Why do I even bother!!!! Grrrr!

[Wish]

Trying hard to save a few bucks by doing my own mechanics work. Well, once again I should have come here FIRST and asked how.

 

GT-40 needed a new thermostatic housing gasket. How hard can that be. Decided to make my own (possible error there). Went to auto parts place, told them what I was doing and they supplied me with a sheet of appropriate gasket material (possible second error). Removed thermostat, scraped off old gasket material and pressed the new sheet on housing to get an impression to cut out pattern (that worked well actually). Put new gasket in, set thermostat in and placed top of housing on. Tightened the two alen bolts. Done!!....until I started the boat and watched is leak. Lots of leaks around the gasket. So, tightened more. Better. Still leaked. So removed housing, checked, all good with gasket alignment, and reassembled, applied some bolt lube and tightened. Much better but now down to one drop every 5 seconds. Ran the boat for 10mn or so up to temp and still drips every 5 seconds off the backside of housing. Drips into a pocket on the engine block making a little puddle. That cant be good. Soooooooo gonna ask here first before being Joe Mechanic. I've saved time and $$$ here. Thank you BOS.

 

Suggestions, thoughts ideas for my slow leak.?

 

[BraceMaker]

Couldn't the autoparts store get you the correct gasket? - If not I would try to get it, or cut a new one.

 

Install with this:

 

http://www.hardwarestore.com/media/product/613357_front500.jpg

[DW]

Don't panic quite yet. Run the boat a few more times before you decide to try a repair. The gasket might swell up a bit and seal itself. I have had that very thing occur for me. If it does not seal itself, then go for either some grease on the gasket surface of some gasket compound or RTV to seal up the area. Be very careful not to either snap the bolts or strip the threads, that will become a much more involved project.

[Horton]

@Wish listen to @DW

I happen to know he knows what the heck he is talking about.

[ScaredOfCorbets]

I'm just curious on why you didn't just buy something like this:

http://www.skidim.com/prodinfo.asp?number=RM0003 for $1.67,

and install it with a very thin gasket sealer.

 

I don't think you need to crank on the housing bolts. As mentioned previously, you don't want to deal with a snapped bolt.

[Waternut]

I was actually expecting that story to end with a stripped manifold. I did this same thing last summer when I swapped heads. The fancy new gaskets weren't good enough for my corroded housing. I bought the thick cork gasket material first and it still sprayed. I added copper sealant (had some readily available) to both sides of the gasket and housings, let it set up, and then squashed it all down. If the gasket doesn't swell and seal like @DW says, go this route.

[Wish]

@Horton I know..... I've listened to him many times with my mechanical questions. Top knotch knowledge to say the least. @BraceMaker how is that product used/applied...thanks. @DW grease...really? Interesting. What kind? Application? Also application of gasket compound or RTV? I'm sure it's easy and simple but so was putting in a new gasket. Not. So I'm asking first this time. Thanks guys ... Very much appreciated.

[Horton]

@Wish funny how a race engineer would know anything about engines

[jerseydave]

sand both mating surfaces with sandpaper, use copper permatex on the correct gasket or thick gasket paper (I always get the proper gasket)

[BraceMaker]

@wish - you just brush a thin coat onto the gasket.

 

All the recommended products work fine, depends what sort of wrenching you like doing. Growing up I was around a lot of old american engines, those folks liked Indian Head, the BMW motorcycle types used hylomar. Yamabond is popular with most.

 

My opinion is that properly made and installed and torqued a gasket should not leak. But since they often do, something is amiss. Usually in my world it is when I go to assemble I displace the gasket, which then kinks or otherwise does not get into the right place before being torqued.

 

For that I like High tack, which keeps things in place till they are torqued - but relies on a perfect sealing surface.

http://www.chrome-addiction.com/prodimages/permatex_59-9190.jpg

 

The other sealants are more of gasket makers, and do seal imperfections.

 

Again perfect world, assembled with the gasket things wouldn't leak. My world, I dont' want to redo my own work due to stupidity, this is all just a hobby.

[eleeski]

Accept the caveats about never listening to me. I never buy gaskets.

 

I apply high temp RTV silicone seal liberally to both sides and let it dry for a few minutes. Let it skin over but not cure all the way through. Assemble the parts and torque to the proper spec. Gasketless repair! I've done too many of these.

 

Paper bags make good homemade gaskets. Coat both parts and both sides of the paper gasket and let everything skin over and assemble properly. I've done a few of these.

 

OK, actually I like to use stock gaskets. But a coating of silicone makes the stock gaskets avoid @Wish 's problem. Old engine parts don't always fit properly and need help to seal. Silicone is a great seal and fills lots of imperfections. Much better than an overtorque.

 

Eric

[BraceMaker]

I almost never recommend removing gaskets. Sometimes - not always - it can create clearance issues between parts, or change in function, in this case maybe not, but the housing is probably machined for the thermostat to fit with the gasket in place.

[Waternut]

The gasket spray works well but it's only designed to pick up very minor imperfections like 0.002"-0.003" or less. The standard gaskets like skidim or the auto parts store sells also require the parts to be in good condition. The biggest problem we face is corrosion on these cooling related parts. Water slowly soaks the gaskets over many years and then the water just sits on the mating surfaces and they corrode like crazy. Then you run the engine and the heats accelerates the corrosion even further to the point where we have two mating surfaces that are about as smooth as carpet. If you don't have the tools to shave them smooth again, you're kind of forced to use some kind of sealant.

 

Just for future reference... Silicone is fine for water related sealing but if you want to seal anything that fuel might come in contact with, you need to use something else because the fuel will break silicone down.

[estrom]

Permatex makes a blue sealant that comes in a tube. Just squeeze some on the gasket and spread it around with your finger. Done deal. I do this on any thermostat/water pump gaskets and it works great.

 

[DW]

@Wish: I usually use the blue RTV (cheap and easy to find) on one side and a coating of either wheel bearing grease or white lithium grease on the other side. That way, when you want to take it back apart because you need to change the tstat, it comes apart easily. Both sides covered with the sticky stuff requires more muscle and chiseling to get things apart and smoothed out and usually tears the gasket apart.

 

One thing you might do if it seems to be more stubborn than you expect is to check flatness by laying a steel rule across both the tstat and housing face. Should be flat but when you torque the tstat bolts a few times, the housing will tend to bow. You can fix with a belt sander if you are careful, or take to a shop to have them skin it flat.

[XR6Hurricane]

I'm a fan of the Indian Head and also the High Tack, but for that application I would probably lean toward the Indian Head. It can be tough to clean off and re-prep the gasket surfaces the next time you have it apart though because it really hardens up. The blue sealant that @estrom is referring to is Hylomar HPF, I don't know if they make it anymore but it is awesome. It stays gooey instead of hardening. I've used that around the spaghetti seal when assembling old OMC two-piece lower units.

 

What @DW said about running it a little bit first - true also. I had a pinhole leak on a thermostat housing on an outboard once because the gasket was reused. A few runs in the silty river and brackish water lake plugged it up.

[BraceMaker]

@dw - depending on how it sits - I've had good luck with small squares of plate glass and various adhesive abrasive sheets.

 

I got the glass from my local glass/mirror shop. You can start with agressive wet sand paper, then move down in grit, and end with lapping compounds, can be done while assembled.

[RichardDoane]

scrape both parts clean with a fresh razor blade, use a permetex product called "right stuff", it's the thickest and best RTV silicone on the market, assemble with an even layer on one side and torque to specs, give it a few minutes to cure and you're done, no gasket required.

[Waternut]

@Bracemaker I've done this and it works well but can be time consuming. Switch directions 90 degrees every now and then too. If doing assembled, I recommend putting a rag down inside the manifold. Probably not a big deal since it's just a water cavity but I prefer knowing that the metal bits aren't messing anything up.

[estrom]

The blue tube of Permatex RTV silicone can be had at any auto parts store, probably even Walmart. Simple and effective.