Passat 1.6 TDI overheating/coolant use

richiegt

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hi all, this Passat is my other halves car, we have it maybe am 2 weeks now it started overheating on day two as usual no overheat on test drive or drove home approx 1.5 hour journey.
so the coolant level drops are sometimes small sometimes large, the car could idle all day no over heat if idled with heating on will only reach 70,C on gauge. no lights on dash apart from low coolant warning once.

things that have been done so far, drain coolant and flush rad and heater core with garden hose, fitted new dealer thermostat old one had failed shut, new coolant temperature sensor, bleed system, new coolant bottle lid. bottle of leak stop.

there was a slight improvement that was short lived, im guessing there is only two culprits left the egr cooler (its like a radiator for exhaust gas before going to intake) or the head gasket is toast.

have not had a chance to bring it to a garage yet she uses it daily but only for very short periods but the parts have come up to around €135. not too bad really thermostat was a pain to fit and was needed anyway.

so heres the kicker the head gasket and egr cooler failing will cause similar symptoms neither are going to be nice jobs for poor me. neither are going to be cheap at a garage poor her lol.

the egr cooler online at the minute would be just under €100 delivered and probly 4-6 hours fitting by myself, is it worth the hassle gamble?

lastly there is a coolant ****** housing on the side of the head which has about 3/4 outlet pipes on it, there seems to be some localised boiling/pressure build up there so either the headgasket is gone there on cylinder 4 or the coolant is being boiled in the egr cooler and causing the hotspot there very hard to tell though without taking it off.
 

Keithuk

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As I asked in your intro what year is this Passat 1.6 TDI?

Overheating check the thermostat is working correctly.

Is that overheating as the gauge says or is it overheating?

Flush the cooling system and get it pressure tested?
 

richiegt

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hi Keith the car is 2010 Passat BlueMotion 1.6 TDI, i have fitted a brand new oem thermostat from the dealer, it appers to mostly be the gauge to remedy this i fitted new CTS but it still shows overheating on the gauge, both lower and upper radiator pipes are relatively cold, Fans do come on, radiator is not hot to the touch, removed the pipe to expansion pipe and coolant flowing, and small pipe on radiator end has high flow, there appers to be only heat at cooling ****** that houses the CTS, hose on the front hot, both heater matrix pipes are hot to the touch. there appears to be localised boiling there.

when the overheat situation occurs cabin heat blows hot air when the gauge returns to 90C it only blows lukewarm to warm not hot using my 2006 A6 as a reference.

the passat does lose / use coolant, there is grey sludge in the charge pipe work and in the breather system to turbo intake hose. the oil on the dipstick is clean, and the recently drained oil was normal to my eye not cream or coolant stained.

from hours of google and soaking up information i havent seem to found the smoking gun, havent got a presure tester here i will have to buy or borrow one
 

Crasher

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Head gasket failure on the CAYC engine is becoming an increasingly common problem. Just changing the gasket, even with a skim, is only a short term "get rid" solution as skimming removes the HIP heat treatment from the heads face so failure occurs again quite quickly.
 

richiegt

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crasher thanks for the reply, i have done a few cars headgasket abeit all petrol cars, none had these symtoms, its like poor circulation? the car can be driven circa 10/20 minutes with no overheating, the degas bottle has some small bubbles inside it constantly normal? never appears to puke out of bottle or look to be boiling but if you open the lid the coolant housing on the gearbox side starts bubbling and you can hear the pipes being expanded in a kind of popping noise. i was hope the egr cooler was introducing the heat to coolant and cause the over heat situation the car has 290km on it
 

Crasher

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Have you ever experienced one with an MLS head gasket? They leak in a very odd manor and often don't leak until under heavy constant load also defying attempts to diagnose with gas or chemical testing. Do you know if the water pump is newish?
 

richiegt

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Crasher, ive done 3 mls, peugeot oil leak from coner of head common problem doesnt cause over heating, an alfa romeo twin spark but due to spark plug shearing in head not because over heating, a little citreon that had hydrolocked itself but never overheated that was a strange one no damage just new gasket and off it went. the other cars i did had the normal symtoms like oil in water, water in oil, coolant tank boiling and puking, compression loss due to car being drive while gauge was in the red etc but anyway the waterpump was renewed 40,000km ago but not by myself so metal or plastic unknown, when i changed the thermostat i should have checked but i didnt remove the alternator and it was almost 0 degrees outside so i was in a hurry lol my other half has informed me coolant loss has stopped since pouring in the bottle of prestone headgasket sealer bit of an ominous sign but im convinced the previous owner did same prior to purchase
 

Crasher

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Yes, a CAYC engine. That head gasket sealer does work for a very short time and can prove the issue but I have also seen it set solid in the expansion tank and block the heater matrix and radiator. It is the sort of product I feel should be a criminal offence to sell, it is so obvious it is going to be used for nefarious purposes...
 

richiegt

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its a pita really but it has seemed to have helped stop the coolant dissappearing but not helped the overheating which i thought would go hand in hand, something odd i noticed today did about 140km today in car, when diving at 100 kph in 5th car would creep the up the gauge now and again especially up slight inclines, but if driven the same speed in 4th @2000 rpm the gauge will stay happily at 90C and i let the gauge go up to 115C popped it back to 4th and about 2100 rpm and the gauge fell back to 90C quickly much more quickly than if i turned the cabin heater on and coasted, so i was almost home and i live in a hilly area and i left the car get up to around 120C on the gauge stopped car in driveway, no cabin heater revved the car up to about 2100 / 2200 rpm and the gauge once again started dropping and quickly much faster than normally would if i just left it idle with cabin heater on high. now i dont know but that seems very odd to me not often when your car is overheating would you pull over revv it up to cool it down! any ideas? ive been thinking about making a small bank to stop egr gas flow and see does this stop the problem occuring and then replace the heater and or egr unit also ive been seeing that clogged coolers can cause overheating on occasion
 

Crasher

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Don’t place any store in the dash gauge reading, it is completely useless and tells lies, you need to monitor the actual readings using a diagnostic system to know what is actually happening.
 

richiegt

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i know the gauge reads 90C upto around 107C ive checked it against the second sensor they are not very far from eachother after 110C but anyway my question is would maybe the egr cooler can cause the overheating or maybe a failing waterpump. dont worry i know im basically clutching at straws here ha ha. seeing as the coolant levels are staying put is giving me slight hope
 

richiegt

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Right a final update i hope, i got a new thermostat and i fitted it car. still overheating when pushed up hill ect, solution i drilled 6 3mm holes around the the thermostat evenly spaced on either side of the bridge im going to call it. This has worked, car gets up to temp and holds it, doesnt start lifting the needle when going uphills in high gear anymore. Delighted now
 

Jay9191

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hi all, this Passat is my other halves car, we have it maybe am 2 weeks now it started overheating on day two as usual no overheat on test drive or drove home approx 1.5 hour journey.
so the coolant level drops are sometimes small sometimes large, the car could idle all day no over heat if idled with heating on will only reach 70,C on gauge. no lights on dash apart from low coolant warning once.

things that have been done so far, drain coolant and flush rad and heater core with garden hose, fitted new dealer thermostat old one had failed shut, new coolant temperature sensor, bleed system, new coolant bottle lid. bottle of leak stop.

there was a slight improvement that was short lived, im guessing there is only two culprits left the egr cooler (its like a radiator for exhaust gas before going to intake) or the head gasket is toast.

have not had a chance to bring it to a garage yet she uses it daily but only for very short periods but the parts have come up to around €135. not too bad really thermostat was a pain to fit and was needed anyway.

so heres the kicker the head gasket and egr cooler failing will cause similar symptoms neither are going to be nice jobs for poor me. neither are going to be cheap at a garage poor her lol.

the egr cooler online at the minute would be just under €100 delivered and probly 4-6 hours fitting by myself, is it worth the hassle gamble?

lastly there is a coolant ****** housing on the side of the head which has about 3/4 outlet pipes on it, there seems to be some localised boiling/pressure build up there so either the headgasket is gone there on cylinder 4 or the coolant is being boiled in the egr cooler and causing the hotspot there very hard to tell though without taking it off.
Hello did you manage to fix this ? As I'm having same issue with my passat same model as yours. It overheats if I go above 50 mph after the temperature has reached 90 its goes to 100 and goes back down to 90 after I slow down. Things that have done on it are cam belt, water pump , new thermostat, new temprature sensor and coolant has been flushed any help would be much appreciated thanks
 
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