My S reg 1998 1.4 VW polo cl started over heating last week out the blue never overheated before this
I emptied the whole coolant system this weekend and refilled on a hill as not to get any air lock in the system but after leaving it for a while on idle noticed the fan is not cutting in checked fuses all good (doesnt overheat at this point) after idling it high (2500 - 3000)revs with the heater on hot the temp got up to a steady 90 degrees but still not fan cutting in and still not overheating
I then took it for a road test and found that the heater warmed up fine and still didnt over heat got back home lifted the bonnet to check radiator fan cutting in which it wasnt and it overheated again. I checked the top hose which was very hot and bottom hose was still cold and the radiator was stone cold also. the next day i cheked to see if it was the thermostat but there didnt seem to be one and ive have had the car since october and no probs so far though
I would appreiciate any ideas as i am getting withdrawls from driving my baby lol, i think it could be the water pump but didnt want to change it if there could of been another simple reason
Many thanks
Kris
P.S How do you change window wipers on a Audi A4 cab......they are stuck on tight
{kicks across to Technical Matters - you might want to ask about the Audi in another question}
Edited by Dynamic Dave on 18/05/2009 at 20:25
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There must be a thermostat somewhere or it would run cold all the time, and that's quite likely what the problem is. The pump must be OK or your heater wouldn't get hot. A blocked radiator is the other possibility.
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never though the radiator could be blocked thanks
would you say to replace the whole radiator or can i salvage the old one in any way?
if there is a therostat where would it be cause i followed the top radiator pipe to the themostat housing and it wasnt there any ideas where else that would be....?
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I wouldn't waste your time trying to unblock it, 10 years is a reasonable life for a radiator, you will probably find that its furred up inside, especially if its not had much antifreeze in it. Shouldn't cost you to much to replace it, look on ebay.
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With a sudden fault like this, it is unlikely the radiator blocked (but like all things - not impossible). Likely that it is the thermostat sticking, not allowing hot coolant into the rad, and therefore not triggering the fan switch. It could be the water pump (but I think unlikely) and the heater could get hot with syphon action. There were issues with VW pump impellers being made of plastic and stripping off. Still would check thermostat. Find it, and drop it in a pan of heating water on the stove and see if it does open or given the low price, just change it.
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am i right in saying that if my car hasnt got a thermostat its not letting the switch turn the fan on because i brigged a live to the fan and it works fine could it be a faulty switch that makes the fan turn on if so any ideas where i would find that will look again for the thermostat and try putting it in hot water and will keep you posted
Thanks for all the help tho
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All cars have a thermostat. From memory likely to be near the hose to the bottom of the radiator.
If it sticks shut (sudden and likely fault after time) once the car has warmed it will start to overheat.
However, VW engines had a problem (not all - can't remember the list) and some engines were fitted with a plastic impeller on the water pump which can come off. Then only syphonic action pushes the water around. Inedequate. If you look at the coolant header tank and take the top off and rev the engine cold or hot, you should get water bubbling through the small hose into it. If not suspect the water pump.
Radiators can sludge up over time, but if no leaks and changed every 5 years with VW pink anti freeze, unlikely, and you would have a history of minor overheating and temp gauge increases over a few weeks. Cheap anti freeze causes more blockages than anything else.
A sudden catastrophic case of overheating is most likely stuck thermostat.
The fan is only needed when car stopped and running. At over 10 mph there is enough cooling air going through radiator. When stopped after a run, the fan cuts in and out. You have proved this is working. If it overheats only in traffic or stopped and fan not working, it is the fan switch on the side of the radiator.
Good luck
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Just had a look in an old Haynes,for the 84-90 model but could well be similar.It shows the stat in a housing under the coolant pump where the bottom hose is attached.
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thanks for the advise guys
what i'll do tonight guys is look for the thermostat again check if its sticking or broke and replace it this weekend if that is the case also will check the bubbling with the the expansion cap off from the small top tube / pipe and will give the fan switch a once over as well
keep you posted
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checked the thermostat last night guys, happen to be a small part of the internal part of the thermostat housing had broken inside. I found it by following the bottom radiator pipe to up to the engine. i have bought a new themostat and housing and will fit it tonight to let you know how i get on. I did check coolant bubbling with the cap off from the top small pipe and it was so guess the water pump is fine ( fingers crossed lol ) will check back in tomorow guys
Thanks again for all the help and advise.
Kris
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