Leaky thermostat housing bolt

[Rusty Dawg]

Any ideas on how to stop a leak around a thermostat housing bolt?  I am certain I'll get several suggestions.  I've already tried teflon tape, but still leaks....actually, it seems to be leaking more now.

[difrangia]

Thermo housing might have a crack in it. If so, could possibly be welded with nickel rod or brazed. It'd seem to me that it would be either cracked housing or gasket problem. If you end up with the housing in your hand, be sure to flat-sand or file the mating surface.

Edited May 11, 2021 by difrangia

[320 Newb]

How about a little water pump RTV?

[Stoffregen Motorsports]

Are those holes for the t-stat housing bolts blind? Or are they wet all the way through?

 

For coolant, I use Threebond 1211 sealer. It flows well, and is great around threads and even under flat washers.

 

Another way to seal at a bolt head or under a nut is to use AN washers. They are softer than regular washers and crush to for a seal. https://www.mcmaster.com/standard-washers/sealing-washers/metal-sealing-washers/?SrchEntryWebPart_InpBox=AN+washer

[banzai510(hainz)]

if one tried to pull the temp sender and it been in there for 50years the housing may crack as it has done for me. I try to leave them alongd beside just pulling the whole unit off the head.

 

I had one crack cause temp sender went bad. I bought a whole new housing and a new sender. Or run a spare part from another motors.

[Stoffregen Motorsports]

These motors have a housing on top of the cylinder head. Not like on an L series.

[difrangia]

25 minutes ago, Stoffregen Motorsports said:

These motors have a housing on top of the cylinder head. Not like on an L series.

 

Right, Matt. The sender is in the lower right front of the head. I can't remember if those three holes are blind or through into the water jacket but I believe blind.

 

[Stoffregen Motorsports]

On the 1275 Sprite, they are wet. I think...Dang it, now I can't remember...

[Rusty Dawg]

On 5/11/2021 at 9:01 AM, Stoffregen Motorsports said:

Are those holes for the t-stat housing bolts blind? Or are they wet all the way through?

 

For coolant, I use Threebond 1211 sealer. It flows well, and is great around threads and even under flat washers.

 

Another way to seal at a bolt head or under a nut is to use AN washers. They are softer than regular washers and crush to for a seal. https://www.mcmaster.com/standard-washers/sealing-washers/metal-sealing-washers/?SrchEntryWebPart_InpBox=AN+washer

Two out of three are wet.  Threebond 1211 sealer?  Never heard of it nor an AN washer, so I will give those a try.  

 

I am using the same housing from the older head that was cracked which was not leaking at the bolt, but now I have a head off of a different motor.  I used a thread chaser to clean the threads before assembly and it seemed good to go.  It did look as though one of the holes had a helicoil, but I couldn't tell for sure and I don't know if it was the one leaking.

 

Thanks for the suggestions.

[Stoffregen Motorsports]

Threebond 1211 is "2 stroke case sealer" and has been used by many mfgs over the years. It is impervious to gasoline too, which makes it an great all purpose sealer.

 

AN washers are also called crush washers.