V8 Vantage Thermostat Replacement

The thermostat in a V8 Vantage is known to go bad after 4 or 5 years or so. More specifically, the gasket goes bad, comes loose, and prevents the thermostat from operating properly.  I discussed this in a blog post. This DIY guide will walk you through how to install a new thermostat in a V8 Vantage. I sell new thermostats in my online shop if you need one.

DISCLAIMER: As always, follow all safety protocols. Don't undertake this task if you aren't comfortable with it and fully understand it. You are ultimately responsible for anything you do. Neither Redpants, LLC or myself is responsible or liable for anything that may occur.

You'll recognize the above pic from my blog post about the V8's thermostat going bad. The problem is the gasket, but the gasket isn't serviceable so the entire thermostat has to be replaced. Aston dealerships sell them for about $150. The ones I supply in my online store are direct replacements from Jaguar and cost a fraction as much. The DIY that follows is on my buddy Justin's car. His thermostat failed the same way mine did, but a bit more seriously - the gasket didn't just come loose, it also broke. That could have led to pieces of the gasket getting loose and going into the coolant system. 

New thermostat and seal
8mm socket
10mm socket
Ratchet for the above sockets
Extension for the sockets/ratchet
10mm box-end wrench
13mm box-end wrench
T27 torx bit
1-2 hours, depending on your pace

NOTE: Let the car fully cool down before beginning!! Coolant systems are pressurized when at operating temperatures. Opening any part of a hot coolant system can result in injury. Don't open any radiator caps, coolant reservoir caps, the thermostat housing, etc, until the car has completely cooled off!

Step 1
A bunch of random prep is best before doing this job. Each of these can be incorporated in the rest of the DIY, but it's easy to get all of it done at the same time since the main purpose is to prep for coolant spillage and clear space around the thermostat housing.

  • Get the car on jack stands and use the T27 torx bit and ratchet to remove the bolts holding up the front undertray.  Removing this makes it easier to deal with any spilled coolant, nuts, bolts, and tools.
  • Use a plastic liner (or trashbag, or whatever) to cover the FEAD (serpentine) belt to help keep coolant off of it. Jam a bunch of towels into the area below the thermostat housing - these will soak up much of the coolant that comes out of the housing and make cleanup much easier.
  • Disconnect the long L-shaped quick-release plastic tube in the pic below where it goes into the intake tube (connects in the top left corner of the pic, which is right in front of the throttle body). You only need to disconnect that one end, allowing it to move around as you work.
  • Disconnect the quick-release plastic tube that goes from the PCV to the intake manifold (It's the 7-shaped hose missing from the picture below - it goes straight through the middle of that pic when in place. Can't miss it.). If you have my oil catch can, remove it per this video. It only takes a couple extra minutes. And hey, you might as well drain the catch can while you're at it. Justin's was almost full after around 7k miles of driving!
  • Use the pliers to get the hose clamps loose from the air-oil seperator, then pull the U-shaped hose aside.

Okay, now we're ready! This picture will be a good reference for the next couple steps:

Step 2
First we're going to remove the PCV. Remove the two bolts holding it in place. Use the 8mm socket and ratchet to remove the two black bolts in the pic above (they're the two in the oval). The PCV will pull straight up and out now. Note the twin O-rings at its bottom outlet.

Step 3
Next we'll remove the air-oil separator (AOS). It looks like the PCV that sits above it, but a bit smaller. There's one 8mm bolt holding it in place. Use the 8mm socket, extension, and ratchet to remove the bolt. Next, pull the AOS aside. It is still attached to a hose directly below it so don't try pulling it out! All you need to do is pull it free of the metal housing it plugs into, then let it sit aside.

Step 4
There's a bracket that sits on top of the thermostat housing. In the pic above, it's held in place by two nuts and one bolt - all 10mm. They're circled in the picture above. The bolt is at the top of the picture - it's easiest to remove using the socket, ratchet, and extension, which will reach past the plastic tubes in front of it, but you can use the box-end wrench if you prefer.  The two nuts are at the bottom of the picture above. The one to the left is easy to access. The one to the right is a bit more tricky due to the stud it sits on being so close to the valve cover. Use the box-end wrench to get it loose and then it comes off easily. Be careful not to drop it!

Once the bolt and nuts are off, you can remove the bracket. It might take a little wiggling to get it over the stud that's close to the valve cover, but you shouldn't have a problem.

NOTE: Some people recommend grinding the stud down 1/8" to give more clearance. I did that on my car without checking clearances. Apparently I didn't need to because Justin's car (the one in the video) was very easy.

Step 5
Below the thermostat housing is an 8mm bolt. You should be able to get to it easily with the 8mm socket, extension, and ratchet. It's dead-center at the bottom end of the thermostat housing. Remove that 8mm bolt, then use the 13mm box-end wrench to get the two nuts on the top of the thermostat housing. The nuts are part of the stud, so they'll come out together. You should be able to wiggle the stud closest to the valve cover out, just be careful not to drop it.

When the 8mm bolt and 13mm nuts start coming loose, expect coolant to start leaking out. Once they're removed, you can pull the thermostat housing away and see the thermostat inside. The gasket on Justin's thermostat was in really bad shape. This is what it looked like when I pulled the housing free:


Step 6
The easiest way I've found to get the thermostat out of the housing is to use your palm and press down on the 'plunger' portion of it as hard as you can and, while keeping pressure on it, rotate it to get it free. BE CAREFUL because this thing is literally spring loaded and will pop out in at least three pieces if you don't keep control of it when you let off pressure!

When the thermostat comes out, you should have every bit of what you have in the new thermostat. Use the pic at the beginning of this DIY as a reference for how it is assembled, minus the bad gasket. If any part is still stuck in the housing, use your pliers to pull it out.

Step 7
Put your new thermostat together. It's a bit wonky to hold since it's all so loose-fitting, but it should look like this:

Install it into the thermostat housing the same way you removed the old one - I use my palm to press it down and rotate it into place. Be careful with the pieces before they're in place as nothing is keeping them together in one piece until they're properly situation within the thermostat housing.

Step 8
Reassemble everything! Just go in reverse order using the steps above and everything will go right back into place.

Step 9
The last thing to do is top off your coolant and check for leaks.The coolant reservoir is in the back-left corner of the engine bay (i.e., nearest the driver in a US-spec car). Add coolant, close it up, and run the car for a minute to let it pull the coolant into the system. Let the car cool off, then top it off. If the level is too low, you'll get a warning in the LED read-out in the gauge cluster.  Check for leaks, weird noises, etc.

Step 10
Reinstall the front undertray, then clean up any mess from spilled coolant. And that's it, all done!