Catastrophic Failure
08-29-2013, 11:52 PM
#12
Join Date: Dec 2001
Location: City Of London / Knebworth
Posts: 39,551
Likes: 0
Received 11 Likes
on
10 Posts
If it was my money ... i'd drain the bottom end, look for debris. Pull the sump and check the crank / bearings and possibly check the bores for scoring - just to be paranoid. I'd also check thrust bearing and possibly replace bearings / shells whilst it was in bits.
Put a known good head back on and enjoy a LOT more miles in the knowledge that the engine is good.
If you can get all that done for less than the cost of buying another engine that may have hidden issues, my head says that's money better spent. However i'd run that past someone that builds engines
Put a known good head back on and enjoy a LOT more miles in the knowledge that the engine is good.
If you can get all that done for less than the cost of buying another engine that may have hidden issues, my head says that's money better spent. However i'd run that past someone that builds engines
It is very possible that the heat from the coil pack failure damaged the cam towers or possibly just fried the oil enough to cause the damage.
I got a set of low mileage cams and valve springs .... if they are of any use to you.
08-30-2013, 12:36 AM
#13
Not had much S2000 related luck of late have you?Maybe a ham-fisted mechanic had rebuilt the top end at some point in the recent past? That'd be my guess. Mine died with camchain failure, which caused extreme badness that was only revealed when the head removed. Could loose cams cause the valves to crash into the pistons in the same way?
08-30-2013, 01:10 AM
#14
Originally Posted by unclefester' timestamp='1377848137' post='22753104
If it was my money ... i'd drain the bottom end, look for debris. Pull the sump and check the crank / bearings and possibly check the bores for scoring - just to be paranoid. I'd also check thrust bearing and possibly replace bearings / shells whilst it was in bits.
Put a known good head back on and enjoy a LOT more miles in the knowledge that the engine is good.
If you can get all that done for less than the cost of buying another engine that may have hidden issues, my head says that's money better spent. However i'd run that past someone that builds engines
Put a known good head back on and enjoy a LOT more miles in the knowledge that the engine is good.
If you can get all that done for less than the cost of buying another engine that may have hidden issues, my head says that's money better spent. However i'd run that past someone that builds engines
It is very possible that the heat from the coil pack failure damaged the cam towers or possibly just fried the oil enough to cause the damage.
I got a set of low mileage cams and valve springs .... if they are of any use to you.
08-30-2013, 02:27 AM
#17
Yeah, me three. Rotten luck. Again.
So what's happened? bolts backed out of the bearing cup halves, or the shells wrecked by oil starvation?
If the former, sounds like someone's not re-torqued them correctly after messing with it. The engine does vibrate a lot at high rpm.That would Muller everything.
But yes; assuming there's no shrapnel in the bottom end, a new head (S/H) simply bolts on fairly easily.
So what's happened? bolts backed out of the bearing cup halves, or the shells wrecked by oil starvation?
If the former, sounds like someone's not re-torqued them correctly after messing with it. The engine does vibrate a lot at high rpm.That would Muller everything.
But yes; assuming there's no shrapnel in the bottom end, a new head (S/H) simply bolts on fairly easily.
08-30-2013, 03:34 AM
#18
Registered User
Been having a chat through alternate means with S2Ki's chief reprobate
Here's a copy paste of the pertinant bits
My first observation with the photo is look at the intake cam and particularly cam cap#1
It's very black/dark compared to the exhaust cam in particular. That would suggest to me that when you pull the cap off it'll be totally bladdered under there. Seized up and generally a mess of bearing surfaces.
This is total conjecture but may well fit with what you're telling me with the plugs not having been tightened properly (i.e. possibly a sloppy work practice previously).
I reckon some work has been done previously on that cylinder head that has required removing the cam-shaft/caps
When you put the caps back on you have to follow a particular sequence and I'm personally one for putting a spanner on them all at least twice.
You should put the centre cap (#3 normally) on first and tighten it
then either #2 or #4 and tighten
then the other one you didn't do in the previous step (#4 or #2)
then go to the one at the other end of the engine and tighten and then go to the other end of the engine and tighten
(it should look something like tightening order #3 => #4 => #2 => #5 => #1 depends on configuration of engine but I tend to try and end on cam #1 since it is under highest load often, particularly with VVT systems and the like)
Unless you're using a multi spindle robot/machine it is impossible for a human to tighten the caps down as one, there are just too many bolts so you start at the centre and work your way out equally so as to take the cam down as level as possible.
If you screw the order up there are two common failures/results
1) The cam is lifted up on springs on the cam lobes. If you start at one end and work your way to the other you can bend the cam (since it is only cast iron normally you tend to break them if this happens)
2) You tighten the first cap down. The majority of bolt torque (I've heard 80% quoted) comes from the bolt head connecting with the surface it is touching so the bolt achieves torque quite quickly. You then start putting the remainder of the bolts into the caps and tightening them up. Remember you're tightening onto the valve springs though! That first bolt will feel tight as you like when you're tightening it. As the clamp loads increase though as more caps are tightened the earlier tightenings have all their clamp load taken away, the bolt heads come away (at least partially) from the surface and voila you have no torque on the cam cap bolts.
That would be my initial diagnosis
Where would I go next?
- If possible get a torque measurement on the remaining bolts, by the looks of the picture that would be best done on exhaust side (lowest failure amount)
- If I'm right you should find one cap totally loose, another a bit tighter, another tighter still etc (since the caps are linked I'd guess if someone did this they'd tighten all bolts on the same cap at the same time and hence you'll find similar results
- Once you've got the torques strip the rest of the head down being careful to keep everything in the correct order (use paint or tipex or similar to mark the positions on the cast surfaces of the cap if they don't have markings on already)
- Examine for varying signs of wear and damage that wasn't obvious on initial inspection of the assembly (there may be a crack/bend that isn't obvious when covered in oil and bolted into position) You may also feel something different as the bolts come out. A bolt more awkward or hanging my be indicative of distortion
That would be my starter for 10 anyway.
If I'm right then the bottom of the engine should be fine so probably you could get away with just a head change which may save a few quid. History does say that F20C's don't respond well to being repaired though so would depend on cost of replacement head vs replacement engine.
And from a slightly later mail
Obviously the head has to come off so yeah checking the bores is worth doing whilst it is off. If possible also get the head before going to [view any second hand ones]. Take it with you and then you can see any obvious things that might be a problem with it or different between the two.
I can't remember if you have to have the pan off on an F20C to get all the timing gear that goes with the head off. It may well be worth checking the pan for any debris as well and easier to see with the pan off. If anything heavy is sitting in there it probably wouldn't wash out in to the oil (thinking nuts/large chunks of debris)
If the pan is off then you're into the realms of it being worth taking the pistons out and checking bearings are all ok.
Start with getting the head off and a bore check (and ask questions about how they plan on doing it) and then maybe work from there.
Here's a copy paste of the pertinant bits
My first observation with the photo is look at the intake cam and particularly cam cap#1
It's very black/dark compared to the exhaust cam in particular. That would suggest to me that when you pull the cap off it'll be totally bladdered under there. Seized up and generally a mess of bearing surfaces.
This is total conjecture but may well fit with what you're telling me with the plugs not having been tightened properly (i.e. possibly a sloppy work practice previously).
I reckon some work has been done previously on that cylinder head that has required removing the cam-shaft/caps
When you put the caps back on you have to follow a particular sequence and I'm personally one for putting a spanner on them all at least twice.
You should put the centre cap (#3 normally) on first and tighten it
then either #2 or #4 and tighten
then the other one you didn't do in the previous step (#4 or #2)
then go to the one at the other end of the engine and tighten and then go to the other end of the engine and tighten
(it should look something like tightening order #3 => #4 => #2 => #5 => #1 depends on configuration of engine but I tend to try and end on cam #1 since it is under highest load often, particularly with VVT systems and the like)
Unless you're using a multi spindle robot/machine it is impossible for a human to tighten the caps down as one, there are just too many bolts so you start at the centre and work your way out equally so as to take the cam down as level as possible.
If you screw the order up there are two common failures/results
1) The cam is lifted up on springs on the cam lobes. If you start at one end and work your way to the other you can bend the cam (since it is only cast iron normally you tend to break them if this happens)
2) You tighten the first cap down. The majority of bolt torque (I've heard 80% quoted) comes from the bolt head connecting with the surface it is touching so the bolt achieves torque quite quickly. You then start putting the remainder of the bolts into the caps and tightening them up. Remember you're tightening onto the valve springs though! That first bolt will feel tight as you like when you're tightening it. As the clamp loads increase though as more caps are tightened the earlier tightenings have all their clamp load taken away, the bolt heads come away (at least partially) from the surface and voila you have no torque on the cam cap bolts.
That would be my initial diagnosis
Where would I go next?
- If possible get a torque measurement on the remaining bolts, by the looks of the picture that would be best done on exhaust side (lowest failure amount)
- If I'm right you should find one cap totally loose, another a bit tighter, another tighter still etc (since the caps are linked I'd guess if someone did this they'd tighten all bolts on the same cap at the same time and hence you'll find similar results
- Once you've got the torques strip the rest of the head down being careful to keep everything in the correct order (use paint or tipex or similar to mark the positions on the cast surfaces of the cap if they don't have markings on already)
- Examine for varying signs of wear and damage that wasn't obvious on initial inspection of the assembly (there may be a crack/bend that isn't obvious when covered in oil and bolted into position) You may also feel something different as the bolts come out. A bolt more awkward or hanging my be indicative of distortion
That would be my starter for 10 anyway.
If I'm right then the bottom of the engine should be fine so probably you could get away with just a head change which may save a few quid. History does say that F20C's don't respond well to being repaired though so would depend on cost of replacement head vs replacement engine.
And from a slightly later mail
Obviously the head has to come off so yeah checking the bores is worth doing whilst it is off. If possible also get the head before going to [view any second hand ones]. Take it with you and then you can see any obvious things that might be a problem with it or different between the two.
I can't remember if you have to have the pan off on an F20C to get all the timing gear that goes with the head off. It may well be worth checking the pan for any debris as well and easier to see with the pan off. If anything heavy is sitting in there it probably wouldn't wash out in to the oil (thinking nuts/large chunks of debris)
If the pan is off then you're into the realms of it being worth taking the pistons out and checking bearings are all ok.
Start with getting the head off and a bore check (and ask questions about how they plan on doing it) and then maybe work from there.
08-30-2013, 08:48 AM
#20
Registered User
Having spoken to you on Facebook before reading this thread it's interesting to see others seem to come to the same conclusion of over rev and top end repair at some point.
The order of tightening of the cam carriers is extremely important so it could be something to do with this as fluffy ninja has suggested. To me though the exhaust area of cylinder #3 looks blacker thank in the intake cam...
Out of curiosity which cylinder did the coil pack fry on?
The order of tightening of the cam carriers is extremely important so it could be something to do with this as fluffy ninja has suggested. To me though the exhaust area of cylinder #3 looks blacker thank in the intake cam...
Out of curiosity which cylinder did the coil pack fry on?