sealing metal to metal surfaces in the seawater cooling system???

[Mike k]

I have a slight salt crystal formation at the joint between the end plate and intercooler main body, I have changed the recommended O ring that fits in a groove in the end cap which is then bolted to the intercooler body. It hasn't fully worked so am about to redo it- this time I have got an o ring one size up ( 4mm was 3.5mm) but because its a pain to do I am wondering whether to supplement the 'o' ring also with a circular squirt of 3M 4200 for good measure. Can anyone see a problem with that ?

Many thanks for any repsonses

 

[PlankWalker]

3M 4200 is more of an adhesive, I would have thought Hylomar blue would be a better choice.

 

[PaulRainbow]

Make sure all surfaces are clean and use a little grease.

 

[Mike k]

3M 4200 is more of an adhesive, I would have thought Hylomar blue would be a better choice.

thank you - I have used 4200 for a new through hull bronze transducer and it was great . I thought Hylomar Blue was non setting- i kinda discounted that because I don't want any residues getting into the tube stack that sits behind the end plate. Perhaps I have misunderstood the properties of hylomar

 

[Mike k]

Make sure all surfaces are clean and use a little grease.

paul can you expand please- grease rather than sealant?

 

[PaulRainbow]

paul can you expand please- grease rather than sealant?

Should be no need for sealant, that's what the O rings are for. Make sure the groove and the flat surface to which the O ring contacts are both spotlessly clean, more or less fill the groove with grease, pop the ring in, wipe off the excess grease (leaving a thin film) and bolt back together.

Same for fitting paper gaskets in similar situations. Clean surfaces and smear both sides of the gasket with grease.

 

[Mike k]

thanks Paul- waterproof grease?

 

[PCUK]

I'd use a smear of Sikaflex on the 'O' ring as the grooves are no longer in perfect condition.

 

[reeac]

My understanding of O rings is that they are designed such that they get deformed from a circular to a "partially square" cross section by the closing up of the grooved metal surfaces that abutt them. That's the beauty of them as, unlike a flat gasket, the degree of compression and deformation is engineered in and you just tighten up until the metal to metal gap is closed. If you use an over sized ring you will upset this design factor.

 

[NormanS]

I smear Coppaslip on (nearly) everything, when assembling.

 

[<152587>]

Not all O rings are impervious to grease, they can rapidly deteriorate with mineral oil, grease, diesel, petrol etc. Better to lubricate with silicon grease. Do not use excessive force when tightening the retaining bolts to cause distortion, just enough to stop the weep.

 

[Mike k]

Thanks for all comments ,Ive ordered some silicone grease and now some red hylomar because it says it sets partially though I am a little confused on what 'non setting' blue actually does. I am thinking of smearing a wafer thin amount of 4200 in the groove and silicone grease on the o ring itself then clamping up with the 4 hex cap screws. The hylomar ( blue or red) is there in case I change my mind or get alternative advice. Sound like a plan?

 

[penberth3]

Thanks for all comments ,Ive ordered some silicone grease and now some red hylomar because it says it sets partially though I am a little confused on what 'non setting' blue actually does...

Hylomar does set but stays quite soft and rubbery. I think the red Hylomar is similar to Red Hermetite which sets harder.

 

[PaulRainbow]

Thanks for all comments ,Ive ordered some silicone grease and now some red hylomar because it says it sets partially though I am a little confused on what 'non setting' blue actually does. I am thinking of smearing a wafer thin amount of 4200 in the groove and silicone grease on the o ring itself then clamping up with the 4 hex cap screws. The hylomar ( blue or red) is there in case I change my mind or get alternative advice. Sound like a plan?

It does, but not a great one.

IMO you either ;

a) Do a proper job and clean the groove and flat surfaces properly, assembling with grease.

b) Do a repair/modification if surfaces are damaged or distorted. Could you make a gasket instead of the O ring ? If not, you may as well just fill the groove with silicon, put the o-ring in and smear the surface with silicon.Loosely tighten the bolts, allow the silicon to dry then re-tighten the bolts. Trim excess silicon for a neat job. This is bordering on a bodge, but should seal it all up nicely and not be too difficult to clean off in the event that you need to disassemble in the future. Avoid adhesive type sealants, such as Sikaflex, as these will make disassembly difficult.

Option a) is most preferable.

 

[rogerthebodger]

I have a slight salt crystal formation at the joint between the end plate and intercooler main body, I have changed the recommended O ring that fits in a groove in the end cap which is then bolted to the intercooler body. It hasn't fully worked so am about to redo it- this time I have got an o ring one size up ( 4mm was 3.5mm) but because its a pain to do I am wondering whether to supplement the 'o' ring also with a circular squirt of 3M 4200 for good measure. Can anyone see a problem with that ?

Many thanks for any repsonses

I had a simular issue with the cooling jacket on an old diesel engine and found the cotton of the O=Ring groove was pitted due to corrosion of the cast iron barrel.

I cleaned the bottom of the groove with acetone the filled the pitting with epoxy metal smoothing off when applying and sanding lightly after set.

This solved my problem.

The other way is to have the groove machined to fit the next size O-Ring

 

[vyv_cox]

Thanks for all comments ,Ive ordered some silicone grease and now some red hylomar because it says it sets partially though I am a little confused on what 'non setting' blue actually does. I am thinking of smearing a wafer thin amount of 4200 in the groove and silicone grease on the o ring itself then clamping up with the 4 hex cap screws. The hylomar ( blue or red) is there in case I change my mind or get alternative advice. Sound like a plan?

I think you are going down a tricky route here! Silicone grease was suggested as it does not react with most O-ring materials. However, very few adhesives and sealants are compatible with silicones, which inhibit their setting. I have no idea whether Hylomar would be affected in the same way but I would not risk it. Either just grease or just Hylomar should do the job perfectly well, although unless the metal faces are badly pitted there should be no need for anything other than a smear of grease.

 

[Mike k]

I think you are going down a tricky route here! Silicone grease was suggested as it does not react with most O-ring materials. However, very few adhesives and sealants are compatible with silicones, which inhibit their setting. I have no idea whether Hylomar would be affected in the same way but I would not risk it. Either just grease or just Hylomar should do the job perfectly well, although unless the metal faces are badly pitted there should be no need for anything other than a smear of grease.

Hi Vyv

hope you are well and everything is going ok- if we find some pitting, which I think we will, what material would be best for sorting that and still be compatible with the silicone grease?

 

[PaulRainbow]

Hi Vyv

hope you are well and everything is going ok- if we find some pitting, which I think we will, what material would be best for sorting that and still be compatible with the silicone grease?

You are still missing the point Mike. If it won't work with the grease alone, you don't use the grease. Option (b) post #14 above is the next best bet. RTV silicon will seal it and be removable. This stuff works in place of gaskets and seals in a number of cases, in fact, you could seal your cover with it without the o ring if you wanted. Engine manufacturers have even used it in engines from new.

 

[Mike k]

thanks Paul
much appreciated , its such a pita to do I just want to get the best certainty .

Would you be happy to suggest the best RTV silicon please and I will order it now

regards and thanks
Mike

 

[vyv_cox]

Hi Vyv

hope you are well and everything is going ok- if we find some pitting, which I think we will, what material would be best for sorting that and still be compatible with the silicone grease?

Thanks Mike - things are looking promising on the health front.

As Paul suggests you could go with RTV silicone. This is marketed as Rapid Gasket or Instant Gasket or similar.
Just a pedantic point - silicon is a metal. Silicones are a huge range of products based upon it. These include sealants, greases, elastomers, high temperature rubbers and many others.