Zari_A8

Dear fellow enthusiasts,

Having been a BMW evangelist for the last decade, last Friday I decided to scratch the Audi itch and bought myself a D4 A8 3.0tdi.
I've been looking for one since December and my tight budget meant I had to go for a high miler. My car currently sits at 125k miles.
The car drives lovely and has FSH with low owners. Its an amazing thing to be in especially when you do motorway miles.

Up on arrival I checked it over with a fine toothed comb, I noticed it needed coolant in one of the ad pics so I brought some coolant with me.
Topped it up and went on a test drive. first thing I do is check the heaters they are blowing hot air once the engine had warmed up. They were..result!

Came back shook hands with the old owner and away I went.

On the way home however. I noticed the blowers started blowing cold air even though I've been driving for about 30 miles and they were set to "HI". Strange I thought.
On a set of traffic lights I decided to do a full send on the 2tonne boat just to see what she was like acceleration wise. Then all at the sudden the hot heat came on again and stayed on for about 10 minutes then bam..cold again...double strange.

Perplexed I jumped on the motorway for the final 80 mile trip home scratching my skull what could it be. Did I buy a lemon?

As an enthusiast, I have a couple of mechanic friends so rung them up and asked for opinions; Two came up with headgasket. (which I doubted at the time but cant rule out) and a German car specialist buddy of mine said there might be an airlock in the heater matrix
as these cars are notorious for them, Its an Audi garage job only as they have the bleeding apparatus to get it out.

This morning I decided to check if its a head gasket. A quick trick I got taught is to let all the pressure out from the expansion tank and run it cold for 4 minutes and open the tank again. If it hisses its head gasket issues. Luckily Mine didn't hiss.
The next thing I did notice though was the coolant level in the expansion tank had dropped well below "Min" again ?! I've driven the car 140 miles home there is no way It should have used 3/4 of a litre of coolant.

I started to suspect that there is a serious coolant leak. Looked around and there is some moisture in the front of the engine and inside the "V" of the block. Even when I started the car this morning I noticed a puff of smoke from the aux belts and squeaking so something is clearly dripping on the aux belt as well.

I don't know enough about these cars at the moment to start going in a direction to eliminate the problem but I want to fix this myself. If you guys have any info or advice for me it would be much appreciated.

Thank you in advance.

Andrew12

Sounds like previous owner knew there was an issue... the coolant should be pink and leaks will get all crusty. Start looking it over. Might be a water pump... might need to get the bottom engine cover off to find. Bright flashlight and start hunting. That amount of coolant should be easy to find. Unless it is going out the exhaust...
pictures of the leaks will help us help you!

MP4.2+6.0

1. Has a leak somewhere. Rarely is it internal on modern Audis--the head gasket type ideas. Per prior reply, start looking all over, especially underneath to start to get at least general location to look further. Failed hose, prior faulty repair with loose clamp or broken line, cracked coolant reservoir that may be hidden, tired o ring that leaks (including sometimes at cold instead of hot), failing and leaking water pump, warped thermostat housing, damaged or leaking primary or auxiliary radiator, etc. Key is look for signs of coolant--faint pink is accumulated, sweetish taste and slightly oily feel if you are up for that, pinkish white stains if dried on a surface, etc. Belly pan under motor area commonly has to come off, and in turn can be a diagnostic tool seeing where it is landing.

2. Heater auxiliary pump conceptually. You describe classic symtoms, though if coolant loss was pretty early it could be just that. If it is run with a known full cooling system and it pumps heat while running at decent RPMs but not at idle or slow, that's a pointer to this component. Search on posts for specific motor and body, and then where it is. Coolant schematic will help you id the set up. On a D3 that pump was built into the heater control valve. Some set ups may have multiple, including afterrun pumpa for residual heat and turbo cooling. It needs the heater related auxiliary pump to circulate adequately at low engine speeds given complexity and size of heater and nuances of engine related coolant flows--heat panels separately controlled on each side, heated air vented around cabin, etc. But again, get coolant leak sorted first. If it has insufficient coolant to pump into heater area, of course it won't make heat at the cabin exchange panels.

2turbos4rings

Sadly that sounds like the EGR/oil cooler leak

Common 3.0 TDI issue. The valley will hold a lot of liquid if it’s leaking there so it can leak a lot before you’ll see it drip. Basically a lake on top of the block

2turbos4rings

Sorry that this is your first experience with Audi. The TDI is mostly a very reliable and stout engine, this is perhaps the ‘Achilles heel’. Here’s some more info for your reading (there are other sources as well but this will get you started and perhaps answer some questions). It’s a lengthy repair though nothing is particularly difficult- just time consuming

EGR cooler leak

Zari_A8

First off, I want to say a massive thank you to all of you guys that have taken the time of day to reply. Its really appreciated.

MP4.2+6.0 - Thank you for your insights. you know your stuff ! I have found a video on YouTube on how to change the Aux pump for my particular motor (3.0l tdi) . It seems to live right underneath the wipers on the slam panel. (https://www.youtube.com/watch?v=A5gv....A.GAutomotive) .. Ill attach a photo;





I will go to my German car specialist friend tomorrow and plug it in see if we can see any codes before I order the OE pump. Although I cant believe the whole pump is plastic !

2turbos4rings - I was dreading it would be that. I've read a lot on that there is a lot of plastic parts in the centre of the "V" that carry the coolant that degrade over time. thank you for the Link I will be checking it out.

However I do have a lot of time on my hands for the next couple of weeks so I have zero excuses.
I will report how its going in the next couple of days

Thanks again guys !

All the best
​​​​​​​
Zari

Zari_A8

First of all,

I would like to thank all you guys for chipping in with your knowledge. Your diagnosis has proven to be correct and has moved me on to the next stage. MP4.2+6.0 and 2turbos4rings I owe you both a beer !


OBD was scanning when... Lo and behold the coolant recirculation pump fired a mechanical malfunction fault. MP4.2+6.0 Thank you again for sending me in the right direction..... I ordered an OEM pump immediately after that

Once I came home from the garage I decided to investigate the leek with an endoscope, see what was going on inside the "V" ... I have to say it didn't take me long to find "Liquid" I call it that because it was actually black but wasn't quite oil. I guess oil mixed with coolant maybe?


You cant see much but the dark round(ish) blob in the centre of the screen is a gallery full of black sooty liquid. Location was near the EGR

Me prodding the "V"


Bottom right black blob is also a gallery near the oil cooler that is full of liquid (coolant mixed with oil)

Thank you 2turbos4rings for pinpointing where to look first for leaks. you were right.


My next step is to research on how to the intake manifold off. Figure out what's leaking but from what I've been researching its better to change as many seals and gaskets/pipes/hoses as possible inside the V. So will have to find diagrams for the parts so I Can order them.

2turbos4rings , I still haven't read the EGR thread you have sent me but tomorrow that will be my job.

MP4.2+6.0

Good luck, but sounds like you have a decent road map of likelies.

Besides dealer type sites we use a lot in USA (without a 4.2TDI here), maybe try this site: https://www.lllparts.co.uk/audi-parts. Get your vehicle model and relevant market loaded in and try. A bit of learning curve on interface and a bit finicky, but quality of diagrams and all the part #'s is often a lot better than currently available ones from Audi or dealers for consumers in USA market. It has all the local market flavors of motors too.

2turbos4rings

Bummed for you.. it very well might look black/like oil as the cooler usually leaks both when it fails. It’s a hefty job, BUT it’s mostly the only big ticket item you have to worry about with the 2nd gen 3.0 TDI

Hope it goes smooth and get a nice price for the repair, good luck my friend

Zari_A8

Great website MP4.2+6.0 ! just what I was looking for !!.. there is currently 48 items in my basket but before I pull the trigger I'm going to take the oil cooler off and egr and see what parts I need.


These are the current state of affairs. Took me 5 hrs and 1 broken connector to get to this stage...It is a really fiddly B**tard of a job. Tomorrow I take the oil coolant out and take the rest of the egr kit off.

I am thinking of doing an EGR+DPF delete considering I'm at this stage + less to go wrong in the future. Is there any parts that I should consider changing now.. I'm thinking of changing the water pump as a preventative measure but I have never heard of one failing on these engines so would rather leave it alone.

I could definitely see the coolant pooling behind the EGR valve once I took the intake off.



Looks like the Intake will need a bit of cleaning.. any cleaner brand suggestions welcome !