Help again, again

[StevieDB9]

ok, to cut a long story short the engine seems to be running cold. The water pumps been changed as has the thermostat and the radiator switch. The cooling system has been flushed and the coolant renewed and i spent ages getting rid of airlocks. The reading comes up to normal after a VERY long time when the car is stationary but as soon as you drive it it cools right down until the temp. gauge practically reads zero. The temperature sensor itself was changed when I got the car about a year and a half ago, could this be the only possible explanation that it has went duff again?

 

[revans117]

is your fan on all the time cause that may be why it is allways cold?

 

[pgarner]

its a pain but did you check the thermostat before putting it back in ? and is it a genuine vw one ?

mehinks the the themostat might be stuck open and the waters flowing constantly through the radiator cooling down before its warmed up. think the thermostat should be set to around 85 degerees

 

[pgarner]

opwn you header tank slowly after having it out for a decent run. if the waters hot then you could put it down to a faulty sensor

 

[obi_waynne]

You should be able to feel the header tank rather than open it up. It does sound like the thermostat to me. Dont the Polos have 2 stats? It could be an airlock though creating a jam in the cooling system.

 

[StevieDB9]

its a strange one, the bottom radiator hose is hot which says to me that its staying open, which as youve said is a bugger when ive just fixed it. especially when it took ages to get those daft hose clips off! and scraped knuckles!

 

[HDi fun]

Quite possibly a false temperature sender signal. Does the heater work? Efficiently?

If so then it's down to a new temp sender. Which, sadly means, another drain, refill and bleed.

 

[StevieDB9]

Quite possibly a false temperature sender signal. Does the heater work? Efficiently?

If so then it's down to a new temp sender. Which, sadly means, another drain, refill and bleed.

Thats what im fearing. That was already replaced about a year ago. For the time being ive partially blocked off the radiator with tinfoil which doesnt help it heat up any quicker but it stops it cooling down whenever the cars driven at speed.

 

[HDi fun]

I'm confused now. Do you have a coolant circulation problem or is it just that the coolant temp guage is giving false information?

Is it using more fuel than normal? Is the exhaust tailpipe sooty? Both would point to poor temperature regulation or reporting.

It's unlikely that the engine management unit is faulty as you'd have so many other symptoms besides. (Q. Does it drive ponderously?).

Give us all some more information and we'll all have a dig into our respective think tanks.

 

[StevieDB9]

haha cheers

i did have a circulation problem but that was the water pump which has been replaced.

Now the basic symptoms are that the car takes a long time to heat up when standing stationary/ driven slowly but as soon as I drive on fast roads it cools right down. I can only think its the thermostat but ive only just replaced that so unless its a dodgy thermostat ive fitted i dont know what it is but as youve mentioned it might be the sender unit. There are no problems performance wise. Been offered £3000 for it though which is a good offer but need to get this fixed before I can sell it to anyone.

 

[HDi fun]

I suppose if the 'stat is stuck open then you'd get this kind of behaviour. Are you certain that the new one went in right way round?

I'm not sure if this still applies, but years ago when I was brave enough to do my own mechanical work I noted that you could get stats with different open/close temperatures for different seasons or climates.

Lots of cars do take forever to warm up when stationary - mine takes bloody ages - DI diesels don't create much excess heat at idle but on the move it rapidly gets to about 90C and stays there.

For the cost of a stat I'd buy another and replace it again rather than draining the system just to have a look.

 

[StevieDB9]

well it takes much longer than it used to and as i said it cools right down when travelling at any kind of speed. ive had enough faffing about with it so its goin in the garage tomorrow and they can fix it while im at uni. thanks for you help HDi.

 

[pgarner]

i know this is going to sound really stupid but did you test the 'stat opened and closed before sticking it in.
put it in water boil it then allow it to cool

if its the temp sensor it should show up in a diagnostic scan. or at least if you looked at its reading you should have a fair idea.

the temp sensors are notorious for failing on VW. think they use nearly the same across the lot. is it a green temp or a brown one the brown ones are the ones that fail alot i im right.

if you want to take a trip down to abington services (roughly halfway according to autoroute ) to give it a scan with vagcom give us a shout and i see what days im off.

see www.ross-tech.com for info on vagcom

 

[StevieDB9]

foolishly i didnt test the thermostat. stupidly assumed a new one would be working.

well the cars going in my local garage first thing tomorrow but thanks very much sincerely for the offer, thats very kind. If i ever have problems again (though im trying to sell the car) is it okay to give you a shout?

 

[HDi fun]

I'd have done exactly the same and fitted it right away.

Always ask anything here mate, that's the whole purpose of such forums.

 

[pgarner]

aye if i can help i will.
not saying im great with the software but learning sowly

its they way you learn things . both making mistakes and from other people