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Tue Nov 01, 2022 9:57 am

Cant believe anyone sanctions using sealant on the main bearing saddles. That looks like orange marmalade jelly. So much for your main bearing crush with that

Tue Nov 01, 2022 1:38 pm

Nothing wrong with proper use of sealant on the main saddles. Think air cooled 911 engines with Loctite 574. :wink:

If a sealant like that makes your bearing crush go out the window, you never had proper bearing crush in the first place. In other words, it is not the fault of the sealant. Either your case line bore is too big, the bearing shells are too small, or both!

With as much clamp load as there is on the mains given the small surface area, any reasonable flange sealant crushes to a negligible thickness in that kind of a gap. I would be surprised if it amounted to any more than 0.0001” with any anaerobic flange sealant. If 0.0001” is going to throw off your crush, you have much bigger problems that need to be addressed. :lol:

Tue Nov 01, 2022 9:18 pm

how many here have used or use 574 on bearing saddle flanges on a T4?

Tue Nov 01, 2022 10:45 pm

Vanapplebomb wrote:
With as much clamp load as there is on the mains given the small surface area, any reasonable flange sealant crushes to a negligible thickness in that kind of a gap. I would be surprised if it amounted to any more than 0.0001” with any anaerobic flange sealant. If 0.0001” is going to throw off your crush, you have much bigger problems that need to be addressed. :lol:

The steel center main holds the case halves about .002" apart at room temp, and filling that gap with acrilic sealant may not be wise.
You need to examine that yourself if you don't believe it.
I'm not saying it's good or bad, that's how it was designed to be. But I agree with you in spirit, that might not be the ideal design.

Wed Nov 02, 2022 6:05 am

SGKent wrote: how many here have used or use 574 on bearing saddle flanges on a T4?

Used to do the whole mating surface with either 574 or 518. I switched to RTVs instead of anaerobic sealants.

Wed Nov 02, 2022 6:11 am

modok wrote: Vanapplebomb wrote:
With as much clamp load as there is on the mains given the small surface area, any reasonable flange sealant crushes to a negligible thickness in that kind of a gap. I would be surprised if it amounted to any more than 0.0001” with any anaerobic flange sealant. If 0.0001” is going to throw off your crush, you have much bigger problems that need to be addressed. :lol:

The steel center main holds the case halves about .002" apart at room temp, and filling that gap with acrilic sealant may not be wise.
You need to examine that yourself if you don't believe it.
I'm not saying it's good or bad, that's how it was designed to be. But I agree with you in spirit, that might not be the ideal design.

This is very true. Once bearings are in there, there can be slight gaps between the saddles. 0.002 sounds a little big to me as I could not fit a 1.5 thou feeler gauge (smallest I have) in anywhere with just the bearings installed, so to me it would seem smaller than that, but that isn’t a very precise way of measuring. It was also more for fun than science. My suspicion is that this jacking apart is why on well used T4 cases you can get a gap in the center large main saddle visible with no bearings installed. It’s almost like it self stress reliefs into that position, and then stays there.

Wed Nov 02, 2022 8:28 am

modok wrote:
The steel center main holds the case halves about .002" apart at room temp,

Vanapplebomb wrote:
This is very true. Once bearings are in there, there can be slight gaps between the saddles. 0.002 sounds a little big to me as I could not fit a 1.5 thou feeler gauge (smallest I have) in anywhere with just the bearings installed, so to me it would seem smaller than that, but that isn’t a very precise way of measuring. .

So herewithin lies a big conundrum in building these engines today..

Just how much crush is supposed to be there?
If the case halves are still being held apart even after case torquing then the bearing is too big, right?
Or do you want all available crush?

Seems to me that if the case halves are still held apart at the center main after the case half studs are tight,
Maybe some sealant there isn't an entirely bad idea.

Wed Nov 02, 2022 9:42 am

Was sealant on the bearing saddles like in the previous pic a factory process or an aftermarket effort?

Wed Nov 02, 2022 3:52 pm

the saddles can be apart a little too as a result of a hot rod or main bearing. If the rod or main gets hot enough to blue the steel it can warp the case in the nearest saddle area. On the engines I have built I come back a day later and retorque the six bolts. Always get a little more. Same for the heads. That said, a bright light will usually reveal any saddle gaps. One can use compressed air too. That said, I am only concerned whether 574 on the saddles is a good thing or not. I put it on a case the first time and for some reason or another had to reopen the case, maybe decided to put the main seal in as the case was pulled together. Anyway, the 574 was like dried old paper, some pieces of it stuck to one case half, other pieces were on the other case half, and some were free. The case was spotless and degreased, wiped with acetone and clean rags before the 574 was applied. It did not stick as well as even the old Gasgacinch used to. Wasn't any harder to get apart than normal.

Wed Nov 02, 2022 6:29 pm

If putting loctite on the main cap surfaces reduced fretting then that would be nice but I'm pretty sure that's been tried many many times before and wasn't a hit.
The vw engine isn't special than others in this respect.

IMo this question is HEADED very profound depths of engine structure design which has no easy answer. I'm not going to try going for the long answer at this time. But the answer is something like the same reason why four bolt main caps work better than just WIDE caps with two bolts.

Mating surfaces with insufficient contact pressure to stay IN contact should PROBABLY just be avoided entirely tho what that would mean for modern engine design and how it could be applied to vintage engines is just beyond the scope of one guy and a tube of goop to figure out.
But the type 4 design they have already reduced the mating contact area right near the bearing and increased the contact area around the bolt VS earlier designs and that's good, probably, I think, tho not totally sure. so it's nice to see some evidence of other intelligent life has thought about it.

Wed Nov 02, 2022 6:39 pm

Vanapplebomb wrote: SGKent wrote: how many here have used or use 574 on bearing saddle flanges on a T4?

Used to do the whole mating surface with either 574 or 518. I switched to RTVs instead of anaerobic sealants.

Hold on a sec...what? Why the heck man?
I know there is no ill will intended but even I am confused by what your claiming, but if we reach the same conclusion in the end then that's at least something important.
There was a situatiion with subarus that I wasn't going to bring up, but it all went nowhere, as far as I can tell they went back to how the factory did it, thin RTV across the whole surface.

Wed Nov 02, 2022 7:19 pm

At the time when I used 574 or 518 on the main saddles I did not use any sealant on the main bearing through bolts (type 4). I never cared for (and still don’t) trying to seal straight threads, bolt heads, washers, etc. Thread lockers work well for sealing straight threads, but I still don’t like trying to seal bolt heads, washers, etc.

As for the switch to RTV, I gave it a go several years back, and really liked it. It is transferred from glass to the case with an ink roller, super thin. I actually let it fully cure before assembly. I actually built up a motor with that technique, realized I forgot the cam plug, took it apart a week later, and reassembled with the cam plug. I never reapplied the sealant. The case halves don’t bond together because the RTV is fully cured before assembly, so you can separate them and slap them back together. How many times? I don’t know. I do know it can be done at least once because after 7 years, still no leaks anywhere.

Wed Nov 02, 2022 9:01 pm

Vanapplebomb wrote: At the time when I used 574 or 518 on the main saddles I did not use any sealant on the main bearing through bolts (type 4). I never cared for (and still don’t) trying to seal straight threads, bolt heads, washers, etc. Thread lockers work well for sealing straight threads, but I still don’t like trying to seal bolt heads, washers, etc.

As for the switch to RTV, I gave it a go several years back, and really liked it. It is transferred from glass to the case with an ink roller, super thin. I actually let it fully cure before assembly. I actually built up a motor with that technique, realized I forgot the cam plug, took it apart a week later, and reassembled with the cam plug. I never reapplied the sealant. The case halves don’t bond together because the RTV is fully cured before assembly, so you can separate them and slap them back together. How many times? I don’t know. I do know it can be done at least once because after 7 years, still no leaks anywhere.
interesting. I ordered some Three Bond 1184. Will probably use than and nothing on the saddle flanges.

Thu Nov 03, 2022 6:47 am

That’s fine, and how most people do it.

Thu Nov 03, 2022 9:09 am

are you coating both sides with a thin coating of 1184 or just one side?

Sat Nov 05, 2022 12:16 am

Vanapplebomb wrote: At the time when I used 574 or 518 on the main saddles I did not use any sealant on the main bearing through bolts (type 4). I never cared for (and still don’t) trying to seal straight threads, bolt heads, washers, etc. Thread lockers work well for sealing straight threads, but I still don’t like trying to seal bolt heads, washers, etc.

As for the switch to RTV, I gave it a go several years back, and really liked it. It is transferred from glass to the case with an ink roller, super thin. I actually let it fully cure before assembly. I actually built up a motor with that technique, realized I forgot the cam plug, took it apart a week later, and reassembled with the cam plug. I never reapplied the sealant. The case halves don’t bond together because the RTV is fully cured before assembly, so you can separate them and slap them back together. How many times? I don’t know. I do know it can be done at least once because after 7 years, still no leaks anywhere.

What about sealant shimming ?? You have just added a silicone shim ,you just shimmed the hole crankcase That is the whole point of liquid anaerobic flange sealants especially the 574 loctite is the least prone to flange shimming.

Sat Nov 05, 2022 6:14 am

I don’t think you understand just how thin it is. :wink:

Even if you follow the directions on the tube, it can potentially jack the case apart too much. If you apply a bead and let it dry, it will be WAAAYYYY too thick.

However, there are ways of thinning RTVs to make them as thin (or thinner) than anaerobic sealants. :wink:

It’s all in the process.

Sat Nov 05, 2022 10:16 am

Is the Three Bond 1184 so thick it spreads the case apart? It does not appear to be the normal silicone type RTV but it is a vulcanizing rubber sealant. RTV is technically any Room-Temperature Vulcanizing sealant. We are accustomed to most RTV being silicone based with acetic acid in them. There are none acidic silicone RTV's. Three Bond 1184 is an RTV but I don't think it is acidic or silicone based. Someone told me it is very thin and flows easily. Supposedly it is rubber based. I haven't tried it yet.

Sat Nov 05, 2022 11:07 am

Ray greenwood has posted on how to roll out rtv really super thin. I assume for a case its only applied on 1 side, since we have studs on the other half. Not easy to use a roller around studs, but maybe there is a work around for that

Sat Nov 05, 2022 11:33 am

1184 is very thin…flows like paint