Overheating problems

[Jimp]

The Vento was overheating last month some time, asked on here, thermostat was suggested, thermostat was changed and it was perfect. It's now overheating again. The symptoms are the same as the faulty thermostat with top radiator pipe warm and bottom one cold, but when I checked the thermostat today it was fine. Gaskets were fine and the housing looked fine to me. Emptied and replaced the coolant anyway and ran water through the radiator to see if it was blocked, but it was still perfectly clean from when I changed the thermostat the first time. After putting everything back together it was still running too hot after a while. The fan wasn't switching on either. I can't find any air bubbles in the pipes, I massaged the various pipes until the bubbles stopped before running it again. The heating inside blows both hot and cold without problems so I kinda doubt it's the pump. Any ideas about the problem? 

[aminorthreat1]

head gasket, go get it tested.

[mrmafyew]

check water pump

[Wayne]

Airlock

[AudiA8Quattro]

I doubt its the water pump as you are getting hot air.
Check for an airlock as Wayne suggested.
Try removing the thin hose that goes into the top of the expansion bottle, these can get blocked and stop the system self bleeding.

[Jimp]

Is checking the head gasket a garage job or is there a way of doing it at home?
I've checked for air locks but can't find any. I checked by massaging the various cooling pipes until bubbles stopped coming out. Is there something else I should be doing when hunting for an air lock?
I'll try removing the thin hose and checking it for blockages, I didn't think of that. There is a trickle coming back into the tank when the engine runs but never more than a trickle.

[aminorthreat1]

i had this problem after flushing my coolant. there just didnt seem to be anything going through the radiator. after a new pump, thermostat and radiator, i took the head off. (even though i'd done compression, cylinder leakage tests etc)

i found a cheap head gasket with holes that barely matched the water and oil gallerys. one water gallery was completely blocked by the gasket (see pic) and behind it was full of gunk, which i must have dislodged from around the system when flushing the coolant, and im guessing it all ended up there eventually blocking the flow of coolant through the rest of the block.

new gasket came last week straight from VW, full set. inc valve stem oil seals etc...  wasn't cheap. hopefully have it back together friday on my day off. and i'll give the whole block a good flush.




fingers crossed yours is something a little simpler though lol

[Jimp]

Bloody hell, I'm hoping it's not that, but now that you said it it has been idling a little rough  I'm paranoid now  I don't remember seeing head gasket replacement in the previous owner's records, but I'll double check.