Engine I think I broke my coolant temp gauge

[slow84lx]

The stock 192-195* thermostat works great in Texas. It's been 100-108* every day here for the last few weeks. You'll be fine.

Just a disclosure, my Mustang isn't running but my 1992 F-150 w/ same engine, same thermostat is. My Mustang has never overheated from the stock thermostat either.

 

[AnthonyA1234]

The stock 192-195* thermostat works great in Texas. It's been 100-108* every day here for the last few weeks. You'll be fine.

Just a disclosure, my Mustang isn't running but my 1992 F-150 w/ same engine, same thermostat is. My Mustang has never overheated from the stock thermostat either.

Awesome, unfortunately I wasn’t able to find a 195 replacement. I think motorcraft discontinued them and now you can only get the 197 ones.

 

[slow84lx]

Awesome, unfortunately I wasn’t able to find a 195 replacement. I think motorcraft discontinued them and now you can only get the 197 ones.

I would move ahead. You should be fine. Monitor closely for the first couple of weeks.

 

[General karthief]

So I pulled out my thermostat and it’s a 160 degree. That explains why I’m running so cold now that I upgraded my radiator and fan clutch. Now I’m thinking my car might run too hot with this motorcraft 197 thermostat I’m putting in. @General karthief I remember you live in Florida like me, do you run a stock thermostat and does it work for you in this FL heat?

Stock,these cars are designed to run 195+ and that's optimal for the computer and stuff.
220-225* sitting in traffic with the ac on is not unusual.

 

[AnthonyA1234]

Well… it was almost a clean job fellas. It’s two weeks later and I noticed a puddle of coolant under the tsat. See the pic below.

I’ll go through how I installed it and if you guys could lmk what I should do different this time I’d appreciate it.

I took off the T stat, scraped both mating surfaces clean, hit them with brake cleaner and dried them, then I put a thin layer of blue rtv on both sides of the gasket… I didn’t do any single bead just a thin layer I spread with my finger, then I put everything together and hand tightened the bolts which I put thread sealer on, then I let the rtv cure and after that I snugged the bolts with a wrench.

Any ideas?

 

[slow84lx]

Well… it was almost a clean job fellas. It’s two weeks later and I noticed a puddle of coolant under the tsat. See the pic below.

I’ll go through how I installed it and if you guys could lmk what I should do different this time I’d appreciate it.

I took off the T stat, scraped both mating surfaces clean, hit them with brake cleaner and dried them, then I put a thin layer of blue rtv on both sides of the gasket… I didn’t do any single bead just a thin layer I spread with my finger, then I put everything together and hand tightened the bolts which I put thread sealer on, then I let the rtv cure and after that I snugged the bolts with a wrench.

Any ideas?

Check ALL of your hose clamps and hoses in that area, clean it up good, and run it a few times checking for wetness as it cools before you take anything back apart.

Try to determine the exact source of the leak.

 

[AnthonyA1234]

Check ALL of your hose clamps and hoses in that area, clean it up good, and run it a few times checking for wetness as it cools before you take anything back apart.

Try to determine the exact source of the leak.

So I couldn’t find for sure the leak but I do know that the hoses are all dry so it’s gotta be the tstat. I’m going to be more liberal with the rtv this time. Last time I put a thin layer just so it’d stick but it probably wasn’t enough to do any sealing.

Also, can I put a dab of rtv on the Tstat itself where it touches the housing to make sure that stays aligned?

 

[Noobz347]

I missed the first go-around but maybe I've caught you in-time for this one...


With the housing removed, flip it upside-down and place the T-stat with correct orientation, into the housing.

--Hold it in place with two small dots of Super Glue and let it dry--

Install as normal with whatever combination of gasket/RTV you prefer. It's impossible for rim of the t-stat to make its way [into the damned way].

 

[AnthonyA1234]

I missed the first go-around but maybe I've caught you in-time for this one...


With the housing removed, flip it upside-down and place the T-stat with correct orientation, into the housing.

--Hold it in place with two small dots of Super Glue and let it dry--

Install as normal with whatever combination of gasket/RTV you prefer. It's impossible for rim of the t-stat to make its way [into the damned way].

Great! I’ll try this tomorrow

 

[slow84lx]

Are all of the clamps tight? I've found this to be a problem a time or two.

In my earlier years I had a habit of putting the bolts in too tightly on the unused sealant. I had fewer leaks using less sealant and less pressure. But, you may need to add a turn or so after the sealant has cured for a couple of days.

 

[AeroCoupe]

Put a piece of 600 grit sandpaper down on a flat surface. Lightly drag the face of the t-stat housing across the sandpaper and see if the t-stat housing is flat. I have seen them not be and you will play hell sealing one up that is warped and believe me it doesn't take much for them to leak. Also make sure the neck of the t-stat housing is smooth so the hose can seal up on it. I think Mustang5L5 had a problem with this and ended up replacing his but I could be wrong.

 

[AeroCoupe]

This is the thermostat housing on both of my cars:

https://www.oreillyauto.com/detail/c/murray-climate-control/murray-climate-control-water-outlet/mry0/84884/v/a/5471/automotive-car-1993-ford-mustang?q=thermostat+housing&pos=4

Be sure to seal the pipe plug with some thread sealer to make sure it does not leak. I cannot remember if the ones I got had it or not but I know I used it as you can see the white sealer. A good one is Permatex 59235 high temperature thread sealant.

 

[AnthonyA1234]

This is the thermostat housing on both of my cars:

https://www.oreillyauto.com/detail/c/murray-climate-control/murray-climate-control-water-outlet/mry0/84884/v/a/5471/automotive-car-1993-ford-mustang?q=thermostat+housing&pos=4

Be sure to seal the pipe plug with some thread sealer to make sure it does not leak. I cannot remember if the ones I got had it or not but I know I used it as you can see the white sealer. A good one is Permatex 59235 high temperature thread sealant.

Ok, I’ve got my game plan to tackle this issue thanks to your guys’ suggestions. First of all I’m against the clock as I’ve got a guy picking up my car to get painted any day now so I’m kind of rushing.

First off I ordered the thermostat aero coupe recommended, I’ll get it tomorrow. I’m going to pick up some sand paper first and test my oem Tstat as I’d prefer to use that one if it’s still good, if so I’ll return the aftermarket one. Then I’ll superglue the Tstat in place like noobz said, and use gasket and rtv to seal it.

Do you guys use so much rtv so that it comes out the edges? Or thinner than that? When I did it the first time I did a really thin coat all over and it wasn’t enough to make it come out the edges when tightened.

 

[keel]

The way I have always done it is with a thin coat of RTV spread around with my fingertip on both sides of the gasket. Then I just fully install it right away, no waiting for the RTV to cure or anything before torquing it down to spec. I use Permatex ultra black RTV and a Fel-pro gasket. The Permatex ultra black does take some time to cure so if you elect to use that RTV then I would wait at least a few hours before driving the car and getting pressure in the cooling system. I prefer to use that over the ones that cure really fast because it gives me more time to work with it before it starts hardening. (I use the ultra black for sealing basically everything on the engine that requires RTV, its awesome stuff.)
Like @AeroCoupe said, none of that will work if the housing is warped or if the gasket surfaces are dirty/jacked up so definitely check that out. The super glue technique that @Noobz347 suggested should keep the tstat from falling down out of its little groove into the way of the gasket mating surfaces which would be the other big issue with trying to get it to seal up. It baffles me why Ford designed their water necks like this especially when the GM small block from the same era had the tstat sit horizontally making it so much easier to install and to get air out of the system, but I digress.

 

[Mustang5L5]

Awesome, unfortunately I wasn’t able to find a 195 replacement. I think motorcraft discontinued them and now you can only get the 197 ones.

Motorcraft 192 is available.

Motorcraft RT1139

 

[AeroCoupe]

Another way to hold the tstat in the housing is to loop a rubber band around one of the bars of the tstat and bring them through the housing so that the tension holds the tstat in place. I use a pen or pencil or whatever and feed that through the ends of the rubber band so that holds against the end the hose goes on. Haven’t had an issue as long as the housing is flat.

 

[AnthonyA1234]

Another way to hold the tstat in the housing is to loop a rubber band around one of the bars of the tstat and bring them through the housing so that the tension holds the tstat in place. I use a pen or pencil or whatever and feed that through the ends of the rubber band so that holds against the end the hose goes on. Haven’t had an issue as long as the housing is flat.

Just did the sandpaper test. The housing shined up on all the holes and slightly around the Tstat. See the pic below. Lmk if that needs replacing. I’d assume the whole thing should’ve shined?

 

[AnthonyA1234]

Here’s a better pic in the sun

 

[AnthonyA1234]

.

 

[Mustang5L5]

This pitting here would worry me.

I've tried to repair manifolds and such with this sort of pitting with a little JB weld to fill the holes. Wait until it's almost hardened to sand it down to form it to shape, and then let it harden and finish it up. Have been successful.

When i doubt, replace it