JPM head gasket failure - advice needed

[starman]

Just asking the same question as before in a slightly more upfront way.

 

No1 head gasket has the symptoms of failing (some oil in coolant; traces of fluid around one of the head nuts)

 

I replaced it some time back after buying the boat having been told it had failed, but on strip-down found no damage to the old gasket.

 

A few questions before I strip down again:

 

Why might it have gone again (and could it have failed before even though the gasket appeared undamaged)?

 

Is it worth just re-torquing the head on the present one - it's only had a few hours running since fitting)?

 

Should I use gasket sealer on any new gasket?

 

Anyone know what size the tube nuts are (my sockets don't go that big so I'll have to get a new one)?

 

Any way I can do a proper check on the gasket integrity before stripping down?

 

Er, that's it I think!

 

 

[MoominPapa]

Are you sure it's No. 1 head gasket that's failed? Oil in coolant could have come from any cylinder, and "traces of fluid" is not definative. You've already had No. 1 head off and found no apparent problems, because you were advised that it had failed. Maybe the failure this time is No. 2?

 

MP.

[starman]

Are you sure it's No. 1 head gasket that's failed? Oil in coolant could have come from any cylinder, and "traces of fluid" is not definative. You've already had No. 1 head off and found no apparent problems, because you were advised that it had failed. Maybe the failure this time is No. 2?

 

MP.

 

 

Are you sure it's No. 1 head gasket that's failed? Oil in coolant could have come from any cylinder, and "traces of fluid" is not definative. You've already had No. 1 head off and found no apparent problems, because you were advised that it had failed. Maybe the failure this time is No. 2?

 

MP.

True enough. My other clue is that when the engine was running I could see wafts of steam like vapour coming from under the No1 rocker cover which would tie in with coolant leaking up past the stud there.

But I guess once I have stripped down enough to get one head off then pulling the other one or two off will not be much more work. Groan!

[Timleech]

True enough. My other clue is that when the engine was running I could see wafts of steam like vapour coming from under the No1 rocker cover which would tie in with coolant leaking up past the stud there.

But I guess once I have stripped down enough to get one head off then pulling the other one or two off will not be much more work. Groan!

 

You've done the hard work by the time you are ready to get one head off.

 

It may be worth trying re-torquing the heads, but not if you have to strip everything else off to do it. If it's No1, you can probably get the rocker shaft out without too much other dismantling. You need to do this to get at the tube nuts, unless you get a special crowfoot socket made up. I think they are 3/4" Whit, though may be 3/4" BS. I can check later.

 

Have you considered a cracked head as another possible cause?

 

If you do take the heads off, check that the top of the liner projects above the block face by the recommended amount.

 

Another possibility is that the top face of the block is not flat, but you won't want to even think about sorting that one out!

 

Tim

[starman]

Have you considered a cracked head as another possible cause?

 

 

 

Tim

No I hadn't considered that cheerful prospect! Is that a known issue and is there any way I can check for it?

[martyn 1]

The tubes are 3/4" BSP which if memory is correct, (not stood next to a JP until this evening to check) is roughly a 3/4 Whit spanner (should be 32mm ish across flats on the tube nuts).

 

Martyn

[Timleech]

No I hadn't considered that cheerful prospect! Is that a known issue and is there any way I can check for it?

 

JPs were notorious for cracking heads, when raw water cooled.

 

Tim

[Tony Brooks]

No I hadn't considered that cheerful prospect! Is that a known issue and is there any way I can check for it?

 

If not raw water cooled check the coolant with head gasket leak detector but that only tells you that you have a combustion leak, not where it is.

 

Seal all side/top entries to the water jacket, invert the head and fill the water gallery with paraffin. Leave to stand fro several days and if it leaks out you have a crack.

 

Take it to a vehicle machine shop for pressure testing - they should have contacts.

 

Get hold of some capillary crack detecting fluid and follow the instructions - may be cheaper to see if you can find an engineering set up who has the stuff because it can involve ultraviolet light.

[Roy n paula]

Also maybe check that the head hasn't warped

[Chris-B]

Gasket in first class post

[monkeyhanger]

Just asking the same question as before in a slightly more upfront way.

 

No1 head gasket has the symptoms of failing (some oil in coolant; traces of fluid around one of the head nuts)

 

I replaced it some time back after buying the boat having been told it had failed, but on strip-down found no damage to the old gasket.

 

A few questions before I strip down again:

 

Why might it have gone again (and could it have failed before even though the gasket appeared undamaged)?

 

Is it worth just re-torquing the head on the present one - it's only had a few hours running since fitting)?

 

Should I use gasket sealer on any new gasket?

 

Anyone know what size the tube nuts are (my sockets don't go that big so I'll have to get a new one)?

 

Any way I can do a proper check on the gasket integrity before stripping down?

 

Er, that's it I think!

Many years ago, in a previous existence, I was involved in motor sport as a drag racer. A tip which I got from the States was to give a head gasket a couple of coats of aluminium paint before using it. In the time I raced a high compression V8 I never had head gasket problems. Having said that, I've not tried it on my JP yet, even though I recently replaced a cracked head. All the advice I was given said there was no need to do it. But it's a possibility.....

[starman]

Just got the head off and though there's no obvious 'blown bit' you can see a blackened zone where it looks like combustion gases have been blowing through. Time to start some checking about why this has happened.

[RLWP]

Whereabout on the head is this blackened zone?

 

Richard

[starman]

Whereabout on the head is this blackened zone?

 

Richard

If the front of the engine is 12 o'clock then it's at about 10 o'clock sort of between the front left side stud and the waterway forward of that and blowing out from the combustion area across that zone....if that makes any sense.

 

I've just checked liner/block face clearance as c. 8mm all round which is ok according to the manual so I'm left thinking I ought to have the head checked for flatness and maybe skimmed.

 

Gasket in first class post

Arrived in today's post - first class service; thanks

[frangar]

Not that it helps much but thats where mine has blown.....seems ok now...touch wood!!...since i have had the heads skimmed and tested...I would also use Wellseal when putting it all back together.....depending on if you know the history I would consider changing the studs as well as they are a right pain when they snap (dont ask how I know this!!).....

 

Cheers

 

Gareth

[starman]

Whereabout on the head is this blackened zone?

 

Richard

I've been wondering why you asked the question, Richard - I was expecting a follow-up. Is this a common area for the gasket to blow?

[bizzard]

I'm not particularly conversant with JP engines but engines are engines and cylinder heads are cylinder heads. I checked heads for warpage or depressions with a precision ground steel bar, I've also used a thick mirror to check them which I've checked for flatness with the test bar and found mirrors to be pretty accurately flat.

So. If you have a decent mirror, get a sheet of fine emery paper or the grey production paper. Spread it flat upon the mirror glass placing some weights around the edges to hold it still. Place the head face down on the paper and drag it around gently with both hands at both sides of it, on no account press down on the top, just its own eight. A couple of whirls around and turn over to inspect. The high parts in contact will be beginning to rub clean leaving any low parts untouched, probably the blackened parts. You can of course keep on dragging the head about changing the paper when it wears out to skim the head yourself, just keep going until the face is being rubber uniformly all over,''it will take a long time''. This can also be done with a large amount of valve grinding paste sploshed upon the mirror.

Engineers blue would also be useful for checking but not absolutely necessary.

[steamraiser2]

I suppose the number of JPs I have done in over forty years runs into hundreds and they remain the commonest engines we restore here. The area Starman referenced is where two cylinder JPs usually crack when frosted. JP3s tend to spilt in a line close to the liner seal weep holes. As a rule my experience is that frosted twins will distort the block but three cylinder ones are unlikely to do the same thing, but neither do as a result of overheating.I doubt that the blowing head issue is block related in this case.

 

Corroded heads crack as you may expect but JPs are not serial head crackers, as Perkins 4108s and BMCs are. They do eat poor head gaskets though. IMHO avoid head gaskets that are not gen Lister ones or made by Coopers , who manufactured them for Lister anyway. Still obtainable from Sleeman & Hawken.I have had awful trouble with aftermarket head gaskets in the past and never use them ..ever. Most are the wrong thickness too!

 

What JPs are prone to do is leak water and oil up around the head studs. Use a sealant when putting the studs into the block and around the studs when placing the gasket on. There is no need to glue the head on with sealant! Just enough where its needed and tighten to the correct torque figure. Don't even think of fitting used gaskets. Set the bumping clearances correctly too. It matters.

[RLWP]

I've been wondering why you asked the question, Richard - I was expecting a follow-up. Is this a common area for the gasket to blow?

It was a prompt for more information as I thought that one of the more knowledgeable would give you a useful answer.

 

I don't know enough about this engine, it's the kind of info that is helpful

 

It looks like Steamraiser2 has come up with the goods

 

 

Richard

Edited May 26, 2013 by RLWP