Engine problems.

[ozgti]

I put a new head on my 8v, torqued it all up, set the timing marks. Checked all the hoses/lines and even turned the intermediate shaft over to prime the head.

Went to start it, started fine, ran for about 2-3 seconds, then a crack and knocking sounds. Killed the motor. Checked timing marks again- all good.

Started it again, same thing, 3 seconds then knock knock. Killed it.

What could this be and do I need to take the head off again to see or what?

It was a brand new reco head.

Any help/ideas appreciated.

[h100vw]

Plugs out and have a look with a torch. Cam cover off and rotate the motor with 19mm 12 point socket on the crankshaft. Listening and feeling for something touching.

I am also wondering if the crank pulley has spun, so the the whole thing isn't timed right. It's not enough to just line up the marks. You need to check that number 1 piston is at TDC when the timing marks says it should be. I have had this personally and it stumped me for quite a while.

What's your oil pump like? Make sure the strainer isn't blocked up by dropping the sump.

Gavin

[Preen59]

Check what Gavin said..

But, what sort of knocking? Does it have oil pressure? It could have no oil pressure causing rod noise.. And that's REALLY bad.

When it idles.. Does it idle smooth? Or is it really ill sounding?

[ozgti]

Pulled the head off (again) and found a piece of metal that was beaten into the top of piston 2 crown. Only small, but enough to knock. BUT now, I have a tap tap sound (which is why i swapped heads in the first place!) only happens when on throttle.

Checked the valves and it was fine. All valves open/close the same amount, no noises or anything.

Idle wise- it's sorta smooth, but I'm not sure if it's the cam that is making it idle lumpier or there's something else. Is there an oil passage that could be blocked? When I turned the intermediate shaft, I get a decent spurt of oil from the oil passage between 3/4 cylinder, but nowt at the 1/2 end of the head.

I have oil, oil pressure is about 3.5-4 bar when warm (Audi VDO gauge and sender) but then I get the oil buzzer/light coming on occasionally.

[Preen59]

Doesn't sound good...

Does it knock at idle, or is it ok until you bring the RPM up?

Sounds to me like you have a fooked big end.. Which would also explain oil pressure issues. Is there any particles in the oil? I'd be pulling the pan off and checking your big end bearings if there is.

[ozgti]

I'll take a video of it tomorrow. There's no knocking, just a tapping sound, like a valve on piston sound, but it happened with my old head and with this one.

It's more noticable when on revs, but I think it could be the 4 branch and the leaky exhausts which mask it abit!

[benough]

Can I ask if new cam followers were put into your new head?

[Preen59]

Probably not bottom end, then.

Can I ask if new cam followers were put into your new head?

Good point.. Make sure all your lifters are pumping up (and staying up) mate.

[ozgti]

??? It was a fully reco'd head, cam and valves reseated and stems replaced apparently. When I had TDC, the bucket/tappet.. Whichever it is, could be spun round by hand. Is it supposed to do that when the valve is closed?

[ozgti]

Piece of metal bouncing around in the cylinder!


Excuse the oil.

[Preen59]

??? It was a fully reco'd head, cam and valves reseated and stems replaced apparently. When I had TDC, the bucket/tappet.. Whichever it is, could be spun round by hand. Is it supposed to do that when the valve is closed?

Yes. When there is no oil pressure and no load on the valve, the bucket should move freely.. But not be sloppy in any way.


First port of call now is to file off those burrs on the squish mate. They can cause detonation.

[ozgti]

Which one is the squish? the head or piston side? (Friggin typical.. just bolted the head together.. AGAIN!)

The bucket spun freely, but the friction of the oil was stopping it from spinning round.

[Preen59]

Which one is the squish? the head or piston side? It spun, but the friction of the oil was stopping it from spinning round.

Oh, sorry..

The squish is the flat section of the combustion chamber where the charge is forced out of, or "squished" into the centre.

I was mainly talking about the head. Those small burrs will get covered with carbon. Because of their position they can't dissipate the heat. The carbon can get very hot, to the point where it acts like a glow plug. This will cause pre ignition, or "pinging".

[ozgti]

ahhh..

Ok.. So head off again!!! I'm getting good at this!!!

Looking like time to FI the Kjet!!! Grrrr. Blow it up good an' proper like!

[Preen59]

ahhh..

Ok.. So head off again!!! I'm getting good at this!!!

Looking like time to FI the Kjet!!! Grrrr. Blow it up good an' proper like!

You don't have to do it... But i'd recommend it, mate.