Engine noise & loss of power

[Dominic]

To quote Victor Meldrew "I don't believe it!"
Passed MOT this morning (phew!) However:-
5 miles later while turning into the driveway at work, it started making a loud clattering noise from the engine. On the way home I tried analysing where the noise was coming from, as on start up after work it had disappeared.
Seems to be when using anything more than slight acceleration, i.e when engine is under load. It sounds as if it's probably originating from a valve, from the speed of the noise. Imagine a very loud percussive rattle from a tappet - sounds as if it's the same frequency.
When ticking over it sounds as if it's missing a beat, very lumpy, and prone to stalling. It also feels as if it's lacking power, though that could just be me not daring to feed it any more accelerator while limping home.
On the over-run while cruising, it also quietens down considerably.
I listened to it with bonnet open - no load, so no noise except for a very slight hint of it when revved.
I took off the rocker cover, all looked ok, but no point in checking tappets yet until cold. In any case it was a very sudden occurrence, no gradual change in the gap. The engine has been standing idle for just over 2 months, and has done about 12 miles since.
Does anyone have any ideas as to what might be the cause please?

[bmcecosse]

Sorry to say - it sounds like head gasket problem. But do check the valve gaps, and if possible get a compression check on the cylinders. You can get a rough estimate of this by turning the engine (ignition off) on the starting handle - if 3 feel 'tight' and one is 'loose' then I'm afraid you should plan for taking the head off. I assume it's not just loud 'pinking' ? You could try retarding the ignition a good bit and see if the noise has gone.

[PSL184]

Classic head gasket failure between 3 & 4 at a guess. At least you can change it in half an hour

[PSL184]

ps, you can check the gaps hot - you are looking for even gapping across each one so no matter if hot or cold....

[Dominic]

Hi folks
Just changed the gasket, it was indeed blown between 1 & 2 - about a 1cm gap!
I'll try & post some pics later
Thanks for advice
Dom

[bmcecosse]

Hmm - hope you didn't drive it for any distance on the blow gasket. And do remember to re-tighten it all after a few miles, and then reset the valve gaps. I would tighten the head nuts to 44 ft lbsf and set exhaust valve gaps at 15 thou and inlets at 12 thou - this to ensure the exhaust valves retain a gap even when very hot.

[Dominic]

hope you didn't drive it for any distance on the blow gasket

I drove it home - a distance of about 4 miles on the flat. By very gentle acceleration (even snails were overtaking me!) and then letting it roll, almost on tickover, it made the majority of the journey fairly quiet. There is no erosion of the block or head, it all cleaned up very well. Torqued just as you advised, will be re-torquing after 12 fully hot - fully cold cycles.
Just back from a test drive seemed to go very well indeed. Fingers crossed it stays that way!
PS has anyone had a copper type gasket that comes without the steel(?) layer next to the block? The one I ordered from a major supplier has a black underside. I didn't quite trust it without checking, so fitted a Payen copper gasket from my local engine rebuilders.

[bmcecosse]

Some say the non-steel type are actually better. Can't really say - I've used all manner of gaskets without problems. Only one major failure just after I got the Traveller - had no fan fitted and garage doing MOT left it idling for 40 minutes and bolied it stupid. It failed next day. I hadn't previously taken the head off and can't now remember what kind of gasket it was! Used all varieties on Minis - and no problems with any of them. I wouldn't wait for 12 cycles - just DO it !

[Dominic]

I wouldn't wait for 12 cycles - just DO it !

Isn't one supposed to re-torque after a time when the head has been refitted Roy? I was once told 500 miles approx, then MGM spares advised that it was about a dozen times fully hot - fully cold.

[bmcecosse]

I would do it now - do again after 12 cycles if you wish!

[mike.perry]

I torque the head down cold, warm it up to operating temp., torque it down again, take it for a good run and check again then check at intervals until it wont tighten any more. Of cause its easier on a side valve engine.

[bmcecosse]

Well - at least you don't need to re-set the valve gaps each time !

[Dominic]

I would do it now - do again after 12 cycles if you wish!

Ermmm - am I missing something here? I have already torqued it to 44ft lb - before setting valves, and was planning on re-torquing as mentioned above. Are you saying I should re-tighten again now it has had 1st run to full temp?

[bmcecosse]

That was always my way - with many Mini and Minor engines. Then - reset the valve gaps. Do it again after 12 cycles if you wish - although can't see the point really. What's 'magic' about 12 cycles ??

[Dominic]

I was told that after about 12 cycles, the gasket and head would have done all the expanding and contracting it was going to do, so by tightening down at that point, it would then remain stable.

[bmcecosse]

Well - I think it's done all that after 1 cycle! But - it's your engine !

[Dominic]

Certainly nothing to be lost by the course of action you advise! Guess what I'll be doing after work tomorrow?
Cheers Roy

[bmcecosse]

With racing engines - including an 8 port alloy head - we always did one cycle of 'gentle' driving - then re-torque. Never had any head gasket problems.