Overheating On Hills Issue

[WOODY1982-1]

i have a 2002 ghia 1.9tdi about a month ago my temp gauge started to go a bit loopy and was bouncing up and down so i changed the sensor on the right hand side at the back of the block and decided to change thermostat at the same time, all was well until climbing a hill ,working the engine, temp gauge will go up slowly until i back off the power then returns to normal,  it has gone in to the red a few times but again once i let the strain of it went back to normal 90 within 20 seconds

 

some info for you  ive never seen the rad fans come on at all 

 aircon is broken (broken pipe) but even when i select low on climate control no fans at all, so change sensor on passenger side of rad but still nothing the do come on when connected to battery and when i cross the wires to the switch( hence why i thought it was switch failure

 

i can clearly see water returning through the return pipe at top of expansion tank and i bought a new cap for it and theres lots of pressure when i undo the cap and the water floods back into tank when the cap is released otherwise it looks empty until i release the pressure

 

top radiator hose gets very hot in fact all pipes get hot except for the bottom hose going to the thermostat, this always feel very cold and so does the radiator

 

 i dont know what else to do, 

i was thinking maybe a relay or something, maybe fans arent being told to come on but i dunno

 

any help would be appreciated dont want to scrap as i just put it through the mot

[BrianH]

Sounds to me like the thermostat is blocked/jammed or the radiator is blocked.

 

I'd remove the thermostat as a first step and see if that allows the coolant to flow and heat the currently cold section of hose - if it doesn't then next step is going to be to drop the radiator out and flush it - if you struggle to get anything to go through it at this point you'd be best to replace it (you may want to do so anyway as it could still be partially blocked, but at least this would give you a good idea if it is blocked).

 

Does yours have a run on pump and does it work? (info on here relates to the booster heater should explain finding it, if its failed no codes will be logged for it doing so, but if its working you should be able to hear it after you shut the engine off for approx 20 seconds.

 

Would doubt its the sensor for the fan (petrol ones use a sensor in the hose, but same applies) - as if you say its in the radiator and the radiator isn't hot that suggests its doing what it should. They are usually a simple 2 pin switch so you may be able to connect the two sides together to test the fan itself, but be aware some will directly feed the fans with power so the wire can get hot if its too small (don't do it for long just give it a quick test to see).

[tim-spam]

Almost certainly the cylinder head gasket starting to leak.