loud knocking under load, 1098cc

[ratrodmog]

Hello,
So I've just been driving home with the car running totally fine, then suddenly it's developed a very load knocking. The engine ticks over fine and the oil light only comes on when started, then goes off. Plenty of oil in. When pulling under load there is a very significant knock but not so much when sitting at idle. It still pulled fine and luckily I was only a mile from home so took it easy the rest of the way. I'm hoping it's head gasket but could it be bottom end bearings?
I could post a video if needed and I'll probably be pulling the head off tomorrow afternoon as a first port of call.
Cheers

[bmcecosse]

Compression test - even just with the starting handle will give you an idea if there is a head gasket problem. If oil light not on I think bearings will be ok - but as always - an OIL PRESSURE gauge is an invaluable extra.

[ratrodmog]

Thanks for the reply Bmc. It is indeed the head gasket. Went between 3 & 4. Everything came apart surprisingly easily, the only odd thing was that two of the pushrods wouldn't drop out of the head. Not sure if that's normal?

[simmitc]

Drop? Correct procedure is remove rockers and lift rods clear before lifting the head. Make sure to rattle each rod so that it does not stick to the cam follower - if you inadvertantly lift the follower then you may have to remove the side cover to replace the follower. Obviously follow correct sequence for loosening and torquing the nuts.

[bmcecosse]

As above - looks like you have pulled out the followers - hope it isn't a 1275 engine........where there is no access to the followers...... Always shoogle the rods before lifting them out.

[ratrodmog]

Hmm, not sure now. When lifting off the head, the pushrods stayed in the block and a couple stayed hanging from the head. I then removed the rocker gear and pulled out the pushrods. Obviously done something a little wrong! Don't think the cam followers came out, only the pushrods. And it's a 1098 so I can remove the side plates in the block.

[amgrave]

We seem to be hearing about a lot more head gaskets failing lately. Perhaps it's time to be increasing the torque on the head nuts, it might help in case the problem is the gaskets are being made in the same tin huts in far away places that some other parts are made in

[oliver90owner]

Increasing the torque on the holding nuts is not a good idea in general, and certainly not for the average diyer. Far more likely is that head flatness is not being checked.

Recent threads have included one poorer owner having the head gasket replaced twice before the root cause of the gasket failure was even checked, one where the failure was followed by a necessary skim and yet another where the head fixings had either been torqued in the wrong order, insufficiently torqued - or maybe another reason.

What we often do not get told is that of the engine being overheated at some stage prior to the failure, pre ignition having occurred (due to faulty timing, wrong grade plugs, coked combustion chambers, etc), or other modifications which may adversely affect running unless other measures are taken to avoid future problems.

RAB

[philthehill]

Increasing the torque of the cylinder head nuts is not a good idea - dramatically increases the possibility of stripped threads and broken cylinder head studs.
I have recently had discussions with Rob Thomasson reference his comment about increasing the torque setting of head nuts/studs as set out in Tak Tak! Minor Matters Technical Tips July / August 2016
If you want to increase the head nut torque use Marina head studs and the flanged nuts as they can be set to 50lbft.
People tend to forget that it takes both surfaces - that is head and block - to provide a good surface for the head gasket to seat on.
It is not very often that I have read that persons with head gasket problems have checked the top of the block to ensure that there are no crowns or hollows especially with the lands between the cylinders.
Both surfaces must be checked for trueness when replacing the head gasket.
If the top of the block is not true it should be skimmed.
The stud holes should be slightly countersink as over time the rim of the stud hole pulls up and can affect the way the gasket around the stud seats.
Phil[frame][/frame]

[ratrodmog]

Sooo, replaced the head gasket as per the Haynes, everything torqued correctly...struggled to fire up then sounded like it was running on 2 cylinders before it died! Not really sure where to start looking? Everything was removed and replaced correctly as far as I know, didn't touch the dizzy but could it be a timing issue? Help greatly appreciated or if anyone is local to Bournemouth a second set of eyes would be great.
Ben

[panky]

Just a thought, are the leads on in the right order 1342 anti-clockwise.

[ratrodmog]

Panky, yes my thoughts where this too but I double checked and they're correct, I even labelled them before removing.[frame][/frame]

[ratrodmog]

Can you install the head gasket wrong, this is the only thing I can think of. The one I've used is copper but it didn't have any markings to say top/front etc so I just made sure it fit over the studs.

[panky]

Pretty sure it will go on either way but that shouldn't stop it from starting unless it's still leaking between the cylinders. Make sure the plugs and leads are OK and re-check the valve clearances

[simmitc]

A compression test will soon tell you if the gasket has sealed correctly. I always do one before attempting to start an engine when the head has been off.

[594rmm]

I had the same problem after replacing my head gasket, it ran on 2 or 3,it turned out I hadn't set the valve clearance correctly, set them correctly and boom ticked over lovely until it broke down a week later but that's another story but it wasn't the had gasket

[bmcecosse]

Head gasket either way no problem - most likely is as suggested above - valve gaps! Have you reset them? 12 thou inlets and 15 thou exhausts.

[ratrodmog]

Did the valves last night with the help of a legendary gentleman. Because I didn't note the order of the pushrods that obviously threw out the valve gaps. Fired up first time after setting them! Drove to work this morning (only 3 miles or so) and he sounded fine. I'll check the head and re-torque. It's on 40lbft currently, so should I increase this to 44lbft?

[bmcecosse]

Well done - and yes go to 44 ft lbf, and the reset the valve gaps again.

[ratrodmog]

No problem, thanks for everyones advice. cheers