2LW - bubbles in header tank

[Rayburn]

I have noticed bubbling in the coolant header tank of our 2LW so I have taken off the cylinder head to investigate. The source of the bubbles seems clear - one of the o rings that seal the waterways has degraded and the gasket is discoloured where combustion gases have been pushed to it. Thought I should share a photo as others might find it useful to see what can go wrong.

I understand that failure of these o rings is not an uncommon issue for Gardners  - is that correct?

 

 

[BEngo]

From the photo, it looks more likely that the copper sandwich gasket has allowed combustion gases to reach the waterway seal, which has in turn failed.

 

Not knowing  much about Gardners, I cannot comment on whether this is common event or not.

N

[john.k]

Unfortunately there may be dip in the  block where its leaking ........a clean up ,and check with a straitedge is needed.........refitting a new gasket may be a cure ...or not...I dont think there is any liner protrusion in a LW,so a surface grind will likely fix the block .........piston protrusion may need to be adjusted .......there are also steel shims available to restore block height,........Refer Works Toolbook 48.2 for details.

Edited November 3 by john.k

[Split Pin]

The seals very rarely fail, I have used them more than once without any problem.

The head gasket is a 12 thou stainless steel shim which is fairly non compressible. liners should be level with the top of the block. It may be that the head wasn't tightened down correctly. It may be  possible to just replace the head gasket and seals, but in the long run it will probably fail again unless the head and block are skimmed. 

[Rayburn]

Thanks for the replies and advice. As you say it is the sort of issue that needs to be sorted properly. The head has already been sent off to be skimmed and the block will follow if it fails a check with a straight edge. 

 

The shim showed signs that a jointing compound was used when the engine was last rebuilt but perhaps only/mostly around the push rod passages. I was planning to use a Hylomar blue spray on it to get a more even distribution - or should it be used 'dry'? 

[john.k]

The rubber rings seal in the coolant ,so there is no point of coating the gasket with anything ..........big risk coating the gasket is sealant getting trapped and  distorting the gasket ...........the gasket may already have a  coating.... ...I d follow the gasket suppliers recommendations .

[Rayburn]

Thanks again for the replies and advice.

 

The straight edge revealed a 3 thou dip in the block deck where the leak was. So the block needs to come off to be machined.

 

I have some more questions! Are there any "watch its" regarding taking the block off the engine? What does it weigh - is it a one person lift like the head? Will I need a ring clamp to get the pistons back in the block? Is it ok to control piston protrusion by skimming them the same amount as the block?

[jonesthenuke]

   This may help?

[john.k]

Even if you lift the block manually,you will need a chain fall to replace it ,without damaging pistons or rings.............slotted ring compressors that knock off the pistons are best ,but as the motor is one up one down ,its quite possible to use only one ring compressor to do both pistons.

[Split Pin]

Chris's copy of the clearances is an old version, they  were revised  giving slightly more compression.

Skimming the top of the pistons is not recommended, you would need to recut the valve pockets as well.

Due to the shape of the skirt they generally cannot be held in a standard 3 Jaw lathe chuck. (Extra long jaws are required).

Far better to make a paper/card gasket for the bottom of the block to compensate. As john.K says you will probably be able to remove the block manually but to refit you need to be able to lower it in increments to get each piston back into the bore. one ring compressor clamp will do the job. Keeping the piston square to the bore and getting the rings to enter needs more than one pair of hands !!!  

Best of luck.

 

Edited November 8 by Split Pin

[Rayburn]

I got the block off today. Following the various advice above I used a chain hoist hung from a bar across the pigeon box that is conveniently positioned above our engine. Once the block was raised I dropped it on to a plank supported on the engine room side hatch frames and simply slid it out of the boat through a side hatch. All quite straightforward, it is almost like the boat was designed with such an operation in mind!

 

The block is clearly heavier than the head, it is still probably a (careful) one person lift, but safer with two.

 

There are a few paper shims/gaskets on the bottom of the block - I will measure their combined thickness so I can calculate the thickness of new gasket needed once I know what depth of skim is done. The top of the pistons were only 0.015" below the top of the block so, with the head shim, dimension A in the table Split PIn posted was low at only 0.028" so that will need to be corrected too. 

 

Thanks again for everyone's support and advice.

[john.k]

Be careful with the block ..the side walls are a lot thinner than you might expect