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Practical Engine Building: Applying Sealant

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Applying Sealant

06.03

00:00 - A lot of the components that we're going to be fitting to our engine such as for example the oil pump housing, rear main seal, and the sump itself, will be sealed to the engine block using a silicon based sealant.
00:13 Now while on the face of it this might not seem like a particularly difficult task, this is an area I constantly see people struggle with, and there's nothing worse than assembling a freshly built engine and finding out a little bit later down the track that you've got an oil leak that's going to require you to remove a lot of components from the engine in order to rectify.
00:35 The other aspect I often see is the situation where excessive amounts of sealant have been applied in the hope of preventing any leaks down the track, and this often looks terrible with big beads of silicon poking out from the sump rails and the oil pump housing.
00:53 Now as well as potentially being a problem as parts of the silicon can break off and end up going through the engine, this also just looks plain terrible.
01:03 And particularly if you're assembling engines for an end user customer, this is often the only part of your workmanship that they're going to be able to see.
01:12 They're not going to be able to see the bearing clearances or any of the components inside the engine so of course even if it's not going to affect the operation of the engine, sometimes your work is going to be judged on those visual aspects that can be seen.
01:27 So we're going to have a look at the correct way of applying sealant here, and for our example we're going to be looking at sealing the sump on a Toyota 2JZ engine.
01:38 Now it's important to start with a good quality sealant, and for this example we're going to be using a Three Bond product and Three Bond do a range of sealants.
01:50 This is one of the products that's often used in OE applications.
01:54 So it's important to start with the right product.
01:57 The next tip is what we want to do is make sure that the applicating tip for the sealant isn't cut down too far.
02:06 What we're going to be trying to apply here is a bead of silicon sealant around about three millimetres in diameter.
02:14 So if we've got a massive tip cut on our sealant, it's going to be very very difficult to be specific and precise with our sealant application.
02:23 So you can see at the moment I've cut just a very small amount off the applicating tip on the three bond, and that's going to allow me to apply the sealant.
02:33 The next task is to ensure that the surfaces we're going to be applying the silicon sealant to are absolutely clean.
02:41 So we're going to begin by going across those surfaces using a clean rag and a brake cleaner or isopropyl alcohol product.
02:49 If we don't do this and there's some oil contamination on the surface this can affect the quality of the seal we're going to get.
02:58 Now we can go through and apply our silicon sealant onto the sump.
03:03 So we're going to be applying this to the sump instead of the engine block.
03:07 And what we're trying to do here is just apply a consistent bead, around about three millimetres in diameter as I already said.
03:15 One of the key parts to watch here is what we do when we get to any of the bolt holes.
03:20 You can see what I'm doing here is applying the sealant approximately in the centre of the sealing surface and when I get to one of the bolt holes, I'm actually applying the silicon to the inside edge of that bolt hole.
03:35 So this is going to prevent any of the oil from inside the sump making it into the bolt hole and potentially leaking down the bolt.
03:43 So in this situation we always want to seal to the inside of those bolt holes.
03:48 So we just continue around that sump until everything has a bead of silicon applied.
03:54 In some instances we will actually find that the sump or component that we're fitting has a groove machined into it which is where we're going to be applying the silicon.
04:05 And you'll also often find that the workshop manual will detail exactly where you need to apply the sealant.
04:13 Now that we've got our silicon applied to the sump, we can go ahead and fit the sump to the engine block.
04:19 Now a lot of engine builders will go and smear that silicon sealant along the sump rails on the sump prior to fitting it.
04:29 That's actually not what we want to do.
04:31 What we want to do is leave that bead, and that bead needs to be proud of the surface and this is going to allow it to smear out and fill in any inconsistencies in either the sump or the engine block sump rails.
04:46 So if we go in and smear this out with our finger and end up with a very thin coat of silicon, this doesn't allow the silicon to perform its task correctly.
04:55 Let's go ahead now and fit the sump to the engine block.
05:04 So I'm just going to flip the sump over, and there's a couple of dowels that locate the sump here onto the engine block.
05:11 So I'm just going to lower the sump onto those dowels.
05:16 And once we've got them on the dowels, just going to gently lower the sump onto the block.
05:21 Now we can go through and apply all of our fasteners.
05:30 Now with our sump tightened down onto the block, what we can see is we have a thin bead of silicon sealant just protruding out from the outside edge of the sump rails and this is very similar to what we'll see on an OE engine.
05:44 So we haven't got excessive amounts of sealant smeared all over the sides of the block and the sump.
05:50 So this should result in a reliable seal and no chance of any oil leaks.