I was not able to find anything on this with a search, so let me start a new post on it.



For anyone that has assembled an engine what have you used on the inner coolant seals? Hylomar or petroleum jelly?



On all of the engines I have assembled I have always used Hylomar. As I am getting ready to assemble my next engine I was wondering if I ought to try just using the petroleum jelly. Every engine failure that the engines I've assembled has suffered has been from a coolant seal going away. Granted - it has never been a quick failure nor could I claim that the cooling system or boost was not to blame but I just would like to hear some opinions on the subject.



Jason

All it does is hold the seals in place during assembly so it doesn't really matter.. and I think that coolant seal failure is usually due to overheating.. but I may be wrong..

i use vaseline, it works great. you just need enough to hold the seal in



mike

PJ is only to hold the seals in place during assembly, it is not going to contribute to sealing the way hylomar will.



J

Hylomar is used in the groves for the coolant seals. I have only heard of vaseline being used to hold the side seals in place. My understanding is that you want the coolant seals firm in the grove.....Vaseline will not keep them there. But then again if the housings are good and flat they should put ample pressure to hold the seals there.

vaseline does a great job of holding the water seals in



mike

So mike do you not use hylomar for the coolant seals then?



J

UH, Vaseline is good for lots of stuff..

I thought this might cause some debate. The Mazda factory manual says to use petroleum jelly on the water seals and doesn't mention Hylomar.



Since Hylomar never hardens I was wondering if it actually contributes to the sealing any once the engine has been heat cycled. I wondered if it might actually make the seals slide around in the grooves since it doesn't harden...



Also - has anyone ever heard of O-ringing the housings much like on a high compression piston engine? I would think a very small, rounded groove milled into both the rotor and side housings and then O-ringed with a copper wire would make a great barrier against heat getting to the actual coolant seal.



Jason

Hm, maybe . . . but there's very little room to put an o-ring, probably no more than 4mm, just going by memory. How big an o-ring would you propose?



J

ive never used hylomar.

mazda used to have metal water seal protectors, i think in the late 70's



mike

If you use the teflon seals, hylomar does NOT hold them in place, you have to use vaseline. I learnt this doing my rebuild.

I have both. I hate the sticky mess that Hylomar leaves behind, but I also don't like the fact that Vaseline makes the outer coolant seal (black colored one) stretch. Since I always use new engine gaskets for all my rebuilds, and my engines last quite some time, I use the petroleum jelly. On the race engines I use the Hylomar. Sometimes race engines popped before you expect it and Coolant seals are still fresh and re-usable..Hylomar is a mess I hate it..

you've prolly tried this, but have you tried something else on the outer water seal? like a dab of silicon to hold it in place?



mike

i like hylomar, i think mostly for the name https://www.nopistons.com/forums/pub...IR#>/bigok.gif

Yes Mike. Works great But I noticed the silicon expand and creep between the rotor housing and side housing every time the engine was heated pretty good (leaned a little for power) https://www.nopistons.com/forums/pub...#>/biggrin.png I kept peeling the silicon strips out the edge of the rotor housings but more kept popping out and growing like a Chia Pet..

In the past I have always used Hylomar on the inners and an extremely thin coat of grey silicone on the outers. I have never had a problem with the outer seals doing it that way.



But, I think this time I am going to try the vaseline on both. Here's a question - when you use vaseline on the outer do you leave it off near the areas where you pick up with silicone beacaust there is no gasket?

yup, you dont need the vaseline all the way around, just enough to hold the seal in



mike

True story I swear... One time I ran out of Vaseline and had some Vicks menthal rub laying around and I used the VICKS Menthol jelly. When the engine fired up, it smelled like the engine had a cold. Vicks smell everywhere when it melted.. https://www.nopistons.com/forums/pub...#>/biggrin.png

haha, thats great https://www.nopistons.com/forums/pub...IR#>/bigok.gif



mike

racing beat recommends hylomar. they've done this for just a little bit https://www.nopistons.com/forums/pub...>/rolleyes.gif so i think they know what the best tricks are. although when i built my motor dor my 1st gen, i used petroleum jelly.



maybe i'll try the vicks vapo-rub thing....that way when i fire up the bridge for the first time, people will smell it and think there is a mad duck with a cold under my hood https://www.nopistons.com/forums/pub...#>/biggrin.png wauk wauk wauk wauk wauk

I know it is mainly to hold the seal in place, but I think there is a secondary reason. It is fundamentally wrong to install any kind of rubber gasket or O-ring without lubricating it in some way. The vaseline, hylomar, and silicone all let the seal move with very little friction as the parts are clamped together. I guess in this particular application there is not a lot of moving, but I still feel better with some kind of lube on the entire seal.



Thanks for all the input!

Jason