"RTV" sealant vs 1-piece gasket.

[BMWTurboDzl]

When it comes to manufacturing what are the trade-offs between the two?

Does one last longer than the other? Ease of removal?

I'm just trying to get my head around as to why some manufacturers use the same failure prone gasket design year over year.

Edit: Found my answer

"Why do some engines use RTV sealer instead of gaskets
For a period in the 1980s, domestic auto makers thought they could lower production costs and improve sealing by using RTV (Room Temperature Vulcanizing) silicone instead of conventional cut gaskets to seal valve covers, oil pans, timing covers, transmission pans, and other parts. In theory, the idea made sense. By applying a thin bead of RTV to such parts, they could be assembled and sealed in one step.

Engineers liked RTV because it does not take a set like a conventional cork/rubber cut gasket. Heat causes a cork/rubber gasket to harden and become brittle with age.

To seal properly, RTV requires both surfaces to be clean, dry and oil-free. Though installers use RTV all the time with no problems, car makers apparently could not keep their parts clean enough on the assembly line to produce a lasting seal with RTV. They found they were having more oil leaks, not less, with RTV.

Eventually, domestic auto makers dropped RTV in favor of molded silicone gaskets which combine the installation ease of a conventional gasket with the sealing properties and durability of silicone.

When working on an engine that has RTV instead of gaskets, the installer can either use RTV to reseal the engine, or replace the RTV with conventional cut gaskets. In some applications, longer bolts may be necessary to compensate for added gasket thickness.

Some prefer to use RTV because it eliminates the need to stock a lot of different gaskets. Others prefer to substitute a cut gasket because of RTV's limitations. Care must be taken when using RTV so excess sealer does not seep out from between the seating surfaces and end up someplace where it does not belong.

RTV takes 30 minutes to an hour to set up (full cure takes about 24 hours). The vehicle should not be driven during this time."

 

[demarpaint]

I prefer a gasket. Here's a recent similar thread. RTV/Gasket Discussion

 

[Dave9]

Nobody should like RTV. A properly made part and/or machined surface seals fine with a gasket and if you need to remove the part, it's much less work to put a new gasket on than to PRY it apart and clean off RTV.

Manufacturers like the cut gaskets or pre-molded silicone because it's quick and easy with no wait, and I'm sure the industry gave feedback about what a PITA it is to service engines that are effectively lglued together.

Just don't. Never use RTV when there is a gasket part # to do the job. If the sealing surface is that bad, time to replace or machine the part(s) true again.

 

[jeepman3071]

For certain applications, a bit of RTV ultra black can actually seal better than the original gasket.

Kohler Courage valve covers on small engines are a good example. The factory gasket and many aftermarket ones are cork, which is useless, and dumps oil on the exhaust enough to smoke after 50 or so hours. I've fixed plenty of them using RTV ultra black and they never leaked after.

Well machined surfaces with a gasket are obviously preferred, but we all know how that goes, especially with aftermarket parts.

 

[maxdustington]

Originally Posted by Dave9
Just don't. Never use RTV when there is a gasket part # to do the job. If the sealing surface is that bad, time to replace or machine the part(s) true again.
So if you had an old head that would not stop leaking from the valve cover with a gasket, you would pull the head and get the VC sealing surface milled instead of trying RTV?

What about old stuff where gaskets are NLA? Do you just throw it out?

 

[BobGoblin]

On my KIA ceed oil pan is sealed with RTV from factory.

 

[Dave9]

Originally Posted by maxdustington
Originally Posted by Dave9
Just don't. Never use RTV when there is a gasket part # to do the job. If the sealing surface is that bad, time to replace or machine the part(s) true again.
So if you had an old head that would not stop leaking from the valve cover with a gasket, you would pull the head and get the VC sealing surface milled instead of trying RTV?

What about old stuff where gaskets are NLA? Do you just throw it out?


If the head itself is that untrue, yeah it probably needs machined. If it's the cover, maybe you can bend it, maybe get a pull from a junkyard, but I have not had a case where I needed to RTV instead.

Old stuff, given the internet it is surprising how many parts are out there but in some cases, buy a roll of gasket material and cut one out. Besides, if something is old and deformed, yet worth the repair, you may find it needs pulled apart again anyway so that few minutes saved with the RTV, becomes more minutes wasted cleaning it back off again next time.

I don't much care for shortcuts but hey it's your equipment and you can do whatever works for you... just don't sell that equipment to me and fail to mention you glued it together instead of gaskets where it had factory gaskets.

 

[das_peikko]

They quit making the thermostat gasket for my car. I buttered Permatex Ultra Black on both surfaces, assembled; and let it cure for 24 hours. No leaks. By the way, do you guys know what "buttered" means? It means not a bead, but spread over the surface evenly with your finger or a putty knife. I don't think Ultra Black is RTV. It doesn't have the typical vinegar smell that RTV has.

 

[RooflessVW]

Butter is for bread.

 

[eljefino]

Also notable some/many manufacturers actually use an anaerobic sealant that cures in 15 minutes. RTV is the service replacement, but if you're cunning you too can find and use the really sweet grey stuff.

 

[andyd]

Aviation Forma gasket skins in 10 minutes and is ready for use upon assembly. This is why I use it instead of RTV . If a gasket is available , I'll use one. I also keep a sheet of gasket paper for eventualities.

 

[doitmyself]

Originally Posted by das_peikko
I don't think Ultra Black is RTV. It doesn't have the typical vinegar smell that RTV has.

Ultra Black is RTV (Room Temperature Vucanizing) without the acetic acid that creates the vinegar smell. Ultra Black is superior for lots of applications, including engines and electronics.

 

[user52165]

I have seen situations where the factory used both together. Something like a "Y" or an internal corner with RTV, or similar, added to the full gasket.

 

[atikovi]

Originally Posted by Dave9
Nobody should like RTV. A properly made part and/or machined surface seals fine with a gasket and if you need to remove the part, it's much less work to put a new gasket on than to PRY it apart and clean off RTV.

Manufacturers like the cut gaskets or pre-molded silicone because it's quick and easy with no wait, and I'm sure the industry gave feedback about what a PITA it is to service engines that are effectively lglued together.

Just don't. Never use RTV when there is a gasket part # to do the job. If the sealing surface is that bad, time to replace or machine the part(s) true again.


RTV is superior to a gasket for sealing. A gasket has potential for leaks on both sides while RTV, since it bonds to the joined parts, technically has no sides. The 70's ended 40 years ago. Most modern auto manufacturing uses liquid sealing solutions over gaskets. I usually use RTV instead of a hard gasket for transmission pans that are notorious for leaking. It can easily fill gaps from sealing surface defects that would cause a hard gasket to leak without having to replace or machine the transmission.

 

[nobb]

RTV is a superior sealant in terms of longevity, flexibility, and durability IF it is properly applied...which is almost never the case unless it is factory applied by a robot. No matter how steady your hand is, there's always a risk of chunks of RTV falling off and clogging passages. That's why I would stick with a gasket.

 

[atikovi]

Originally Posted by nobb
No matter how steady your hand is, there's always a risk of chunks of RTV falling off and clogging passages.


I don't have a very steady hand but think I can do a fairly good job applying it. And little chance of "chunks" falling off as long as you put it on too thick.

 

[nobb]

Originally Posted by atikovi


I don't have a very steady hand but think I can do a fairly good job applying it. And little chance of "chunks" falling off as long as you put it on too thick.

Is that a Ford Ranger backend? I was just doing one this week, but this time instead of RTV I bought a Fel Pro gasket. That looks like a pretty typical, thin RTV application but I guarantee some of it is going to show up as little blobs on the inside. It's most likely ok and won't break off, but a gasket is just so much easier to work with.

 

[WyrTwister]

I have seen several videos where someone used too much RTV and it oozed out , into the inside of the engine , diff , trans , transfer case , etc. .

The excess RTV messed up stuff ! :-(

 

[nthach]

Originally Posted by das_peikko
. I don't think Ultra Black is RTV. It doesn't have the typical vinegar smell that RTV has.

Sensor-safe automotive RTV cures differently than architectural-grade RTV. One is a oxime cure, the other one releases acetic acid and methanol during cure.

 

[atikovi]

Originally Posted by nobb
Is that a Ford Ranger backend? I was just doing one this week, but this time instead of RTV I bought a Fel Pro gasket. That looks like a pretty typical, thin RTV application but I guarantee some of it is going to show up as little blobs on the inside. It's most likely ok and won't break off, but a gasket is just so much easier to work with.


Yes it is. If these trucks are still around in 10 years I'd like to see how the rear ends look for leaks. No chance of little blobs breaking off, RTV is pretty strong stuff once it's dry. Anything that oozes beyond the flange will just harden there. Used gear oil RTV specifically made for this.