Fuel filter change and bleed

[Njanman]

I think my fuel filter needs replacing on my 2013 Leon 2.0 tdi, can’t see it as having been done in service history and it’s at 145k.
My question is do I need to do anything particular to bleed the system of air?
I’ve tried to search online but nothing gives me a definitive answer, something is suggested then someone else says no do this, also can’t find anything specific for my model year.
Thanks

 

[SuperV8]

Yes, you should prime your fuel system following fitting a new filter. Need to be done via diagnostic interface. VCDS etc..

 

[Njanman]

Yes, you should prime your fuel system following fitting a new filter. Need to be done via diagnostic interface. VCDS etc..

So you’re saying it needs to be done by a mechanic? I’d rather not have to pay someone to do a 10min job, is there no way of doing it manually? I’ve seen some suggestions that you turn the ignition on and off a few times, enough to let the fuel pump push fuel through and disperse the air

 

[tracktoy]

Just butting in, no you dont need a mechanic just a diagnostic tool that allows you to do stuff to the car.

vcds, obd11, Carista and multiple other ones as well, lets you check out DTC Codes, Reset Service Warnings as well as changing the setup on your car and doing stuff like this.

I will let @SuperV8 answer about your suggestion.

 

[Njanman]

Just butting in, no you dont need a mechanic just a diagnostic tool that allows you to do stuff to the car.

vcds, obd11, Carista and multiple other ones as well, lets you check out DTC Codes, Reset Service Warnings as well as changing the setup on your car and doing stuff like this.

I will let @SuperV8 answer about your suggestion.

Ah I thought VCDS was the specific tool needed and I don’t have the need for that type. I do have a diagnostic tool - TopDon CarPal - but doesn’t seem to allow me to do much, 6 basic functions really

 

[Mr Pig]

I've done this twice. I removed the lid on the filter can and slowly lifted the filter out so that as much of the fuel dripped back into the can as possible. Then I put the new filter in and surprisingly little fuel was lost, it came close to the top of the can. I didn't prime the system or anything, I just started the car. If I remember correctly it took a second longer to start but it started and ran perfectly with no skipping or anything.

Maybe the result could have been different but I've just swapped the filter twice with no issues. Sometimes you can overthink things. Incidentally, used a genuine filter both times.

 

[Njanman]

I've done this twice. I removed the lid on the filter can and slowly lifted the filter out so that as much of the fuel dripped back into the can as possible. Then I put the new filter in and surprisingly little fuel was lost, it came close to the top of the can. I didn't prime the system or anything, I just started the car. If I remember correctly it took a second longer to start but it started and ran perfectly with no skipping or anything.

Maybe the result could have been different but I've just swapped the filter twice with no issues. Sometimes you can overthink things. Incidentally, used a genuine filter both times.

Im just worried that if I do that, something might go wrong and end up being more expensive, is that likely you think?

 

[Mr Pig]

Im just worried that if I do that, something might go wrong and end up being more expensive, is that likely you think?

I don't know what terrible thing could happen? The way I did it would pretty much guarantee that some air would be introduced at the top of the filter can. It did no harm, the car started fine and ran perfectly for years. I don't know what the 'correct' method does differently?

 

[nd-photo.nl]

This is in the workshop manual for TDI engines with regards to bleeding the fuel system

1.3 Filling and bleeding fuel system

Caution
The high-pressure pump has very close tolerances and must not be allowed to run without fuel. To prevent this and to enable the engine to start quickly after parts have been renewed, it is important to observe the following:

-If components of the fuel system between the fuel tank and the high-pressure pump have been removed or re‐newed, the fuel system must be filled and bled before the engine is started for the first time.

Special tools and workshop equipment required
Vehicle diagnosis tester

Proceed as follows to fill high-pressure pump with fuel:
-There must be sufficient fuel in the tank.
-Connect vehicle diagnostic tester
-Switch on ignition and select the following menu item in the vehicle diagnostic and service information system: Fuel system: bleeding of air

The fuel pump starts running
The fuel pump must run for approx. 3 minutes to ensure that the high-pressure pump is filled with sufficient fuel

-Start the engine after filling the fuel system.
-Let the engine run for a few minutes at average speed and then turn it off again
-Check that the fuel system is completely sealed
-Delete event memory entry with the vehicle diagnostics tester
-Then test drive the vehicle, accelerating to full throttle at least once
-Then inspect high-pressure section of fuel system again for leaks

 

[Mr Pig]

This is in the workshop manual for TDI engines

Where is the fuel pump?

 

[Compo1]

I've done this twice. I removed the lid on the filter can and slowly lifted the filter out so that as much of the fuel dripped back into the can as possible. Then I put the new filter in and surprisingly little fuel was lost, it came close to the top of the can. I didn't prime the system or anything, I just started the car. If I remember correctly it took a second longer to start but it started and ran perfectly with no skipping or anything.

Maybe the result could have been different but I've just swapped the filter twice with no issues. Sometimes you can overthink things. Incidentally, used a genuine filter both times.

Exactly what i do despite having VCDS although maybe an overkill i syring out all the fuel pop in the filter and top the housing off with fresh fuel. I understand the fuel lines may have drained but its doubful all the way back to the fuel pump.

Never any issues.

 

[Mr Pig]

Exactly what i do despite having VCDS although maybe an overkill i syring out all the fuel pop in the filter and top the housing off with fresh fuel. I understand the fuel lines may have drained but its doubful all the way back to the fuel pump.

Never any issues.

Where is the fuel pump? If the pump was after the filter then yes, I can see it being a problem. If it is before the filter then realistically, no. Ok, you managed to drain the lines and get air in the pump then yes but that's not happening. As long as the pump and line before it remain full of fuel any air in the system is getting pushed out pretty rapidly.

 

[SuperV8]

Where is the fuel pump? If the pump was after the filter then yes, I can see it being a problem. If it is before the filter then realistically, no. Ok, you managed to drain the lines and get air in the pump then yes but that's not happening. As long as the pump and line before it remain full of fuel any air in the system is getting pushed out pretty rapidly.

The 'fuel pump' is the high pressure common rail fuel pump after the fuel filter.
This pump is lubricated by your diesel fuel. If it runs dry it will be destroyed. (they are expensive)
The fuel prime function is to ensure this main high pressure fuel pump does not suck air.
I'm sure many have just changed the filter - and done nothing, and it's been ok - but there is a low risk, with a high (cost) severity.

 

[SuperV8]

So you’re saying it needs to be done by a mechanic? I’d rather not have to pay someone to do a 10min job, is there no way of doing it manually? I’ve seen some suggestions that you turn the ignition on and off a few times, enough to let the fuel pump push fuel through and disperse the air

You need to ensure your main (expensive) high pressure fuel pump doesn't run dry. It uses diesel fuel for lubrication.
The official way is to run a fuel pump prime sequence.
If you don't have any diagnostic interface which can run the prime you could probably manually ensure the canister is full of fuel and cycle the ignition a few times.