Overheating 1.9 Tdi Ahu

[rmas]

Hi... i have a problem with my car related to overheating and this is what happens:

bought the car a year ago, had a blown HG, replaced it (head had water passages blocked with rust), cleaned all and reassembled everything, when i bought the car it did not have a thermostat and was running only with water.

Once i placed the thermostat i have the problem that the temp gauge starts to climb almost immediately after i start driving and it start to climb until it reaches the mark above the middle one (this in less then 15 minutes of driving), is i stop the car and check the water pipes, the top is hot, lower is cold and radiadtor is cold.

I already replaced the water pump, placed a new thermostat (opens at 84Ã,ª), replaced the thermal switch on the radiator (starts the fans at a lower temp also), replaced the radiator, replaced the fan, replaced the expansion tank and cap and it remains the same, already its the 3rd temp sensor beeing that the last one was a original VW sensor (35Ã,£)

the temperature only rises that much if i start to press the pedal, at slow cruise it passes a little of the middle,but when i press it it can go almost at the last mark before the red, If i slow down, the temperature decreases and if i stop the car and check the hoses, both are hot, no pressure in the circuit and the fan is working also.

i am baffled at this... already changed everything i can think and problem still persists please help me

[Mirez]

If I'm reading that correctly, the gauge reads around normal until you accelerate and then it shoots up? To me that would indicate a restriction or partial blockage in the system, the water pump is driven off the cambelt so the faster the engine is reving then the faster the water pump is turning, effectively forcing the hotter water past the obstruction.

[bigdave982]

Thought mk1 had a seperate belt,dont remember doing cam belt when i changed my mk1 pump

[rmas]

yes the MK1 has a separate bet however the faster the engine revs it does speed up the water pump and it just might be a blockage. What do you guys use to clean the system of blockages (bits of rust or similars)? This one has the radiator on the tailgate also and it could even be a blockage there, so no chance of finding it without stripping the car appart.

[insanitybeard]

You say there's no pressure in the circuit- do you mean the system isn't carrying excess pressure or it isn't actually pressurising? Is it using any coolant at all?

[rmas]

its not having excess pressure in the circuit The coolant its G12 and its always been that about a year ago, before it ran on water

[insanitybeard]

Although you have already replaced it, is there a possibility the radiator has been blocked by rust dislodged from the coolant system caused by it being run with no antifreeze? If you've checked/ replaced the usual suspects- water pump, thermostat, radiator, sensors etc and the system is holding pressure & not boiling over then I can only think that the dislodged rust you mentioned has partially blocked the system somewhere & is restricting coolant flow as Mirez previously said. Do the heaters blow hot air?

[rmas]

the one in the front yes, the one on the rear not sure, will test this weekend.