960 coil on plugs

[Laird Scooby]

The boroscope is an amazingly useful bit of kit for problems like this. Last summer a friends 820 Vitesse (2.0 turbo, 200bhp) committed hara kiri on his way from Blackpool to Milford Haven (his parents live there) just north of Leyland of all places!

Long story short he got it recovered back here (nearest place to home he could park it while determining its ultimate fate) and we whipped the plugs out after discovering the timing belt had jumped.
One piston had melted, another had broken around the land as described - this shot a piece of piston out the exhaust port which damaged the turbo and at some point before ejecting said portion of piston had caused the cam belt to jump and had bent both exhaust valves in that cylinder.

The other two cylinders showed signs of excessive carbon but no other damage which suggests he had two duff injectors running hideously lean and dropping the average CO content in the exhaust. The ECU obviously compensated by adding more fuel (hence the two pots showing excess carbon) but this presumably wasn't enough to save the two that melted and broke.

With this in mind, it may well be worth checking the other cylinders as well as your suspect one to see if you can get any clues as to what's happening.

[liamcafs]

That certainly is a cooincidence, Milford is a small place I probably know your friends family.

I tried the borescope, unfortunatley the results were inconclusive. I got a fair look at the central portion of the piston but couldn't get the out to the edges. I'm going to try again tomorrow and I've ordered a leakdown tester also which should provide some more clarity.

I ran the engine after the compression test and there was a pronounced tappety type noise too which I hadn't noticed before.

[Laird Scooby]

You probably do!

I've had a thought, it's a bit of a long shot but it just might work. Add about a litre of synthetic ATF to the engine oil and take it for a decent run. The idea behind this is you may have sticking hydraulic tappets on the dodgy pot, the ATF cleans them and revives the oil seals - helps clean the rest of the engine internally as well.

If it doesn't fix it, it won't do any harm and will clean the rest of the engine, revive the oil seals and generally improve things.

I could list umpteen examples of where this has worked, i still use it as preventive maintenance (i usually add about 0.5L in between oil/filter changes) even on engines without hydraulic lifters.
It could be something this simple, especially if oil/filter changes have been allowed to get a bit overdue.

Worth a try before you start pulling the engine apart!

[GreenBrick]

if the "bad" cylinder looks cleaner than a "good" one then it is burning coolant, as this does clean the engine as it is burned off.
A tappety noise can also be a blown HG, sorry to say.

[Laird Scooby]

Originally Posted by GreenBrick

if the "bad" cylinder looks cleaner than a "good" one then it is burning coolant, as this does clean the engine as it is burned off.
A tappety noise can also be a blown HG, sorry to say.

That's true enough but it could also be running excessively lean. Burning coolant will destroy the Lambda sensors in the exhaust bringing the engine management light on.

The tappety noise of a blown HG is usually more of a chuffing noise but i have to admit, sometimes they can sound similar.

Given the compression is down it could still be either but i'd try the simple things first like sticking tappets and the ATF trick.

[liamcafs]

Ok so heres the plan

Plugs out and try and get some better borescope images to compare the condition.
ATF in the fuel and try and get/keep it running as long as I can.
Try the leakdown check early next week to further drill down the fault

Thanks for all the suggestions guys.

If its a HG I 'm not that bothered. The engine is coming out anyway as its going in my 240. Its a bottom end rebuild I was trying to avoid!!!!

[Laird Scooby]

Originally Posted by liamcafs

ATF in the fuel and try and get/keep it running as long as I can.

Don't put ATF in the fuel!!! Add it to the engine oil!!!

[liamcafs]

Lol typo, I didn't mean fuel.

Originally Posted by Laird Scooby

Don't put ATF in the fuel!!! Add it to the engine oil!!!

[liamcafs]

So the atf has stopped the clacky noise!!

Will try the borescope and comp test again tomorrow

[classicswede]

Any change to the running since adding the ATF?