More problems with Son's POLO - coolant temp
karlak - 22/1/12 at 12:35 PM
Right, next issues..
We have fixed the exhaust which in turn has fixed the Lambda erros we were getting, So time ot move on to the Next.
I have the VCDS (VAGCOM in old money) which has been reporting an
"implausible coolant sensor" reading.
So I decided to get a new coolant sensor and renew the Anti-freeze at the same time.. We were getting a Enigne warning light when this error was
reported.
Anyway, now it seems that the the water is overheating. HAve just sat with it idling and the coolant temp reading has gone the wrong side of 90
(which it normally never goes above) - This is backed up on the OBDii readout on VCD which hit 114 degress, before I decided to turn her off. The rad
cooling fan never came on.
So I guess that leaves me with a Thermostat and a Radiator Temp/FAn Sensor.
I guess the only other thing could be a coolant airlock?
Any ideas where to look next ?
cheers 
rusty nuts - 22/1/12 at 12:54 PM
Water pump impellers have a habit of coming off on VWs and causing overheating. Does the heater blow hot air ? if not then it's likely to be the
pump but the thermostat is now U.S.
karlak - 22/1/12 at 01:05 PM
quote:
Originally posted by rusty nuts
Water pump impellers have a habit of coming off on VWs and causing overheating. Does the heater blow hot air ? if not then it's likely to be the
pump but the thermostat is now U.S.
The heater is blowing hot.
Just checking online it seems airloacks are common with these after renewing coolant. I will let it cool down and then re-check.
Also, not possible to check the theromstat with the boiling pan method as it seem it is all part of a "unit"
austin man - 22/1/12 at 03:03 PM
My Mk 4 Golf had a couple of problems 1 being the impellor detaching itself from the shaft (new pump) the other being the coolant level sensor would
occasionally play up giving a warnng for overheating for some bizzare reason
rusty nuts - 22/1/12 at 03:50 PM
The thermostat breaks the plastic housing internally, Take it off and check it out
britishtrident - 24/1/12 at 11:00 PM
My be an idea to check the actual cylinder head temperature ---- could be the wrong sensor type.
tegwin - 24/1/12 at 11:59 PM
You dont state which polo it is....age and model.
The 6N and 6N2 (1999-2001 ish) has issues with temp senders. I get through one every year or so.... Causes all sorts of issues... Another known
fault is a dodgy earth to the sender.
If your not sure I would get another temp guage somehow into the water and see if the VW sender is telling you porkies!
karlak - 25/1/12 at 12:17 AM
Yep, sorry it is a 9N.
I seem to have sorted it now. Gave all the coolant pipes a good squeeze and ran with the heater on for a good run. After it cooled down there was
room to top up the header tank. After that all was fine, so I think it was just a Airlock somewhere.
Cheers for all the replies.