If I replace one camshaft, do I have to replace the other?

[forevertruetome]

I am very lucky to come from a family of mechanics. Given how well my 2010 A4 is holding up, and that it needs to last our family for about 4 more years, we are replacing the cylinder head, timing chains, etc. The valves were bent when it jumped time. The intake camshaft is scared pretty good (we think the bearing/screen damaged it). The exhaust camshaft looks good.
Do I need to replace the exhaust camshaft just because I am replacing the intake one? I don't think so, but wanted to see what others thought.

[Flight930]

You’ll be fine just replacing the intake camshaft. It’s a good idea to replace the intake cam after valve damage since the lobes are pressed onto the shaft and can move after valve to piston contact.


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[Wbulk]

If you replace the intake cam, check to see if you have the new style rocker arms. The sides that go over the valve stem are wider/deeper almost going down to the top of the valve spring retainer. During initial rebuild startup, when the lifters are not pumped up, the longer sides on the rocker arms keep the rocker arm in place. During low oil pressure the rockers can come loose and ruin the cam. The key to fixing the CAEB engines is knowing and fixing the defects.

CAEB DEFECTS not in order
1. Replace the old design oil pump. The pressure springs were too light and the main gear piston was too tight. This would cause low idle pressure and contribute to the timing chain tensioner not being able to do it's job. On this item do not trust the after market pumps. They may not have the changes in their design no matter what part number they stamp on their part. The new pump it slightly smaller and lighter. You can see the difference when side by side.
2. Replace the oil filter drain back valve under the oil filter, or at least replace the the two O-rings on the bottom. They should not have flat sides and not be hard. This simple valve can ruin your engine causing low oil pressure and all of it's side effects.
3. Replace the one way check valve in the plastic tray in the pan. Also replace the gasket under the valve. This valve is at the end of the oil drain-back circuit from the PVC oil separator. It keeps oil from being sucked back up the circuit to the intake during very high vacuum. My opinion, this system is a bad design. The valve is still under the oil level in the pan and some oil will still get sucked back up under very high vacuum. It's cheap, under $8.00.
4. Replace the intake rockers stated above. You can ruin a new cam using the old style intake rockers with low oil pressure.
5. Timing chain tensioner and chain. You know this. Even the new tensioner is not that good. It has too much play before it locks into the next click. But the newer engines with the updated tensioner do not seem to have the same problems as the old design. A friend that owns a foreign car repair shop swears the real problem is the old oil pumps not having enough oil pressure on lower rpm oil circuit. He has replaced a ton of them.
6. Replace the low oil sender "brown" switch. If this is weak it will cause low oil pressure. Most mechanics don't understand, this controls the signal to the computer that controls the lower oil pressure below 3500 rpms. It's cheap insurance, around $10.
7. Remove that small screen in the cam bridge/bracket. Terrible design that does far more damage than good. Even with a new bridge remove the screen.
8. Replace pistons and rings. I use the U.S. made Hastings rings. They have higher tension and a three piece oil ring.

That's about it. Good luck.

P.S. I had a conversation with an Audi Dealer shop foreman a few months back and discussed several of these items. He told me they are not allowed to use discretion when trying to fix an engine problem. They have to use the solution/fix that Audi gives them. In thinking about this, so do they just want parts replacing robots? If this is an overall Audi policy could they reduce recalls if they know otherwise unknown to the public causes to reduce liability. With this engine, 2009-2012 CAEB, the public seems to have been the R and D department for Audi.

[Lbizzle88]

YouÂ’ll be fine just replacing the intake camshaft. ItÂ’s a good idea to replace the intake cam after valve damage since the lobes are pressed onto the shaft and can move after valve to piston contact.


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Is there anyway to tell if the lobes have moved? Just rebuilt my 2009 2.0T after purchasing with a timing chain failure. All intake valves were bent. I had a valve job done on the head and got everything back together, it started up but throwing a misfire code on cylinder one(p0301) and low idle RPM(p0506). I've checked timing numerous times and am positive it is correct(Chains).
I've replaced/ruled out the following possibilities:
spark plugs
oil separator/PCV
ignition coils
Injectors
Intake leaks
After replacing/ruling out the easier causes I performed compression check on all cylinders and got the following results:
Cylinder 1-74psi
Cylinder 2-90psi
Cylinder 3-145psi
Cylinder 4-75psi
After the compression check I performed cylinder leak-down tests. During the testing I was able to achieve less than 10% leakage on all cylinders, here comes the caveat, only cylinder 3(which had good compression) achieved this with its piston at TDC. All other cylinders achieved the 10% mark with their respective piston NOT at TDC. This is what puzzles me, everything points towards lobe movement but wouldn't I be getting a p0016 camshaft crankshaft correlation code being thrown? I'm trying get a sanity check before I spend the money on a new intake cam.

[Smac770]

P0016 would correlate the crank position wheel and the cam position wheel. The cam position wheel is on the intake cam and separate from the lobes that impact the rockers. You'd have to physically inspect the lobes on the cam to see if they are not at 90° separations around the cam. But you'd have to check the exhaust cam too as maybe those are off too. I know one youtube vid where the guy showed how the exhaust cam had spun on the toothed wheel, so the whole cam was off timing.

Someone with known good cams laying around would need to document in a vid or such how to inspect the cam and confirm the physical attributes of the cams are correct.

[Lbizzle88]

I was able to look back through pictures from when I was assembling the head and the lobes on the intake cam were in fact rotated on the cylinders with low compression. I wish I would have noticed it while I had it apart! You can see the lobe rotation in the picture below.20201114_215309.jpg20201114_214853.jpg