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Please can anyone help ,Pesky red coolant light flashing 1.2 polo

21K views 7 replies 4 participants last post by  Crasher  
#1 ·
Hi,

I Have a polo 1.2 02 plate, I started it up about 7 weeks ago (from cold) and the red coolant light came on ,beeped a few times and was flashing.

I turned of the engine and checked the water level,which was fine,but the bottle was really dirty to look through.

I restarted and it didn't come on,,restarted all that day and no problems.

Next morning ,,back on,,flashing,,so i decided to check the web.

Header tank bottle sensor seems like the fix,,so I bought a brand new one,fitted,new coolant and away i went.

That was 6.5 weeks ago,,so you guessed it,,its back!!

Any ideas,,?ive had the ECU read and no fault codes.,

Things I am wondering it might be,

*engine temperature sensor (does that control that light)
*water getting into car from rain
*instrument panel

considering bridging the wire out if I cannot find the fault,as the car is running,not overheating & no coolant loss.

Thanks
 
#2 ·
I think this is likely to be either a bad connection at the tank, a nearly broken wire near there, or a cracked solder joint on the instruments module circuit board.
Pin 16 carries coolant level signal. The immobiliser connections (Pins 1, 17) at the other end of the 32 way green connector also suffer these problems. You can get in there to inspect and re-flow the joints without excessive disassembly, you probably don't need to remove the needles from the gauges. I'll dig out a photo and a mini 'how to' description tomorrow.

I think high coolant temperature can also make this light flash, but you would normally notice the gauge going into the red at the same time, I guess.

Bridging the connector, plus careful inspection of plug contacts and nearby wiring would eliminate most other possibilities than the solder joint one, if you continued to get warnings.
 
#3 ·
Hi pete,

Thanks for your help.

I wonder if it is a solder joint,I have just been out to inspect the plug and wiring,It looks fine at that point.Bridging the connector stops it from coming on,(so far)

I am wondering,the water looks a little ,dirty,not oil,,but like rusty,,I am wondering if this probe in the header tank is more than a simple probe,more detects antifreeze mixture,or if its just simple,temperature and level.

It doesn't happen when its warm,only when cold.I am debating on flushing system,and doing mixture again,,seems excessive though after just 6 weeks.

if the bridging works then i assume panel solder may be ok??

I may replace the temperature sensor on the water housing,euro car parts has one but says (radiator fan switch) fan is working ok though and its only one listed.
 
#4 · (Edited)
The sensor in the expansion tank is only level, not temperature. I think it just measures the conductivity of the coolant between two 'prongs'. If the level is low, less of the prongs are covered, so less conduction. It may well be that cold coolant is less conductive than hot (genuinely no idea), which would fit with more warnings when cold, if the system is a bit compromised for some reason.
I'm not sure what sort of conductivity measurement technique is used, but I seem to remember that the first component connected from pin 16 is a capacitor, in the signal path, which suggests it's not a direct current measurement.
I would have thought that most contaminants in the coolant would make it more conductive rather than less, so less likely to trigger a warning?


I think I've seen that mis-description on ECP. I would personally buy a genuine coolant temp sensor, but I doubt it is relevant to this issue.
 
#5 ·
Hi pete,

Well found the problem today,its not great.looks like the head gasket.

I decided to take the brand new header tank of the car,and when I drain i noticed the sides was really brown,slimmed up,,I rotated the bottle i could see where the 2 pin run down was really dirty.

So with the header tank off I blocked holes and put some white spirit in shook and turned bottle pristine,loads of brown gunk come out,,Refitted and light didn't come back on.

So sadly it looks like oil is getting into the water and crudding up the sensor.

Not sure what to do,as don't think there is any quick fix.and I need the car,,It will probably drive for a while,if I change water every few 100 miles.

Annoyed as the chain slipped on this car 3 years ago,and garage did all the head and chain then,obviously out of warranty now the work.
 
#6 ·
Sorry to hear that, fella.

I hadn't thought about the sensor prongs getting coated with insulating oil, but that certainly makes sense of the symptoms/history.

May be time to find another car, sadly, if you can't DIY a gasket change. I'd have no qualms about recommending the 1.4, BBY engined Polo.
 
#7 ·
Hi im having problem with Polo 2002. 9n, 1.4 tdi, water temp light starts flashing, AC stops working and blows hot air, fuel level drops to 0, and outside temp shows -45, does anyone knows what is the problem? I replaced outside temp sensor, sensor in the water expansion canister, and the water temp sensor, problem persisted.
 
#8 ·
If the HVAC system sees the outside temp that cold it will shut the AC off to prevent freezing. You need it on a diagnostic system with live data so you can view the signals, voltages etc.