I actually get it now. The two probes start above the water level and go down into the water some way. A low electrical current is passed from one into the other through the conductive liquid. The ideal resistance is set at the level where the water is on the level line. When the water level goes down, the resistance will hence go up and the voltage reading will become lower, setting off the bells and whistles.

SOOO, if there is gunk on the probes the electrical resistance goes up aswell, meaning less current is passing from one to the other making the bells and whistles go off.

SORTED. gimme a toothbrush!!!

Thanks for the input George and biko!

PS, I use the terms "current" and "voltage" interchangably, I sat beside a pretty girl in my electical engineering modules.... I was distracted. :P

Coolant Resevoir Level - Warning Light

Comments