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View Full Version : Head Removal: Questions about valves, pistons.. HELP!



kink7
06-28-2009, 04:27 PM
2So here's the long story so you know exactly what happened. I missed 3rd gear at high rpms on my 01 1.8t qm and over revved. Shortly after (maybe 20 seconds) I got a flashing cell. I scanned my car and had a misfire on cylinder 4. I changed the spark plug, still a misfire I switched coilpacks and fuel injectors, still a misfire. When I was taking ignition coil off cylinder 4 I broke the little capacitor that connects to the ignition coil and the engine harness. ( I don't know if that was my problem or not but didn't think it would cause a misfire) I did a compression test and at first had compression in cylinder 4 but than did it again another day and didn't have ANY compression. I repeated just to make sure and got the same results. I just took off the head thinking I had a bent valve but everything looks ok. My pistons have a couple of small marks in the same place on all 4 and I don't think they are supposed to be there but I'm not sure. I need HELP!!! I'll post pics incase you see something I can't. Since I have everything off I'm going to put performance valves in and most likely do pistons and rods. I would love to put in a BT but I just dont have the money right now for it and all the supporting mods. Please let me know if you see anything out of the ordinary or if there is anything else I should do that is small that I should do while im in here. TIA!!

http://i66.photobucket.com/albums/h248/Cuthbert_photos/IMG_1044.jpg

Black capacitor that broke off.

http://i66.photobucket.com/albums/h248/Cuthbert_photos/IMG_1051.jpg

Pistons

http://i66.photobucket.com/albums/h248/Cuthbert_photos/IMG_1050.jpg

Close up of marks cylinder 2 and 3

http://i66.photobucket.com/albums/h248/Cuthbert_photos/IMG_1052.jpg

Closer close up of marks

http://i66.photobucket.com/albums/h248/Cuthbert_photos/IMG_1053.jpg

Valves

http://i66.photobucket.com/albums/h248/Cuthbert_photos/IMG_1054.jpg

Cylinder 4 valves are darker than the rest. Dont know why. Input?

jrock
06-28-2009, 04:30 PM
Time to rebuild for a big ass turbo!

kink7
06-28-2009, 10:06 PM
anyone? What would cause those marks on the piston and why wouldn't I get compression if the valves look fine on cylinder 4? Any input would be greatly appreciated

djwimbo
06-28-2009, 10:42 PM
Since you already have the cylinder head off, check it for warpage.

The downside to already having the head off, is that you can't run a leakdown test and know exactly where the problem is.

I haven't ever had a car with a broken off capacitor, but I doubt it would cause a misfire.
What scares me, is that you had compression one day, and none the next. What were your actual compression numbers?
I dropped compression on cyl #4 in my A4 b/c the rings were fried (and cylinder wear), looks like you might be in a similar situation, just without the smoking.

If you have the head off, you can take it to a machine shop and have them check the valves, guides and inspect for warpage.

Here's the bad news, those marks on top of the pistons WILL NOT and CAN NOT exist in an engine that hasn't had the pistons smack the valves. It's either happened while you owned the car, or the previous owner snapped a T-Belt. Those marks don't look real new though.

The next thing I'm curious about is why there are 7 clean exhaust valves and one dirty one.

Check the piston to cylinder clearance. Here's what mine looked like. To clarify, this is bad. I really should have had the block bored and put in oversized pistons, but it wasn't my car at that point and the new owner didn't want to pay for that.

http://i305.photobucket.com/albums/nn218/djwimbo/The%20Silver%20Saloon/DSCF1715.jpg

onemoremile
06-29-2009, 12:51 AM
Those marks are on all four pistons and look like they should be there. They look like valve reliefs. The valves would be marked if they contacted the pistons.

I agree with Dan that the one black valve is suspect. Turn the cam pulley over and see if that valve is stuck.

DarrenTT
06-29-2009, 08:57 AM
Hi kink7 - I have exactly the same damage to mine currently, except mine was caused by a stripped cam belt [:(]. The marks on those pistons are caused by clipping the exhuast valves. Its hard to tell from the pics, but they may be old wounds, cambelt failures are common on these 1.8T lumps. Have you checked your cam belt that it hasn't snapped or stripped teeth?

If your cambelt has failed, then in terms of other damage to the engine, I suggest you have the head sent away to be pressure tested as that will tell you whether you have any hair-line cracks. Have it re-faced also so you get a nice clean fit to the block when you re-assemble.

Jake39454
06-29-2009, 09:05 AM
Those marks are on all four pistons and look like they should be there. They look like valve reliefs. The valves would be marked if they contacted the pistons.

I agree with Dan that the one black valve is suspect. Turn the cam pulley over and see if that valve is stuck.

Jim that is not how they should look. Obviously the valves impacted, the question is how long ago and if it was on the current valves. Pistons should look like these OEM pistons:

http://i239.photobucket.com/albums/ff52/crazyass713/0307081629-1.jpg

onemoremile
06-29-2009, 09:08 AM
Jim that is not how they should look. Obviously the valves impacted, the question is how long ago and if it was on the current valves. Pistons should look like these OEM pistons:




I thought that but all four pistons are identical and no valves have any damage. Maybe this engine was rebuilt with new valves at some point?

Jake39454
06-29-2009, 09:20 AM
I thought that but all four pistons are identical and no valves have any damage. Maybe this engine was rebuilt with new valves at some point?

Most likely. Or he has been driving around a while since the valves kissed.

And to the OP, just replace that black piece with a 4.7 micro fared capacitor, you can get them at Radio Shack for less than $2. I've done this before for a customer.

onemoremile
06-29-2009, 09:33 AM
Seems like a bad cap would cause a misfire.

Jake39454
06-29-2009, 09:34 AM
Seems like a bad cap would cause a misfire.

According to my investigation a few months back, it's a ground noise dampener. And an open ground could surely cause a miss.

Beemer832
06-29-2009, 11:10 AM
ouch....... i hate to see this. maybe its the new "in thing" cutting reliefs for the exhaust vales :p

Yea definitely time for a whole new valve job. i would put in a decent set of OEM sized exhaust valves. Go with supertech or something like that.

You will need all new valve guides and seals and miht as well have them clean the head up completely and recut the seats for all the valves. (will need to do that for the new valves anyways)

As far as the pistons go, I guess thats not good, but its not necessarily bad. if you are going to do the engine rebuild, might as well get it done now...

-josh

kink7
06-29-2009, 02:08 PM
Those marks are on all four pistons and look like they should be there. They look like valve reliefs. The valves would be marked if they contacted the pistons.

I agree with Dan that the one black valve is suspect. Turn the cam pulley over and see if that valve is stuck.

I cranked it by hand and the valves seem to be sticking at all.

I also checked the cam belt for stripped teeth and didnt find any. Now since that exhaust valve on cylinder 4 is black compared to the others, if I replaced the valves would this still occur or is this something that might get taken care of with replacement. If not what could be causing it?

Also is it possible to do pistons and rods without taking the block off or is it just easier to take it off?

If I have to take it off Im thinking maybe 2.0 stroke but Im a broke college student and don't really have that much money so i mght just replace it with performance parts. Do you think I should even pay to take the head to a machine shop and have them look at it or should I just buy an AEB head and exhaust manifold and go that route? Thanks for your help

djwimbo
06-29-2009, 02:19 PM
You really need to get that last exhaust valve checked out.
I would not doubt one bit that it's burnt, bent or stuck. The rest of the valves are clean because they get to be 1000*F or more. That last one is not clean, making me believe that it wasn't heated as much as the others. It's quite possible it's been leaking for awhile now, and finally fried.

The reason I don't think your valves contacted the piston is because of the contamination on top of the divots. Normally, when the valves hit the pistons, they leave nice new shiny marks from the metal distorting. Those have carbon build up on top of them, making it seem like it's been like that for quite some time.
Either way, those don't belong.

Beemer832 - SOME people do clearance the pistons for the valves, exhaust or intake, sometimes both. Without increasing static compression there's no need to clearance 1.8T pistons more than the factory does for the 5th valve (intake side)

Beemer832
06-29-2009, 02:43 PM
You really need to get that last exhaust valve checked out.
I would not doubt one bit that it's burnt, bent or stuck. The rest of the valves are clean because they get to be 1000*F or more. That last one is not clean, making me believe that it wasn't heated as much as the others. It's quite possible it's been leaking for awhile now, and finally fried.

The reason I don't think your valves contacted the piston is because of the contamination on top of the divots. Normally, when the valves hit the pistons, they leave nice new shiny marks from the metal distorting. Those have carbon build up on top of them, making it seem like it's been like that for quite some time.
Either way, those don't belong.

Beemer832 - SOME people do clearance the pistons for the valves, exhaust or intake, sometimes both. Without increasing static compression there's no need to clearance 1.8T pistons more than the factory does for the 5th valve (intake side)


thanks for the info DJ. I was just being a smartass thought. I've never seen exhaust valves clearanced before but I guess it may be necessary in some cases depending on the clearances between the pistons and valves.

and to the starter of this thread. it would most likely be cheaper to have the valve job done at a reliable head shop then it would be to buy a new head. Even a used head in working order is expensive. at least in relation to a valve job and a set of exhaust valves.


-josh

Nebone
06-29-2009, 04:32 PM
I cranked it by hand and the valves seem to be sticking at all.

I also checked the cam belt for stripped teeth and didnt find any. Now since that exhaust valve on cylinder 4 is black compared to the others, if I replaced the valves would this still occur or is this something that might get taken care of with replacement. If not what could be causing it?

Also is it possible to do pistons and rods without taking the block off or is it just easier to take it off?

If I have to take it off Im thinking maybe 2.0 stroke but Im a broke college student and don't really have that much money so i mght just replace it with performance parts. Do you think I should even pay to take the head to a machine shop and have them look at it or should I just buy an AEB head and exhaust manifold and go that route? Thanks for your help

Yes its possible to remove pistons and rods without removing the block. Just remove the and oil pan and you will have full access. Might want to remove the subframe too to give you more room.

DarrenTT
06-30-2009, 02:02 AM
You really need to get that last exhaust valve checked out.
I would not doubt one bit that it's burnt, bent or stuck. The rest of the valves are clean because they get to be 1000*F or more. That last one is not clean, making me believe that it wasn't heated as much as the others. It's quite possible it's been leaking for awhile now, and finally fried.

The reason I don't think your valves contacted the piston is because of the contamination on top of the divots. Normally, when the valves hit the pistons, they leave nice new shiny marks from the metal distorting. Those have carbon build up on top of them, making it seem like it's been like that for quite some time.
Either way, those don't belong.

Beemer832 - SOME people do clearance the pistons for the valves, exhaust or intake, sometimes both. Without increasing static compression there's no need to clearance 1.8T pistons more than the factory does for the 5th valve (intake side)

I agree with you... I have *exactly* the same size divots on the top of all my piston's and all 8 exhaust valves were bent... you wouldn't get that sort of damage to the piston tops without bent valves.

Although, if he doesn't decide to change the pistons, wouldn't it make sense to feather out the divots with sand paper so there are no sharp edges, as these will cause hot-spots on the tops of the pistons?