F355 Thermostat Replacement

Hi all. I was unable to find a very complete how-to for replacing the thermostat in my F355, so here’s my attempt. To be honest yelab’s post here is incredibly accurate (his first line especially!) and far more efficient than this write-up. But if you’re like me, having a bit more detail and some pictures gives you confidence.

1. Jack up the rear of the car and drain some coolant. I drained the passenger side radiator following the instructions here. I think if I had drained from the engine freeze plugs, I might have made a little less mess later. Lower the car back down so it's easier to reach the thermostat.
   
   
2. Remove the cover that goes around the coolant reservoir and power steering fluid reservoir. There are 6 nuts and 6 washers. It’s easy not to notice the washers and lose them when you pick up the cover (if you’ve done any work on your car before, you already know this). Also don’t forget there are 4 collars around the 4 rearmost bolts/studs; those are easy to lose/drop when you pick up the cover.
   
   
3. Remove the coolant reservoir. There are two small hoses on top and 2 larger ones below. I had to wrestle it quite a bit to get to the hose clamp nuts. An electric screwdriver with extension really helps. Also note the orientation of the nose clamp nuts for when you reassemble later.
   
   
   
   
4. Suck the fluid from the power steering fluid reservoir. I used a vacuum pump like this one:
   
   
   
   You won’t be able to get it all, but the more you get, the less mess in the next step.
   
   
5. Loosen the two hose clamps on the two hoses connected to the power steering fluid reservoir. Be ready to catch/absorb fluid.
   
   
6. Remove the two 7mm hex bolts fastening the semi-circular bracket that holds the power steering fluid reservoir and remove the reservoir. There are washers under each bolt; don’t lose them. Here’s what mine looked like at this point. You can just see the thermostat housing behind the right power steering fluid hose.
   
   
   
   
7. This is where yelcab recommended to remove fuel lines, but I found I didn’t need to. The kind soul that assembled my engine at Scuderia Rampante oriented the hose clamp holding the 40mm thermostat housing hose to the large pipe running between the two radiators such that I could access it with my electric screwdriver and the right length extension. You can see the hose clamp here, although this is after it was loosened and rotated down. (I didn’t need to loosen the hose clamp where the 40mm hose connects directly to the thermostat housing.)
   
   
   
   
8. You’re on the home stretch now (how’s your back so far?). Now it’s just removing the 3 nuts holding the thermostat housing on and wrestling the housing off (you’re counting on the 40mm hose rotating where you loosened the clamp). Two of the nuts had washers, and one holds a throttle cable bracket. Oh, this is going to be messy too, depending on how thoroughly you drained coolant (I just drained a radiator, and this leaves about a cup or two of coolant above the thermostat housing). As yelcab said, I think “that is OK”. Here’s what mine looked like at this point:
   
   
   
   
9. Pull out that broken thermostat, put in the new one, and zip everything back up. Don’t forget to make an appointment with your physical therapist and/or chiropractor.

I was happy to see that the old thermostat was visibly degraded. It couldn’t possibly close completely, and this confirmed that I was solving the right problem (car ran cold on the highway per this discussion.)

Finally, thanks to Daniel at Ricambi for getting me the new part quickly. Also, I whined to him that his photo of the part was out of date, and he quickly updated it. Thanks Daniel!