Thermostat blown into housing
 

Anyone seen this before? Couldn’t figure out why my 400 wouldn’t come up to temp as I replaced the thermostat with a superstant 2 years ago. Found it jammed in the housing to the point I can’t push it out. Would have to pry on it to get it out it’s that stuck!

Never seen that before and I will take a guess that’s it’s due to that stat housing since I have used those stats before with no issue, that is unless something has changed with them.

Crazy part is all the edges are bent back, how could there be that much pressure in the water crossover to push it that hard to bend it and shove it into the housing?

Did this just happen?

Freezing could do that if you did not have enough antifreeze mix.

No freezing in Vegas lol, honestly it could have been like this for a while. Have always had issues with it not liking to stay at temp unless it’s hot out but I have tried multiple thermostats. Best guess is the crossover is machined wrong. I kinda remember when I first got it (over a decade ago) it had issues sealing housings with a gasket but o ring types worked perfectly.

I guess it boggles my mind the stat could be that loose it would shove it into the housing. That flow kooler must have some real ass behind it.

New crossover ordered from Kauffman.

Since it is not a stock water outlet, could the ID be too large? If the t-stat was not centered there may not have been any support on the one side that blew in to the water outlet. I would guess that at a high RPM with the t-stat closed there would be plenty of pressure against the stat. Possibly newer stats are made with thinner and softer material. That could aggravate such a condition.

When I was wrenching for Mother Mopar,I seen alot of t-stats let go on one side of the bridge that the center pin sits in. My thinking was the way it was made wasn't strong enough to contain the spring pressure.

On your deal I think the t-stat housing didn't provide enough overhang to keep the stat in place. I could see a overheat situation, the pounding action of the water that sometimes occures, doing what you have.

John

Makes sense. Ordered a Robertshaw, a billet housing, and a crossover, not worth risking a motor so replace it all.

That housing is gonna live on bench for a while. That’s an impressive amount of force

Yeah. Happened to me on my 67. That 60 year old GM t stat housing had enough corrosion over the years so that the thermostat could inject itself into the housing. I was having wacky coolant behavior and discovered it.

https://youtu.be/FHUtY2uQkkY

Had something similar happen to my GTO: it blew the center LH block freeze plug near the end of a 1/4 mile. That takes a huge amount of pressure as well. Bart may remember that day.

My engine is a 428 with aluminum heads. Originally assembled it with a standard thermostat, plus the coolant circuit which ties the water cross-over to the pump housing was blocked, and I only took water off the RH head to the heater core.

Best I can figure out, the water boiled in at least the LH head since there was zero water movement there with the thermostat closed. Aluminum conducts heat much better than iron.

Since the freeze plug blow-out, I added a water outlet to the LH head and tied that together with the RH one to at least get some water to flow when the T-stat is closed. Also added a couple of holes in the T-stat ring such that water can bypass a bit as well.

After doing those things, never had another problem.

Not a bad idea, on a side note is it normal for the thermostat to have this much movement. Seems like the o ring water necks don’t keep pressure on the thermostat like a gasket would.

https://youtube.com/shorts/zrISIHkJh...m8QiM0Q2qea167

Ironically on yesterdays episode of Vice Grip Garage on YouTube, the exact same thing happened to Derek's Monte Carlo. What are the chances of that! It looks like he may have the same thermostat with oring too if that's a clue. Its at 19 minutes into the video.

Why’s everyone gotta be a copy cat 🤣

Figured I would update this thread with some additional information. I measured a factory housing at 1.905” and a Mr Gasket 2667 housing at 2.015” so the thermostats are not the issue here. With ~0.11” extra diameter on the o-ring housings and water hammer, it looks like a bashed in thermostat is the end result not the cause.

Looks like the o-ring housings are junk and not designed for a Pontiac. Likely they all come from the same factory in Shinaland too.