TDi 75 AMF coolant leak from hoses tandem vacuum/fuel pump seals?

froggy

Member
Today was a good day. The oil cooler pipes are fully fitted. Quote a tough little job but with the right tools not too bad. I couldn’t get the last top hose clip fully on with the cable type pliers, as access was tight and decided to give up for the night. Opening the front door a parcel had been delivered whilst i was working on the car. It was my replacement ordinary hose clamp pliers and they did the job in 2 minutes! Even managed to resync my key thanks to a tip from @Proghound - key in ignition, turn to position 2, press lock then unlock, done 👍🏻
Next up is a hose pipe flush of the coolant system and hopefully replace the tandem pump over the weekend.
 

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audifan

A2OC Donor
@froggy This is how I replace tandem pumps.
Please completely cover the engine area above the gearbox. I split 2 black bin bags length wise and completely cover the whole area then wrap around the EGR valve and around one of the fan support spokes. I then add a layer of news paper on top to absorb any spilt oil or diesel. Clamp the supply line into the tandem to slow the gravity return back to the tank when you disconnect it. Make sure the head seal and tandem are spotlessly clean before you reassemble and fit all bolts hand tight before torquing them in a diagonal pattern. Reconnect the vacuum port hose and the inlet hose to the tandem. I then fit a hand squeeze fuel bulb onto the return port of the tandem and suck the fuel into the tandem pump releasing the clamp on the inlet hose. This saves killing the starter and battery trying to turn the engine to suck the fuel all the way back into the tandem. Once fuel is up disconnect the bulb and refit the return line. With all the plastic and newspaper still covering the area, start the engine but make sure nothing with be caught in the radiator fan. Let the engine idle for a minute and carefully check for oil or fuel leaks. If all good remove the news paper and plastic making sure that any fuel or oil spilt is not able to run off onto the rubber pipes.
 
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froggy

Member
@froggy This is how I replace tandem pumps.
Please completely cover the engine area above the gearbox. I split 2 black bin bags length wise and completely cover the whole area then wrap around the EGR valve and around one of the fan support spokes. I then add a layer of news paper on top to absorb any spilt oil or diesel. Clamp the supply line into the tandem to slow the gravity return back to the tank when you disconnect it. Make sure the head seal and tandem are spotlessly clean before you reassemble and fit all bolts hand tight before torquing them in a diagonal pattern. Reconnect the vacuum port hose and the inlet hose to the tandem. I then fit a hand squeeze fuel bulb onto the return port of the tandem and suck the fuel into the tandem pump releasing the clamp on the inlet hose. This saves killing the starter and battery trying to turn the engine to suck the fuel all the way back into the tandem. Once fuel is up disconnect the bulb and refit the return line. With all the plastic and newspaper still covering the area, start the engine but make sure nothing with be caught in the radiator fan. Let the engine idle for a minute and carefully check for oil or fuel leaks. If all good remove the news paper and plastic making sure that any fuel or oil spilt is not able to run off onto the rubber pipes.
Thank you very much for this @audifan, I will add pictures of the process in due course in case it helps future novice mechanics! What would you use to clean down the head seal (brake cleaner?) Also, if I may, are there any ‘how to’ threads to show the best coolant flush procedure on the 1.4 tdi? @Pinkythelabrat had a lot of fun (not) replacing the coolant sensor and that thread is of great help as I need to do this too. There are a lot of threads available with people who need to or have done a coolant flush, but none I can find on the actual process - ideally step by step. I know, I’m asking for a lot of help, but I’m determined to get this done correctly! The tip on sucking the fuel into the tandem pump is especially helpful - the car will have been stood for a couple of weeks so doubt the battery would hold up to continuous cranking for long 👍🏻
 
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audifan

A2OC Donor
Once again Rod you are wrong .... There is indeed a return pipe on the tandem pump.

Engine.jpg

Depression is the vacuum port and fuel entry the fuel feed. The last port is fuel RETURN.
 
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froggy

Member
From earlier in the thread, the manual on how to change the pump courtesy of @Catnip64
 

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philward

A2OC Donor
I guess you were unlucky and still had a leaky Luk?
Two tips at this stage:
Buy a genuine VAG gasket, or at the very least one with blue silicone blobs applied.
There is no torque sequence but I tighten across diagonals in 4 stages, nip up all bolts (4), torque all bolts to the lower torque again in diagonal sequence. Torque the two larger bolts. Check the torque of each bolt is to spec.
It's a bit of a faff but for the first time in years my engine is dry.
 
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Deleted member 16918

Guest
I checked my pump again. There is wetness in the region of the two bottom bolts, which is where the high pressure lines leaves the tandem pump and enters the engine. The recommended torque on these bolts is only 10 nm so it would be an idea to check them , maybe slacken them off and retighten and see if there is any improvement. I like the diagrams that have been posted, but they do not really show you where the problem might be.
 
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froggy

Member
I guess you were unlucky and still had a leaky Luk?
Two tips at this stage:
Buy a genuine VAG gasket, or at the very least one with blue silicone blobs applied.
There is no torque sequence but I tighten across diagonals in 4 stages, nip up all bolts (4), torque all bolts to the lower torque again in diagonal sequence. Torque the two larger bolts. Check the torque of each bolt is to spec.
It's a bit of a faff but for the first time in years my engine is dry.
I haven’t witnessed the LUK leaking, but the damage to the pipework below can only be as a result of the tandem pump. I am about to attempt removal of the old pump and have a Bosch replacement (with an Elring blue silicone gasket) ready to go. Does the gasket need any sealant applied to it? Fingers crossed It will then be easier to get to the coolant flange and sensor and do all of those jobs in one go. I’ve decided to leave the coolant flush until all this is completed.
 

audifan

A2OC Donor
No additional sealer or grease, just perfectly clean surfaces. Try to get the tandem in the bore rather than drag it in on the bolts, then finger tight and as I and others have said diagonal torquing to spec.
Yes once the tandem is off there is more access to the coolant flange and temp sensor. If you remove the coolant flange replace the O ring, but also check the seal groove in the flange is perfect with no cracks or little nibbles missing from it. The leaking diesel or engine oil does attack that area also ( the little nibbles ).
If the tandem leaks down the drive shaft the diesel gets into the oil and dilutes it. Even worse there is now a second fuel source for the engine and a chance of a "run away condition". The most common leak is external, remember the pump operates at a very high pressure so a very small leak causes a lot of damage.
 

froggy

Member
Ok help! Does this return fuel feed pipe just pull off? What kind of crazy clip is holding it in place and how do i remove it? 🤔 Has the clip snapped?
 

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froggy

Member
Ok managed to get it to this stage but still wont budge
 

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audifan

A2OC Donor
Do not remove them from there instead remove them directly where they join the tandem pump.
 

froggy

Member

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froggy

Member
Do not remove them from there instead remove them directly where they join the tandem pump.
Oops. I followed the manual and damaged the return pipe. There are more of these clips on the vacuum pipe from the back of the tandem and the fuel return pipe at the front. These will need to be removed but I’ve already damaged one pipe and don’t want to ruin any more - does anybody know a way of removing these without damaging the rubber hoses?
 

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philward

A2OC Donor
I haven’t witnessed the LUK leaking, but the damage to the pipework below can only be as a result of the tandem pump. I am about to attempt removal of the old pump and have a Bosch replacement (with an Elring blue silicone gasket) ready to go. Does the gasket need any sealant applied to it? Fingers crossed It will then be easier to get to the coolant flange and sensor and do all of those jobs in one go. I’ve decided to leave the coolant flush until all this is completed.
No the sealant should already be there it is just two blue blobs. I went OTT and cleaned the head and pump with brake cleaner. Oil leaks from the tandem pump have been a problem on my car for many years. At long last it appears to have sealed.
 

philward

A2OC Donor
Ok help! Does this return fuel feed pipe just pull off? What kind of crazy clip is holding it in place and how do i remove it? 🤔 Has the clip snapped?
It pulls off, move the clips up the pipe. Get a hair dryer to it if it is solid.
 

philward

A2OC Donor
I had no trouble getting the clips off. Most likely used a pair of clip pliers but I can't check which style as it's raining and blowing out there.

Also I suggest you clean up the pipes particularly around the ends. You don't want any of that muck in your fuel system, pump or injectors.
 
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froggy

Member
Lots of fun in the rain today 😉 at last the fuel pipes were removed, I needed a little pick tool to pull the hoses off the tandem pipes and the clips were not to bad in the end. Audi no longer make the fuel hose, so a metre of Halfrauds finest (8mm) fuel hose will have to do. Unfortunately I have encountered a third type of clip, on the vacuum pipe at the back of the tandem and as usual it won’t budge. My hose clamp pliers will not close up that tight. Am I right in thinking the only tool that will remove this type of clip is the pincer pliers? Also, I have a replacement Febi coolant flange and gasket ready to go, should I make sure the battery is disconnected before pulling the sensor? Many thanks to everyone who has helped me get this far, it never would have happened without you!
 

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philward

A2OC Donor
That looks like a tamperproof clip. If it is the removal tool is an angle grinder.
If it is the type of clip you have posted with the tool then you can usually get them with pincers.
I’ve never disconnected a battery to replace a sensor. I avoid turning the key while the sensor is disconnected. Avoids risk of error codes.
 
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