head gasket dilemma

[Vambo]

I have a 20 year old Yanmar 3gm30 f and there appears to be oil in the header tank and the level has dropped considerably. I suspect that the head gasket has gone. I intend to do the job myself as I have been quoted between £650 and £850 for the job. New genuine gasket is £80 and a pattern one is half that, is there any real difference? are there any pitfalls on this job and has anyone got any tips.Whilst the head is off I intend to regrind the valves crack test it and skim if necessary.

 

[Jim@sea]

If you have had a head gasket fail I would say it is essential to take the head to an engineering firm and have the head checked and skimmed if necessary. Get a genuine gasket purely because you are replacing something which has failed.
(years ago I was told by a mechanic to smear grease on both sides of head gasket (if it is copper to both sides) and to re-torque the head down after a few hours running, and of course checking the tappet adjustment)

 

[tawhiri]

There is a reason the head gaskit failed. Normally due to localised over heating at some point. Check the cooling system as well!
Generally the head gaskit will come with adhesive already prepared on the surface if it is an asbestos type gaskit, so both surfaces should be clean.
If you are doing the valves, then get a gaskit kit it will come with several other bits and bobs. There is very little difference between genuine and after market gaskits. However with the genuine parts you will have peace of mind.
I know with petrol engines you can skim off quite a lot, but with diesel I don't know how this would affect the piston clearance. If the head is measured to be flat I would just give it a light sanding.

 

[VicS]

A couple of comments.

Greasing gaskets was something we did in pre-history. Modern gaskets are usually coated and require neither grease nor any form of gasket sealer.

If the head is skimmed you may have to fit a special thicker gasket.

 

[lexi]

Greasing as said, was for copper gaskets. An aftermarket gasket is fine if it is made by one of the top boys like Payen of Germany. Normally composite with steel inserts and resins that bed down on heat.
Get head tested and cleaned throughout waterways. Probably a light skim of 5thou will be a minimum requirement even if head is flat.

 

[Lakesailor]

I have recent experience of a head gasket failure (on a Petter). http://www.ybw.com/forums/showthrea...d-Gasket-Problem&highlight=petter+head+gasket
The problem was not the original gasket (the engine was stripped for a re-bore) but the new gasket. The head was checked and very lightly skimmed. It's not too likely to be distorted as they are relatively massive for the application. The Petter gasket was useless. The agent assured the owner (not me) that it was correct but a call to another engineer found that he had an engine in the workshop with the same problem as ours, which he hadn't diagnosed, using a genuine gasket.
I'm not suggesting that this would be the case with your engine, but the indication is that older engines may have their spares made in batches by people other than the original maker. (I suspect, to a price, and not in Europe)
Don't put anything on the gasket. It's coated and should work best if fitted as is.

 

[30boat]

I reinforce the point about checking and skimming if necessary.

 

[Jim@sea]

I reinforce the point about checking and skimming if necessary.

I bought a horsebox from one of my stable tenants, she had previously had the engine overheat and a garage had charged her a fortune to repair it, which basically involved replacing the head gasket. When she took the vehicle out for a long run it overheated again. The garage would do nothing and said that they had checked the head. (they probably had, to their standard) She could not afford to repair it again so I bought it.
I sent the head to an engineering works who said that "In engineering terms it was shaped like a banana" It was skimmed and refitted, the fault solved.
For peace of mind its worth having it checked professionally. If they are not too dear I would even consider replacing the valve springs, but then again where boats are concerned I often spend money unnecessarily.

 

[CAPTAIN FANTASTIC]

when you take the gasket out see where it failed and try to find out why; likely to have a problem with the cylinder head being warped, however, you need to skim the head regardless before you re assemble. I suggest that you get a good gasket and re torque the head a couple of times after assembly and after the engine has been in operation for a few hours. The torque sequence it is absolutely important. Use copper grease for the studs; take pictures of the head when dismantling.

 

[lexi]

There is no harm in re-torqueing head......I do it as habit on old Land Rovers. However that is another throwback to copper head gasket days.
The advantage of composite, is that head does not actually need torqueing again............if your head is true and flat.

 

[30boat]

One thing to bear in mind is that ,unless otherwise stated,torque figures are given for dry assembly.No grease should be used on the studs.

 

[Sailfree]

One thing to bear in mind is that ,unless otherwise stated,torque figures are given for dry assembly.No grease should be used on the studs.

Is this true in so much as studs should be clean and I thought lightly lubricated so that torque is mostly translated to bolt tension and not to overcome friction.

 

[Latestarter1]

I have a 20 year old Yanmar 3gm30 f and there appears to be oil in the header tank and the level has dropped considerably. I suspect that the head gasket has gone. I intend to do the job myself as I have been quoted between £650 and £850 for the job. New genuine gasket is £80 and a pattern one is half that, is there any real difference? are there any pitfalls on this job and has anyone got any tips.Whilst the head is off I intend to regrind the valves crack test it and skim if necessary.

Be careful of some of the pre historic advice you are getting..........Greasing gaskets, re-torquing head studs etc. I did technical evaluation on this engine when it first came out, for sure they have a few quirks.

For example head gasket requires fitting with Three Bond, head studs have three step torque torque procedure unlike later Yanmar motors which are TPA. In addition there is a very limited machining tolerance for cylinder head and crack testing is vital.

I may still have copy of Yanmar shop manual which has all the data you require, if I can find it will PM you.

 

[Sailfree]

For example head gasket requires fitting with Three Bond, head studs have three step torque torque procedure unlike later Yanmar motors which are TPA.

For those like me that find this subject interesting can you expand on that please?

 

[Latestarter1]

For those like me that find this subject interesting can you expand on that please?

Expand on which subject??

 

[garvellachs]

Be careful of some of the pre historic advice you are getting..........Greasing gaskets, re-torquing head studs etc. I did technical evaluation on this engine when it first came out, for sure they have a few quirks.

For example head gasket requires fitting with Three Bond, head studs have three step torque torque procedure unlike later Yanmar motors which are TPA. In addition there is a very limited machining tolerance for cylinder head and crack testing is vital.QUOTE]

In fact the three bond may not be necessary any more either - I changed the head gasket on my 3HM last year using a Yanmar new one and the consensus on the web seemed to be to do it dry. But I had the head skimmed and cleaned and checked by a specialist - they would have serviced the valves too had it been necessary - for not much money.

 

[Sailfree]

Expand on which subject??

I assumed three bond was a head gasget cement and its name was derived from needing a three step torque procedure but I don't know and assumptions can be wrong nor do I understand why the three steps are necessary unless its a very flimsy head/compressible gasget. Also don't know what TPA stands for. Be pleased to learn more.

Done extensive work rebuilding car engines in the past including Hillman Imp alloy engines bit no experience of Yanmar other than having one on current boat!

 

[Latestarter1]

Be careful of some of the pre historic advice you are getting..........Greasing gaskets, re-torquing head studs etc. I did technical evaluation on this engine when it first came out, for sure they have a few quirks.

For example head gasket requires fitting with Three Bond, head studs have three step torque torque procedure unlike later Yanmar motors which are TPA. In addition there is a very limited machining tolerance for cylinder head and crack testing is vital.QUOTE]

In fact the three bond may not be necessary any more either - I changed the head gasket on my 3HM last year using a Yanmar new one and the consensus on the web seemed to be to do it dry. But I had the head skimmed and cleaned and checked by a specialist - they would have serviced the valves too had it been necessary - for not much money.

Not sure of date of my manual, suggest a simple call to Barrus technical for correct up to date procedure, one would have to order Three Bond from them anyway. Certainly not sensible to get answers by Googling, look at the quality of the feedback received so far. Always safer to RTFM.

Assume 3HM was typo, did you use correct three step torque procedure when you nailed down the head? (Just found shop manual which is for GM AND HM Series)

Did not say that head could not be skimmed, just very little tolerance to play with when compared with Kubota which we were benchmarking against.

Once had a complaint re: bolt heads on TPA engine pinging off like champagne corks, turned out that numpty had re-torqued cylinder head cap screws after running the engine not realising that the torque plus angle procedure had already taken caps crews to yield.

 

[Latestarter1]

I assumed three bond was a head gasget cement and its name was derived from needing a three step torque procedure but I don't know and assumptions can be wrong nor do I understand why the three steps are necessary unless its a very flimsy head/compressible gasget. Also don't know what TPA stands for. Be pleased to learn more.

Done extensive work rebuilding car engines in the past including Hillman Imp alloy engines bit no experience of Yanmar other than having one on current boat!

Apologies

Three Bond is a range of sealing materials used originally by Japanese manufacturers however now adopted by most European and some U.S manufacturers.

Japanese engine manufacturing is to very precise standards which is why their engines work and ours (Hillman Imp) did not.

 

[pagoda]

I have a 20 year old Yanmar 3gm30 f and there appears to be oil in the header tank and the level has dropped considerably. I suspect that the head gasket has gone. I intend to do the job myself as I have been quoted between £650 and £850 for the job. New genuine gasket is £80 and a pattern one is half that, is there any real difference? are there any pitfalls on this job and has anyone got any tips.Whilst the head is off I intend to regrind the valves crack test it and skim if necessary.

I think part of the key to this is VERY careful observation when lifting off the head. I have a (more) aged 3gm30, which was puffing more steam than I liked last year. Never set of the overheat alarm, but there was always a bit of steam once running steadily.
I took off the head and checked things out. Some of the passages between block and head were filled with calcareous deposits. I carefully removed most by simple mechanical means. The head was fairly clean, but I removed any deposits from it and the pistons with a thin hard wood scraper. Not much came off.
Once re-assembled (pattern gasket! with a tiny thin smear of blue Hylomar (showing my age!) it was torqued down as per Yanmar figures - then after running. They do NOT run very hot. Particularly the raw water cooled variants.
I took apart the exhaust manifold cooler cover and cleaned out the interior with a rotary wire brush. Lots of gunge removed.
Once the engine warmed up I ran it on a closed loop with 50% white vinegar and 50% patio cleaner to remove calcareous salt deposits. It frothed like blazes for a while then slowed down. Since then, touch wood , it has been fine.
Don't be afraid of pattern gaskets- if from a reasonably well known source. If you have purely gasket damage- consider swapping it alone. If unsure about that - take the head to an engineering shop (non - boaty will do!) for straightness checking. As pointed out - you can't skim much off a diesel head.
If you do most of the work yourself -it should not break the bank!

Graeme


PS remove pencil anodes before using any acid concoctions to clean out the engine.- and put them back!