AUDI A4 1998 tdi lacks power

[drairbrake]

Hi,
Have an ongoing problem with A4 TDi, cam belt broke a while ago, took out 4 valves had head off and recon refitted all new bits, but crap power and poor fuel consumpsion. Checked everything then removed head had it checked all ok, tested turbo boost, intercooler, Cat, wastegate & boost control etc can't seem to find the problem. Spent a fortune in time and money and its sitting with head off at present I have both VAG software & code reader, but no faults logged. Any ideas anyone plaese!

[kenney]

Hi What you should have done before you took the head off again was to do a comp test,however since you have the head now off i would suggest measure the height og the pistons,i have experienced the conrods have been damaged after a cambelt failure.

[drairbrake]

Hi Kenney,

I did do a comp test it was 150 PSI 10 bar equal on all cylinders, I have clocked the tops of the pistons and there is only 0.005" difference, so I kind off ruled that out because I would expect 2 pistons to be down if con rods had bent.

[kenney]

Hi 10 bar is the comp on a petrol engine your engine should have about 19 bar.Did you use a comp tester for diesel engine??????,if you did! then, i fancy all 4 rods are bent.

[kenney]

Hi again Here is a diagram for the choice of head gaskets,it will give you an idea how much projection the piston should have and as you can see anythng under 1mm,then there is something wrong
Piston projection
Identification
Holes/notches

0.91 mm ... 1.00 mm
1

1.01 mm ... 1.10 mm
2

1.11 mm ... 1.20 mm
3

[drairbrake]

Hi Kenney,
Thanks for the piston projections, I fear you may be right about all four being bent as that would explain alot, but I will check actual piston protrusion as opposed to just comparison and get back to you. I knew 10 bar was low, but I had to take the head off again to make sure it wasn't tracking between bores.

Thanks again

[drairbrake]

Hi Kenney,
Checked piston heights today all four are 1.20 to 1.25mm protusion above cylinder block. I have had the head checked again and they say it had a set of alternative hydraulic tappets fitted, which have a slighty different spring than the originals. This would not help with the lack of compression though, as its the oppersite i.e the valves would not open wide enough when running. So I'm at a loss, guess I will refit head and see what happens.


Thanks

Jeff

[kenney]

Okay if you retest the comp and find it to be the same 10bar then you will need to do a leakage test on the cyls,do you know how to do this?

[drairbrake]

No never done that

regards

Jeff