Paul Heneghan

Hello folks,

Car suddenly started making a VERY load metallic knocking sound at low revs - reduced at higher revs. It was so loud that when I stuck my head in the engine bay trying to locate the sound for a couple of minutes, I had tinnitus for an hour afterwards!

I had a vague impression the noise came from the top back of the engine, so I thought it likely that it was the famous cam chain tensioner. I ordered a replacement kit (about £200!), and then got busy with other things and the weather got cold, so I left it for a few months. Now that it's nice and warm, I am enthused to tackle it. I've dismantled all the necessary bits, and I've finally exposed the chain that links the two cams at the back of the engine (BWE).

When turning over the engine to get to TDC, I heard a sharp bang from the top of the engine. I cautiously turned the engine over a bit more, and it turned freely - then I noticed that although the exhaust camshaft was rotating, the intake shaft wasn't! But, when I carried on turning the engine, the intake started turning again. After another bit of rotation, there was another sharp bang, and the intake camshaft whizzed around a little bit and then stopped moving again. As I turned over the engine, this repeated, and I think the bang is coming from the inside of the camshaft adjuster. Is this normal (when a tensioner has failed or is out of hydraulic pressure)?

Or have I got a failed camshaft adjuster?

Either way, I'm replacing the adjuster - ebay has a few sources for about £70.

But I'm curious about the failure mode. I'm pretty convinced that the sharp bang when the intake camshaft leaps forward is the noise we were hearing at idle (I think you get two or four bangs per revolution). It probably went away at higher speeds as the rpm of the driving torque from the camshaft adjuster exceeded the natural speed of the intake rotating of its own volition.

Any BTDTs gratefully received.

Paul

p.s. anyone who says that the barbed hose adaptor on the inlet side High Pressure Fuel Pump is better than the banjo is almost certainly lying! I haven't done the banjo one, but getting the fuel hose off the barbed adaptor is a horrible job. I had to remove the brass adaptor on the outlet side to get at the hose clip on the inlet side and in so doing I dropped a washer I wasn't expecting to be there into the void of the lower part of the engine bay, and then it took me about 30 minutes of swearing to get the hose off the barbed adaptor. I should probably just have cut the hose, and bought a new one and two clamps from Audi.

Airbag

You broke the tensioner.
Go to Audizine and look up a thread labelled " thats all she wrote " for the a4b7
You may already have damaged the valves.
That thread is one of the best i have ever seen for fixing your exact issue. He developed a method with pics to guarantee timing is dead on and its super easy
He even does tests to see if the valves are bent before he starts.
Has links to great youtube vids too.
Definitely stop trying to turn it over till you read that thread.

Yeah i have banjo and its piece if cake. But guys with the hose dont detach it. They just undo the 17mm and bend the rubber tube over

Paul Heneghan

Thanks for the link - great web page. I'd already looked at all the youtube videos referenced. I think my engine (top end at least) is still in sync as the timing mark on the big cam sprocket at the front of the engine aligns when the cam lobes on #4 point towards each other the same amount - and the cam-locking tool fits perfectly (although with the same slack that many others have noticed. It was too dark down the front of the engine to see if the crank was aligned, but I've rotated the engine several revolutions without any alarming noises other than the clang that the cam adjuster makes when the inlet cam shaft spins over (due to valve springs and no tension on the chain?) - I'm hoping that no valve/piston collisions happened during that uncontrolled rotation. And when the engine last ran, it was ok at higher revs, but had this horrible metallic knock at low revs - which I realise now was coming from the cam adjuster.

I've got a leakdown tester somewhere - if I can find it I'll to a test to see if the valves got a whack

Will carry on this weekend - waiting for cam adjuster and replacement HPFP to arrive.

Airbag

The cam adjuster itself us an inert piece and should make no noise. Are sure it isn't the tensioner ?

tha adjuster is just a big round piece, its really the TENSIONER you need as that fails 99% of the time in the head.

DO NOT use that compression tester until you do the repair or you will smash valves. Get the vacuum pump off and timing cover before you do anything else and take a look .
you can buy kits that include the tensioner, chain and the gaskets to put it back together. others will include the adjuster but they are more expensive.

yes if the belt is fine the exhaust cam is still in sync. you need to put a new chain , tensioner, and maybe cam adjuster and inspect the rings in the cover, then retime intake cam using that guys guide. .

Anyway good luck

Paul Heneghan

It can't be totally inert, otherwise it wouldn't adjust anything?!? I'm speaking from profound ignorance here, as I haven't taken one apart, and haven't seen an exploded diagram of the insides of one. However, when I rotated the engine using the crank pulley, the exhaust cam stayed in perfect sync with the crank, but the cam adjuster and intake cam every now and again, would spin forward a few degrees (and something would make a metallic clang), and then stop, wait for the exhaust cam to catch up with it, and then carry on rotating in sync for a bit.

Anyway, I've taken the old tensioner off, and discovered lots of iron filings in the little screen - see photo - is this a disaster, or typical?


Audi 2.0 TFSi cam chain tensioner - with added iron filings

Cheers,

Paul

Paul Heneghan

Having replaced the cam chain tensioner and the camshaft adjuster, I can now turn the engine over without the metallic clangs. The exhaust cam and intake cam now stay synchronised. I'm pretty sure it was the adjuster that was mostly to blame, as it was allowing a large phase shift between the exhaust shaft and the toothed gear to suddenly happen when the valve springs pushed the intake cam forward. The new tensioner seems to have a slightly stiffer spring as well. Of course, at the moment, there's no oil to pressurise either of them.

I'll put the rest of it back together at the weekend and see what happens.

Having examined the 'iron filings' further, they're not as large as I first thought. They are a mixture of iron and brass (can't tell if there's any aluminium in there), and are quite fine as when I rubbed them between my fingers, I couldn't really feel them. The engine has 80k miles on it, so it's not surprising that there's something in the screen, otherwise they wouldn't have put one there. Or am I kidding myself?

Airbag

Well you have nothing to lose i guess
Id be changing your oil pretty often
Were the three rings in the timing cover intact ?

Paul Heneghan

All done. Engine purring like a kitten. More brass filings in oil filter bowl and sump. If anyone's got any theories as to what they might have come from - I'd be very interested!

Lessons learned:

1. The worst bit is the hose clips - you need a good hose clip pliers set (which I had), and you will still struggle due to the limited access - particularly if you have the HPFP with the barbed hose connector (instead of the banjo) - disconnect the hose at the t-junction at the far end, not at the pump end.
2. Just replace the oil breather hose clamps on the larger of the two breather hoses at the front left. I spent ages trying to bend them into a sensible shape so I could recrimp them.
3. Invest in a mini bit ratchet driver set - I have a DeWalt DT71516 - fabulous and only £20.
4. Invest in a small mirror on the end of a telescoping stick. Some of the bolts on the back of the vacuum pump and cam chain cover are nearly impossible to see without some kind of mirror.
5. You'll need a good selection of Torx and even a spline (triple square) drive (for the cable bracket).
6. The stretch bolt that hold the camshaft adjuster in place has a polydrive head. The correct tool is a T40080, but they don't seem to be available in the UK. I had a high-quality Wera Ribe bit, and that did not fit - it was approximately the right diameter, but all the splines were a little too large. The polydrive bit that came with the AST5060 timing kit that I got from AST tools in Redditch fitted the bolt head perfectly, but was too long really - would be OK on A3s or VWs, but the longitudinal Audi A4 engine has so little space between it and the firewall. I managed to get the bolt undone using the AST tool and an 18" breaker bar with a flexible head, but I couldn't manage to get the bit perfectly in line with the bolt, so I was very nervous about damaging the bolt head - then it becomes a cam out job. There was no way my torque wrench would fit when I it was time to tighten it, so I ordered a cheap Laser equivalent off eBay that worked fine.
7. The force on the T10252 cam-locking tool when you break the camshaft adjuster bolt loose is enormous. The AST version of the tool is a good one, with the two big pegs pressed all the way into the base plate. Apparently there are some inferior models where the pegs only go part way through and are held in with small bolts, - they might not withstand the force. I estimate a torque well in excess of 100Nm is required to break loose that bolt on a 10-year-old car that has never had it apart before. If the flats on the indentations on the cam are 1 cm, then the sideways reaction force between the camshaft and the tool must be at least 20,000 N - 2 tonnes!!!
8. Take the cam chain cover off very carefully - making sure it stays square-on all the time. Otherwise you risk cracking one or more of the three oil seal rings.
9. I counted 19 links between the mark on the camshaft adjuster and the mark on the intake gear. This meant that when I took up the slack (by rotating the intake camshaft anticlockwise while the exhaust camshaft, the notches in the two camshafts were angled identically. Apparently, there is enough slack when you use the cam-locking tool, that you can phase the intake shaft one tooth out, hence putting an anticlockwise (as viewed from the front of the engine) torque on the intake shaft to take up the slack.
10. Some joker on one of the forums says this is a two-hour job. It took me three days! Admittedly not every hour of every day, but I had to keep stopping to look at bits of youtube videos, or stop and wait for parts or tools to arrive. Very annoyingly, my Bentley manuals is crap - not mentioning this particular job at all. The Haynes mentions it, but it doesn't sound like the author ever tried to do it!!
11. It's not a cheap job, if you buy genuine parts from Audi. The camshaft adjuster alone goes for nearly $500. I went with a kit (originally not including the adjuster) of all genuine Audi parts for £239 off eBay. Then when I found that the adjuster was broken, I bought an aftermarket version for £69 off eBay, but despite claiming that it was just the bare unit, it did come with a chain and a tensioner - pretty good value! I also replace the cam follower as the old one showed a small amount of wear - I think that was another £25 or so. By the time you add in an oil change, the cam-locking tool kit and a new-old-stock fuel pump, I must have spent about £500. If I were doing it again, I probably wouldn't bother with a genuine tensioner or chain - there are some reputable companies selling what appear to be OEM quality equivalents for less than half the price.

Anyway it's all back together, running smoothly and quietly. I'll change the oil after 1,000 miles or so and see if there are any more brass filings.