I have a 1997 A6 quattro 2.8L and I just got done doing a compression test and I have 0 psi in cylinders 2 and 3? tried wet test with no difference, just want to know what you guys think should be the next step! this is my friends car and I havent worked on audi's before but am capable of doing major work on cars...hopefully!!

my guess is either cracked head or jammed/broken lifters/ stems....and obviously cracked block is a lame possibility!! He says they had about 50psi of pressure about 3months ago when he had is tested by a shop!! car runs on 4 cylinders and my frined has driven it couple of times per month for fairly long distances! car burns oil and he has been topping it off as needed!!

so do basically need to pull the head of and have it and the block inspected? I really cant do a leak down test right now but can pull something if it has to be done!

any help appreciated,

 

The most likely is bent or burnt valves but if the car was preigniting, you could have holed pistons. Pull the head and see how much damage there is, then you can plan your solution. If you have access, a borescope will save a lot of effort, at least you will know what happened without taking the head off.

 

Holy Pressure Leakage Batman!

I agree, the block on these engines is very robust, cracking is unlikely. It might just be me but 50 psi seems low for a car that runs over 8.1 compression. Pull the heads, its probably a bent valve or something. On natural aspiration cracking a head even if it is aluminum is unlikely granted the coolant system runs.

 

Prob. bent valves like huff said just pull the heads and take a peek

 

With 0 psi, the opening has to be really big, like a piston hole or really damaged valve, a headgasket leak or cracked block will deliver some psi, just not very high.

 

Im gonna say the timing belt slipped a couple teeth and the valves hit the pistons, at least thats what i have found the most. The 2.8L engine is fairly easy to remove the cylinder heads, so if you have experience with any engine work at all it should be a snap. However you need to buy the tool to remove the head bolts.

 

http://www.ecstuning.com/Audi-C5_A6-.../Engine/Tools/
Scroll down the page half way to see the tool.

 

thank you all very much, I will probably get the head off the car within the next week or so...will probably update the thread once its off! I really hope its just the valves like you guys think!!

good news I forgot is that I have about 180psi in all other cylinders...lol

 

#2 and #3 are on the rear of the same bank -

pull the valve cover and check the cam. I'll bet the bearings starved for oil, they seized, and you have a broken the cam.

 

Carbon deposits on intake valves will prevent valves of closing tightly => hence - low or no compression.
If a breakage of a camshaft due to starvation is possible - then start with checking the cams.
Then the priority would be the eventual starvation - unless you fix it, any further repairs will be in vain.
Decarburization could make a real difference - I've got my 4kq with 2 cyl dead - 20 min purge with LubroMolly and compression was restored to 174.

BTW- you do immobilize the fuel pump before the compression test, right?