Hylomar universal blue failed to seal oil?

Following earlier recommendations on here, I used some Hylomar Universal Blue to seal 2 tapped holes in the body of the oil filled gearbox on my mill. However 10 days later there is a small witness of oil (granted better than with no selant).

The packaging did say it will seal threads. One is 2BA and other is sight glass ~ 0.75" x 20 tpi.

I can only think it's not designed for small fxings becuase the threads' tpi is too fine? I noticed the Hylomar did 'lump up' whilst applying it. Was impossible to get a smooth smear.

I followed the sintructions of :

clean threads, smear of hylomar,

disassmebly to dry,

final reassembly

I plan to remove remnants and start again with PTFE tape (which has never failed before). Can someone can give an explanation as to why this supposedly great sealant failed? Thanks in advance.

Was the Hylomar new or have you had it for some time? I have never had the slightest problem with Hylomar. If you carried out the cleaning procedure to the letter, then perhaps you had a faulty batch?

Andrew.

how did you clean the threads as that would be my thoughts on the most likely cause

Hylomar is a non curing sealant. Methyl Chloride is the usual solvent.

It is not designed to seal huge gaps, but has been used in industry for MANY years.

Personally, I would not let it skin over, but, having applied it to clean threads (including my best attempts at the internal thread as well as the external ), would then have proceeded with the assembly,

Industry (Rolls Royce, who invented it, and Perkins ), never spent time letting it skin, but used wet application.

Don't be too sparing with the application. Better to wipe off an excess and get a seal than to be frugal and still have a seep.

Howard

My experience;

I remember swapping over from Hylomar to the silicon type sealants when I replaced seals on my old Vauxhall Viva (back in the early 80s - remember them?). The great Hylomar failed to seal several times - hence the change.

Phil H.

I'm open to correction on this, my understanding of Hylomar is that it was developed by Rolls Royce for use with cork gaskets. With this in mind I've had great success sealing Velocette primary chaincases with cork gaskets and Hylomar.

There are much better sealants for sealing screw threads, I favour Loctite products, 542 for instance.

John

Ps; the RR connection, beaten to it by Howard L!

Not tight enough maybe? Or perhaps the thread is damaged badly enough to leave a gap? I don't recall my Hylomar 'lumping up', maybe past it's sell by date? Another mystery!

Dave

I'd use Wellseal for that as I have some handy, or a Loctite sealant. But your Hylomar shouldn't have been lumpy?

Rob

Used with asbestos based gaskets, and with fixings tightened for a dry gasket, Hylomar would lubricate the gasket so that it slid and split!

R-R Research Dept developed Wellseal and then Hylomar to solve sealing problems in their Aero, Car and Oil Engine Divisions.

We used Wellseal, (horrid smelly stuff ), to seal the top of the liner to the block. Like Hylomar, it was difficult to remove if you got any on your hands. Trichlorethylene (now banned ) was the only solvent that would eventually remove it. Distance does lend enchantment to that view!

Howard

It certainly is - thank heavens for disposable gloves and brushes It's great for metal to metal joints though.

Rob

Wellseal - that brings back memories. I used it between the crankcase halves of Honda motorcycle engine/gearbox units - a horizontal joint without a gasket - back in the 1960s. The engines remained oil-tight, without exception. It had been used on the farm by Dad, prior to me adopting it for rebuilding engines - he probably used it on Landrovers.

I recall using blue hylomar on a Landrover cylinder head gasket (diesels were renowned for failed head gaskets). It worked but head removal (much later), for other engine repairs, proved very problematic!

To answer some follow on queries:

• It was a brand new tube. I broke the foil seal on the end. Can it go off in an unopened tube though?
• Perhaps the threads weren't scrupuloulsy clean. I only wiped them with blue roll. Should degreasant have been used?
• Youtube Hylomar demo's on engine manifolds stressed intermediate dissambly is needed to allow solvent evaporation. I think it's this "skinning" (didn't know this was what it's called!) caused it to prematurely coagulate when I started threading them together
• To reiterate; the Hylomar did *not* come out of the tube lumpy. It was toothpaste consistency.

Is PTFE tape my best choice for both a) removablity (vs pastes which can be a pain to clean off of threads) and b) performance? I imagine it's inert with oils?

Hylomar is a non setting jointing compound. Disassembly becomes difficult, when large areas are involved because of it "stickiness"

If it weren't so good. a ) It would not have come to market. b) it would never have lasted so long in the market place.

Possibly the problem arose because having dried out , it became lumpy and so was not distributed all around the threads.

Yes, ensure that the threads are clean and dry, apply, and assemble would be my suggestion.

Howard

Prefer to use ‘HYLOTYTE RED’ - formerly Hermetite Red (semi hardening) for most gaskets or low pressure threaded connections - same requirement to evaporate Solvent & clean surfaces as Blue Hylomar though.

Loctite 542 is reserved for hydraulic or high pressure applications.

The instructions "clean threads" could mean anything between a wipe with a rag, to vapour phase and ultrasonic cleaning. Beware of the liquid in a parts washer, it could seem to clean, but if the fluid is well used, it will leave the parts covered in a film of oil. The parts washer at the museum is like that, I got hold of 30 litres the older type solvent cleaner and we topped up the rest with Avtur (fuel for gas turbines), but now it has a lot of oil contamination, and anything cleaned in it may require further degreasing. Spraying brake degreaser down a threaded hole will work better than most things, as the cleaning fluid is always clean.

Its a machine, you will have to oil all the moving parts frequently if you intend to ever use it, or are you worried that a drip of oil will spoil the display in the glass cabinet?

I have always used Wellseal, and petrol will remove it from casings and hands easily.

Colin

I don't think Hylomar is intended for metal-to-metal joints, I always assumed it required some kind of gasket and then it would work quite well. It was about the only thing which would make a reasonably oil-tight joint on the card gaskets of the old (pre- 1969-ish) Jaguar polished alloy cam covers. Smearing it on the copper washers for the hold-down nuts of same didn't help a bit though.

For sealing threads like this, I'd use PTFE tape - easy, no need to degrease, and non-seizing when you need to disassemble.

You can get different kinds of PTFE tape - the stuff for gas fitting is thicker, which is handy for larger clearances.

n.b. if you need to seal threads on oxygen fittings, you must use PTFE tape made specially for the job. The ordinary stuff contains a lubricant which might just turn your oxygen bottle into a rocket...

Both Hylomar, and red hermetite have been reformulate due to VOC regulations. I noticed the change in Hylomar first, because I have had a large bottle and brush style hermatite for years. TBH I find them now to be about as good as water based gloss paint, that is, effin useless! I have managed to obtain 3 tubes of NOS hermetite, but who knows what I will use for the hylomar jobs, maybe a loctite product?

Phil

Slightly OT, but for water-based paint, Albany (Brewers own brand) will give a true gloss (I hate fooling around with horrible, stinky solvent-based* paint and refuse to use it now).

*Yes, I know water-based paint has water as the solvent - or does it? Are these paints solutions or emulsions?

old mart Quite! A serially incontinent 7 series Myford is a reminder to lubricate! Robert Butler