Finally got around to reinstalling the radiator, putting new hoses on, and so forth on the '73 Custom Cruiser I bought about a month ago. We actually had a day today where the temperature got into the upper 40s.

Anyway, no problems on the radiator reinstall nor the hoses, but I did run into a problem replacing the water outlet valve where the thermostat is. There was nothing wrong with either the outlet valve or the thermostat as far as I know, but I figured what the heck, I'm replacing everything else anyway, so why not spring for a new valve and thermostat. Not that much money, and the new valve would look better than the old one.

My problem is that the new valve and gasket leak. I've taken a photo of the old valve and the gasket that came with the new one. If you ask me, this is a design that's destined to leak as there is no pull on the front part of the gasket with there being only two screws holding everything down, and they're on each side. You can see pieces of the old gasket adhering to the old valve.



My question is, can I/should use a silicone gasket sealant instead of this gasket? Should I use the sealant AND this gasket? With this gasket alone, I get a leak no matter how evenly and snugly I tighten the bolts.

I bought a tube of silicon gasket material that says it's for thermostat housings and waterpumps, so it seems appropriate. What do people typically do? And yes, I have cleaned the old gasket material off of the mating surface as darned best I can, but it still leaks.


Another question, while I'm at it, concerns the thermostat itself. The old one has a label on it that says "toward radiator" to help you install it in the proper orientation. The service manual mentions, too, about making sure the thermostat is installed facing the right way.

The new one, which is a Duralast brand from Autozone, does not have any marking on it directing you to install it a certain way. Does it not matter with aftermarket thermostats? Should I just quit horsing around and put the old one in?


Thanks.

 

I would use the gasket and sealant both. I'm not sure about the thermostat I looked up the Duralast on online and the design looks different from the one that would have been in the car. I would want to put a new thermostat in the car. It looks to me that the Duralast one it doesn't matter the orientation with it.

 

Clean both services thermostat housing and intake with sandpaper if possible (as nasty as that looks). And like 70C/S stated both gasket and sealer (blue RTV will work) and put it on both sides of the gasket. The thermostat goes on the intake, then the gasket, then the housing.

 

There is a little step down seat on the intake surface that the thermostat sits it to give it clearance from the housing. Make sure it is cleaned so that there is the proper clearance. The thermostat must face in the proper direction so that the hot water in the engine will open it. If it is upsidedown, the radiator water will keep it closed. Compare the old and new and it should be obvious which way it goes. The larger side goes inside the intake manifold. If you have doubts, hold the one side in a pan of hot water to make sure it opens. Just a light coating of sealant is all that should be necessary. Be sure to put sealant on the bolt threads to prevent leaks there.

 

When Jaunty was talking about orientation he wasn't talking about right side up. He was talking about the way it is turned. The old thermostat has on it "towards radiator" which has to do with the orientation of the bridge in relationship with flow of water. The Duralast brand has a different design bridge if the one he bought is like the one I saw on online. So as far as I can tell it doesn't matter the orientation. Just my two cents.

 

Yes, Cutlass S is exactly right. It's easy to tell upside down from rightside up as the water valve will not fit over the thermostat if it is installed upside down.

What I'm talking about is how it is rotated in the plane. As Cutlass S says, there is inscribed on the old one "toward radiator". The new one, which does look different in design, has no such marking.

Here's some more photos. The first two are of the old and new thermostats, one from the top and the other from the bottom. They are a bit different in design. The old one is a "Stant" brand. The new one is a Duralast.

The third photo shows that "toward radiator" marking on the old one. It's difficult to see. There's also an arrow pointing up between the words.








I think I will do what several of you have suggested and put the sealant on both sides of the gasket. In looking at the old water valve more closely, it looks as if the old gasket was stuck on and not just clamped between the pieces as it was darn hard to scrape off, harder than it should have been if adhesive had not been used.

 

Another thing I noticed is that the old thermostat is rated at 180 degrees while the new one is 195. When I bought the new one, the Autozone parts guy looked it up in their system, and 195 is the original specification. The service manual doesn't say which one to use. It only says don't use one rated above 195. So I'm guessing I'm OK with the 195 degree thermostat.

Somebody please tell me if I'm wrong!

 

I went on two different sites and both had 195 degree as OEM for the car.

You can use a drill with a wire wheel with the thermostat housing in a vise to clean it. Just don't tighten the vise too tight. Just enough to hold it.

 

i am using 180. modern cars go as high as 220. I have a 4 core, clutch fan, and 180.

 

Thanks. I actually bought a new water valve, so that has no crud on it at all. I took a wire brush to the mating surface on the block. Like I said, it isn't exactly as smooth as a baby's bottom even after I got done working on it. I'm kind-a hopin' that what I've done plus the new gasket and sealant will be enough.

 

I have (or had) the same thing. Four-core radiator, clutch on the fan, and 180 thermostat. Now I'm going to 195, which the service manual indicats is ok and which seems to be the OEM specification according to Autozone and whatever sites Cutlass S looked at. The manual warns against going above 195.

 

It should be fine. Yeah I forgot you said that you bought a new water valve.

Its hard to get them perfectly smooth that's what the sealant is for.

 

A bit of advice when changing t-stats.

be sure ALL coolant is removed from the bolt holes. any fluid in the holes can crack the manifold when the bolts are tightened!

my old's radiator has only one core. that core happens to have 3 rows of cooling tubes.

 

good for you.

 

Thanks for the tip.

 

I have a habit of sanding these on a flat concrete surface before reinstalling. I used 400 grit I think... I have part of a cinderblock i reserve for this chore that I have verified its flatness.
Sanding gets rid of the crud and rust and also smooths the area around the bolt holes (these bend first). After smoothing, cleaning both surfaces with alky and applying permatex to the paper gasket, never had one leak.
I like 180 stats, but 195 is OEM spec.

 

your thoughts are duly noted

 

Lady72nRob71, thanks for the tips.

I'm curious. Why do you prefer the 180 over the 195?

 

That "tward radiator" means; that end of the thermostat should face tward the radiator, as opposed to tward the engine block? Where any side of that thermostat sits, how it's rotated in the hole, means nothing. It's giving you the direction that end of the thermostat points in the system. Stant, Autozone, or whatever brand...

 

I do like Rob, my hero. I clean and rough up the surface a little, Permatex not silicone, never a problem.
Rob is the guy in the movies that gets the totally smashed radio working after the plane crashes in the Himalayas, using only a stick and a rock.

I use silicone around the water cooling ports on the intake gasket and as a replacement for the end seals, otherwise nowhere on the engine with or as a gasket, just my personal preference, never any luck with that stuff on semi-permanent things.
I do use a thin coat of Permatex on the radiator and heater hose necks too. It is actually recommended by Permatex and the old timers always did, the hoses don't seize to the fitting and come off a lot easier too, never leak.
My case of Permatex please Mr. Permatex man?
Their distribution center is about three miles from my house.

I always use a 180 degree thermostat and run around 190-195. It seems that the 195 t-stat puts it in too high an operating range, doesn't start opening until 195 and isn't fully open until well over 200. It just stays too hot, I like to see it below 200 all the time.
I used to get up there with the 195 in my GTO. It seemed like the cooling system was overwhelmed, dropped it to a 180 and it never any more problems, warms up and runs fine.
It has something to do with temperature momentum and the cooling systems ability to cool as it goes up but that's way out of my league.
If it works, it works, and don't look for trouble is my motto.
The 60's cars were 180 or even 160 until they started using permanent anti-freeze as standard equipment towards the end of the decade.
New cars have to be 195 or the computer will go nuts.

 

Yes, "toward radiator" means exactly that as opposed to facing rearward toward the block. That thermostat DOES have to be rotated in the hole until that side is pointing forward. I know it seems a bit weird in that a valve is a valve, and when it opens, coolant flows through. But the service manual is very specific about this and has diagrams showing how the coolant will flow when the thermostat is installed correctly and when it is installed incorrectly. The manual says that installing the thermostat incorrectly can cause coolant flow through it to be restricted and lead to overheating.

My question is about the aftermarket thermostat I bought from Autozone, which does not have any kind of "this side forward" marking on it. That suggests that it doesn't matter how it's installed as long as it's rightside up.

 

I don't mean to belabor a point here, but how do you define "too hot?" As long as the engine isn't overheating, how do you even know how hot IS too hot? I would think that, if the manufacturer calls for a thermostat of a certain rating, that's what you use.

I don't know that 15 degrees F makes that much difference, but, thermodynamically speaking, the higher the temperature the engine runs at, the more efficient it is. I would think one would want to run at as a high a temperature as one could without overheating.

If not running too hot is the issue, why stop at 160? Why not 140 or 120 or 100? Any of these would still be warm enough to provide heat on a cold winter day and defrost the windows. Run as cool as you can and never worry about overheating.

I'm not saying that running with a thermostat rated at a lower temperature than what the manufacturer calls for might not be be a bad idea. I just haven't heard a decent argument in favor of it! People are mostly giving essentially "gut feelings" or "this is the way I've always done it" type arguments. Let's hear some science!!

 

Looking at both thermostats in the pic the old one the bottom has two openings in it one small one and one larger. Which is more like a closed designed that helps directs the coolant flow. The bottom of the new one is an open design which leads me to think that the orientation doesn't matter with it.

 

Wow, you get the gold star award! This car DOES have a heavy-duty cooling system, which is a closed cooling system according to the manual. Maybe I shouldn't tempt fate and just go ahead and use the old thermostat after all or get a new one like it. As I said at the beginning of all this, I have no reason to suspect that the old thermostat doesn't work. I just thought I'd change it since I had the system apart. I'll look further into this "closed' vs "open" cooling system business.

 

I looked on O Reilly website and found a Mr Gasket one that looks like your old one. The rest of the thermostats are similar to the Duralast one. The only thing that has a question with the Mr Gasket one it said race only?

 

All thermostats have a "correct" orientation. Although some are not labeled "this end to radiator", the copper slug in the center needs to be at the engine side, as this is what senses the engine temperature. If installed backwards (copper slug up), it may never open because the coolant in the hose will be too cool, resulting in engine overheating.

I have grown to like 180 stats, for several reasons, though no science was applied.
Since heat makes power, and engines are most efficient at temps above 160 or so, running cooler than that is not recommended. Emission controls require a 195-200* range for most efficiency, so cooler temp stats are not recommended, which is why the cooler temp ones are labeled "race only". My Caddy runs at 200*.
The old stat on the left is an aftermarket "high flow" design. the new one on the right is a standard stock type.

My 86 seems to make a little (as in a smidgen) more power with the 180 vs the 195 because it possibly fools the computer in thinking the engine is not warmed up, and slightly richens the mixture. (Or is it my imagination??) If a cooler stat was used, the computer would not go into closed loop and set error codes. I checked all this before hand putting a fixed resistor in place of the temp sensor, and I liked the results (but still wonder if it was just my imagination...) That 307 needs all the help it could get.

My old Ford had a 195 stat long ago and would run at that, unless very hot outside in stop and go traffic. Then it would start creeping up to 210-220. When i got moving it dropped to 195 again. It never came with a fan shroud, so that is part of the problem. With the 180 stat, it will hit about 200 at the most, then go back to 180 when i get moving. I am not sure what temps are actually dangerous to an engine, so a 180 makes me feel more comfortable. The 180 adds a little more reserve in the cooling system for big demands.

I would also love to see some dyno testing with various temperature thermostats.

Allan, I have not have built a short wave radio with a stick and rock, but I once used a rock to signal someone. I converted its potential energy into kinetic energy and it made its signal when its motion seized at the receiver's end, according to Newton's law. I got an acknowlegment from the receiver afterwards, which was an "augh--damyou" sound........

 

Good find. Thank you.

I've visited a several other websites. NAPA has the same selection as Autozone. They all look like the one I got from Autozone.

Car Part Wholesale.com also has a large selection of thermostats that look like the one I got from Autozone and starting as cheaply as $3.00. They also have the Mr. Gasket one that OReilly sells, and they also have a "For Race Only" comment, but they have more info about it:

MR GASKET HIGH PERFORMANCE THERMOSTAT -- 180 Degrees Opening Temperature Rating, High-Flow, Designed To Resist Large Variations In Coolant Pressures That Occur At High RPMs, Opens At The Right Temperature Regardless Of Engine RPM, Legal For Sale Or Use On Race Vehicles Which May Never Be Used On Highways, Constructed From High Quality Copper/Brass Material, Gasket Not Included, With Mr Gasket's Limited 90-Day Warranty

Fit Note: For Race Only


So maybe the one that was in my car was not the correct one.

Rock Auto sells Gates, Stant, and ACDelco brands, and they all look like the one from Autozone. The cheapest they have is a Stant for $1.54. At that price, you wonder how well it works. Their highest price one is the ACDelco at $7.26. All the rest of them are under $5.00. When you can get the best one out there for all of seven bucks and a large array of pretty good ones for under five, why would you settle for the buck-and-a-half one? It's not like you replace a thermostat monthly.

Maybe I should stop worrying about this and just put the new one in? I don't know. This car does have the heavy-duty cooling system, which the manual keeps making a point of talking about separately as though what applies to the regular cooling system doesn't necessarily apply to it. Maybe I'll just put the old one in and keep the new one on a shelf.

 

Interesting to know, but if this is the case, I would think there would be some sort of marking on the thermostat itself or some instructions that come with it to tell you this. Otherwise, how would the average joe know this?

Well, certainly I-sleep-better-at-night type arguments are fine, and I can see that running at a lower temperature is less taxing to the engine and puts less of a demand on the cooling system. Also, as time passes and crud builds up in the passageways and radiator, the cooling system gets less efficient, and if you're operating right at the edge, you run the risk of overheating the next time you're sitting in traffic on a hot summer day.

 

I think Rob was talking about it being right side up.

Rob the orientation we where talking about had to do with the way the thermostat is turned and coolant flow. The design of the thermostat.

 

You might want to use the same temp range as the old, running at the same temp all the time means the tolerances are the same all the time ...

 

I did exactly this. I threw in the towel. I let sleeping dogs lie. How many other cliches can I come up with?

I put the old thermostat in because it looked fine, it worked fine, and it's what was there. The engine was used to it. I'll keep the new one for a spare.

Thanks, everyone, for all the advice. It's always useful to pick people's brains.

 

let bygones be bygones

 

Yes, I guess I could look at it this way.

 

Yes, meaning; when it's in the wrong direction, NOT to do w/ the way it's spun in the hole.

 

I did not get involved in this as there is nothing left to pick in my tired old brain

 

This got really involved for a fat end to engine, cone toward radiator answer. I also like 180 stats because here in Chaleston SC a 180 stat has my 461 running at 195-200 in traffic.

 

Sorry, thats Charleston SC

 

Go back and read through this thread again because you've apparently missed the point. It was never in doubt which end was up and which was down. The "fat" end, obviously, goes down, or toward the engine, and the "cone" end has to go up, or toward the radiator. It can't go in the other way because the water outlet won't fit over the top of it if the thermostat is in upside down.

What was in doubt was how it should be rotated, if at all, AFTER being set rightside up in the opening. There are in theory an infinite number of possibilities because you can rotate it through a complete 360 degrees, stopping anywhere you want. The old thermostat indicated a certain point that should be forward. That arrow pointing up in the photo below doesn't mean "this end up." It means this end toward the FRONT of the engine, or in the direction of the radiator. (It says "TOWARD RADIATOR" on either side of the arrow.) The factory service manual makes a considerable deal out of making sure the thermostat is oriented properly and has diagrams showing how the coolant will flow when the thermostat is installed correctly and when it is not. The new thermostat had so such marking.

 

You can go back and edit a message after it's been posted.

 

I never have orientated a stat when installing, I just dropped them in the hole and have never had a problem with the installation.
I did think of one other thing that I had a problem with when I used an old t-stat housing, it was not flush, I had to sand the base flat before it would stop leaking.