*Another* 2000 Audi a4 B5 1.9 tdi pd limp mode

[Crasher]

Private Message me your REG number and tomorrow I will look up the vacuum source point.

[Crasher]

It is an AJM engine and left hand drive which are slightly different to the right hand drive AVF in the picture disconnect the vacuum hose 9 where it goes to servo vacuum feed pipe check valve pushed into the plenum chamber wall rubber bung and apply the vacuum there

This is the EGR vacuum system

1. To vent port on charge pressure control solenoid valve -N75
2. Mechanical EGR valve
3. Vacuum hose from EGR valve -N18 to mechanical EGR valve
4. To charge pressure control solenoid valve -N75
5. Vacuum hose to vent connection on air cleaner housing
6. EGR valve -N18. Fitting location: on rear of air pipe
7. Vacuum hose to fuel cooling circuit cut-off valve
8. Cut-off valve for fuel cooling circuit
9. Vacuum hose from tandem pump
10. Vacuum hose from tandem pump

This is the turbo vacuum system

1) Non-return valve, Installation position (light/dark side): As shown in diagram
2) Intake manifold change-over valve -N239
3) To EGR valve -N18
4) Vent line into air cleaner housing, to EGR valve -N18
5) Intake manifold change-over vacuum unit
6) Vacuum unit for charge pressure control. Cannot be replaced separately
7) Turbocharger
8) Vacuum reservoir
9) Charge pressure control solenoid valve -N75 at front right in engine compartment

[Disco_jo]

Wow ! Thank you so much for this. Hope this helps others too.

I pulled the 3mm off number "9" in first photo and can easily draw air in. The air is entering through the Cut-off valve for fuel cooling circuit, number "8" on first photo. Does that mean he has gone belly up?

[Crasher]

Remove the hose, plug it and see what you get then. the valve is 4A0 819 809 and £63 here but normally all the bits attached fall to pieces so the full assembly 8D0 203 514 A at £116 makes more sense. When that valve fails it can cause cold weather running problems. A few aftermarket companies list the basic version from about £10 up

[Disco_jo]

If I plug the 3mm hose that goes to the cooling system cut off valve, the whole system holds vacuum. Looking at the cut off valve it seems that it should let air in? Or should the system hold vacuum WITH the cut off valve? If needed I will order the whole assembly


If I may add, I have never had a problem with my car heating, or in cold weather. Its has always started first time even after sitting a couple weeks in the cold


Could I drive the car with the cut off valve plugged to stop it going into limp while waiting for parts? Or would that be a bad idea?

[Crasher]

The valve should hold vacuum, the exhaust for the system is the vent line into the air cleaner. The valves job is to regulate the coolant flow of the fuel cooler, a very important function on a PD as the returned fuel is so hot it can damage the fuel tank and lift pump so if it fails, it defaults to open and maximum cooling. Later PD’s used a radiator under the right front floor. Yes you can plug the vacuum pipe to test it, it will be just as it was except not leaking.

[Disco_jo]

You are a life saver, I can't thank you enough for your time and help. I will proceed to ordering the parts and will update when replaced.

I thought that I knew what all of the vacuum lines did, didn't have a clue about that one, thank you for explaining its function to me

[Disco_jo]

Had to come by to thank you again for your time helping me with my audi, been driving the car today and feels like a 130hp, no limp mode in sight ! I have had this issue for a couple years now and can't believe that in a couple days you pointed me in the right direction. Just waiting on the parts now. If ever you come to Brittany in France be sure to send me a PM I will have a bottle of wine or 2 for you.

[Disco_jo]

Hi guys,

Back for the conclusion, recieved my parts on tuesday, fitted them strait away. Really easy fix, I am still stunned at how many parts I have changed, and how much time I have spent on the car for it to turn out to be such an easy fix.

Anyways, the car is driving perfectly now, really fast, no limp mode, no choking at red lights or stops, no black smoke.

I could never thank you enough Crasher for your help.

Kind regards, Jo

[Crasher]

My pleasure