Passat - Was Overheating, Now Heater Dosn't Get Hot!

[Lordbenny]

As the title says, overheated on motorway last night, crawled home, checked coolant this morning, seems ok. No visible leaks and temperature gauge is fine (bang on 90 degrees).Trouble is that the heater now only blows cold air.

Question - If the water pump has packed up would it affect the temperature gauge? Surely if the water wasn't being circulated the temperature would rise?

Can you think of anything else that would cause this problem?

Thanks in advance.

 

[^neo^]

Will more than likely be an air lock.
Leave the engine running on tickover, with the coolant reservoir cap off. Keep the bottle filled right to the brim with coolant. When the thermostat opens coolant will spew out from the coolant bottle. As soon as it does, turn off engine, top up coolant to the right level and whack the cap back on.

If the expansion tank cap looks a bit old, get a new one from VW as these can also cause problems when the pressure valve packs up. Under a tenner from the dealer

 

[crank39]

I would check the thermostat first as its the cheapest.

It could of stuck shut which is why it overheated as your engines water wasnt being replaced with cold water from the radiator, it could of also stuck in the open position now meaning the water pump is constantly swaping engine water with radiator water meaning the engine water doesnt get hot enough for the heater matrix to blow warm air.

 

[timtheenchanter]

best way to check it, whip it out, if its cold is should be closed, if its open, bin it, if its closed, put it in a pan of water and heat it up, it should open up, if not.... you get the idea.

use an old pan, OHs tend not to like you useing the best tefal stuff (mine went mad when I did for an oil bath)

 

[bongos]

As the title says, overheated on motorway last night, crawled home, checked coolant this morning, seems ok. No visible leaks and temperature gauge is fine (bang on 90 degrees).Trouble is that the heater now only blows cold air.

Question - If the water pump has packed up would it affect the temperature gauge? Surely if the water wasn't being circulated the temperature would rise?

Can you think of anything else that would cause this problem?

My Golf did exactly this. Turned out the water pump had gone and it sent the head gasket with it.

The heater would only blow cold air and the temp gauge still sat on 90C until I drove it any distance and then it would overheat again (no water circulation obviously).

 

[davieboy]

what year and what engine?? engine code would be great!

a few common faults cause this, but depends on above info.