[vertigto]

Nowadays...what brand are you having good results with when buying new?

Installed is a NOS Stant Superstat 180, but started having cooling issues (temp spikes idling/in stop-n-go traffic) on a newish build. Fan clutch seems to be operating correctly, lower radiator hose doesn't seem to be collapsing. I have the lower rad hose spring to install, but thought I would start with the thermostat to avoid draining. Timing might be off slightly, but don't think that's the issue.

Thinking about starting with the thermostat, but have no idea what brand is best now. Can't find another Stant. Reviews on Motorad don't seem as good. Napa Gold? AC Delco? Something else? I've read about drilling small holes in the flange, but have yet to see a good pic.

While we are on the subject...is Hylomar or Gasgacinch the 'go to' for sealant?

Any recommendations/tips would be greatly appreciated.

[camerjeff]

I have had good luck with Robert Shaw High Flow thermostat's even the couple I have used after Flowcooler bought the company

[78w72]

Ive used stant from rock auto on a few Pontiacs with great results... have used the robertshaw high flows in the past and had one freeze up for some reason, the stants have been great for 10-15+ years in my current cars.

For a stock T stat housing/gasket, i just use a thin layer of ultra black or grey RTV, but I prefer the chrome O-ring housings I have been using for as long or longer than mentioned for the stant thermostats, they seal great in my experience on stock iron or aftermarket aum intakes, have removed & installed 2 or 3 times using same Oring, if/when it needs repalced its easy to just buy a new O-ring. Some dont like them but using name brand or even summit house brand, they seal great for me.

[burd]

Delco 160°

[67Lemons]

I like the MotoRad Ultra Stat, I sold them for a few years and they were always quality.

https://www.summitracing.com/parts/SNN-5200-180

[burd]

More important is the rad cap.

[vertigto]

Additional info…

- Cold Case radiator
- GMP high flow WP (aluminum body/cast impeller - clearanced)
- stock shroud, fan/clutch

[Mario64]

just out of curiosity, do you guys drill a hole, or holes in the thermostat disc when installing a new one?
thanks,
mario64

[78w72]

Never have or had to drill a hole in a T stat. The stant and most other brands come with a small vent opening, some come with a jiggle valve that does the same thing, bleeds air out of the block.

[Squidward]

I drilled 6 holes in the body of the stat I have in now. My testing basically pointed at the small radiator in a 1st gen caused poor cooling, which doesn't exist so much in an A body like yours. I found a big difference between stat and no stat, so it showed my standard tstat was restricting flow too much.

A high flow tstat means that you have more surface area when open, and it doesn't require opening so far to maintain program temp.

Arizona is unforgiving in the summer. Hopefully you have friendlier ambient temps.

[68 Firebird]

I think I have run every type and temp rated stat there is.
Humbly found my car like NOS AC Delco 170 degree stat.
It does have a small notch to bleed out air when refilling
system.

Gerry

[Mario64]

thanks all for the replies. different strokes for different thermostats...
mario64

[HWYSTR455]

The intake to timing cover passage bleeds air out, no need to drill holes.

Believe stats that come with a valve is so they cross to diff apps.



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[Skip Fix]

AC Delco.

[76TA462]

I changed to the Mr. Gasket 160°F High-Flow Thermostat (MRG4363) with noticeable improved results.

[vertigto]

So...I've read too much online. Some say to absolutely drill a hole(s) and some not. Also read not to use sealant (not just when using o rings), most say to use a thin coat of gray RTV on the housing side, and a few say both sides depending on mounting surface condition.

When I can finally get to this, I think I'll forego any additional holes and use one thin coat to be safe and hold the gasket in place. Preferably a high flow thermostat.

[HWYSTR455]

If both surfaces are square, I usually only put sealant on the housing side. That allows you to be able to remove the house/gasket and swap a stat without having to use another gasket.

I prefer the thick fiber-type gaskets too, not the thin paper ones.


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[vertigto]

After some more investigation/testing...turns out the thermostat is not the issue. When I pulled the radiator cap, no coolant to be seen. Took a gallon+ (@ 5qts) to bring it back up to about an inch from the top. Drained the oil pan and didn't appear to be milky looking like coolant mixed in or any separate liquid (see pic). It was a bit dirty, but that's a different story. Couldn't get the oil filter off cold with a filter wrench, so will be trying again when I run another heat cycle. No apparent exhaust signs either.



Put in some new oil and took it for probably a 30 mile drive in traffic and out and stayed perfectly cool. Let it cool a few hours and checked the radiator...maybe a 3/8" lower, but not much. No noticeable coolant smell (but my sense of smell is bad), no wetness on passenger floor (i.e. heater core) and no visible leaks on the ground either. That has always been the case.

Background...new build/restoration, maybe 2-3K miles since. Looking back, seems like the cooling issue became more apparent over time. Small leak somewhere? Head gasket? Should have checked the coolant awhile back, but no odor and initially chalked it up to Pontiac cooling issues. Also, first oil change (by me), the shop did the first two after break-in and 1K and didn't notice anything.

I plan on taking it for another ride/heat cycle to see what happens with the coolant and to hopefully get the old oil filter off (if that doesn't work, not sure what to do). Any ideas on either issue?

[vertigto]

Update...the car has not moved since my last post and coolant has vanished from the radiator (can't see anything with the cap off) and no apparent leaks that I can find. Is it save to assume this is a head gasket issue?

I really don't want to have to tear apart this newly rebuilt motor.

[HWYSTR455]

If it's a head gasket, and it's leaking while it sat, you would see it in the oil.

If it's not in the oil and leaking while it sat, you would see puddles under the car.

Are you sure it was topped off properly? if you topped it off when it was cold, and didn't start it for a brief time and check it, it could have just not filled all the passages.

Fill it, put the cap on, start it, and let it run for about 2 min and shut it off. Release the psi on the cap and pull the cap, see where the level is then, top it off if it's low. Do that a couple times until you don't have to add any and drive it again.

If in fact it is a head gasket, it could fill cyls and hydrolock during an attempted start, but still think it would seep past the rings sitting and not running.

Does it have a overflow tank?


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