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Old 11-10-2018, 16:40   #1
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Use Gasket sealant on new gaskets?

I had a marina replace my sealing ring on the timing gear housing and when th eye put the sea water pump back on they did not replace the gasket. I had supplied 2. So it now leaks there. When replacing a gasket do you need to put a gasket sealant on both sides of the gasket then remountthe pump. Or can you just replace the gasket then put the pump back on?
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Old 11-10-2018, 17:11   #2
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Re: Use Gasket sealant on new gaskets?

If you don't use some sort of coating, it's often hard to remove again. I always use something on a gasket unless it's a modern gasket with a silicone bead or cork etc. I'm into anaerobic sealants, really good stuff.
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Old 11-10-2018, 17:18   #3
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Use Gasket sealant on new gaskets?

Me, if itís just a paper gasket like it sounds like, I just smear grease on it, that has always worked and made removal easier.
If a gasket is real tough to get to stay lined up, usually you glue just one side of it to the part to maintain perfect alignment, you donít do both sides as then you have a real rob to get one off.
If you do much mechanical work, youíll have a bench grinder with a wire wheel, the wire wheel is great for eating off old glued on gaskets.
Itís my opinion that almost always gasket sealers cause more problems than anything else.
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Old 11-10-2018, 19:15   #4
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Re: Use Gasket sealant on new gaskets?

Whether you need sealant, depends on what kind of gasket it is. And whether you can re-use a gasket, also depends on what the gasket is. If the gasket is thin and it distorts or takes a set to make a good seal (which is pretty normal) the practice is to throw away the used gasket, which has compressed to fit and may not be able to re-seal properly. Or may have been damaged in the removal, so it is simpler to just have the replacement on hand and use it.

If you were going to use sealant on both sides? That would be a waste, you could use a product like Form-A-Gasket and have no need for any other gasket at all!

The only good rule of thumb is "do what the factory says" in the belief that the folks who built it, had a reason for a particular gasket type and installation, and you'll be safe repeating it.

Whatever the guys did, since it now leaks, they did it wrong.
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Old 11-10-2018, 21:07   #5
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Re: Use Gasket sealant on new gaskets?

Everyone has their favourite methods but for some time now, for general paper type gaskets, I like to coat all four surfaces with a thin film of Hylomar non setting joint compound. Let it tack off completely and then assemble. Haven't had one leak in ages!

Always comes apart and usually easy to remove.

If difficult to get in place, leave two surfaces slightly tacky and it hold in place until you get to other piece on.

I cut the gaskets from manila folders but some swear by using old charts.
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Old 11-10-2018, 21:33   #6
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Re: Use Gasket sealant on new gaskets?

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Everyone has their favourite methods
Like he says^^^

In general, if the mating surfaces are in good shape, smooth, shiny, without nicks, scratches, and gouges, the gasket by itself is good enough.

I am not a fan of slathering sealant on every surface without reason. It has its own issues. And I don't have leaks. I prefer to keep it simple and follow the equipment manufacturer's recommendations unless there is a good, identifiable, reason for doing otherwise.
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Old 11-10-2018, 22:24   #7
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Re: Use Gasket sealant on new gaskets?

I don't have blind faith in manufacturers as have seen so many OEM design FAILS. I like Loctite 518 flange sealant, still easy to get apart & much better results than putting on dry. It's only drawback is it's pricey. The other ( cheaper)option is use silicone. I like to put a thin smear on both sides of gasket & let it go off overnite before assembly if you have time. You can even coat both mating faces like this & don't bother with a gasket IF the gap between the faces is not critical.
So you have conflicting views here, take your pick
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Old 12-10-2018, 09:38   #8
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Re: Use Gasket sealant on new gaskets?

If the surfaces are flat and true, no sealant.
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Old 12-10-2018, 10:01   #9
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Re: Use Gasket sealant on new gaskets?

Timely thread for me. Had a chronically leaking thermostat housing on my generator. Didn't have a spare gasket so gooped up the old one. The leak persisted. Ordered up new (paper) gaskets direct from the mfg (Westerbeke), cleaned up all surfaces, reinstalled, but still no luck. Went back to the service manual (a little late, I know) and it says to reinstall with new gasket and goop on both sides.

I think the problem is that the lower thermostat housing is steel and the upper part alloy, so maybe the heat causes some distortion with the mating surfaces. I may have to try and level the surfaces, or maybe coating the gasket will cure it. To that end, anyone have a recommendation on goop type? I normally use black ATV but maybe plumbing dope would be better since it's designed to prevent water leaks.
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Old 12-10-2018, 10:26   #10
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Re: Use Gasket sealant on new gaskets?

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Originally Posted by Compass790 View Post
I don't have blind faith in manufacturers as have seen so many OEM design FAILS. I like Loctite 518 flange sealant, still easy to get apart & much better results than putting on dry. It's only drawback is it's pricey. The other ( cheaper)option is use silicone. I like to put a thin smear on both sides of gasket & let it go off overnite before assembly if you have time. You can even coat both mating faces like this & don't bother with a gasket IF the gap between the faces is not critical.
So you have conflicting views here, take your pick
It depends on the gasket material too. If it is, say neoprene/butyl..., it can be just rubber, or it can have a fiber core. If it is just rubber, do not use sealant, (unless it is very thin, and it has set before assembly), otherwise it will push out as you torque up the assembly. (Same with cork). If there is a woven fiber core the rubber will be more resistant to distortion, and sealant may be used. With paper gaskets a little grease or anti-seize is OK. As with painting or fiberglass repair, preparation is most important. Scrape or wire-wheel/wire-brush all old gasket off, and make sure mating surfaces are in good shape.
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Old 12-10-2018, 15:35   #11
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Re: Use Gasket sealant on new gaskets?

Sounds more like the pump seal to me?
Should only be oil behind that gasket?
What motor is it?
Grab a mirror & see if the water is leaking from the weep hole.
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Old 12-10-2018, 16:48   #12
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Re: Use Gasket sealant on new gaskets?

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Originally Posted by hellosailor View Post
The only good rule of thumb is "do what the factory says" in the belief that the folks who built it, had a reason for a particular gasket type and installation, and you'll be safe repeating it.

Whatever the guys did, since it now leaks, they did it wrong.
I support this comment 100%. I just rebuilt an engine that was done not long ago and it was covered with excess silicone and extra sealer. Says a lot about the previous builder. I fit all the mating surfaces before final assembly, valve covers, timing covers, pan gaskets, head gaskets etc... cleanliness is the most important issue when assembly of all parts. Even use brake cleans to all mating surfaces, I never use any other sealant except in rare occasion where the manufacturer recommends. May I add that the most important procedure in assembly is to observe the torque required. Never over tighten because you think it is better. My 2 cents worth...
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Old 12-10-2018, 21:27   #13
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Re: Use Gasket sealant on new gaskets?

There is also a big difference between sealing old surfaces and "as new" surfaces; they often require different techniques.
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Old 12-10-2018, 22:37   #14
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Re: Use Gasket sealant on new gaskets?

Using grease on paper gaskets usually allows you to use them again. It depends on how smooth the surface is. Gasket materials that compress are usually found on less than perfect mating surfaces. A sealer is a little like insurance against leaks, not really necessary.
I've assembled a lot of engines. From radial to diesel. Sometimes with only the gasket and sometimes with only a silicone sealer on racing engines that are disassembled often.
The sealer I use most often is Permatex Aviation Form-A-Gasket. It has a brush applicator and is good for holding a gasket in place while lining everything up. Usually I grease the other side.
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Old 12-10-2018, 23:25   #15
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Re: Use Gasket sealant on new gaskets?

^^ and it smells nice too
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