Water Leak on my thermostat housing of my 240z

[jalexquijano]

just removed the thermostat on my 240z, cleaned it, cleaned and sanded the thermostat cover thus removing all dirt and grime. once reinstalled with new thermostat cover gasket and tightened the bolts took the car for a drive and noticed there is a small wáter leak. Is this normal? I am also looking for a 71 C (160 F) original nissan oem thermostat but havent had any luck yet. Mine is 76.5 C thermostat (Tropical weather). Any clues on how to prevent the wáter leak? should i also sand the housing?

[datzenmike]

The top of the thermostat you can sand on a sheet of glass covered with sandpaper. This will flatten and true it up. The housing you may have to unbolt from the head to do this. 

[jalexquijano]

so i need to sand both surfaces and clean them out completely before installing another new gasket and thermostat? Where do i get an original oem 71°C (160°F) nissan thermostat for my 240z?

[Draker]

I would use a gasket and a light skim coat of RTV to fill any imperfections.

[datzenmike]

I cut my own gaskets. Take a look on the housing and cover surfaces for erosion. No idea on the 160F.... most of the manuals show 170F for tropical. Doesn't have to be a Nissan one.

[banzai510(hainz)]

I scrap it and use another gasket  and or add a slight thin film of rtv.TRY ANOTHER BRAND OF GASKET

 

If still leaks  maybe you cracked the state housing. I did this when removing the temp sender hex nut.

[racerx]

Not normal for it to leak.  Don't use a grinder if you sand, it will cause uneven spots.  As long as you take off the old gasket and or sealer you should be good to go.  Did you try tightening it a bit?  If it was not leaking before, then it should not leak.

[Ranman72]

clean the groove the thermostat sits in and clean both surfaces 

i always use permatex b in water applications it is a thin pasty brown sealant and it works great 

[jalexquijano]

i found another new gasket in my deposit. Will remove the used gasket and install a new one. Which permatex high temp do you recommend as extra sealant besides of the gasket.

[racerx]

you can, as long as the brand says okay for water and usually it will say good for water pump.

[MikeRL411]

I use Permatex Aviation form a Gasket number 1.  It is non drying and of a pasty texture ideal for sealing not perfect mating surfaces.  Water, fuel etc compatible.  Apply to block and thermostat housing surfaces, sandwiching the gasket.  Advice to clean up the seating groove is right on target.

[Stoffregen Motorsports]

I'm a purist and I would just surface both gasket surfaces and then use Gasgacinch on the gasket. If you want to use RTV, you should still make sure the surfaces are straight and clean.

 

Today's RTV selection is pretty impressive. Plenty of new engines don't even use gaskets anymore.

 

For oil applications I use "The Right Stuff" brand black RTV.

 

If I don't want to see the black (like on a front engine cover), I use grey RTV.

 

For exhaust I use the high temp orange RTV.

 

For water, "Threebond" brand  "liquid silicone gasket" (1211) is my pick, but most of the others will work just fine.

[jalexquijano]

just cleaned sanded the housing, installed new gasket and new stainless Steel set of screws. No more leaks. I also installed a 160F thermostat to keep the temp down.