JP Headgaskets

[flatplane8]

Hi,

 

I suspect I know the answer, but worth checking. Our JP3 gently leaks oily water out between the heads and the block. Looking at the join I can see evidence of gasket compound in there as well as the gaskets, and knowing that the previous owner was 'thrifty' they may have been re-used.

 

Last week while testing the new oil pressure gauge, I took the covers off the heads to watch the valves going up and down (as you do...). I noted that on two of the cylinders there appeared to be air bubbles coming up into the oil around the pushrod tubes. On the middle one there seemed to be drops of water coming up too. These bubbles appeared every now and then, rather than constantly. So I think the gaskets are leaking on the compression stroke.

 

Does this sound like a reasonable conclusion, or is this some charming JP feature?

 

I've got a set of three gaskets handy so could replace them, just trying to avoid the dangers of taking a working engine apart.

[frangar]

That sounds like the head gaskets to me!

 

You will need a selection of Whit sockets and spanners...let me know if you want the sizes

 

It may be beneficial to have the heads skimmed just to make sure they are true and it might be a good idea to replace the studs if they havent been changed for a while cos they can snap...ask Baldock as they keep the spares. I would also use "Wellseal" as a jointing compound when refitting...also check that the cylinder liners are slightly proud to make a good seal.

 

I have done this job a few times now (!!) so feel free to ask anything else...!!

 

Cheers

 

Gareth

 

PS the heads a rather heavy to handle as well!!

[Chris-B]

Yes we do have gaskets in stock

Chris

[mykaskin]

If you've not done it before, you'll need a lot more than just spanners. In the end a couple of rachet straps did the trick!

 

Mike

[flatplane8]

Thanks guys, will look up 'wellseal'.

 

What were the ratchet straps for?

[Timleech]

Thanks guys, will look up 'wellseal'.

 

http://www.cromwell.co.uk/HRM7202291M

 

 

What were the ratchet straps for?

 

The mind boggles.

Perhaps it's safer not to know

 

 

Tim

[frangar]

I have no idea what the straps were for....!!

 

If the heads are tight once all the nuts are undone then a quick spin over on the electric start usually loosens the heads enough to take them off!...could be an issue if its hand start only!

 

Also see if you have shims with the gaskets to get the bump clearnace right.....if you do then you probably need to reuse them depending on the thickness of the new gaskets that you have.

 

Oh and once you have done it once it does get eaiser!!!

 

HTH

 

Gareth

[by'eck]

I hope Mike won't mind me borrowing his neat video on loosening JP heads

 

[flatplane8]

I have no idea what the straps were for....!!

 

If the heads are tight once all the nuts are undone then a quick spin over on the electric start usually loosens the heads enough to take them off!...could be an issue if its hand start only!

 

Also see if you have shims with the gaskets to get the bump clearnace right.....if you do then you probably need to reuse them depending on the thickness of the new gaskets that you have.

 

Oh and once you have done it once it does get eaiser!!!

 

HTH

 

Gareth

 

Thanks Gareth, I'll keep an eye out for any shims. Is it worth measuring the clearance between piston and heads as per the manual? I'm planning to grind the valves in and give the heads a good clean and paint while they're off. Of course, it all depends what I find......

 

Ours is hand start only so will have to figure out another way of getting the heads off if they're tight.

 

I hope Mike won't mind me borrowing his neat video on loosening JP heads

 

 

I've seen that one, hopefully it won't come to that but useful to know as a last resort;)

[frangar]

I'll keep an eye out for any shims. Is it worth measuring the clearance between piston and heads as per the manual?

 

 

I did the last time I put the heads back with new gaskets....it is a bit of a pain with a marine JP cos of the raised hand start etc but it did mean I knew they were ok.....I used some plumbing solder from screwfix to measure the clearance.

 

Please feel free to ask if you have further questions!

 

Cheers

 

Gareth

[Thewatchmaker]

Yes we do have gaskets in stock

Chris

 

Sent you a Pm ( while ago)

Hope all's going well?

[flatplane8]

http://www.cromwell.co.uk/HRM7202291M

 

I've been using heldite on other parts of the engine and it seems pretty good. Looks like similar thing to wellseal, can anyone comment?

[MoominPapa]

I've been using heldite on other parts of the engine and it seems pretty good. Looks like similar thing to wellseal, can anyone comment?

I've used it lots for diesel pipework joints and been very happy. It was recommended to me by someone on CWDF.

 

MP.

[frangar]

I've been using heldite on other parts of the engine and it seems pretty good. Looks like similar thing to wellseal, can anyone comment?

 

 

Not used it but it does sound similar.....Wellseal always stays a bit tacky...is Heldite the same?

 

Gareth

[flatplane8]

Not used it but it does sound similar.....Wellseal always stays a bit tacky...is Heldite the same?

 

Gareth

 

I've found it very good on diesel joints too, it does seem to dry out a bit. I've found since posting that it's suitable for copper head gaskets. I used it on the crankcase doors and gearbox cover on the engine and it helped fix some minor leaks there. I'll try it and see how it goes.

[DHutch]

I still want to know what the rat-straps are for....

[mykaskin]

I still want to know what the rat-straps are for....

 

The engine turn over didn't loosen them enough - the soot and carbon from thousands of hours of heavy running had blown into the tubes the valve linkage goes through, and I needed them as lifting tools. A fair amount of weight as well, even needing a tube to tighten them enough!!

 

Don't use any sealant on the gaskets - pain to get them off again apparently, and not really worth it if reassembled and tightened properly. Do make sure the mating surface is clean anyway.

 

Cheers,

 

Mike

[frangar]

 

Don't use any sealant on the gaskets - pain to get them off again apparently, and not really worth it if reassembled and tightened properly. Do make sure the mating surface is clean anyway.

 

Cheers,

 

Mike

 

Have to disagree with this....doesnt make it any harder to get them off (esp if using a non setting compound like Wellseal) and helps sort out any imperfections from the last 50 years! Also helps seal the water passages which can suffer erosion esp if the engine has been used on salt water.

 

Cheers

 

Gareth

[steamraiser2]

Have to disagree with this....doesnt make it any harder to get them off (esp if using a non setting compound like Wellseal) and helps sort out any imperfections from the last 50 years! Also helps seal the water passages which can suffer erosion esp if the engine has been used on salt water.

 

Cheers

 

Gareth

 

I'm with Gareth. Probably done five hundred of them over the years and only ever had trouble(usually salt water used ones) when attempting to go sealant free. Goop is God!

[flatplane8]

I'm with Gareth. Probably done five hundred of them over the years and only ever had trouble(usually salt water used ones) when attempting to go sealant free. Goop is God!

 

I'll try the heldite then. Ours was run from Hull so would've had some salt water through it.

[BEngo]

I'll try the heldite then. Ours was run from Hull so would've had some salt water through it.

 

Heldite is good stuff and will seal them well but will set like Araldite after a couple of years- so if you have to get the gaskets off in future be prepared for a load of work just removing the gaskets and cleaning up.

 

 

Wellseal on the other hand does not set and can be easily removed with thinners.

N

[flatplane8]

Thanks for the info about Wellseal, maybe that would be best. I've got the three heads off today. I removed all the exhaust studs so that the manifold was undisturbed as I've read it can be difficult to reseal.

 

 

 

They came off easily enough, just a few taps with a lump hammer and wooden block to loosen them off. I'm going to take the heads to a local engine shop for a clean and check. Is there anything I should look for while its apart? The bores all look ok, with no ridge at the top of the cylinders, there is no scoring on the bores. The middle cylinder seems to have some parts that look more matt than others, perhaps this is the Listard lining wearing off?

 

There is evidence of gasket goo being used around the water passages, but it didn't do much good as this is why I've taken it apart. Hopefully a cleanup and re-assembly with wellseal will help.

 

The changeover valves came out quite easily and I noted that the nuts around the pushrod tubes were much easier to loosen than the others.

[flatplane8]

Another picture of dismantled engines

 

 

I took this just before loading them into the car this evening for dropping off at the engine reconditioners tomorrow. Left to right its #3, #2 and #1. The middle one (#2) was the one leaking water, and by the marks round the combustion chamber it looks like there has been some leakage. I can't see any evidence of cracks between the valve seats, but I'll leave the assessment to the experts.

[frangar]

See...it wasnt that bad was it!!...hope you get good news back from the engineers...please do keep us posted.

 

Cheers

 

Gareth

[flatplane8]

Minor update. I heard today that the middle head in the picture above has the most corrosion, so they are pressure testing all three to check for cracks. Other than that, I'll need a couple of exhaust valves and some guides. The current ones aren't beyond redemption, but it's recommended.

 

Worst case scenario and the middle head is damaged, what/where/how much for a decent second hand head?