Turbocharger TDI AMF 75 Repair

rotifer II

rotifer II

A2OC Donor
United-Kingdom

CHRA​

Centre Housing Rotating Assembly​

20241106_221339.jpg

​

The internet has plenty of videos showing CHRA removal.
The work to get to the turbo requires removing a great number of engine bay parts. But you will eventually reach the six exhaust manifold nuts.
20231129_153716.jpg


IMG_20241027_200317.jpg


I take the exhaust manifold and turbo out together because I find it easier that way. The inconvenience with this job is the lack of room behind the engine. Doing the job this way allows the mating surfaces of the manifold and cylinder head to be cleaned ready for a new gasket.
*see note

20241110_184222.jpg


Remove the 4 bolts on the exhaust side and 6 on the compressor side; corrosion will have stuck the CHRA to the exhaust side of the housing; with gentle hammering on alternate sides, it should work its way out.

*Note
... extracting just the turbo unit without the manifold? This can be done by undoing the two bolts and one nut.
20241112_113440.jpg
 
Last edited:
The end 😆... If only it were that simple.

This thread does not aim to provide information on how to remove a turbocharger or fit a CHRA.

Its more a collection of pictures and short descriptions. Some ideas worked out for me, some did not.

The PDF for the GT15 turbo lists the recommended torque settings. 🙂👍

A turbocharger website​

 

Attachments

Last edited:

Stuck Bolts​

Unless you are very lucky, you will be battling nuts and bolts that haven't been removed in a while.
The most effective way to remove these is to use well-fitting sockets and spanners. Its simple stuff, but when a spanner is on the bolt head, there should be no slop; otherwise, bolts can become rounded off if the spanner frequently slips from the bolt.
If a nut becomes rounded, a nut splitter may get you out of trouble.

20241028_145424.jpg

Ample leverage for an M6 bolt, and two of the four bolts lost their heads. 🔩

IMG_20241028_150622.jpg

The bolts are the AF 3/8; I used an old BRITOOL spanner; it fit perfectly.

IMG_20241110_202948.jpg

Take a look at the two ring spanner shapes. They are manufactured with different depths. The best choice for this job is the spanner with no gap.

The bolt heads on the exhaust side are not tall; therefore, filing down the 3/8 spanner with an angle grinder creates a better fit. The spanner can engage the nut as soon as it is placed upon it; increased grip reduces slipping and rounding of bolts.
🙂

Heat​

I have a blow torch, which I used to heat the bolts before trying to loosen them.

Hammer​

A hammer was used a couple of times to hit the bolt squarely on the head in hope that the shock wave would release some of the rust holding the threads.
 
Last edited:
Sweet! What was your issue with the original turbo? Where did you get the CHAR from?
My silver ones burning a bit of oil so could do with some love when I get chance, presume it's the turbo passing oil
 
Hello @Howey,

It was from eBay.
Its a Melett from Barnsley
20241024_140550-COLLAGE.jpg
Dropped it in the eBay basket and got a bit knocked off the price after about 5 days.
🙂👍
My last turbo was second-hand; it lasted well. It was just a stop gap; I did not have the confidence to do a CHRA swap, so I did a like-for-like swap instead.
Regards to problems
  • smoke on start up
  • smoke when you give it the boot (fully accelerator)
  • MOT smoke test that was getting worse year on year
EDIT
I thought it was the injectors; I rebuilt the head and fitted new injectors, and it still smokes. The turbo is the next 'engine item' on the list to try and stop the smoke. 🙂
 
Last edited:
Is it now on the car and working okay? Are there any settings to adjust on the unit? Like on the 90 variable there's limit adjustment etc?
 
Hello @CrispyEdd,
I have not made time to put the TDI back together, but I will let you know once it starts how the new CHRA turned out.
The AMF turbo has a vacuum-activated waste gate that is set by the manufacturer; there is no need to adjust that.
🙂👍

EDIT
The AMF turbocharger is a basic design easy to work on and set up.
 
Last edited:

Threads​

I broke two of the bolt heads clean off the exhaust side of the turbo; I don't think I used enough heat to free them.
20241028_163829.jpg


Kept drilling in half-sizes until the bolt fell apart, the metal shavings were tidied away, and a new thread was cut.

20241106_222611.jpg


Not my finest work; number 1 threads are damaged.
 
Last edited:

Evenflow​

Free flowing exhaust and more air powering in.

IMG_20241027_202125~2.jpg


The build up of carbon and rust on the exhaust side of the turbo can be removed with a rotary tool fitted with the grinding stone. The vacuum actuator had been removed so that the waste gate door can be swung open when cleaning.

20241106_222438(1).jpg


The compressor side of the turbo air channel depression was cleaned up using 1200 grit wet and dry paper. Followed by metal polish and a soft fiber attachment on the rotary tool.
A final clean with metal polish and a soft cloth.

20241106_205609.jpg


The alloy air channel is not smooth when it leaves the factory and polishing it up was satisfying work I hope it makes a difference.
 
Last edited:

Turbine Wear​

IMG_20241027_200946.jpg

The leading edge of each fin on the intake side of the turbo is worn, which will put it out of balance. It was time for this CHRA to be retired.

20241111_131056.jpg


There is no need to remove the turbo to check the condition of the fins. There are two bolts holding the solid plastic intake hose to the turbo inlet.

IMG_20241027_150251.jpg


IMG_20241027_160040.jpg
 
Last edited:
Interesting write up, I considered doing this but my replacement AMF came with a very good turbo.
When I saw the lever I thought some bolts will shear. Have you got oxy acetylene? Essential for this type of work. You may have saved thread 1.
Nice final result though 👍
 
Hello,
Many thanks, @Little Dog A few images of the completed turbocharger and the gasket reference numbers are still lacking, but I'm almost finished with the write up. I would like one of those induction heaters for bolts, but to answer your question I utilised a small blow torch because I have no access to oxy-acetylene.

Are you considering a rebuild on the old engine turbo?

Broken bolts can be fixed and there's not an excessive amount of torque on the turbine side bolts. 🙂👍

EDIT
See post number #2 for the torque spec PDF.
 
Last edited:

Assembled​

I used the photos I had taken to position the CHRA, but I would mark the housing with a pen next time. The CHRA is easy to install, but removing the four turbine bolts was not easy.

20241117_184453-COLLAGE.jpg

Loaded the CHRA with engine oil and have been spinning the turbo by hand its the smoothest turbo I have have ever fitted to a car, usually I buy second hand ones.

Picked up a set of gaskets from Darkside Developments number 4 in the image below I bought online.
20241117_193921.jpg
🙂👍
 
Last edited:
Have you got a part number please for the gasket you have already used? The triangular one between the turbo and exhaust manifold. I’m having trouble finding one, can’t even find it on a parts diagram.
 
Little Dog said:
Have you got a part number please for the gasket you have already used? The triangular one between the turbo and exhaust manifold. I’m having trouble finding one, can’t even find it on a parts diagram.
Click to expand...
The AMF turbo diagram is notoriously bad as it depicts a 4 cylinder manifold and corresponding turbo off the 1.9tdi, although the listed parts appear to be correct.

However, if you really squint at the parts list -


there is a non-numbered (and not depicted!) item between the turbo units and the other parts - see red arrow.

looking up this part number shows that it appears to be common to other tdi Audis of the same era doing the same sort of role and it looks like the right type of shape to be the part you are looking for.

1733899058369.png
 
You must log in or register to reply here.
Back
Top