Broken

[T.F.S.]

hi guys

the way im seeing this at the mo is that the engine has a substantial drop in compression on cylinder number 4

this is either a timing issue (the cam jumped) or its an indication that there is a breach in the cylinder....we presume the valves

now if the cam is at blame for the drop in compression this would drop compression by the same amount on each cylinder because all of the cylinders are driven by the same cam, that cam must be at least two teeth out to drop compression but the others are ok in terms of compression

what we have does not fit the story and i seriously suspect that it is indeed the valves that have kissed the piston and thus are leaking compression

also the noise you describe upon cranking last night indicates that its the inlet valves leaking compression (hence the "pop" through the intake)

please advise me if i have missed something in that diagnosis lol

kind regards, brian

[Noel]

conclusion is jumped Belt, due to some stray debris from the drive belt breaking up......

were on the case

But were any of the belts broken this time....?

would the covers allow debris to enter the timing belt area...?

[Mr Singh]

conclusion is jumped Belt, due to some stray debris from the drive belt breaking up......

were on the case

But were any of the belts broken this time....?

would the covers allow debris to enter the timing belt area...?

Yes, the drivebelt from Alt to CS broke, and made a bit of a mess of the bottom cambelt housing cover.. I removed a nice chunk of melted plastic from near the crankshaft on removal of the covers!

The covers shou;dn't let crap in, but if a belt was to wrap around the crankshaft pulley for long enough, the heat would burn through the plastic making all sorts of mess... the mess i'm in now

[Monster-Mat]

hi guys

the way im seeing this at the mo is that the engine has a substantial drop in compression on cylinder number 4

this is either a timing issue (the cam jumped) or its an indication that there is a breach in the cylinder....we presume the valves

now if the cam is at blame for the drop in compression this would drop compression by the same amount on each cylinder because all of the cylinders are driven by the same cam, that cam must be at least two teeth out to drop compression but the others are ok in terms of compression

what we have does not fit the story and i seriously suspect that it is indeed the valves that have kissed the piston and thus are leaking compression

also the noise you describe upon cranking last night indicates that its the inlet valves leaking compression (hence the "pop" through the intake)

please advise me if i have missed something in that diagnosis lol

kind regards, brian

this is eactly what we discussed earlier on the phone,

Am on my 3s, the 2 pulleys line up with the head castings, when the crank is a 5 deg BTDC...so as suspected yours has jumped on both cams!!

[Mr Singh]

Woah...

Off with the cambelt tomorrow and see what i can muster from it!

Any tips once the belts off with regards to lining the cams? i assume they will move freely.... Obviously i will mark the crank pulley when i remove it.

[MacRS200]

Turn the engine as before till #1 is 5 degrees BTDC with the cam shaft timimg marks as near to lining up with the castings as you can get. Mat says that this is correct and I am sure it is.

You should not need to mark the crank pulley as it will be keyed and can only go back in the correct position.

Don't be tempted to turn the cam shafts any more than you need to to re-align the timing marks just to be on the safe side.

In a previous post you said that the compression was "8" on three cylinders, I take it that is Bar. That sounds a bit low should be nearer 10-11 bar which is probably some leakage past valves not closing properly on the compression stroke. The lack of compression on #4 is more of a worry, would suggest to me some valve damage.

[T.F.S.]

yes, this concerns me aslo...

if both cams jump it can affect compression but as i mentioned this should be in a uniform manner

8 bar is so low for a N/A engine..... i am hopeing that this is due to cam timing, if we are wrong it will be at least 6 bent valves and two very bent valves

to get the belt off

rotate engine till all of the lines match up (or in your case Am, as close as you can go)

then try to get the front pulley off, car in gear, person on the brakes with screwdrivers through the brake vents to help (just use the csrewdrivers if there is nobody to help)

it may not be easy to remove......some main crank bolts can be 200lbft followed by another 75 degrees of angle tighten, this means even with a three foot toruqe bar you will be farting like crazy!

after that you take thre front pulley off but it may not want to leave home....you may need a puller (go to Halfords or summat) but give it a few taps first, some do come off easier than others

then you will see the whole belt...give it a good visual inspection looking for a tear, break, split in teeth etc, take pics!

now ease the tensioner off, remove the one next to it too (the "idler)

belt should now slip off

remove the exhaust manifold and inlet manifold

remove rocker cover

now try to get a socket/allen key fitting to fit the head bolts if you have to remove the cams in order to reach the bolts thats no prob, just remove the nuts/bolts on "the caps" but in a uniform manner from the outside in

you must be sure the cam lifts evenly or it can bend!!!!!, easy to get right....easy to get wrong!, it wont want to come up in a uniform manner as only some of the valves are pushing up against the cam (dependant on cam position) but if you do 1 turn on each nut/bolt from the outside in (first the two on cyl1 then cyl4, cyl2, cyl3, repeat, repeat, repeat)

head bolts are the same thing, they will be tight so be careful to use the right tool that sits in there nice and make sure the bar you are using is held "square" as you turn...dont angle the tool in its seat

(1/2 turn on first the two on cyl1 then cyl4, cyl2, cyl3, repeat, repeat, repeat)

when thats done you can lift the head off

ill be adding the head stripdown process to the skyline thread this weekend so check in if you want to read further

http://www.skylineowners.com/forum/showthread.php?t=40350

if i have any of that wrong please mention it as im not a tezza expert lol, never stripped one but have done so on many a simular engine

regards, brian

[Mr Singh]

Turn the engine as before till #1 is 5 degrees BTDC with the cam shaft timimg marks as near to lining up with the castings as you can get. Mat says that this is correct and I am sure it is.

You should not need to mark the crank pulley as it will be keyed and can only go back in the correct position.

Don't be tempted to turn the cam shafts any more than you need to to re-align the timing marks just to be on the safe side.

In a previous post you said that the compression was "8" on three cylinders, I take it that is Bar. That sounds a bit low should be nearer 10-11 bar which is probably some leakage past valves not closing properly on the compression stroke. The lack of compression on #4 is more of a worry, would suggest to me some valve damage.

What are the 'casting' marks i'm looking to line timing marks with?

Here's a pic if someone can point it out

[MacRS200]

From mats description these are the casting marks you want Am.

[Mr Singh]

Thought so :)

Thanks mate.

[Pip]

You lot are some really knowledgable guys out there.

Hope it gets sorted soon.

[Mr Singh]

Right

I can't set the crank to 5 deg BTDC :(

Soon as the mark comes round @ 15 deg the crank is stiff with alot of resistance, when i pull it with some might it overcomes the stiff/lumpyness and it goes past the 0 deg mark.

Can't be good surely

[Monster-Mat]

yep, those are the 2 head idents

am, any chance of a couple of pics looking down onto the camshafts

[Mr Singh]

Sure, brb mate

Here we go

[Monster-Mat]

am, any chance of a couple of pics looking down onto the camshafts

ok i think its gonna have to be a head of jobbie............the resistance will be a valve head!

[Mr Singh]

yeh, its way to much resistance to be anything else.

The cam timings look like only 1 tooth out.

doh

[MacRS200]

One tooth out

From those pics it is miles out. Bearing in mind that the camshafts turn at half engine speed, 5 degrees on the crank is only 2.5 degrees on the camshaft. Those cams look about 60 degrees out to me.

The crank shows on TDC and the cam timing marks should be at the top (12 O'clock)

Don't look like belt jumping, could the VVTi have screwed up?

Also agree with Mat, head off and have a look.

[Monster-Mat]

they may be 1 tooth out in comparison to each other, but as mac has said and i stated on the phone yesterday it looks around 60deg difference top/bottom of engine!

Don't look like belt jumping, could the VVTi have screwed up?

Also agree with Mat, head off and have a look.

nope i think the belt has jumped, Am told me a piece of belt was found wrapped in the bottom crank pulley, this i suspect was dragged round and over the cam drive sprockets, hence the mis alignment of the 2 cam sprockets

cant see it being VVT as this is geared to each cam

Edited April 8, 2006 by Monster-Mat

[MacRS200]

nope i think the belt has jumped, Am told me a piece of belt was found wrapped in the bottom crank pulley, this i suspect was dragged round and over the cam drive sprockets, hence the mis alignment of the 2 cam sprockets

cant see it being VVT as this is geared to each cam

The cams are 60 degress advanced, if the belt had jumped would it not be the other way round with the cams retarded?

Was thinking more of the VVT control rather than a mechanical fault.

[Monster-Mat]

nope i think the belt has jumped, Am told me a piece of belt was found wrapped in the bottom crank pulley, this i suspect was dragged round and over the cam drive sprockets, hence the mis alignment of the 2 cam sprockets

cant see it being VVT as this is geared to each cam

The cams are 60 degress advanced, if the belt had jumped would it not be the other way round with the cams retarded?

Was thinking more of the VVT control rather than a mechanical fault.

the cam control of the vvti system is oil, pressure on ther camshaft drive gear alters the cam angle, it doesnt alter the camshaft sprocket

[Mr Singh]

Yeh you did state that Mat. Ummmmm

Now my techy knowledge is getting thin at this point. I've never removed a head before, i'm not sure i want to be taking things apart with next to no experience of doing so. only thing that worrys me is the VVTI stuff, don't want to mess about with something i don't fully understand for it to go pair shaped...

Looks simple though, but without the experience i'm not sure i want to attempt it on my pride and joy.. call me a wimp or whatever

[Monster-Mat]

Yeh you did state that Mat. Ummmmm

Now my techy knowledge is getting thin at this point. I've never removed a head before, i'm not sure i want to be taking things apart with next to no experience of doing so. only thing that worrys me is the VVTI stuff, don't want to mess about with something i don't fully understand for it to go pair shaped...

Looks simple though, but without the experience i'm not sure i want to attempt it on my pride and joy.. call me a wimp or whatever

you wont damage the vvt components removing the head, the only thing that is intrusive on the vvt system is cam removal......

which at this stage isnt required

[MacRS200]

the cam control of the vvti system is oil, pressure on ther camshaft drive gear alters the cam angle, it doesnt alter the camshaft sprocket

That makes sense, understand now :D

[Mr Singh]

But to remove the head aren't the bolts under the camshafts?

I guess i need to take rocker cover off and have closer look again

[Monster-Mat]

im taking the head of my engine :D

Edited April 8, 2006 by Monster-Mat