Question about HLA's

[T45]

While reassembling my heads, I noticed there is a black ring around the HLA's, almost like an O-ring. Then while scratching it with my fingernail it broke out into tiny pieces almost like burned oil and dirt that had caked itself into the groove on the HLA.

My question is....what is it? I looked in the FSM and also Alldata and have not found anything on an HLA o-ring. The only thing I can assume is that it's just accumulated dirt and burnt oil and that the groove in the HLA is supposed to be clean. Anyone?

[Mettler]

Got pics?

[T45]

I'll try to get one. I found that the exh side seems to crumple very easily but when I tried one on the intake side I had to dig it out with a screwdriver and now I am thinking that it's some kind of plastic? I dunno...

[ultrapulse]

I had that when i removed my main bearing shells?! I could only have thought that it "spread" the oil out around the circumference, although this happens anyway. The "plastic" was not crumbly or gumbed up though. It was also put in "unsymmetrically' and not real clean-cut so to speak. Well since I have probably made everyone reading this to think WTF, sorry about that.

[maxnix]

I thought they were made of delrin. Should neither crumble nor crumple unless way overheated.

[Mettler]

Delrin is a trade name for Acetyl plastic. (Just in case this information would be useful to anyone)

[mtcookson]

I'm 99% sure they're o-rings (though from pictures online of other HLA's most don't have any... so I'm not sure)... I actually just encountered this problem yesterday myself. After some searching I found here on NICO someone making a post about rebuilding the VH. Basically the o-rings aren't available from Nissan, you have to replace the entire HLA. He instead got the proper measurement for the o-rings and got some Viton o-rings from a hydraulic shop (Viton would definitely be my recommendation, they're like silicone but handle oil much better and handle temps up to 400 degrees F). I've found many o-ring places to get them from... but have no idea what size the o-ring should be as the size was never posted in that thread.

I measured 15 mm for inside diameter of the o-ring hole and the total hla diameter is 17 mm. I didn't measure the thickness of the o-ring hole though, I need to do that to get a better estimate on the o-ring size.

[T45]

I had suspected this engine of overheating before as the coolant hoses were ruptured under the intake. I'm going to have the block and heads checked even further now.

What's the purpose of the delrin? Does it act as an isolator?

[Mettler]

Yeah, Viton are the goes. N70s (nitrile) will just melt/break down easily.

mtcookson perhaps you could measure the HLA's hole where they sit, and then speak to a seal company regarding how much orings will squash to, to select an appropriate diameter?

[mtcookson]

I've actually been thinking about just getting a new HLA and measuring the stock o-ring for a perfect fit. If the local dealership has one I'll go ahead and do that and if not, I'll see what seal company thinks.

[Raxephon]

The HLA's out of a SR are roughly the same size and they don't have the "O"-ring that the VH45DE HLA's do. Why would th VH need "O"-rings if the SR doesn't use them?

The "O"-ring is a hard plastic of sorts new, exact material I'm unsure of.

My '91 has all the hard plastic "O"-rings from the HLA's removed and I haven't had/do not have any problems.

[mtcookson]

If they are hard plastic stock, that'd definitely explain why Nissan doesn't sell any. If some sort of seal is required the Viton rings would definitely work... though I don't really see why they would be needed since most of the others I've seen use none and you personally aren't having any issues not using them.

Q45tech... any input?

[T45]

My '91 has all the hard plastic "O"-rings from the HLA's removed and I haven't had/do not have any problems.

That's what I wanted to hear.