Hi all ,

recently bought a mk4 Polo off an old lady , everything is sweet on it 42k on clock full VW history , tidy body work ,

but here is the problem , i bought it and the Radiator fan Was working.. 2 days ago my temperature shot right up to 110 , i didnt hear the fan kick in so i got out of the car popped the bonnet and they fan wasn't spinning ... Water was Boiling like a kettle would from the Topup tank thing . so naturally i poo'd myself and drove home , i have checked all the fuses they are all sweet , i have checked the wires that lead directly into the fan via one of those Clips ,

what could it be ? fan broke ? radiator broke? Temp sensor not telling fan to come on ?

any help would be much appreciated

thanks

Could be a number of things, an air lock could do it but that more likely if you've emptied the coolant and refilled it. Fan switch on the rad could of died so isn't switching the fan on. Or it could be that your thermostat has died which would stop water from circulating around the rad.

Start it and leave it ticking over, keep an eye on the temp so it doesn't over heat and keep checking the hoses that go to the rad. The top one should get hot first and after a little the bottom one should get hot too, if not its more than likely the thermostat at fault. If they do both get hot then its more than likely the rad switch that is at fault.

Edited 10 July, 201115 yr by McLOVIN

Nice one for info mate , I will take a look at that in the morning when i have some daylight . Ill let you know the outcome of what you have suggested

thanks

I'm guessing airlock or stuck thermostat.

You'll see a couple of wires going into a plug on the radiator, take the electrical plug off it, and bang a bit of wire between the connections on the end of the wires. Mind your fingers, because the fan should spin, this confirms your fan wiring's ok.

Yeti , your right mate , the relay switch has gone by the looks of things , i have bridged a bit of wire in the Connection and the fan turns on , and cools the engine down which is all good ,

I've been and ordered a Relay fan switch from euro car parts its getting dropped off at shop this afternoon , so fingers crossed it will fix the issue

ty

Was the engine temperature high when you bridged out the fan switch?

If you bridge out that switch when the engine is ice-cold, the fan will still start.

If the engine wasn't over hot when you tested it, I would still do that thermostat check, as outlined above.

By the way, if the thermostat does prove faulty, buy a new thermostat housing as well as the 'stat itself, or you might find that the problem is still there.

Also, as it has boiled water out, you will need some fresh coolant. VW G12 Plus Plus is the best and most economical.

regards.

yeah after bridging the connection the fan came on , and the water is no longer boiling over , its keeping a nice steady heat between 85-90 on meter , haven't seen it rise over 90 by much today , I'm picking the switch up in the morning because they didnt get it in this afternoon , so ill fit it at work and then take car down to my mates garage get him to check thermostat ect

cheers

is the water defiantly circulating though? as with the bridge in the fan.. all the fan will do is cool the water in the radiator.. your water pump could also be screwed or you are thermostat and putting that bridge in could have actually just disguised the problem and you are engine could blow any minute.. i wouldnt drive too far until that switch is in...

Gauge takes the temp front the thermostat housing not the rad, if the rad fan being on is keeping the the temp down on the gauge then it must be circulating. That said if your fan is on all the time I'm suprised the temp got as high as 90, with the fan constantly on I'd of expected it to run pretty cold all the time

Right , so after having the switch replaced , the fan kicks in at 110 ... too hot for my liking ,, doesnt stay on long enough to cool it back down to 90. then cuts out , so i bridged it again , i cant tell weather water is circulating , id guess not as the fan isnt cooling it down at all , could this be a dodgy thermo ? if so what would happen if i took the thermo out ? could i run the car cold ? and how can i check if the water pump is broke?

cheers

Right , so after having the switch replaced , the fan kicks in at 110 ... too hot for my liking ,, doesnt stay on long enough to cool it back down to 90. then cuts out , so i bridged it again , i cant tell weather water is circulating , id guess not as the fan isnt cooling it down at all , could this be a dodgy thermo ? if so what would happen if i took the thermo out ? could i run the car cold ? and how can i check if the water pump is broke?

cheers

Turns out waterpump , Thermostat and Headgasket was all dead ....

Fun times

thanks for advice guys you helped me source the problem :)