Thermostat housing gasket leaking

[The motor guy]

So I changed the thermostat housing gasket on my boat, fired it up and this one is doing the same thing. The gasket looks like it absorbed the coolant and is now wet. The old one was just a tiny seep. I think it lost maybe 8 oz over 20hrs. I don't know what to do now..... I used some good thick gasket maker so I'm surprised. Maybe the cover is warped.

 

[ls1mike]

Engine type?

I had a warped housing a few times on my 1989 BBC. Replace the housing leaked stopped.

 

[Chris142]

Put the housing on something flat and see if its warped. If it is grind it in circles or file it till it's flat.

 

[The motor guy]

350 Chevy

 

[ls1mike]

Housing, they are cheap. Get one and try it out.

 

[928]

If you have one of those cheap mr gasket type chrome ones, throw it out & get a cast iron one.

 

[user52165]

Did you remove 100% of old gasket and residue?

 

[The motor guy]

Originally Posted by user52165
Did you remove 100% of old gasket and residue?


Yes

 

[Driz]

Some Mercruiser have a ground (of all things) via the gasket. That's why you need a marine, mercruiser or Sierra, not regular chevy car or homemade one. It screws up one of the sending units or gauges at least on mine unless you ground another way. Just so you know...‡.
Check the mating surfaces for square. Use a short ruler or straight edge to check flatness. If it's off and not cracked just sand it flat with a small block of 2x4 ect and some black 220 Wet n Dry sandpaper. It should true up fast.

 

[The motor guy]

I don't think it did. It was just a gasket, no metal or anything.

 

[jeepman3071]

Get a new thermostat housing, use a gasket with a thin layer of Permatex "right stuff" gasket maker on both sides. Wait about 30 min and make sure the bolts are torqued to spec. Also be sure the thermostat is sitting properly in the engine, I've seen a few sit crooked and cause a leak.

 

[wings&wheels]

Originally Posted by motor_oil_madman
I don't think it did. It was just a gasket, no metal or anything.

If you have a sender in the housing above the gasket, you need the marine gasket which has a metal button to provide a ground. If no sender in that location, you are OK. There are also a number of variants and revisions to that cooling system over the years to add confusion. I just went through this. seepage and all, on our old Century Resorter w/ the same motor. After talking to a few folks w/ experience, I finally settled on the Mercruiser gasket set w/ Permatex High Temperature RTV as a dressing. Unless your housing is really warped, some smoothing and this should be good.

What type of boat?

 

[The motor guy]

Well maybe it was a residual drop of coolant cause before it would leak a tad just sitting there dead cold.

 

[The motor guy]

Nope she leaks like a sive.

 

[The motor guy]

Gonna take a sanding block to it and get it flat. I haven't seen if it's warped, but it must be.

 

[The motor guy]

Is it possible the coolant leaks from the bolts on the housing?

 

[The motor guy]

Through the water jacket that is?

 

[mk378]

They should be blind holes. Drilling too deep to re-tap them would create a leak that is really only fixable by replacing the manifold.