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Discussion Starter #1
Sorry for my first post being one asking for help/advice..... I promise to try and not make a habit of it :D

So, a while ago I got in my car to go to work (sohc vtec), turned the key and got what I recognised as a very familiar sound; that of a broken cam belt flapping around and the subsequent banging of valves on pistons :(

I did a compression test and got very nearly nothing on all four cylinders.

Today I've stripped the head off. A couple of small issues, first of all the belt is intact and seems to be tensioned ok, second, i've looked at the valves and piston crowns and they appear to be undamaged. In fact the tops of the pistons look good. Really good.

I'm sure you can guess my question.... 3:)

What the hell happened? Non starter, no compression, but definately no damage on piston tops and the valves look good, although I've yet to check for a good seal on them.

Is there some vtec trickery I'm not aware of that can hold valves open and make the comression magically disappear? I don't think so, and with the head on the bench and turning it round manually, everything seems to be behaving itself. Yet I was under the impression that these engines smacked their valves every time if the timing fell out for any reason.

Your thoughts please :)
 

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strange one, you said the belt wasn't snapped? have any? and it aint starting, is the engine turning over?
 

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Discussion Starter #3
Correct. Belt intact and correctly tensioned. The engine whizzed over as normal, but it had that sound and feel of a motor with no compression - if you get me. That's why I was so sure I was going to find a bunch of bent valves. As it is, I cant even see any marks on top of the pistons. :confused:
 

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this is a tricky one, ive been through my haynes and struggling to troubleshoot it, did your compression test show no compression on the first test, or was it after you poured oil into the combustion chamber? and all 4 cylinders are affected? as you may know if you test showed no compression after the second test with oil it will be your vavles leaking and not the piston rings, what year is your car? have you tried running a diasnostic test on it?
 

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gd thought paul, but would it be the head gasket? it would still run even with that gone, and you would have a trail of white smoke, plus mayonaisey oil cap, have you? or is your engine shaking like mad while idling?
 

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Discussion Starter #9
Ok chaps, thanks for all the replies and ideas. To answer some questions.....

Prior to this little incident, the car was used daily, drank no oil or water, ran faultlessly and was smooth as silk. Absolutely nothing to suggest any head gasket issues, or anything else for that matter.

The head is off now and on my bench. It's clean as a whistle, as is the rocker cover. I've given the pistons a little wobble around in the pots and there is no visible play at all. The engine never smoked when it ran anyways, and was always strong. Nothing to suggest a lack of compression historically.

As for the head gasket, well it's intact, and I can't see any signs of a gas, water or oil leak. Although I know that's not conclusive.

I didn't bother doing a wet compression test as the readings were so low (summat like 0, 20,20,40) and I'd heard this familiar banging noise upon turning the key. I was convinced I'd find a broekn or stripped belt and a pile of bent valves.
 

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Discussion Starter #12
Paul20v, that's my next job as it happens. Will be doing that this evening. I'll keep you posted ;)

Stug45, unlikely mate, I don't see the connection there. Definately not a cam bearing, I can turn the cam ok by hand. Bottom end bearings would have no effect on compression so far as I know :)
 

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i think i just concentrated on the noise and the fact that the engine appears to look and turns over okay rather than other issues. piston rings?
 

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Discussion Starter #15
It's definately a puzzler, this one. I'm not going to get chance to leak test tonight, it'll have to be tomorrow now...

Thanks for all the input so far, I'm sure we'll get to the bottom of it eventually :)
 

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Discussion Starter #20
Kircaldy - there's no reason for me to think it's warped, but I will have it checked and skimmed if neccessary before it goes back on the car. :)

Paul - nah mate, I've been dragging my arse...... still got the head sat on my bench :redface:
 
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