Valve dropped at idel, is my head salvageable ?? let's talk about how this happened.

[chinaren]

I have a stage 3 S4 motor that has been sitting for a year, and i have recently transplanted into a C5 Allroad.

The engine did not start at first, i unplug the MAF and the car barely start and ran very rough.

The second time it started, it was as rough as the first time, and a few seconds later, i heard something dropped and bounced around in the engine. i turned the car off right the way. upon a inspection camera in the cylinder # 6, i found a broken valve in the cylinder. i then proceeded to remove the drive side head and found the following...See pictures below

My timing belt and all components were changed less than 5000 miles ago, only one cylinder suffer a broken valve, and only one broken valve in that cylinder. What cause this? this is my SECOND APB motor that has this problem.

My questions are:

1. what caused this?
2. is my head salvageable?
3. what should i do to prevent this?(Maybe change ALL of my valves to supertech valves?, should i change my springs and retainer too?)

My thoughts on my 1st question is that my motor has been sitting for a year, due to inadequate lubrication, this broken valve had a "sticky" condition, where it did not fully retract, when the piston came up and bent it at first, and after a few more times, it broke off and felt into the cylinder.

Now on to the pictures...











Thank you, I hope through this thread, we can all learn something about our valve train, and hopefully we can come up with some idea that will prevent this on our motors.

[zillarob]

It is prob salvageable, but for the $$ you might be better off getting a used set of heads. Maybe even 2.8s.

If the piston kissed it while doing the tbelt or from a sticky guide, it will stress the stem every time it opens and closes.
Kinda like bending a paperclip back and forth, it eventually breaks.

PS: Mop that coolant up before it ends up in the oil pan.

[chinaren]

what do you do to salvage it? Machining? Will clean up. thanks

[zillarob]

Clean it up and replace the seat.
Check the guide and maybe surface the head.

Machine work adds up quick so prob cheaper to just find a nice used set to drop in.

[Monty23]

Used head would be the cheapest way to go here. And smooth out the nicks in that piston to help prevent knock.

[flips4]

replace the piston, used ones can be had for 50 or 75 bucks on ebay. Will need new rings and connecting rod bolts. If you smoothing it out it will still have hot spots. might last forever or might die soon. better safe than sorry and its cheap insurance. If you do replace the piston check the bearings on that one, the manual has wear tolerances. mine at 140k miles were within "NEW" specs still.

As said above you can replace the valve and have the seat either reground or replaced.

[airjawed]

But the question of why it happened... and why twice?

[rtl5009]

Used head. Done.

[01audia4]

But the question of why it happened... and why twice?

This is what I was thinking.

[chaos2984]

I would just replace that valve , valve guide, and seat and be done with it. Just smooth out the nicks in the piston and your fine. Those little nicks wont cause hot spots for you to really worry about. But when you have the machine shop fix that valve I would have them go threw the entire head and check the rest. other than that your fine.

The question is what caused that to happen. Did you check the timing before you took it apart. What did that valve look like from the top side where the cam and lifter bucket is? What does the valve spring look like is it broken? Are the keepers still on the valve stem with retainer? For the valve to break off like that, it had to be way the hell out of wack for timing. Even if the engine is bone dry it shouldn't of done that. Was your timing belt tight when you took it off? What did the cam chain look like and was it tight? Ive put junk yard engines in before and they have sat longer than that. It should of been fine unless something broke or it jumped time. Did you just try to start it or disable spark and crank it first to build oil pressure. I do that with every engine I build just fore peace of mind.

I think you need to try to figure out y it broke in the first place.

[MalibuMafiaV]

When my valves bent I was considering just getting a used set of 2.8 heads. But comes out to only be 12 bent valves, 8 exhaust 4 intake.

In your situation I would just get a used set of heads from the 2.8.

[chinaren]

Clean it up and replace the seat.
Check the guide and maybe surface the head.

Machine work adds up quick so prob cheaper to just find a nice used set to drop in.

Do you know where i can find a procedure on replacing the seat? where i can buy a seat for it, plugs the tools...? i can do all the work myself. Thanks

[chinaren]

Used head would be the cheapest way to go here. And smooth out the nicks in that piston to help prevent knock.

This is an option, but i have three engines in my garage that all have this same issue, two of them i bought them that way, and this one happened to me. So if i can some how repair them for cheaper price, but again used head should be easier to do. thanks

[chinaren]

When my valves bent I was considering just getting a used set of 2.8 heads. But comes out to only be 12 bent valves, 8 exhaust 4 intake.

In your situation I would just get a used set of heads from the 2.8.

I have some 2.8 heads, but i do not think my K04s can utilize them, but thanks.

[chinaren]

These valves are under tension all the time, the tension is released only when the valve opens, so there is a fatigue associated with it. But again maybe the fatigue life of the valve has been calculated, and 140k miles is nothing compare to calculated fatigue life. When i have multiple engines that all suffer the same, i am trying to make sure i address the issue appropriately.

I will take apart the spring chamber and provide pictures later.

[MalibuMafiaV]

I have some 2.8 heads, but i do not think my K04s can utilize them, but thanks.

What do you mean?

[01audia4]

What do you mean?

2.8 heads on k04 moves the Tq/hp far to the right; K04's can't utilize this. 2.8 Cams on K04's inside 2.7 heads seems good though, but that doesn't help the OP.

[T.pops]

How do dimples create hot spots? Thanks

[Drehmoment]

2.8 heads on k04 moves the Tq/hp far to the right; K04's can't utilize this. 2.8 Cams on K04's inside 2.7 heads seems good though, but that doesn't help the OP.

No

The RS 4 has large intake ports with smaller exhaust ports and uses KO4's

Small exhaust ports retain low end tq
2.8 heads gain more peak and under the curve hp but loose a little tq down low because of the larger exhaust ports.There is definite gains to be had with 2.8 heads utilizing KO4's

[Scotty@Advanced]

Valve seat will need to be replaced which means the head is probably beyond economical repair. Piston is toast.

[01audia4]

No

The RS 4 has large intake ports with smaller exhaust ports and uses KO4's

Small exhaust ports retain low end tq
2.8 heads gain more peak and under the curve hp but loose a little tq down low because of the larger exhaust ports.There is definite gains to be had with 2.8 heads utilizing KO4's

You're arguing semantics. As I said. It moves the curve to the right. 2.8 cams in 2.7 heads is better then 2.8 heads/cams on K04s. This is at least for every dyno graph I've seen for an S4 not an RS4. Which will have different intake components anyway. Regardless of k04s. But please I'd like to see a graph that says otherwise because I have been interested in adding 2.8 cams in.

[chinaren]

You're arguing semantics. As I said. It moves the curve to the right. 2.8 cams in 2.7 heads is better then 2.8 heads/cams on K04s. This is at least for every dyno graph I've seen for an S4 not an RS4. Which will have different intake components anyway. Regardless of k04s. But please I'd like to see a graph that says otherwise because I have been interested in adding 2.8 cams in.

This is my understanding too, when the curve shifts to the right, this means boost kicks in in a higher RPM, but will keep the boost until redline. I like my car with relative low RPM boost, which is more enjoyable on normal street driving.

How about grinding the valve seat which valve seating compound until the seat is seal again, will this cause any problems later on?

[chinaren]

Valve seat will need to be replaced which means the head is probably beyond economical repair. Piston is toast.

Why do you say the piston is toast?

[chaos2984]

Why do you say the piston is toast?

Its not toast don't listen to him. Just smooth down the high spots and it will be fine. don't look back. Ive done that a lot in the dealership world and no issues ever. Even on vette engine and turbo cobalt engines. Unless there is a hole or crazy gouged or any sort of cracking it will be fine. If the car was a race car only yes i would replace it, but for your application i wouldn't worry about it one bit.

Also fatigue in the valves? You can't be serious. The only way that happens is if there was a manufacturing defect in making the valve. Valves will outlast the engine unless you burn them or they pit on the face. Get out of here with valve fatigue.

You are going to want to let a machine shop to replace the guide and seat for you. I wouldn't do that yourself. Once they get the seat in there they will have to cut the seat and valve to fit right and get a good seal.

Also with used 2.8 heads I wouldn't put them on my car without having them checked either. I don't know how the engine ran with them on there and if there could be any issues with the valves or guides. I guess you could put water in the ports and see if any of the valves leak but that can only tell you so much. But i would like just peace of mind that the heads are a ok.

Just fix that one head an be done with it.

[julex]

^^ this. Piston will be ok just dremel anything sticking out with the deck. I would get new head though and then have it checked out. This one is pretty beat up and since one valve already was giving you issues, chances are rest is not far behind.

[Scotty@Advanced]

Pistons are cast and those indentations probably have small hairline cracks protruding from the dents, which as the pistons heats and expands those cracks will propagate. Id' at least have it dye tested. BTDT with another similar issue, the piston fails 15,000 miles later.

As far as repairng the head, I'd just find a used one, seats are cast with the head and if you replace a seat you risk it dropping later with the same results.

[julex]

Pistons are cast and those indentations probably have small hairline cracks protruding from the dents, which as the pistons heats and expands those cracks will propagate. Id' at least have it dye tested. BTDT with another similar issue, the piston fails 15,000 miles later.

As far as repairng the head, I'd just find a used one, seats are cast with the head and if you replace a seat you risk it dropping later with the same results.

Pistons in this engine are forged. Seats are press fitted into machined socket in the aluminum head...

[chinaren]

how about i grind the seat with grinding compound, will this cause any problem in the long run? thanks

[chaos2984]

how about i grind the seat with grinding compound, will this cause any problem in the long run? thanks

Your not going to be able to use grinding compound to fix that. Your going to have to use a cutter and cut the seat. compound will fix minor pitting and dirt. It won't fix gouging without a lot a lot of effort. It will be easier to cut it. But with cutting it you risk pulling the valve higher up in the head and if you go to far you can have issues with valve float at high rpm and the keepers can come off the valve and it will really drop. Honestly I would call a machine shop and have them replace the seat. Its a easy job for them.


Also if a seat falls out It can't and won't damage an engine. It will damage the head thats it. Ive seen this happen first hand. But I've only seen this once.

Honestly Id call a machine shop and talk to them and maybe take the head up to them so they can just look at the damage and they will tell you whats best to do.

[Scotty@Advanced]

Seats are press fitted into machined socket in the aluminum head...

Do you have any supporting information on this? When I went down this road everyone said they were cast in place and many machine shops wouldn't replace a seat, but whatever. I guess the cast versus forged piston debate goes on..

[chinaren]

my understanding of our heads were, cast aluminum, and machined to accept the cast steel valve seat. The valve seat can be cast in the head, but you have to machine the cast steel seat. So from a manufacturing stand point, it would make sense to machine aluminum head and press in the cast steel seat with tolerance fit.

If you look close at my 1st and 2nd picture, the pilot hole for the valve seat looks machined, which means the valve seat was not cast in the head.

[jibberjive]

That sucks Wei!
I have had a set of 2.8 heads that had the lifters completely seized (which could cause this issue), but those heads were separated from an engine and sitting on the shelf of a machine shop with the valve covers off and no oil in them for probably a couple of years. Countless junkyard motors sit for longer than a year and have no issue. Seems you are having terrible luck:(

You won't want to do the valve seat work yourself, if you choose to get them repaired. I would definitely have a machine shop do it. If it were me, I would just replace the head with a good used one (assuming you're not looking to build/upgrade the heads anyways).

Some of those gouges in the pistons look pretty bad, but if you're looking to go the budget route, might as well smooth and polish them with a dremel and throw it back together. Much less work than disassembling, replacing piston, rings, honing, bearings etc.

If you're still running my tune on your setup though, we definitely need to update the tune asap (before you romp on it after repair). I'm still waiting on logs from like 2 years ago! lol

[jibberjive]

Pistons in this engine are forged.

I was going to say the same thing.

[chinaren]

[QUOTE=jibberjive;10513014]That sucks Wei!
I have had a set of 2.8 heads that had the lifters completely seized (which could cause this issue), but those heads were separated from an engine and sitting on the shelf of a machine shop with the valve covers off and no oil in them for probably a couple of years. Countless junkyard motors sit for longer than a year and have no issue. Seems you are having terrible luck:(

You won't want to do the valve seat work yourself, if you choose to get them repaired. I would definitely have a machine shop do it. If it were me, I would just replace the head with a good used one (assuming you're not looking to build/upgrade the heads anyways).

Nice to hear from you, Mike, thanks for the tips. Hopefully i can get this sorted out and pay you to finish the tune. keep in touch my friend.