2001 passat tdi 130 133k - passat tdi130 heaters going hot n cold overheating

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Fri 2 Jul 2010 02:01
2001 passat tdi 130 133k - passat tdi130 heaters going hot n cold overheating - saxopower

hello all could anyone shed some light on a problem iv just started experiencing.

over the last month i have noticed when the heaters are on warm when the car is up to temp 90oc they have been blowing cold air until the car is driven a bit harder then they get warmer.

but tonight i had to tow my friends discovery a few miles which broke down, when i got back in it to go home the temp needle was around 110oc i have never seen it over 90oc

while driving home i put the heaters on warm to get the temp down but it fluctuated between 90 and 110, when the temp got to 110 then heaters got warm till it dropped to 90-95 then they got cold and so on.

i got home and the radiator resovoir was under a lot of pressure and hot i let the pressure out and it took 4 litres of water, there dosent seem to be water in the oil or any leaks.

so can anyone shed any light on the problem i cant see any leaks but will check and see how it is tomorrow.

many thanks

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Fri 2 Jul 2010 10:11
2001 passat tdi 130 133k - passat tdi130 heaters going hot n cold overheating - craig-pd130

Have a check of the dipstick and under the oil filler cap for emulsification, it's losing water somewhere. Either a small external leak (cracked or loose hose); or the cylinder head gasket has failed and coolant is getting into the cylinders.

If you don't see any mayonnaise then have the cooling system checked by a garage.

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Fri 2 Jul 2010 11:13
2001 passat tdi 130 133k - passat tdi130 heaters going hot n cold overheating - Collos25

If there aare no leaks which I doubt then it is almost certainly the head gasget.

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Fri 2 Jul 2010 12:47
2001 passat tdi 130 133k - passat tdi130 heaters going hot n cold overheating - saxopower

thanks for the replys, im going to have a look at it now, when i checked last night the oil level seemed normal and didnt feel like there was any water in it.

but i will go check it now.

also the intercooler has started hissing under boost but this shouldnt be part of the cause should it.

cheers

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Sat 3 Jul 2010 11:22
2001 passat tdi 130 133k - passat tdi130 heaters going hot n cold overheating - Peter D

When towing you may have overboosted and fractured your intercooler or one of the pipes has split. Do to a garage and hve then use a gas analysor to sniff or sample the header tank for signs of combustion gases in the water, a sure sign of a HG problem. If all is well I would suspect the impellor of the water pump has let go of the shaft and is free wheeling as such. However the erratic nature of the heater does not support that but air in the system does either because the HG is leaking combustion gases or the bater is boiling due to a circulation problem. Regards Peter

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Sat 3 Jul 2010 17:45
2001 passat tdi 130 133k - passat tdi130 heaters going hot n cold overheating - saxopower

hi thanks for all your help. iv found the leaking boost pipe one has a little split in it.

iv been running the car for the last few days on short journeys its not gone past 90oc since and not used any water, i have noticed that when its left to heat up on tickover for half an hour the top hose is real hot as normal but the bottom one is cold also the header tank is cold when driven a few miles the header tank does warm up but dosent get really hot. im thinking the water pump or thermostat. i have ordered a water pump and will let you know if it cures it on mon when i fit it.

thanks again

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Sat 3 Jul 2010 18:06
2001 passat tdi 130 133k - passat tdi130 heaters going hot n cold overheating - Collos25

What about the 4 litres of water you lost why don't you save time and expense and have the system tested properly instead of stabbing in the dark costing time and money.

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Thu 8 Jul 2010 15:03
2001 passat tdi 130 133k - passat tdi130 heaters going hot n cold overheating - hirsty

i checked the waterpump and all was fine. in the end it was the thermostat had stuck.

all is good now

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