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1999 STS - diamond white
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Discussion Starter #1
I have to change mine this weekend on the '99 STS. It's leaking. Any problems I need to be aware of? I plan to use an ACDelco gasket. Pump seems to be fine. Already replaced hoses and the belt and pulley. T-stat works.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,441 Posts
I like to place washers under the 4 bolt heads in order to spread the load over a bit more of the pump cover flange surface.
 

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1999 STS - diamond white
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5,229 Posts
Discussion Starter #3
Thanks Sub. Good idea.

Have you all used this 'universal' coolant in the N*? It would be nice to just be able to keep one type in the garage. I've only used Dexcool in it to date.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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My 2002 is presently filled with 60/40 Prestone yellow universal coolant. Just fine since about 06/2011.

(same as the Ford trucks.)
 

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1999 STS - diamond white
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Discussion Starter #5
My wife brought the car home this afternoon and it puked coolant all over the garage floor! Looks like the car has decided how I will be spending Saturday :mad2:
 

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White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
It's odd that a WP cover gasket would do much more than seep.
 

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1999 STS - diamond white
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5,229 Posts
Discussion Starter #8
Yeah, before it puked I had told the wife that the small drip was okay for her trip to KC. Luckily she didn't go.
I replaced the gasket. I also replaced the t-stat and seal. It was working fine but it was falling apart internally. There's some rubbery gasket material inside the stat on both sides that was dangling loose. Didn't need for it to separate and clog the cooling system somewhere.
Buttoned it all up and topped it off. So far, driving it around has produced no more leakage.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Where's the rubber seal that was "rubbery.................dangling" ?

Inside the t-stat copper cylinder there is a special wax compound - that expands and contracts as temperature varies - it's the motive force for the t-stat "valve" plate.
 

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1999 STS - diamond white
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5,229 Posts
Discussion Starter #12
In your picture, it's all around the inside of that flat area in the top of the pic. The arrow from the "coolant inlet from lower hose" points to one side where the material is. There's matching material on the flip side as well. If i haven't thrown it away already, I can try and post a pic.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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That's the thermostat "gasket" - it's a U-channel formed black rubber ring that can be removed from a new 'stat. Once squashed and heated/cooled a skrillion times the things turn to snot.
 

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1999 STS - diamond white
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5,229 Posts
Discussion Starter #14
That's the thermostat "gasket" - it's a U-channel formed black rubber ring that can be removed from a new 'stat. Once squashed and heated/cooled a skrillion times the things turn to snot.
We're not communicating. Again, I know what the outer gasket/seal is. It's the black outer ring in your pic. What I am trying to describe is adhered to both sides of the t-stat inlet flange. I don't know how else to describe it.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Is your rubber mess shown in Post #9 ? That black rubber ring IS on the inlet flange - FROM the lower hose.

If there's something stuck around the smaller flange - heater circuit bypass/return bleed - then it's not supposed to be there.

EDIT: Just took apart a Stant thermostat. You're right - the entire center "valve plate" is covered - both sides - by a softish rubber pad - so if that's coming apart/off, then the t-stat replacement was worth it. The 'stat I have in my hand is stamped "54mm" and "USA" on the outer rim flange. Down on the spring bridge is stamped "STC" and "001".

Looked at the t-stat picture again - that barely indicates that the valve plate is black, not metallic in color.

I wonder what ate that rubber or made it gooey ?
 

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1999 STS - diamond white
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5,229 Posts
Discussion Starter #16
No it's not in the pic. It's integral to the t-stat. I don't know how to explain it any better than I have. If I still have the part I'll post a pic.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Black rubber covered center valve ????

That smacks of an old submarine engineering observation: "You know what an elephant is ??" ...... "No, What ?" ............ "A Sperry-developed mouse.". (Sperry Gyroscope could overbuild anything on earth)
 

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1999 STS - diamond white
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Discussion Starter #20
Black rubber covered center valve ????

That smacks of an old submarine engineering observation: "You know what an elephant is ??" ...... "No, What ?" ............ "A Sperry-developed mouse.". (Sperry Gyroscope could overbuild anything on earth)
Funny you mention Sperry Gyro. My 89 year old father-in-law was a chief engineer there. He was on the team that designed the Sparrow missile. Designed a lot of global navigation systems before GPS.
 
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