First off, don't tell me to search. There's too much vague, irrelevant and contradictory information - as you can see I have searched.

I need to reseal the water pump housing and water pump.

As these are machined surfaces, is a gasket required?

I don't want to take this apart again...

Also, some may object that Hylomar should not be used if RTV has previously been used. The data sheet that mentions this is not referring to Hylomar Universal Blue in this case:

http://www.hylomar.com/index.php?opt...=90&Itemid=107

So, I'm off to pick up my tube of Hylomar Universal Blue - just need to know if it should be backed up with gaskets.

 

Hylomar is a non-hardening sealant. I wouldn't use it in that application.

The water pump housing to block has a gasket. If you use the gasket, there's also some thin shims on the studs that the water passages aren't by that must be used, the shims compensate for the thickness of the gasket.

Water pump to housing I usually just just RTV.

On my engines I use grey RTV almost exclusively, it seals wonderfully, is easy to work with, and even smells decent. For the water pump gasket, coat the gasket with a thin coat of RTV and make sure both gasket surfaces are clean and true and you're fine. Give the RTV some time to cure, fill with water, done.

The thermostat has a rubber O-ring of sorts that goes around it, that ring seals perfectly, no RTV needed there. RTV can actually cause a point of failure if used on that ring.

Dale

 

For what requires a gasket, I only use the Hylomar with no gasket (IE: oil pan), unless that gasket is metal (IE: the front cover).

If it is an o-ring, I use Hylomar in addition to the o-ring as a dressing and to hold it in place (IE: oil pedestal, water seals, ect...)

 

Thanks for the info Davin.

What kind of success have you had? Any leaks due to using Hylomar without a gasket?

 

Why not?
This is exactly the kind of application it is recommended for.

Here's why I think my water pump housing developed a leak.

Three years ago I replaced the water pump. The act of removing the water pump caused enough movement in the housing to damage the gasket ( which also had grey RTV), leading me to removing more parts from the motor this winter than I had planned on. (I discovered the leak in the housing when removing the lower alternator bracket bolt)

Had it been sealed with Hylomar, the housing would have just sealed up fine when the new water pump was installed.

Just trying to separate fact from fiction and personal preferences here.

If the stuff works, I want to use it. If it doesn't, then I don't want to use it.

 

Mazda recommends RTV sealant for those surfaces. That's what I use. I've used grey RTV on water pumps and housings for 15 years now and have built about 30-40 engines like that. Never had a leaking water pump.

This is not a job I'd want to try something different to fix a problem that doesn't exist.

The rear water pump housing to engine seal quite possibly would have leaked with Hylomar as well. With the seal broken you have water going in between the gasket surfaces and contaminating the seal. I feel that most anything there would have ended up leaking in the end.

Also, FD water pumps VERY rarely fail. It's not logical to try something different to reduce the probability of a leak in 150,000 miles when the new water pump goes. Seal it up right and you'll likely be doing major engine work before doing anything with the water pump.

Dale

 

Maybe it would have leaked, maybe it wouldn't - I don't know that for a fact, which is why I started this thread. There's a lot of talk about Hylomar on this forum, and it is nearly all subjective.

I do value your opinion however, don't get me wrong. I will probably just use the RTV, as I don't feel like experimenting with Hylomar when there is not enough hard experience with it in this forum. ( kind of ironic, considering how long Hylomar has been around - longer than the FD )

When using grey RTV (I have The Right Stuff for Imports as well) do you think it necessary to use a gasket for these components? It seems to me the gasket is likely the weak spot in the seal.

The pump didn't fail, it was replaced with a Mazmart Remedy pump - this is a race only car. Who knows why or when I may need to pull it apart again. The fewer components I have to remove, the better.

 

I use both RTV and gasket. That's just me

 

I have had good success with it with no issues since it works best with metal to metal surfaces and a good addition to o-rings since it aids in holding it in place. However, Dale Clark is more knowledgeable and I would listen to him over me.

 

Davin>Dale Clark any day of the week

 

I have been using Hylomar HPF for over 10 years now and love the stuff. You want the surfaces to be clean and use the gasket. Just take a dab of the stuff in your fingers and lightly coat both sides of the gasket and install.

In all of my customers cars I have yet to see a leak, and love the ease the gasket comes off, if for some event you have to tear back into it again.

 

Hylomar is fine, especially for things that are or might be periodically disassembled.

What I have traditionally done for all engines is attach the gasket to the pump or front cover with a contact cement (e.g., Gasgacinch) and grease the other side. Comes off clean and easy every time and no leaks. Using Hylomar on one side rather than grease accomplishes the same thing and is likely to seal better against a marginal surface.

RTV works fine as well, but use it sparingly as a little goes a long way. It's a bit more permanent--and is a pain to cleanup if you anticipate needing to disassemble the piece.

 

I would use rtv where mazda says to use it. Hylomar sealent isnt some kind of magic sealent. You can get an equivilant from wurth called dp300. I use this non hardening sealent on things that have a tendancy to change their shape or size from what ever it be. Normally temperature or age. Something like the half moon that seals the cut out on the end of a piston motors head. Or to hold something in place (the coolant o-rings that sit between our rotor housings and irons). I would never use it for a metal to metal seal. There is flange sealent for that. Something that hylomar is not is flange sealent. I know these things because i used to be a factory trained audi mechanic. And if there is one car that i have come across that leaks more oil from everywhere than a rotary, its an audi.

 

I have used only the OEM gasket multiple times with no issues. If I had to add something, it would always be HondaBond. It's my favorite.

 

Since this thread is on the subject kind of, what do you guys use on the intake gaskets and the elbow o-ring to stay in place?

Thinking of using something like this Permatex/3 oz. (85 g.) tube Ultra Copper maximum temperature RTV silicone gasket maker (81878) | RTV Adhesive | AutoZone.com

or this

Permatex/9 oz. aerosol can Copper Spray-A-Gasket hi-temp adhesive sealant (80697) | Gasket Sealant | AutoZone.com

Also would either of these allow me to reuse a gasket? I have gaskets for LIM and UIM but forgot to get one for TB. My gasket appears to be in good shape still. Also is Turbos to downpipe gasket reuseable? Sorry for thread jack.

 

I use only the OEM gasket in the manifolds, as Mazda did. I use a few small touches of HondaBond on the TB. Honestly, just about anything will work with the TB gasket as it's really there to hold it in place.

 

Should just a used TB gasket work fine without anything on it?

 

for reference, Hylomar is basically a material you would use to hold materials in place that may fall or slip during assembly. it will move and wash away or dry out in certain areas, etc.

no it isn't a sealant for a water pump, solely.

additionally, not all hylomar sealants are created equally. some may work for various applications where a different blend will give less than adequate results so i just use it for a retainer.

 

They are a few dollars for a new one from Ray.... Get a new one.

Typically they can be re-used. But like any gasket, as it begins to age, it collapses and deteriorates removing much of its sealing capacity.

 

Few bucks? Lol I wish. Last I check TB gasket was 20 bucks+10 bucks shipping hahaha. Ill get it after I finish up a few things, I'm going to try to make the list I have to buy from him grow so it'll be worth it.

 

Didn't you know that a "few" in the FD world means 20. Btw, a "good deal" means you got it for under $1k.

 

if you can save a few bucks why not and put that money where it counts?

mazda o-rings are notoriously overpriced and barely adequate. i used to use only OEM parts, then i used the gaskets and seals direct from the manufacturer mazda gets them from then i pitched it all out the window and spent a few days measuring and ordering various sizes to see what works.

that said please don't inundate my inbox asking what and where i get them, some information i just don't give out freely. most of the info is actually already on this forum in various places.

 

Just repaired a leak on my water pump housing. Just used oem gasket and rtv sealant. Sealed up fine.

 

I L-O-V-E Hylomar and have been using it for around 11 years on my rotaries, but even so I have found it isn't good for everything.

As OP said it is made for sealing close tolerance machined surface with high torque load (close spaced bolts) relative to the pressure of the fluid to be contained.

In areas like waterpump where there are relatively few fastners I use Hylomar with stock cloth fiber gaskets and then the stock gaskets can be used over and over. The gasket will become permeated with Hylomar after several applications.

If you use Hylomar alone in such a spot there is a chance for momentary distortion with heat/torque in operation and a gap will open and the Hylomar will be washed out and start to leak even when the surfaces come back to true.

Taking torque off the joint (partial disassembly) will also most likely create a leak with Hylomar alone as it is squeezed to a very thin film when assembled. Take it apart and that film sticks to one side or the other or both and you get displacement of the super thin film of Hylomar you had.

 

Something new I am trying is making Viton sheet gaskets (high durometer) instead of the stock metal FD intake gaskets so I can use them over. So far its working great.

I tried cheaper (unreinforced) silicone sheet gaskets and it was too soft and distorted when torqued down.