Heat exchanger repair

[MagicalArmchair]

I have the Heat Exchanger back - and it appears I have a lot of time now to adore it and get it ready before I fit it to the boat (seeing as I'll next get to see the boat in October ). The steps I want to go through to prepare it (let me know if these sound correct, or if I have missed anything.)

• Remove remains of the old Gasket between the engine and heat exchanger. It's pretty baked on, so I'll try using some brake cleaner on it and use plastic scrapers to remove it (razor blades etc being too hard for the soft ally).
• Take the raw water chamber apart and inspect the stack. Soak it in white vinegar (I do have some Rydlyme mind you that I was saving to flush the whole raw water circuit with, I could use half a litre of this instead I suppose...).
• Put the raw water chamber back together with the new rubber gaskets supplied by Parts4Engines, greasing those up with a little marine grease. Pressure test the raw water chamber again to 15psi.
• Test the thermostat whilst its out as per the workshop manual.
• Degrease the Heat Exchanger, mask it up, lightly sand the old enamel, wipe down, and then respray the heat exchanger.
• Use air gun to carefully spray through the exhaust passages and fresh water passages to remove any debris from the above.

The workshop manual contains no torque settings for any of the nuts and bolts on the heat exchanger itself, nor the fitting bolts, and "locking" nuts that secure the heat exchanger back to the engine. I presume its just 'snug it up' then and tighten in a diagonal pattern?

 

[PaulRainbow]

• Take the raw water chamber apart and inspect the stack. Soak it in white vinegar (I do have some Rydlyme mind you that I was saving to flush the whole raw water circuit with, I could use half a litre of this instead I suppose...).

Mix some Rydlyme, use it on the tube stack, put it in a container and re-use it to clean the rest of the system later. Not that there's much else to clean.

 

[VicS]

I have the Heat Exchanger back -
>
>
>

The workshop manual contains no torque settings for any of the nuts and bolts on the heat exchanger itself, nor the fitting bolts, and "locking" nuts that secure the heat exchanger back to the engine. I presume its just 'snug it up' then and tighten in a diagonal pattern?

The VP workshop manuals often have a table of general torque settings vs bolt size that can be used where specific / critical values are not given.
I dont see such a table in the manual for your engine but here is the table snipped from another VP manual

 

[Beneteau381]

The VP workshop manuals often have a table of general torque settings vs bolt size that can be used where specific / critical values are not given.
I dont see such a table in the manual for your engine but here is the table snipped from another VP manual

View attachment 106760

I have the Heat Exchanger back - and it appears I have a lot of time now to adore it and get it ready before I fit it to the boat (seeing as I'll next get to see the boat in October ). The steps I want to go through to prepare it (let me know if these sound correct, or if I have missed anything.)

• Remove remains of the old Gasket between the engine and heat exchanger. It's pretty baked on, so I'll try using some brake cleaner on it and use plastic scrapers to remove it (razor blades etc being too hard for the soft ally).
• Take the raw water chamber apart and inspect the stack. Soak it in white vinegar (I do have some Rydlyme mind you that I was saving to flush the whole raw water circuit with, I could use half a litre of this instead I suppose...).
• Put the raw water chamber back together with the new rubber gaskets supplied by Parts4Engines, greasing those up with a little marine grease. Pressure test the raw water chamber again to 15psi.
• Test the thermostat whilst its out as per the workshop manual.
• Degrease the Heat Exchanger, mask it up, lightly sand the old enamel, wipe down, and then respray the heat exchanger.
• Use air gun to carefully spray through the exhaust passages and fresh water passages to remove any debris from the above.

The workshop manual contains no torque settings for any of the nuts and bolts on the heat exchanger itself, nor the fitting bolts, and "locking" nuts that secure the heat exchanger back to the engine. I presume its just 'snug it up' then and tighten in a diagonal pattern?

Since Hitler was a Lance Corporal, non critical bolts have been tightened by nipping them up and experience. Most spanners were designed so that the length was about right so that bolts etc were not overtightened.

 

[PaulRainbow]

Since Hitler was a Lance Corporal, non critical bolts have been tightened by nipping them up and experience. Most spanners were designed so that the length was about right so that bolts etc were not overtightened.

All too often, blindly tightening bolts up in old engines with a torque wrench, especially into ally, will result in thread stripping. Better to tighten those up by hand.

 

[VicS]

Since Hitler was a Lance Corporal, non critical bolts have been tightened by nipping them up and experience. Most spanners were designed so that the length was about right so that bolts etc were not overtightened.

Yes you have trotted this rubbish out before.

Trouble is spanners come in different lengths for the same bolt head size as in photo.

Very easy to overtighten with the standard length, less so with the short pattern ones ... but the standard ones are what people mostly have

 

[VicS]

I have the Heat Exchanger back -
.

The workshop manual contains no torque settings for any of the nuts and bolts on the heat exchanger itself, nor the fitting bolts, and "locking" nuts that secure the heat exchanger back to the engine. I presume its just 'snug it up' then and tighten in a diagonal pattern?

The VP workshop manuals often have a table of general torque settings vs bolt size that can be used where specific / critical values are not given.
I dont see such a table in the manual for your engine but here is the table snipped from another VP manual

Although it dos not say the table I snipped would refer to bolts threaded into steel or iron. If any of yous thread into aluminium alloy then it does not apply. Torques would be lower

 

[Laysula]

Yes you have trotted this rubbish out before.

Trouble is spanners come in different lengths for the same bolt head size as in photo.

Very easy to overtighten with the standard length, less so with the short pattern ones ... but the standard ones are what people mostly have

View attachment 106800

Top spanners for boys and the bottom one is for girls.

 

[jwfrary]

Although it dos not say the table I snipped would refer to bolts threaded into steel or iron. If any of yous thread into aluminium alloy then it does not apply. Torques would be lower

assuming the new gaskets are the green caf type, They take a bit of compressing. So take your time.

Just be gentle, use one finger on the wrench and tighten up evenly. in a diagonal pattern out from the middle of the manifold. Go in 1/3’s so after you assemble just each bolt or stud down to meet the housing finger tight tighten a third of the way the 2/3 and then just below final... max torque.

if youonly have a cheap torque wrench then it’s likely to have a similar value inaccuracy!
R emember they are only accurate on the middle of the scale on the wrench so it’s a quarter inch one for these!
they are only m6’s I think on those....can’t remember but in any case they are easily overtightened.

Trust your gut and don’t be tempted to give it one last nip up!

oh and I would replace the hardware if you can, studs are a bit more tricky but standard bolts and nuts are easily changed for new for pence!

 

[jwfrary]

Top spanners for boys and the bottom one is for girls.

And impact wrenches for cowboys....

 

[MagicalArmchair]

@VicS the casting is aluminium, however, the bolts that hold it in are into the casting of the engine, which I believe is steel. When undoing these, they were not desperately tight, so I will still snug them up by hand based on experience. Thank you @jwfrary , that is useful advice, I will go carefully.

I've taken the face off the raw water chamber, and suffice to say it was pretty well "stuck" on there:

First I resisted the urge to use steel tools to separate the front cover, trying plastic and wood wedges and pry bars, however, this got me nowhere and either flattened my wood wedges, or shattered my plastic tools. I then, very gently and carefully reverted to the most filthy, amateur, tool of all for this application - a wide chisel. After many gentle taps, carefully lined up, the front cover came away, and then, using the chisel in the same way, the bronze gasket came away in one piece too. It has a little scoring on it, but not much.

Is there a better way of doing this? Or do I proceed in the same way for the other end?

 

[Beneteau381]

Yes you have trotted this rubbish out before.

Trouble is spanners come in different lengths for the same bolt head size as in photo.

Very easy to overtighten with the standard length, less so with the short pattern ones ... but the standard ones are what people mostly have

View attachment 106800

Sigh!

 

[Beneteau381]

Although it dos not say the table I snipped would refer to bolts threaded into steel or iron. If any of yous thread into aluminium alloy then it does not apply. Torques would be lower

Given that the whole thread has been about welding aluminium with pics of the steel studs threaded in to aluminium why did you post the misleading values? ????

 

[Beneteau381]

assuming the new gaskets are the green caf type, They take a bit of compressing. So take your time.

Just be gentle, use one finger on the wrench and tighten up evenly. in a diagonal pattern out from the middle of the manifold. Go in 1/3’s so after you assemble just each bolt or stud down to meet the housing finger tight tighten a third of the way the 2/3 and then just below final... max torque.

if youonly have a cheap torque wrench then it’s likely to have a similar value inaccuracy!
R emember they are only accurate on the middle of the scale on the wrench so it’s a quarter inch one for these!
they are only m6’s I think on those....can’t remember but in any case they are easily overtightened.

Trust your gut and don’t be tempted to give it one last nip up!

oh and I would replace the hardware if you can, studs are a bit more tricky but standard bolts and nuts are easily changed for new for pence!

Why change the studs? Also iirc the studs are 8mm

 

[jwfrary]

@VicS the casting is aluminium, however, the bolts that hold it in are into the casting of the engine, which I believe is steel. When undoing these, they were not desperately tight, so I will still snug them up by hand based on experience. Thank you @jwfrary , that is useful advice, I will go carefully.

I've taken the face off the raw water chamber, and suffice to say it was pretty well "stuck" on there:

First I resisted the urge to use steel tools to separate the front cover, trying plastic and wood wedges and pry bars, however, this got me nowhere and either flattened my wood wedges, or shattered my plastic tools. I then, very gently and carefully reverted to the most filthy, amateur, tool of all for this application - a wide chisel. After many gentle taps, carefully lined up, the front cover came away, and then, using the chisel in the same way, the bronze gasket came away in one piece too. It has a little scoring on it, but not much.
Is there a better way of doing this? Or do I proceed in the same way for the other end?

once the bolts are out, then a gentle knock with a rubber mallet should do it, and then perhaps a poke with progressively more aggressive tools as needed. I have some nice plastic cold chisels but they are little specialist for a one off!

as long as where the oring sits is clean and unmarked your good.

 

[PaulRainbow]

@VicS the casting is aluminium, however, the bolts that hold it in are into the casting of the engine, which I believe is steel. When undoing these, they were not desperately tight, so I will still snug them up by hand based on experience. Thank you @jwfrary , that is useful advice, I will go carefully.

The tightening sequence and method posted by jwfrary is sound. Personally, i would not use a torque wrench on these, there is no need and you could do more harm than good.

"snug them up by hand based on experience" is the best way

Leave torque wrenches for this type of job to the armchair experts.

 

[jwfrary]

Why change the studs? Also iirc the studs are 8mm

to clarify these are the studs/bolts securing the manifold to the engine.

if they look fine then don’t change them out, but quite often I find they are corroded abs best changed out for peace of mind

 

[Beneteau381]

to clarify these are the studs/bolts securing the manifold to the engine.

if they look fine then don’t change them out, but quite often I find they are corroded abs best changed out for peace of mind

Agree, personally, ive never seen them in need of replacement. ?

 

[RichardS]

Trust your gut and don’t be tempted to give it one last nip up!

I realise that we are all talking somewhat philosophically/theoretically here but I must say that if "giving it one last nip up" is likely to strip the thread then it is already too tight.

Richard

 

[jwfrary]

Agree, personally, ive never seen them in need of replacement. ?

I find they are either perfect or knackered! Had an engine in not long ago where the customer tried to take the unit off and broke every stud! But it’s rare. - safe than-sorry!