While I haven't changed lots of them in my day, I never did either...until today!!

While I wasn't surprised that there could be something like this involved, I was surprised that I could buy a replacement thermostat that didn't have the kind of markings or warnings that the one that was in the car to begin with had. Hence this thread!

 

Dude, I missed the point too until after reading this one very clarifying post. It had went right over my head blindly until now.
I never thought about a thing about how it is rotated in the block.
When i saw that "TOWARDS ^ RADIATOR" note, I always assumed the arrow was pointing to the radiator end. I followed the UP arrow, through the hose, and there was the radiator! Thats what I thought it meant.

As for truth to how it is turned - I am now very curious. I have put those high flow 180 stats in every car I can and never really had a problem with them . Only exception is my 86. It runs more at 170* on the highway in summer with a 180 stat. Restriction is not an issue I'm sure...

Same here.
As long as it fits nicely in the clean groove in the block, I was happy! On goes gasket and water outlet and bolts.

VERY interesting topic... I guess my old mind is not worth picking, either.

 

Here are the relevant parts of the '73 Olds Chassis Service Manual.







The key thing is in View B. In both situations, the thermostat IS installed rightside up. But if is not oriented correctly relative to the bypass hose inlet, the coolant coming up from the waterpump, which is normally directed under the thermostat and exits through the side of the thermostat away from the bypass hose is instead blocked and must reverse direction to go out through the side of the thermostat toward the bypass hose. This creates a region where the fluid stagnates (which I've noted). Fluid flow though the thermostat is thus slowed down, and, as the book says, overheating can occur.

 

Yea, I remember that picture. However, I asked myself then "what an unusual looking thermostat!" It is like a flap of some sort - that really needs to be positioned properly. Has anyone seen these and does someone actually have one? I just though there were the very old style.

The newer units, do not seem to matter. Your above photos show them cold & closed, now here are some with them HOT & open!

Note the standard one (picture 1) has a smaller hole for coolant flow. The ""high flow" stat (picture 2) opens wider. One thing to note is how the coolant flows through these. Coolant does not actually flow through the holes at the bottom. Coolant flows around the whole bottom unit. The holes are mainly to control the delay in opening (according to parts store guy)..
Picture 3 shows bottom turned to align the holes, allowing hot coolant to surround the upper part of the copper slug easier, allowing the stat to open sooner.
Picture 4 shows the holes misaligned, restricting coolant access slightly to the upper part of the sensor, allowing the stat to open just a little slower. Not sure of how useful this "feature" is. I never knew about it until after installing them all...
Makes sense to me though....

 

That is interesting Rob. Sometimes to answer a question you have to test the part in question to get a better understanding of how it works. I wasn't sure about the older one. I know I have seen them but never used that style. I have thrown away a few that where in engines that I have worked on. Replaced them with the other style never questioned it. Thanks for clearing it up.

 

I have a 1969 455 engine in my 67 442. When I had the engine work done two years ago I put a chrome thermostat housing on the Offenhouser aluminum 360 manifold. If has leaked on and off over the past year a few drops now and then. So, I decided to replace the housing gasket. Drained the antifreeze, cleaned the housing and manifold well, used a small amount of silicone (per NAPA) and reinstalled everything...refilled...and it leaks something awful. Took it apart and redid it again...still leaks like crazy...replaced the formed hose clamps..to no avail. Rechecked the housing for cracks, but couldn't find any. I am ready to go and buy a new housing (non-chrome), new formed hose, etc. Any suggestions? I see in this thread that someone dicussed permatex...my Dad always used that. Maybe trying that may help...Thoughts??? As always...Thanks

 

permatex - will make a difference in the spelling

http://www.permatex.com/

 

chrome t'stat housings are notorious for leaking.

 

OK...I have used permatex on the housing and hoses. Put it all back to gether and let it dry a few days...still leaks at the hose connection and slightly around the housing. My question is this, I am going to get rid of the chrome housing, since I have an aluminum intake manifold, should I use the aluminum thermostat housing (with the formed hose) or go with the cast iron (straight hose)? I just want to get rid of the leaking (not a lot, but it can be seen on the intake.) Thanks

 

Last year I bought a cheap (chinese) thermostat housing and it leaked like crazy. Turns out it was really warped.
My father told me about an old trick of sanding it on a mirror. You need a mirror, you put a piece of sand paper on the mirror then sand until the sandpaper scuffs the metal evenly.

The housing I had was horribly warped and it never would have sealed correctly had I not straightened it with the sandpaper.

 

Aluminum mated with iron creates a slow corrosion due to metal differences. If the style does not matter, the aluminum one would be more compatible with your intake.

This trick works very well. In my machinist's days, we had a flat granite sanding block. At home, i found a cinder block to be amazingly flat, too. I checked it for flatness and used it as a sanding block. Even newer plate glass can work fine. Just be careful with it to prevent breaks or cuts if edges are sharp.

Leaks around the hose can usually be cured by sanding and scraping the accumulated rust and deposits from the housing's hose neck.

 

I tend to agree with Lady72nRob71, but disagree with most of the above comments stating that a higher temperature is more efficient. I ask you then, for who and what purpose are higher temps more efficient? You often get what you pay for. Opinions are free, and low cost thermostat is what they are.

Yes, the OEM thermostats are typically 195°F, and EPA likes this because it reduces the emissions. While an engine running a under a computerized fan system etc., needs to use the 180°F or higher thermostat, this higher temp is not more efficient, unless you are referring to emissions control.

Any engine performs better in the 160°-170°F range (water temp). A cooler running engine also requires less octane (10°-15°=1 octane) which is especially beneficial to a supercharged or turbocharged engine (-20° engine coolant = 1 psi boost). Remember when driving in the rain or high humidity after the rain, there seemed to be more power. Aside from the moisture being sucked into the engine, it was running cooler and purpose.

I installed a special designed 4 core radiator in my heavy 1987 Cadillac Brougham with original 307 engine and 185 thermostat in 1999 due to high running temps. When I installed a 350 engine and instrumentation, I saw all temps easily run up to and above 200.

I’ve since built and installed a 403 and redesigned the EGR and AIR systems such that my tested emissions as verified by DEQ, are hardly noticeable. I also, installed a Robertshaw high performance (flow) FlowKooler 160F thermostat (~$20). My engine water temp is consistently between 160°-170°F and my synthetic oil (great stuff) temp is consistently between 170°-180°F around town in the Portland cooler weather. If I run in low mountain weather temps, then I’ll use a 180 thermostat. In summer, all my temps may rise by ~10-20 degrees.

You need to consider the purpose of your engine when selecting the components appropriate for that specified purpose.

Differences in metal when wet will corrode more easily due to a process called electrolysis, but there is a gasket and a rubber hose separating those metals, and will tend to reduce this. I have the aluminum intake, an aluminum spout, and an aluminum high flow water pump with a reversion plate welded to the veins. I like them. They work well for my temp control as designed.