Vernatherm Seat Face Tool

[Untainted123]

Anyone have a homemade (or not) Vernatherm seat surfacing tool?

I am chasing a high oil temp problem. I replaced my Vernatherm with an (assumed) good one, and my temp problem got way worse. Looking at my old Vernatherm, it looks like it was wearing pretty bad, with a very solid indented ring, and maybe not completely round on the mating wear? I also measured my old Vernatherm at 185*, and it measured correctly right at 3.280 of the spec (at the wear ring).

My engine is an O-360, 1250 hours, in an RV-6. Never had any trouble until all of a sudden the last couple of flights oil was reaching 215* at cruise. Verified gauges and all that already (I have 2, a mechanical old Van's one at the back of the filter adapter, and a JPI in the port on the front oil galley. They agree within 8* of each other, and both are showing hot).

I have purchased the 62415 plunger and 69436 spring to test with, hopefully removing the Vernatherm from the equation for troubleshooting, but in the meantime, has anyone had success honing the seat face?

Here are 2 photos of the old vernatherm, hopefully you can see what I mean about the wear marks. Each photo is 180* rotation.

 

[Bavafa]

Does the face look like rubber/soft material or is it in the pix that looks that way.
I have looked at mine and it is a shinny metal of some type.

 

[hgerhardt]

Have a look at this thread: https://vansairforce.net/community/showthread.php?t=188143

You may borrow the tool for the cost of shipping both ways.

 

[Untainted123]

It's definitely metal, like smooth shiny steel. It's a typical vernatherm, PN 75944. The newer ones, after following SI-1565, is 53E22144, which is what I put in to test, but made my problem way worse (had to throttle back to keep the oil at 225*), which led me back to the face in the housing and/or this face of this VT being the problem. It could be possible the replacement 53E22144 VT is bad (I had it on the shelf, but supposedly was only used a few hours if that).

My assumption is that a new VT won't seat into the face this VT has worn into the housing, and this VT is also wore enough to not seat well either. I don't recall seeing one previously with a groove quite so pronounced.

This VT does seem to expand to the correct size though (3.28 total length at 185*F).

 

[Untainted123]

Have a look at this thread: https://vansairforce.net/community/showthread.php?t=188143

You may borrow the tool for the cost of shipping both ways.

That is much appreciated. I sent you a PM with details.

I did read through that thread a couple times, which is how I saw that you (and you apparently convinced Dan ) that the total length is what matters, at ~3.277 or 3.28. I haven't gone back and read the referenced article yet about why the face wears in the first place.

I see you used a cutter, some people used something else with grinding compound? Any concern about the chips in the engine? I assume it's cut a little, check, cut a little so as to not enlargen the opening too much? Any way to clean up the mating surface on my old VT, or just try again with the newer VT?

Sorry for the shotgun blast of questions.

 

[hgerhardt]

That is much appreciated. I sent you a PM with details.

I did read through that thread a couple times, which is how I saw that you (and you apparently convinced Dan ) that the total length is what matters, at ~3.277 or 3.28. I haven't gone back and read the referenced article yet about why the face wears in the first place.

I see you used a cutter, some people used something else with grinding compound? Any concern about the chips in the engine? I assume it's cut a little, check, cut a little so as to not enlargen the opening too much? Any way to clean up the mating surface on my old VT, or just try again with the newer VT?

Sorry for the shotgun blast of questions.

Using a single-hole countersink cutter ensures it doesn't chatter (even though you're turning it very slowly), but the single hole makes it easy to pack the hole with grease to hold the chips. There's a stop collar which clamps to the shaft to prevent going deeper than necessary. I did mine by bottoming the cutter against the seat, then tightening the clamp, then rotating the cutter to see if the seat is even concentric with the threaded end (mine was a bit off, which you can see in my photo). Then I used a 0.005" feeler gage to reset the clamp, to allow the cutter to go that deep. That was enough for mine to get a good surface.

Grinding wheels typically get clogged with aluminum, plus cleaning out the dust from the hole is pretty much impossible (at least on my Dual-Mag engine where the VT housing is integral with the accessory case).

If you try to re-cut the VT to get rid of the wear ring, I would think that you'd lose too much length.

 

[Untainted123]

I think I got the idea, thanks for the describing that, now I can visualize how to do it.

Once I receive the tool and give it a shot, I will report back here.

Regarding the old VT face: after running the tool, I will try a test with the newer VT (53E22144), and if that resolves the issue, I will leave that alone and just toss the old VT (unless someone needs a cadaver for science). If that doesn't work, I guess I will move on to other problems with the oil cooling system.

I also still have the plunger and spring on order to see what happens there if I need to investigate that line further (it's so hot in TX right now that before my engine starts for the first time in the day, the oil temp is already above 100*F).

Thanks again for your help.

 

[Bavafa]

Just to confirm my thought process, in addition to the expansion length, a complete and round witness mark on the face of the Vernatherm should be a good confirmation of a good seal.

Is there any flaws in this thought process?

 

[lr172]

Just to confirm my thought process, in addition to the expansion length, a complete and round witness mark on the face of the Vernatherm should be a good confirmation of a good seal.

Is there any flaws in this thought process?

I would say not really. The OP's pics are a great example. There is a full ring, however, that steel piece is really hogged out. If there is enough wear that the steel is worn into, I can only imagine what the aluminum seat looks like. Generally speaking, a full round light witness mark is a good indication of a full contact seating. However, carefull examination of both parts is required, as that witness mark may have developed BEFORE there was some damage or wear to the seat that is now preventing a good seal. An incomplete round witness mark, OTOH, is a pretty good indication that a full seal is NOT occurring.

Larry

 

[Untainted123]

If MY understanding of all this correct also:

The TL;DR from that article in the other thread: as the VT closes and starts diverting oil to the cold oil cooler, especially when you don't preheat the oil cooler, something similar to water-hammer occurs. Hydraulic shockwaves occur as the cold oil cooler oil is brought up to speed and temperature, and these shock waves are absorbed by the spring and mating surfaces of the VT. Over time, that hammering together wears both.

I can only assume Heinrich's tool will only work so many times before you just need a new housing. Most probably don't make it that far before some sort of engine tear down occurs. I am at almost 1300 hours and this is the first trouble I've had with the VT, and it looks like it's the original.

In addition, as you get further and further from the spec length (~3.277 depending on where you measure from), because of needing to reach out to the bottom of the seat face, the temp of your oil has to be a few degrees higher to get a little more length on the VT until it eventually runs out of distance. Assuming all else is constant, over time you might see that your oil temp slowly creeps up over the life of the VT/housing. This probably isn't noticeable in real life, but the wear in my case looks rough and uneven, finally letting enough oil bypass to get a high oil temp alarm.

I'll know more after cleaning up the face of my housing, and further testing.

 

[hgerhardt]

Going by the chart I had in my linked thread and here, my properly-functioning VT moves 0.055" between 180F and 185F (this VT seats at 180F), so if I hypothetically removed 0.055" from the seat, the VT would close the port 5F higher than before, or right at design temp of 185F.

0.055" is a HUGE amount to remove from the seat, so it looks to me that a 0.005-0.010 cleanup cut, plus the amount worn off from use, really won't make much difference in oil temp.

In the chart below, look at the gray line, which is the new VT which I bought in 2020. The others are older VT's; the original-to-the-engine 1980 one and the 2008 one which I installed when I overhauled the engine then.

 

[A1AVIATON47]

oil temp

Buy a new one.

 

[Untainted123]

Buy a new one.

That’s certainly an option, but I want to exhaust other options first

1. Vernatherms now run close to $500, so there is a lot of incentive to get the maximum life out of them
2. If my seat face isn’t correct, a new one isn’t going to help
3. Haven’t verified proper length yet, but I have essentially a brand new one from another engine, and I am assuming because my housing face is trashed, that actually made it worse (the old VT and seat had wore each other into a matching set possibly)
4. Based on the excellent work of Heinrich, we can just spec out the VT, look at the condition of the matin surfaces, and know what we are dealing with. If that leads to needing to buy a new one, so be it.