Head Gasket or Rings or something else?

[PW@Woodsport]

Just thought there's another quick test before taking the head off, but it's all really pointless as i don't think anything bar a stuck bucket is going to revive compression..... anyway.... take #4 plug out and dribble a little oil down the plughole, repeat the compression test on that cylinder, if it shoots up momentarily to healthy it's a ring/HG issue, if it only goes up slightly or not at all then it's valve burnt/stuck open or holed piston.

That only delays the inevitable which is head off anyway.

Another test involves using a tool i made, not sure if you want to go to the trouble but i'll mention it anyway, i hollowed out an old spark plug, so it was just the threaded part and the "nut", then welded a 6" tube onto that and then welded an air line fitting onto the end of the tube, so it was plug/tube/air fitting.

This allows you to screw it into the cylinder and carry out all sorts of magic tests by applying 50psi to the cylinder and watching/listening where it goes to.

With valves shut, you should only hear a very slight hiss as air blows by the rings, but with the oil cap off if you can hear a lot of air then it's a good indication of rings. If you can hear air in the plenum then it's a burnt out/open inlet valve, if you hear it in the exhaust it's a burnt out/open exhaust valve.... if the coolant starts bubbling it's a HG breach between bore and waterway, it's a great diagnostic tool without taking anything apart and has saved me countless hours over the years.

Not sure if that is any help but there you go

[pk_090]

That Paul sounds like an awesome tool! Not heard of a technique like that before.

[PW@Woodsport]

I invented it after being tired of having to strip engines for fault diagnosis, customers don't want to pay to have an engine taken apart only to be told it's beyond financial repair, so the tool lets me tell them what is wrong without dismantling anything.

It is 100% effective at HG diagnosis when all other methods can be ambiguous at best, downside is it requires a small compressor, but most have one in their home garages these days.

Found a pic of it if anyone fancies making their own, it will save you hundreds in garage diagnosis bills....



I'm off to pitch it on Dragons den, who's in for 20%?

[pk_090]

ill give you a snickers for 7.5%.

[kaiowas]

Cylinder leakage tests have been about for donkeys years.

You'll be claiming to have invented the wheel next Paul.

[ian08]

clever bit of kit

[Lauren]

Thanks, Paul. We'll be doing a 'wet' compression test anyway.

[Icsunonove]

Leak down testers are very useful

I've misplaced (or lent out ) my 18" straight edge (or flat block) that I was going to lend to Lauren to check flatness of the head and block so I made another one.

It's made from 1 1/2" (38mm) square ground square grade 01 tool steel!

I've made it 500mm long which should cater for most four cylinder in line engines and should allow in situ block checking (i.e not too long).



To confirm categorically that it was completely flat I used a milling machine bed and fine wet or dry paper to confirm that the entire face is flat and it is





Just need to made a wooden padded box for it now to ensure it remains undamaged. Should last me a lifetime

Hope Lauren finds that it's just the cylinder head that needs skimming .... Should know later today

[pk_090]

Also looks like a good doorstep salesman basher Tom!

[elbon50]

Also looks like a good doorstep salesman basher Tom!

Nah, just keep a cricket bat handy for the salesmen Aex

If you start hittin' em with Tom's special tool you might bend it

[Lauren]

And so it began:


Before we started:


4 plugs. No.4 seen on the right:


Compression reading on No.4 showing about 55psi:


And on No.2 for comparison. More like 230psi:


Mark squirting oil into the bore. I don't think we put enough oil down because it made no difference to the compression test:


Inlet cam cover off:


Bearding beer (it's alcohol free):


Cams are out as is the exhaust manifold:


Rocking the head, it came off easily:


Cams and things that were no longer fitted:


Indy chilling:


Detonation can be seen on inlet side (left):


More clearly here:


Oh dear.

[Lauren]

Observations:

Looks like it's been running hot. Could indicate too much advance on the timing.

However this is spookily a bit like last time and I can be sure the timing wasn't an issue last time round.

There is a possibility that there is too high a compression. Need to check the head to see if it's been skimmed a lot previously.

Not quite sure, what I'm going to do as of yet.

Options are:

source another short engine
rebuild one of my blocks I have.
Buy a complete engine and put that in.

[elbon50]

Hmmm, bore damage in same orientation as the evidence of detonation Lauren

Ring lands will be damaged similar to before

I'd bet the previous owner had same problems at least once, gave up & sold the car

[kaiowas]

Are you still running that modified ECU? Did you ever work out exactly what it was doing?

[Lauren]

I'd figured that a ring has gone, Peter!

Phil, this engine has been on the stock ECU since we put it back together.

We will never know exactly what that ECU was doing. There is just no way to tell unless we take it to pieces.

[elbon50]

I'd figured that a ring has gone, Peter!

Yes, as I expected, the problem you have now is the same as before

The question is what is causing the detonation in No 4 cyl

That end of the engine runs hot as we know

[PW@Woodsport]

That is pretty much as i guessed, it was too much of a coincidence that the same cylinder would lose compression the same way.

I would have the injectors flow tested before going further.

Kaiowas, the leak down tool was made many years ago, i'd never seen anything like it at that time or heard of anyone testing that way.... fair play if it existed before then.

[Lauren]

What is causing it? Well best guess is heat which is likely a result of either too much advance or too much compression.

Well, we will be getting the injectors cleaned, though I would be surprised if that was the issue, but, it's not worth the risk not doing it.

LOL, Paul about leakdown tests! Think they've been around since the internal combustion engine was invented!

Compression was 230,230,215 and 55psi.

Considering my options. Looking like it may be a rebuild of this engine but we still think doing it ourselves the parts and machining costs are going to come to about £750 or so.

[PW@Woodsport]

I know leakdown tests have been around forever, i'd just never seen a tool like the one i made before, it's not that special, just showing you lot how easily it can be made for home diagnostics.

Lauren given that the timing can't be off on just one cylinder and we can't really blame overheating on that cylinder (#3 would show at least some sign of failure too) , my money is on fuelling for that cylinder.

Double check the injectors are all the same, not impossible someone has mistakenly fitted a larger one during some tuning in Japan, however i would guess #4 injector is not flowing correctly= running lean in open loop and detonating on that cylinder.

The flow test will tell you more.

[Lauren]

Will do, Paul. Cheers for the info.