Thermostat housing leaks—cause?

[Soylent]

Getting hot out here. Truck is running without overheating or boiling over. Hits about 220 in traffic. I popped the hood and noticed dried coolant around the housing bracket and some spray on the valve cover. Realized that my radiator cap is 20 pounds? Is this likely the issue? I changed it last night to a 13 lb. T-stat is the 190 from WH.

Motor details in my sig. The T-stat is new but sat for a few years before motor was first started. I also have a 5 blade fan. Radiator I assume is the stock 1969 for a V8 but it does look thin.

 

[gnpenning]

You need a clean FLAT surface for a proper seal. Most get it clean but few verify if it is flat.


Do you have a fan shroud, if so how much or the fan is inside?

Do you have any obstructions in front of the radiator, if so what?

How well sealed is the area around the radiator allowing air to go around the radiator and not through it.

 

[Soylent]

Yes, shroud from WH. Doesn’t look like fan goes very deep and pitch of blades quite flat. Perhaps I should do the 7 blade from Tom’s and space it 2/3rds in?

 

[joebronco73]

You need a clean FLAT surface for a proper seal. Most get it clean but few verify if it is flat.

Exactly this. Also, that radiator does appear to be stock size.

Just asking for the sake of diagnosis: what makes you certain this is coolant spraying?

 

[Broncobowsher]

Is that a chrome thermostat housing?
I've fought issues that I think were finally narrowed down to the groove in the housing that the thermostat is supposed to sit in not being deep enough. The thermostat bottoms out and the paper won't compress enough to be solid.

 

[gnpenning]

That shroud probably works fine for most applications but you may need more fan in the shroud. What was your coolant level when the temperature went to 220? Do you have a temp gun so you can verify the gauge reading.

Have you done any other work recently?

Sealing the edges to force as much air as you can through the radiator is a plus.

When is the last time you had the radiator and heater core flushed?

What happens when the temperature is rising and you turn in the heater and fan?

 

[Soylent]

Exactly this. Also, that radiator does appear to be stock size.

Just asking for the sake of diagnosis: what makes you certain this is coolant spraying?

Smells like it and there was a little puddle under the housing in one of the recesses of the intake manifold.

 

[Soylent]

Is that a chrome thermostat housing?
I've fought issues that I think were finally narrowed down to the groove in the housing that the thermostat is supposed to sit in not being deep enough. The thermostat bottoms out and the paper won't compress enough to be solid.

It does look shiny near that clamb but it is plain aluminum like the intake manifold.

 

[Steve83]

That's a sorry excuse for a fan shroud - it's more of a blade guard to keep your fingers out than for airflow, which is its real purpose.

Those spots on the valve cover are splash from the belt when you drive in rain or puddles. They have nothing to do with the t'stat gasket. Is it a modern self-adhesive gasket, or just plain paper? Did you apply any sealant to the gasket? I recommend shellac around all coolant connections, including hoses.

https://www.amazon.com/dp/B0008KLOG6/?tag=classicbroncos-20

 

[Oldtimer]

. . .there was a little puddle under the housing in one of the recesses of the intake manifold.

When mine puddled like that, I had to tighten the water pump mounting bolts.
Finally pulled the pump and replaced gasket between pump & back plate, and the gasket between plate and timing chain cover.