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Hi,

Looking for some help please!

We have a T5 2.5L TDI 2007 van which has developed a fault whereby it starts cold, runs perfectly until the temperature reaches 43.8 degrees and then cuts out. Once cooled it will then re-start and runs until it reaches the same temperature, then cuts out again.

We have changed the coolant temperature sensor in the block and the crankshaft sensor. There are no fault codes present. Any ideas of where we should look next?

Thank you in advance!

Jemma and Rob
 

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think if you have a good diagnostics you need to read the data and then you may have a chance of fixing it
i would do an engine service first just to rule out filters being blocked
 

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We did have a 1.9 doing this recently but I don't think they came back with any fix.

I don't know about other kit like snapon etc but with VCDS you could log all the blocks that show temperature together as live data and drive it until the van cuts out and see if anything looks wrong. The temps should all show roughly match ambient when cold and climb as you would expect on driving with no missing or implausible data in the readings. The fuel temp is found in another group of blocks but you you should be able to log that with the others. On some some 2.5's the blocks are not fully marked, if it's like that on yours here are the places to look:

062,1,Coolant Temp. (G62) Engine Coolant,
062,2,Coolant Temp. (G83) Engine coolant Radiator Outlet temp
062,3,AmbientTemp sensor (G19)
062,4,Intake Air Temperature (G42)

007,1,Fuel Temperature,(G81) Range: 20...90 °C

The 062/007 etc numbers are the group. The 1,2,3 and 4 are the positions from the left. So if you find group 062 first, the third from the left will be ambient temperature if it is not already labelled as that.

The above check just eliminates some possibilities so you can move on to other things.

I'm always suspicious of the main unswitched (terminal 30 relay) at least enough to check if a unswitched supply is present when the engine cuts out. They can fail when warm and correct themselves as they cool.

Live data can show the status of the terminal 30 supply to various things. This block shows the main unswitched supply to the alternator but it is worth checking what that says when the engine cuts out because the same relay supplies most things that need an unswitched 30 amp supply. It should be battery voltage with the engine not running.

016,4,Supply Voltage,(Terminal 30)

The ECU itself is another possibility because they can certainly pack up when hot but you would need the pinout and a scope to see if the outputs are what they should be. Otherwise you can send it off to ECU testing etc for checking/repair. They will keep your immobiliser working.

The ignition switch is another thing that might fail when hot.

Obviously it's worth checking all earths, especially near the ECU. It's also important not to only check the ECU for fault codes but all of the other controllers just in case. Logging live data on the road might save a lot of time if you can record something misbehaving as the van cuts out. Good luck! :)
 
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