20 replies to this topic

[croc7]

How good is Hylomar Blue as a thermostat gasket sealer?

[nicklouse]

it works. and has been used for years.

 

thermostat gaskets cab e be problematic though it depends on which you are using and what issues you are having.

[croc7]

Gaskets, problematical? Yep. I’ve used paper, cork with and without sealant. Seems to be whatever the moon’s phase...

[unburntfuelinthemorning]

Indeed Hylomar is very good.

[whistler]

The 'old' Hylomar Blue used to be much better as it allowed old gaskets to be peeled off intact. This modern version needs scraping off, just like Hermatite Red used to.

Originally it was only available from Rolls Royce dealers down my way (Howells of Cardiff)

[TheFabMini]

Claims to be used on Rolls Royce plane engines... so should be good enough for our little A series

[unburntfuelinthemorning]

Hylomar Aerograde PL32 is apparently the original formula.

[DeadSquare]

The holes in replacement thermostat housings are far too large.

 

Try and find some off-cut Butyl pond liner from a fish/garden center;  the latest is very thin so you might need 3 layers;  punch the holes 1/4" to seal on the studs and cut them slightly oversize.

 

Use Hylomar on the head;  put on one sheet of butyl and Hylomar it;  insert the themostat which should sit on the just oversize sheet;  put the other two Hylomared sheets on top of the thermostat before fitting the Hylomared housing.  Don't do the nuts up too tight.

 

Hylomar needs to be smeared fairly thin and the Toluene allowed to dry out before assembly.  Barrier cream helps to stop it sticking to your fingers.

[Magneto]

Wow, that seems like a lot of effort, I just buy the blue thick cardboard gaskets from MiniSpares, they don't seem to leak. Worst case, some Permatex sealer on the gasket takes care of it, but that's rare. In the last 10 engines I've built I've only had to use gasket sealer on one - and the head was slightly damaged from having to break the thermostat cover to get it off.

 

Also Dead Square - the thermostat is supposed to sit in the recess in the head, isn't it? Why put the gasket under it?

[DeadSquare]

Wow, that seems like a lot of effort, I just buy the blue thick cardboard gaskets from MiniSpares, they don't seem to leak. Worst case, some Permatex sealer on the gasket takes care of it, but that's rare. In the last 10 engines I've built I've only had to use gasket sealer on one - and the head was slightly damaged from having to break the thermostat cover to get it off.

 

Also Dead Square - the thermostat is supposed to sit in the recess in the head, isn't it? Why put the gasket under it?

 

Because I found that it worked. With the M/S supplied gasket, I couldn't stop a weeping leak from at least one stud.

 

With the layers of butyl, no coolant got round recess under the thermostat and none got out above it.

[Magneto]

Well, I'm all for whatever works, I've just never had that much problem with one....

[Spider]

I use an RTV on Thermostat Housings. As DeadSquare mentioned, the holes in the Housings are too big and if used, there's often some corrosion, to nit a dead flat / clean surface like we'd all like. I alsi have a (factory) steady that goes in here too, these are steel and also corroded.

For these reasons, I've found something, like an RTV that can fill, works well.

 

The other thing is some gaskets have a 'coating' on them. I've found with the water jacket, these seldom work too good. I found an un-coated gasket works better, especially if you do an initial fill with plain water as it then causes the gasket to swell up.

[Cooperman]

History lesson: When Rolls-Royce developed the wonderful V12 Merlin engine for aeroplanes such as the Hurricane, Spitfire, Lancaster and Mosquito, the engines tended to leak oil.

Hylomar was developed to cure this problem, which it obviously did and it became commercially available in the late 1940's.

It is still great stuff.

[beardylondon]

Thread resurrection, I’ve got a leak that won’t stop and I’m going to buy the Hylomar blue aero grade stuff, but there’s 3 types, light, medium and high, which one is good for mini thermostat gaskets?

[Gaz66]

Only ever used hylomar once many years ago.
Didnt really rate it as I continued to have leaks.
After that I used hermatite red gasket sealer.
Awesome stuff, set like plasticine with no leaks on successive engine builds.
Not sure if that's still available after all these years.