willv8 Posted July 16, 2011 Report Share Posted July 16, 2011 As the thread suggests, ive an overheating lupo! The temp guage only reads to 90c, no higher. Meanwhile, if i slightly rev the engine, water comes out the expansion tank overflow. The fan doesnt kick in (ive replaced the fan switch, thats working fine.) and the rad top and bottom hose get hot.Theres a slight air lock as the heater matrix isnt filling up properly/no hot air outta heaters. Head gasket seems good, im thinking thermostat or water pump?Or what about expansion tank cap not letting the system pressurise properly? Quote Link to comment Share on other sites More sharing options...
treblet Posted July 16, 2011 Report Share Posted July 16, 2011 I'd try another expansion bottle cap for starters. For the amount it'll cost you to get a new one you could save yourself a fortune in other parts if it's only that. Quote Link to comment Share on other sites More sharing options...
Bickerton Posted July 16, 2011 Report Share Posted July 16, 2011 Theromostat may also be the issue Quote Link to comment Share on other sites More sharing options...
Defcon5 Posted July 16, 2011 Report Share Posted July 16, 2011 If it pours out when you rev the water pump is working. If it gets up to temp and stays at 90 through various driving the thermostat is OK. Fan should only come on after its being standing a while.As Treblet said, replace the expansion cap first, then bleed the system of air. Quote Link to comment Share on other sites More sharing options...
willv8 Posted July 16, 2011 Author Report Share Posted July 16, 2011 I bought it last week, its not been on the road yet so driving it isnt an option yet till i get it MOT'd, it seems to be pouring the water back into the expansion bottle via the small overflow hose that comes from the thermostat housing, plus getting bubbling hot via the bigger hose that comes into the base of the expansion tank, yet rad fan doesnt come on.It has in the past (before i bought it) spat a whole load of coolant out the top of the expansion tank through the blue cap, as its covered the engine bay. (Thats why i got it cheap.. the old lady didnt know what to do so got rid of it!)My GF has a lupo, ill pinch her cap tonight and try it, though i dont think its that, because as soon as i switch it off, im able to undo the cap with only a slight "pffft" of pressure, if that.If the thermostats failed, would it still allow a bit of water through to heat all the hoses, and likewise, if the pumps failed would the water travel round the system by convection somewhat?Oh, and whats the best way to bleed the air out? ta! Quote Link to comment Share on other sites More sharing options...
Defcon5 Posted July 16, 2011 Report Share Posted July 16, 2011 If the thermostats failed, would it still allow a bit of water through to heat all the hoses, and likewise, if the pumps failed would the water travel round the system by convection somewhat?No it wouldnt travel by convection, the pump must be working for it to heat the hoses. If the thermostat was stuck halfway I would expect it to get too hot. Quote Link to comment Share on other sites More sharing options...
treblet Posted July 16, 2011 Report Share Posted July 16, 2011 If the cap is knackered then you'll not get much of a hiss when you undo it as the system isn't sealed properly so isn't holding pressure properly.A knackered cap could also explain the coolant spraying everywhere if coupled with a sticky thermostat. Quote Link to comment Share on other sites More sharing options...
Rich Posted July 16, 2011 Report Share Posted July 16, 2011 You know, it'd help if you said which engine this was, I've had this recently with a TDI and after a lot of playing about I managed to sort it. Quote Link to comment Share on other sites More sharing options...
willv8 Posted July 16, 2011 Author Report Share Posted July 16, 2011 Sorry, its a 1.4 automatic, not sure of the engine code exactly. Quote Link to comment Share on other sites More sharing options...
Rich Posted July 16, 2011 Report Share Posted July 16, 2011 what's the pressure like in the pipes ? Quote Link to comment Share on other sites More sharing options...
willv8 Posted July 16, 2011 Author Report Share Posted July 16, 2011 What does anyone think to head gasket failure? Ive been speaking to my mechanic who is a bit doom and gloom, and thats what he says-Eeek! There doesnt seem to be any contamination of water, but if its combustion pressure pressurising the cooling system then there wouldnt be would there? Quote Link to comment Share on other sites More sharing options...
Defcon5 Posted July 16, 2011 Report Share Posted July 16, 2011 HGF doesnt cause overheating, overheating causes HGF.From what your saying, it isnt even overheating, its just your expansion tank cap is knackered. Just replace that then come back of it hasnt worked. What makes you think its overheating - you even said the temp gauge never goes above 90How someone can look at this and instantly think HGF I have no idea Quote Link to comment Share on other sites More sharing options...
Rich Posted July 16, 2011 Report Share Posted July 16, 2011 I had this on the lupo, seemed to be losing water and the system was super pressurised. Release the cap slowly and the level returned. Had a test done and it turned out that there was residue from the exhaust in the cooling system. It never went above 90 degrees, but the water light flashed, caught it just in time. four hours, 45 quid and cleaning a LOT of gunk out the intakes it's running a lot better, smoother and more importantly a lot quieter. I did search here and club polo for some history of this happening before, nothing. Searched an A2 forum and it's a common thing. Quote Link to comment Share on other sites More sharing options...
willv8 Posted July 16, 2011 Author Report Share Posted July 16, 2011 Sorry Rich, im not getting what you mean-do you mean there was exhaust gas in the cooling system? And what do you mean by cleaning intakes? My water light has started flashing now despite me topping the expan. tank right up, and no water is being "taken" as the car cools or anything.....I must admit, i dont think its HGF, it takes a good 5 mins for the water to look like its getting hot, im thi nking (hoping) its thermostat...I hate not knowing whats wrong! Quote Link to comment Share on other sites More sharing options...
Derv Posted July 16, 2011 Report Share Posted July 16, 2011 I've had quite a few VAG thermostats go over the many years I've owned various VAG cars, and they have always stuck open, meaning the cars run too cool.I agree with the posts about checking the cap. for a start it's a cheap check. If you can try the suspect cap on a known good car. If the system cannot pressurise, then it will not be able to get hot enough for the fan to kick in. Water boils at a higher temperature at higher pressure.A failed head gasket usually shows up by combustion gas pressurising the coolant tank. You can check this by unscrewing the cap to vent the tank (carefully), retightening the cap,then starting the engine and running it briefly, then checking for pressure in the coolant tank again. If the pressure is back, suspect the head gasket. Quote Link to comment Share on other sites More sharing options...
Rich Posted July 16, 2011 Report Share Posted July 16, 2011 As Derv said, the head gasket can fail in many many ways, on mine it was just allowing some exhaust gasses into the cooling system. I really tried absolutely everything before it was gasket time, trust me, it wasn't something I wanted to do. Quote Link to comment Share on other sites More sharing options...
willv8 Posted July 17, 2011 Author Report Share Posted July 17, 2011 Ill be having another look tonight, pipes arent getting too solid, and its defo the overflow pipe from the stat thats pouring most of the water back to the tank, but not at idle, just when i increase the revs slightly. My mechanic obviously said gasket, (even though hes never seen it do it yet), but once its boiling (-He said its not boiling, its exhaust gases coming through the coolant...... :/) and you switch the engine off, it continues to boil for a minute or so... ive had cars with head gasket go before, and if you can see bubbles, its tiny, tiny, almost like a "fizzing" effect in the water.Ill keep you posted with what i find out..... Quote Link to comment Share on other sites More sharing options...
Defcon5 Posted July 17, 2011 Report Share Posted July 17, 2011 Is he a Rover mechanic?Have you tried the expansion cap off your other Lupo yet? Quote Link to comment Share on other sites More sharing options...
willv8 Posted July 17, 2011 Author Report Share Posted July 17, 2011 Doing it in 5 mins....... Quote Link to comment Share on other sites More sharing options...
willv8 Posted July 17, 2011 Author Report Share Posted July 17, 2011 Its ticking over now with the new cap on...... Quote Link to comment Share on other sites More sharing options...
willv8 Posted July 17, 2011 Author Report Share Posted July 17, 2011 Right, its ticking over fine with no loss of coolant? Fingers crossed....?Its probably a little low on coolant due to the past day or two's messing about so ill have to add some asap.What temp does everyone elses reach when ticking over, mines sitting at about 105 at the min, but the fans not kicking in, even though its got a live feed to the (new) fan switch, and when you bridge the connections the fan starts okay, could this be down to maybe not enough coolant in the rad and not heating the fan switch up enough?Where is the temp sender for the temp guage? And any ideas on bleeding the system and getting all the air out, as currently im getting no heat through the heater vents?Ta! Quote Link to comment Share on other sites More sharing options...
Defcon5 Posted July 17, 2011 Report Share Posted July 17, 2011 It should stay solidly at 90 (the very middle dot), the gauge is dampened so it shouldnt fluctuate. Are you sure its reading that high? Quote Link to comment Share on other sites More sharing options...
willv8 Posted July 17, 2011 Author Report Share Posted July 17, 2011 Yeah, i was revving it to 2k to push it a bit/get any air worked through it, and like i said its gonna be a bit low on coolant. Any ideas on bleeding air out of it?? Quote Link to comment Share on other sites More sharing options...
Defcon5 Posted July 17, 2011 Report Share Posted July 17, 2011 They are self bleeding as far as Im aware. How quick does the temp guauge go to 105? Gradually or quickly? Does it stay there? Quote Link to comment Share on other sites More sharing options...
willv8 Posted July 17, 2011 Author Report Share Posted July 17, 2011 It took a while, it was sitting nearer 90 most of the time, then only when i revved it solidly for 2 mins or so did it rise to 110.Its cooled down now and its got no water in the expan. tank at all, ill get a cap for it tomorrow, and try get more water into it. At the min its sitting facing slightly downhill, will this affect the bleeding of it at all? Quote Link to comment Share on other sites More sharing options...
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