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Just thought I would document my thermostat replacement. I was pretty sure mine had been stuck open as it took forever to get to operating temperature (and made the heater pretty useless in the winter). I had seen the Autozone part number (15378) listed elsewhere and decided to make a go at that, knowing that I could always order the entire unit from Centerline if I messed it up.
Removing the old T-stat
Just a note, this is much easier with the hood removed. Like many others here, one of my T-stat bolts sheared off when I tried to remove the housing. If viewing the engine from the front, it was the rearward drivers-side bolt. It wasn't the threads that were siezed, it was the unthreaded shaft part of the bolt that passes through the T-stat housing. By disconnecting all of the hoses and wires, I was able to rotate the upper housing around (counterclockwise) the sheared bolt. This gave me enough room (as it had unscrewed at least one thread or so) to get a prybar between the upper and lower T-stat housing, and I was able to pry the upper housing free from the sheared bolt (there are no threads in the upper housing, just the lower). The stock bolts are 70mm long or so, I was able to make due with the largest that Home Depot had in stock (60-65mm) for a cheap replacement. I also replaced the twin small water hoses that go to the engine block with some Autozone bulk hose trimmed to fit.
Modifying the housing
The stock housing has two "ears" that need to be removed to fit the new thermostat. Here is the stock housing:
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First I ground off the two ears with my Dremel (I don't have fancy air tools and such):
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Then I sanded down and cleaned up the surface around the whole housing so it was smooth (Dremel again, with sandpaper cylinders and some hand sanding):
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Here is the new thermostat sitting in place:
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Now, for the important part so y'all don't have to run to Autozone and buy a second T-stat like I did. You need to drill a small hole in the perimeter so the water can flow through to the bleed screw (orange arrow above). However, you can't just drill it anywhere as the "wings" on the new thermostat (blue arrow above) will only fit into the housing in a few different orientations, because of the trio of water temperature sensors. Hence, test fit everything together so it fits, then send a small drill bit or other marking tool down the bleed screw opening so you know where to drill/grind a small cutout for the bleed screw (I think grind is easier since its hard to drill a hole that close to the edge).
Here is my finished install (don't use this a guide for notch orientation, as I think this is from my first attempt where I ground the notch in an arbitrary place).
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Reassembling the housing
Once everything is lined up (I stuck a piece of wire through the bleed screw cutout to keep it from rotating) you can reattach everything. Since I'm impatient and didn't want to wait for a new gasket, I just used the thermostat gasket maker goop. Big gotcha here: The thermostat sits slightly proud of the housing, as you can see in the above pictures. Without a gasket, the upper housing bolt holes can crack (they are thin small castings) if you tighten it too much, so tighten it just enough to seal. Then just refill with coolant, drive and enjoy!
Mine's been working for a couple months now, temp gets to 180 or so in a hurry and sits there steady, even in stop and go traffic. I'll let you know how it handles the peak of NC summer in a couple months!
Removing the old T-stat
Just a note, this is much easier with the hood removed. Like many others here, one of my T-stat bolts sheared off when I tried to remove the housing. If viewing the engine from the front, it was the rearward drivers-side bolt. It wasn't the threads that were siezed, it was the unthreaded shaft part of the bolt that passes through the T-stat housing. By disconnecting all of the hoses and wires, I was able to rotate the upper housing around (counterclockwise) the sheared bolt. This gave me enough room (as it had unscrewed at least one thread or so) to get a prybar between the upper and lower T-stat housing, and I was able to pry the upper housing free from the sheared bolt (there are no threads in the upper housing, just the lower). The stock bolts are 70mm long or so, I was able to make due with the largest that Home Depot had in stock (60-65mm) for a cheap replacement. I also replaced the twin small water hoses that go to the engine block with some Autozone bulk hose trimmed to fit.
Modifying the housing
The stock housing has two "ears" that need to be removed to fit the new thermostat. Here is the stock housing:
First I ground off the two ears with my Dremel (I don't have fancy air tools and such):
Then I sanded down and cleaned up the surface around the whole housing so it was smooth (Dremel again, with sandpaper cylinders and some hand sanding):
Here is the new thermostat sitting in place:
Now, for the important part so y'all don't have to run to Autozone and buy a second T-stat like I did. You need to drill a small hole in the perimeter so the water can flow through to the bleed screw (orange arrow above). However, you can't just drill it anywhere as the "wings" on the new thermostat (blue arrow above) will only fit into the housing in a few different orientations, because of the trio of water temperature sensors. Hence, test fit everything together so it fits, then send a small drill bit or other marking tool down the bleed screw opening so you know where to drill/grind a small cutout for the bleed screw (I think grind is easier since its hard to drill a hole that close to the edge).
Here is my finished install (don't use this a guide for notch orientation, as I think this is from my first attempt where I ground the notch in an arbitrary place).
Reassembling the housing
Once everything is lined up (I stuck a piece of wire through the bleed screw cutout to keep it from rotating) you can reattach everything. Since I'm impatient and didn't want to wait for a new gasket, I just used the thermostat gasket maker goop. Big gotcha here: The thermostat sits slightly proud of the housing, as you can see in the above pictures. Without a gasket, the upper housing bolt holes can crack (they are thin small castings) if you tighten it too much, so tighten it just enough to seal. Then just refill with coolant, drive and enjoy!
Mine's been working for a couple months now, temp gets to 180 or so in a hurry and sits there steady, even in stop and go traffic. I'll let you know how it handles the peak of NC summer in a couple months!
