Snapped cam chain but no bent valves?

[sarxworks]

I'm going to try to be as detailed as possible.

Currently got myself a B7 Audi 2.0T from someone who sold it at a cheap price that did not start. After I got the car and installed a new battery I found the same issue and found there was no compression in the cylinders. Doing ALOT of research on here and the internet, I found this is usually a problem with the timing chain/belt breaking so I decided to tear the engine apart.

While tearing the car apart, I found the timing belt is still intact but yes the timing chain was snapped in half with the tensioner in pieces all around the engine.

So I was expecting bent valves and possibly piston damage however I got a weird sight. After pulling the cylinder head, I found all the valves still intact with the cams in okay condition.

I turned each cam using a wrench with no problem and the valves extended out and sealed back in again with no issue. I also did the water test where I poured water on the cylinder head and no water leaked out (this test was a bit annoying because when one set of valves went in, the next in the sequence was already out, not sure if this is normal)

I also checked the pistons and I can't see any visible damage and they were all still tightly in the bores.

My question is am I maybe testing this head incorrectly? This seems a bit strange that there isn't a single bent valve.

Pics:
https://imgur.com/a/Wq5mpSD

[Theiceman]

this is not uncommon , depends the scenario in which it snapped.

Mine snapped the chain with zero bent valves.

if you had posted earlier i would have had you do some basic tests before taking the head off, i could have saved you a ton of time and money. essentially throw a chain on time her up and do a compression test

https://www.audizine.com/forum/showt...ighlight=wrote

oh and i dont use water for this test as it has too much surface tension , i use gas...

[sarxworks]

Blast. Yeah I saw your forum and thought to myself, "yeah that's definitely not happening with me." Took me a while to get to this stage XD, well it's a learning experience. Will do and get back results!

[VinnysS4]

At this point with the head off, i would pressure/vac test the ports. Last thing you want is to bolt it all up, to find out you just wasted a head gasket, bolts and a whole lot of time, just to do it again and spend even more money. Might as well do the valve seals and clean that carbon off of them. It only takes a minute or two each on a bench grinder with a wire wheel. And in the process you can run each valve across some glass and see if they are bent.
A friend of mine mis shifted his s4 and hit north of 10k and bent all his valves in the process. They looked fine and seemed to seal but every single one of them was ever so slightly bent. Just food for thought.

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[Theiceman]

At this point with the head off, i would pressure/vac test the ports. Last thing you want is to bolt it all up, to find out you just wasted a head gasket, bolts and a whole lot of time, just to do it again and spend even more money. Might as well do the valve seals and clean that carbon off of them. It only takes a minute or two each on a bench grinder with a wire wheel. And in the process you can run each valve across some glass and see if they are bent.
A friend of mine mis shifted his s4 and hit north of 10k and bent all his valves in the process. They looked fine and seemed to seal but every single one of them was ever so slightly bent. Just food for thought.

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oh yeah now that it IS off , have to do it right ..

[VinnysS4]

oh yeah now that it IS off , have to do it right ..

I mean... you don't HAVE to, but speaking from personal hands on experience, I would. Thats like doing a clutch job and not doing the rear main seal. While its apart, it makes more sense.

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[Jayz691]

As mentioned, use gas, and spray compressed air into the ports. Could "seem" fine, buy nit fully hold compression. If all test out ok, id still tear the head down, change the seals, and lap the valves.
It is pretty rare, but some people get lucky. Imma guess your prob ok, cuz don't even see any contact marks on your valves/pistons.

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[sarxworks]

At this point with the head off, i would pressure/vac test the ports. Last thing you want is to bolt it all up, to find out you just wasted a head gasket, bolts and a whole lot of time, just to do it again and spend even more money. Might as well do the valve seals and clean that carbon off of them. It only takes a minute or two each on a bench grinder with a wire wheel. And in the process you can run each valve across some glass and see if they are bent.
A friend of mine mis shifted his s4 and hit north of 10k and bent all his valves in the process. They looked fine and seemed to seal but every single one of them was ever so slightly bent. Just food for thought.

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Fair point, that will be my next step and might change the valve seals as well. Unfortunately, I don't have a bench grinder but can look into getting one. What do you mean "run across some glass?" Like compare it on a glass mirror?

Yeah believe me I get what you mean. I just want to make sure EVERYTHING is okay before putting this head back on because it took FORVER to get here with the amount of rust I ate through.

- - - Updated - - -

As mentioned, use gas, and spray compressed air into the ports. Could "seem" fine, buy nit fully hold compression. If all test out ok, id still tear the head down, change the seals, and lap the valves.
It is pretty rare, but some people get lucky. Imma guess your prob ok, cuz don't even see any contact marks on your valves/pistons.

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Will do!

[VinnysS4]

What do you mean "run across some glass?" Like compare it on a glass mirror?

Lay the valve stem on some glass with the head of the valve hanging off. Then roll the valve stem across the glass and look for any amount of movement/wobble from the valve head. If the valve is bent, you will visibly see it wobble



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[tractoman]

Fair point, that will be my next step and might change the valve seals as well. Unfortunately, I don't have a bench grinder but can look into getting one. What do you mean "run across some glass?" Like compare it on a glass mirror?

Yeah believe me I get what you mean. I just want to make sure EVERYTHING is okay before putting this head back on because it took FORVER to get here with the amount of rust I ate through.

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Will do!

Glass is flat, you will notice a bend when you roll them across.

[sarxworks]

Great, I stripped the poly-drive bolt and two torx cam bearing bolts. Looks like this is gonna take alot longer then expected IMG_9568.jpgIMG_9569.jpg

[VinnysS4]

Great, I stripped the poly-drive bolt and two torx cam bearing bolts. Looks like this is gonna take alot longer then expected IMG_9568.jpgIMG_9569.jpg

Vice grip the cM bolts out of there. The poly bolt, thats a tough one. Once you get the cam out you can go from there

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[Theiceman]

Vice grip the cM bolts out of there. The poly bolt, thats a tough one. Once you get the cam out you can go from there

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yeah thinking same think , i have a small vice grip for exactly this purpose, you only have to crack it.

i have actually seen someone cut right through the phaser to get the bolt out before .. those things are kind of expensive though . That one my be a hardened drill attempt with the cam in a vice.

[sarxworks]

We're getting there....one out but second one is proven to be the real test. I don't remember this one making a crack when first turning it unlike the other one

[sarxworks]

Okay, so I got the bolt off, and am currently in the process of installing the new chain and tensioner. Is it possibly for me to cut off the adjuster bolt or will I have to drill it out? Or should I just keep it in?

[Jayz691]

Okay, so I got the bolt off, and am currently in the process of installing the new chain and tensioner. Is it possibly for me to cut off the adjuster bolt or will I have to drill it out? Or should I just keep it in?

Drill the head off. Once the head is off, the bolt should spin right out. Good to fix it while the cam is out..

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[Theiceman]

I'd say depends on your tools/ ability and plans for the car. everyone is different . if you are going to be keeping the car long term I'd do it right .
but part of me says I've never heard of any b7 having to change the tensioner and chain twice in its lifetime.. so....

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[Jayz691]

I'd say depends on your tools/ ability and plans for the car. everyone is different . if you are going to be keeping the car long term I'd do it right .
but part of me says I've never heard of any b7 having to change the tensioner and chain twice in its lifetime.. so....

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Well, im it the point mine needs done again.. Almost 100k miles since I did it. All just be replacing with my rebuild. But should just do it right, esp while the cam is out, and it'll be easy. Just need a drill/bit. If he ever needs to remove it down the road, he'll be kicking himself in the ass. Plus, don't like screwing the next guy.
Imagine going to do the chain/tensioner on a cars ya bought, and find it already stripped.. Be quite pissed, why do that to someone?

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[sarxworks]

For now it seems like it's gonna be my car so I'm not gonna worry on it for not. Probably will fix it in the future. I have got the timing chain on and THINK I have it timed correctly.

For my compression test, I'm getting:

Cylinder 1: 150psi
Cylinder 2: 135psi
Cylinder 3: 120psi
Cylinder 4: 135psi

May have missed a tooth or two while timing it but not entirely sure. I went by the marks on the exhaust cam, watched the cams line up, and where the crank pully was at TDC

[Jayz691]

Damm, should have just fixed it..
But compression #'d don't look great either. All kinda low, and 30psi dif from high to low. How many valves did ya wind up replacing? Did you tested them with some liquid, and compressed air? For timing, ya make sure your marks are on from crank to exhaust cam sprocket. For chain, count links. With the coooer link on the 1 mark, count 18/19 pins, and second mark shiuld be between those links. Another reason to gix that stripped bolt, is its much easier to time the chain, with the phaser off..

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[VinnysS4]

For now it seems like it's gonna be my car so I'm not gonna worry on it for not. Probably will fix it in the future. I have got the timing chain on and THINK I have it timed correctly.

For my compression test, I'm getting:

Cylinder 1: 150psi
Cylinder 2: 135psi
Cylinder 3: 120psi
Cylinder 4: 135psi

May have missed a tooth or two while timing it but not entirely sure. I went by the marks on the exhaust cam, watched the cams line up, and where the crank pully was at TDC

120 to 150 is 20% difference between low and high compression cylinders. It's not the end of the world, but typically you want to see them all within 10 to 15%.

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[sarxworks]

Nvm. I botched my test. Coincidentally, my long time church mechanic friend was over for my dad's car and he helped me with the test. I didn't crank it long enough and did it at varying times.

Reading are all the same now.

Cylinder 1: 150psi
Cylinder 2: 150 psi
Cylinder 3: 150psi
Cylinder 4: 150psi

[sarxworks]

Quick question, I nearly have everything back together but where does the ground plate attach to again? Does it attach to the firewall or the timing cover plate?

[Theiceman]

timing cover.
make sure it is absolutely flat and oriented correctly and dont over torque the bolt it is easy to strip out. it is the torx bolt with the larger pan head at the bottom of the timing cover of the three that fastens this bracket on and the vacuum pump.



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[Jayz691]

Quick question, I nearly have everything back together but where does the ground plate attach to again? Does it attach to the firewall or the timing cover plate?

Like iceman said. This little notched will lock onto a spot on the cover. A rear view pic would help, but hard to find.Screenshot_20230601-123653~2.jpg

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[Theiceman]

i believe it locks round an area of the vac pump.. but it's been a while

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[Jayz691]

i believe it locks round an area of the vac pump.. but it's been a while

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It does, but hard to explain where. Need to find a good rear pic, cuz this question comes up a lot. Will have to take some pics when my engine is out, lol.

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[sarxworks]

Got that fixed but now on my first start, I have fuel leaking from somewhere and the car won't start (expected). It's leaking from just before the radiator and the oil pan, I took a look down there but nothing is out of the ordinary. Any ideas? Maybe I didn't torque the intake Manifold correctly?

I already taken off the HPFP and retightened all the connectors and checked the two 17mm nuts

[Older_not_Wiser]

hmmmm, that could be an injector o-ring that got pinched when installing the IM

[Jayz691]

I second and o-ring, possibly. Had that happen to mine, was pretty easy to find/hear though.

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[sarxworks]

I third that, this wasn't happening when I first started the car. Also I hear a weird growling coming from the IM. Will take it off probably later today.

[Jayz691]

Ya should be able to shine a light around the IM, and find it. But when I had it happen, it almost tore the o-ring in half.. So you'll see it when ya remove the IM.

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[sarxworks]

Well guys good news, she runs! Bad news, I ended up getting too excited and closed the hood without making sure the latch was installed correctly and now I can't open it. I'm currently trying to get to it from under the car but even with all the force in my hand, I can't push the lever?

Also, I'm unable to get the coolant reservoir return line back onto the nipple on the quick release.

[sarxworks]

Well guys good news, she runs! Bad news, I ended up getting too excited and closed the hood without making sure the latch was installed correctly and now I can't open it. I'm currently trying to get to it from under the car but even with all the force in my hand, I can't push the lever?

Also, I'm unable to get the coolant reservoir return line back onto the nipple on the quick release.

Nvm guys, got it open and fixed the latch. I also got the pipe back on the quick release. Thanks for all the help!

[Theiceman]

yeah looks like you snapped off the nipple..

i just stretched the crap out of the hose with a pair of needle nose pliers and put it over the bigger piece. did this 4 years ago and its been fine.

[sarxworks]

Sorry, that isn't my photo, it's just a very good example at the time because I couldn't open up the hood.

Yeah essentially I did that and got it on and used a worm clamp

[Theiceman]

Sorry, that isn't my photo, it's just a very good example at the time because I couldn't open up the hood.

Yeah essentially I did that and got it on and used a worm clamp

good job me too .. I don't think it is ever coming off lol.

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[williamloh]

It's quite fascinating how a snapped cam chain can sometimes spare the valves from bending, preserving the engine's critical components. This resilience mirrors the way the ultimate chicken sandwich combines various flavors and textures to create a harmonious culinary experience, proving that sometimes, unexpected combinations can yield delightful results.

[Theiceman]

It's quite fascinating how a snapped cam chain can sometimes spare the valves from bending, preserving the engine's critical components. This resilience mirrors the way the ultimate chicken sandwich combines various flavors and textures to create a harmonious culinary experience, proving that sometimes, unexpected combinations can yield delightful results.

not really.. when the chain snaps the cam is basically free wheeling and if at low revs the piston hits the valve and just makes the cam turn. AT high revs i doubt you would be that lucky though. As a follow up the car it happened to for me ( my sons now ) has done over 50K miles since this occurrence.

[CrickiKaze]

not really.. when the chain snaps the cam is basically free wheeling and if at low revs the piston hits the valve and just makes the cam turn. AT high revs i doubt you would be that lucky though. As a follow up the car it happened to for me ( my sons now ) has done over 50K miles since this occurrence.

Yeah...that's a spammer/scammer that you replied to.