Paper gaskets and sealant

[Quandary]

In my research for the rebuild of my raw water pump I have been reading a lot of stuff. An area where there seems to be distinct differences is in advice regarding the bedding of paper gaskets. Some sites like Compass Marines excellent illustrated 'how to' instructions recommend always using non setting non silicone jointing compounds like Honda? Hermetite or that blue stuff, but others, including Volvo Penta's workshop manual do not recommend sealant. Back in my youth when we took motor bikes to bits every few weeks, my recollection is that I used oil or grease to keep the gasket in location and that this was intended to cause the paper to soften and swell, Hermetite was used when there was a leaking problem,(not uncommon on frequently dismantled Velocettes or BSAs when you had big choices in cam lift and compression ratio). When you were always dismantling stuff Hermetite became essential and you learned how to accurately cut paper gaskets.
In the past when replacing the impeller I have rubbed a finger wet with glycerine lubricant over the gasket surfaces and to date this has worked fine. However for bits like access panels on fuel tanks I apply a generous layer of red sealant.
I will probably not change my habits but I am interested in establishing what the up to date experts recommendation is.

 

[RichardS]

If the mating surfaces are in good condition and have no warping or scoring I would just use silicone grease, red rubber grease or white marine grease depending upon the gasket material.

If surfaces are not perfectly smooth and parallel and cannot be honed (also long distant experience with Triumph, Aerial, BSA and Royal Enfield) I would use gasket goo of some kind. I have even resorted to araldite on a vertically split BSA crankcase but that is a mark of desperation!

Richard

 

[rob2]

Agreed! Always a Triumph for me. Paper Gaskets and cylinder head gaskets were always assembled with a smear of grease unless the sealing surface was marred in some way. Everyone will tell you that a vertically split crankcase leaks and I must admit to using a little sealant on that one - it's such a thinseal and so long... Of course a very slight weep of oil from the outer covers (mirror polished) was anadvantage as IU always wiped over the cases after a run at speed, so the nano film of oil prevented the aluminium from tarnishing.

The impeller housing on my engine has the gasket stuck to one side (don't know how) so I simply apply a fresh lick of very ordinary grease before reassembly. It may weep a little, but that's not a problem. Must admit if the original gasket fails I'd be tempted to manufacture a new plate with an o-ring seal! I do carry a range of gaslet materials for improvising on board.

Rob.

 

[lw395]

Sometimes, if you anticipate wanting to remove a cover and re-use the gasket, it pays to stick the gasket to one face with something like golden hermatite, then grease the other side.

 

[cryan]

I would agree with the above. generally if the surfaces are good just grease the gasket but if the surfaces are a bit suspect then use sealant instead. My preference is for Hylomar Blue because that's what I'm familiar with and it has never caused me any issues. Chart paper makes excellent gaskets.

 

[ghostlymoron]

Wouldn't the use of sealant with the gasket on a water pump lift the cover and hence decrease compression ?

 

[mtb]

In my research for the rebuild of my raw water pump I have been reading a lot of stuff. An area where there seems to be distinct differences is in advice regarding the bedding of paper gaskets. Some sites like Compass Marines excellent illustrated 'how to' instructions recommend always using non setting non silicone jointing compounds like Honda? Hermetite or that blue stuff, but others, including Volvo Penta's workshop manual do not recommend sealant. Back in my youth when we took motor bikes to bits every few weeks, my recollection is that I used oil or grease to keep the gasket in location and that this was intended to cause the paper to soften and swell, Hermetite was used when there was a leaking problem,(not uncommon on frequently dismantled Velocettes or BSAs when you had big choices in cam lift and compression ratio). When you were always dismantling stuff Hermetite became essential and you learned how to accurately cut paper gaskets.
In the past when replacing the impeller I have rubbed a finger wet with glycerine lubricant over the gasket surfaces and to date this has worked fine. However for bits like access panels on fuel tanks I apply a generous layer of red sealant.
I will probably not change my habits but I am interested in establishing what the up to date experts recommendation is.

spot on and plus one from me
the thing I find difficult these days is getting hold of decent gasket material, the modern approach " lets buy it from china because it's cheaper " means there are gaps for example I cant find thicker grades of gasket material to connect manifolds and so on.
Not that I'm old but even during the 1970's you could buy much more in the way of engineering supplys and what you buy these days just isn't the same BRITISH QUALITY

 

[lw395]

Wouldn't the use of sealant with the gasket on a water pump lift the cover and hence decrease compression ?

I only use a thin smear, so I don't think it's significant.
I think a typical impeller pump has the blades of the impeller an interference fit with the cover? So the rubber is compressed a bit?
So there is tolerance to cope with fraction of a mm of 'snot'.
I would avoid using any thick sealant, such as a bead of RTV based stuff (e.g 'instant gasket'), because it tends to flow into the body of whatever you're sealing.
I've found strings of RTV in the sumps of various things over the years...

But if you make your own cover with an o ring, or make your own gasket etc, possibly best to check the pump still performs OK.

 

[ghostlymoron]

Speedseal machine a recess in their replacement covers to compensate for the thickness of the gasket (they say), I wouldn't have thought they would bother if it's not that critical.
Does anyone know the dimensions of the recess in the speedseal cover and the size of the o-ring? I'm thinking of getting one made as they do not do one for my pump. (no remarks about copyright please).

I only use a thin smear, so I don't think it's significant.
I think a typical impeller pump has the blades of the impeller an interference fit with the cover? So the rubber is compressed a bit?
So there is tolerance to cope with fraction of a mm of 'snot'.
I would avoid using any thick sealant, such as a bead of RTV based stuff (e.g 'instant gasket'), because it tends to flow into the body of whatever you're sealing.
I've found strings of RTV in the sumps of various things over the years...

But if you make your own cover with an o ring, or make your own gasket etc, possibly best to check the pump still performs OK.

 

[lw395]

Speedseal machine a recess in their replacement covers to compensate for the thickness of the gasket (they say), I wouldn't have thought they would bother if it's not that critical.
Does anyone know the dimensions of the recess in the speedseal cover and the size of the o-ring? I'm thinking of getting one made as they do not do one for my pump. (no remarks about copyright please).

Typical o ring might be 2 or 3 mm.
Typical gasket paper 0.2 or 0.3mm?
smear of golden hermatite 0.1mm?
Tolerance on width of impeller, depth of pump body.... 0.2mm?

It might be a useful starting point to measure the uncompressed impeller, pump body and gasket thickness with at least a decent vernier.
My guess would be there is some compression on the impeller to take up the slack?
Even if there was a clearance, the pump would still work, obviously water might leak past the impeller, but so long as that's a small amount compared to the pump flow, it won't matter.
Gear type pumps work well enough on this basis.

You could have the o ring sitting in a square section groove of slightly higher cross section area than the ring, so long as the pump body is flat enough.
The pressure on the o ring would be whatever it takes to squeeze it into a square section. That should be higher than the pressure the pump is working at, not hard to achieve?

You don't want to compress the impeller significantly more than standard, it would mean more friction, more stress on the blades and a shorter life?
Provided water still flows, I'm happy to err on the side of running the impeller a bit slacker than standard.

 

[NormanS]

For an engine cooling pump, where there is very little "head", I wouldn't want the end plate bearing against the impeller. Different if you're trying to pump up a fair height. The standard gasket is just a bit of brown paper. Think parcel paper, but I've been known to use a Cornflakes packet. It's not rocket science.

 

[Lakesailor]

I got a mixed pack of gasket paper from Beals ( http://www.beal.org.uk/automotive/gasket-paper/cat_100077.html )
If you have never wandered through their website you are in for a treat. When you buy from them they send you a massive catalogue of all the workshop sundries you thought you couldn't buy any more.

 

[Sarnia]

In my research for the rebuild of my raw water pump I have been reading a lot of stuff. An area where there seems to be distinct differences is in advice regarding the bedding of paper gaskets. Some sites like Compass Marines excellent illustrated 'how to' instructions recommend always using non setting non silicone jointing compounds like Honda? Hermetite or that blue stuff, but others, including Volvo Penta's workshop manual do not recommend sealant. Back in my youth when we took motor bikes to bits every few weeks, my recollection is that I used oil or grease to keep the gasket in location and that this was intended to cause the paper to soften and swell, Hermetite was used when there was a leaking problem,(not uncommon on frequently dismantled Velocettes or BSAs when you had big choices in cam lift and compression ratio). When you were always dismantling stuff Hermetite became essential and you learned how to accurately cut paper gaskets.
In the past when replacing the impeller I have rubbed a finger wet with glycerine lubricant over the gasket surfaces and to date this has worked fine. However for bits like access panels on fuel tanks I apply a generous layer of red sealant.
I will probably not change my habits but I am interested in establishing what the up to date experts recommendation is.

Your instincts are correct, like you I have have cut out many brown paper gaskets in my time, and always used hermetite, (an exception was to use vasiline out of my mothers first aid kit) still do on my boat because it works despite the passage of time.