Friday, August 8, 2014

How to change the thermostat housing on your Jaguar XJ

Here is the how to for changing the thermostat housing on your Jaguar. This plastic housings leak all the time and is a most likely repair. 

You'll need:
You need to pick the right thermostat housing. It's easy, just look at the coolant temperature sensor (the grey connector at the housing) If it is at the front pick the first one. If it is at the back of the housing (like in the pics of this procedure) then pick the second one. 
Here is the procedure:
  • First remove the engine cover, remove the oil cap (make sure nothing falls inside), turn the four phillip bolts (notice they don't come out) and pull the cover up.

  • Remove the intake air duct that goes from the throttle body to the mass air flow sensor.

  • Remove the throttle body. For that you need to clamp the two hoses going to it, remove the hose clamps and carefully wiggle the hoses out without braking them. I like to place all the houses at the side with the weight of the VISEGRIPS, you'll see what I mean in the next pics.

  • Now is to remove the hoses that go to the housing. There should be two big hoses, two small hoses and a medium hose (if I remember correctly). When all the hoses are detached, carefully, move them out of the way the best that you can. I push them down and to the side. If your sensor is at the front unplug it now.
  • After the hoses, there are 4 bolts securing the front of the housing to the engine. Remove those bolts. There are either 8 mm or 30T torx screws. With those four bolts removed you can pull the front of the housing and remove it. If your sensor is at the back unplug it now.
  • With the front of the housing removed you can remove the four bolts securing the intake pipe from the throttle body to the intake manifold. Then disconnect the vacuum hoses at the top and the two screws that secure the EGR to the side. Make sure you catch the gasket from the EGR you don't want to lose that one. With all that removed you can pull the pipe out and it'll look something like this:
  • Now we need to remove the plastic base (the other part that came with your housing.) Four bolts should do the trick again either torx 30T or 8 mm. 

  • The surface should be clean, but if it isn't clean it with come razor blade and brake cleaner. Then place the new base (just the base it should pull out of your new housing.)
  • Now place the intake metal part of the intake back. Catch the four bolts, connect the top vacuum hoses and the two EGR bolts with the gasket in between. Placing the gasket and catching the EGR bolts without dropping them is the hardest part of all this. Make sure you have a magnet handy!
  • Now grease the rubber of the plastic base with any grease is fine. 
  • If your sensor is at the back plug it in now. Place the front part of the housing, catch the four bolts (pain in the as* I know) and tighten them, MAKE SURE THAT THE RUBBER SEAL YOU PUT GREASE ON IS NOT STICKING OUT.
  • If your sensor is at the front plug it in now.
  • Catch all the hoses back, if you put new clamps is better but I never find it necessary.

  • This is a good time to clean your throttle body with some throttle cleaner I recommended!
  • Place the throttle body back, catch the hoses, make sure you get that gasket seated properly, and catch the bolts and tighten them.
  • Place the intake hose back.

Place the top cover back. Fill it back up and start it up. Let it run but stay around and make sure is not overheating. Drive it around, let it cool and top it back up. Keep you coolant in your car and check it the next morning and a couple of days after.


  1. This article was extremely helpful. Thank you very much, Daxter! Unfortunately my coolant leak is from the hose which runs under the intake manifold, so after replacing the thermostat housing I have had to take it all apart again! Great pictures and fantastic photos.

    1. Thanks! Good luck with the hose!

    2. On pic 4 the L shaped hose that is removed, how on earth did you "wiggle it off" It feels like hard plastic. Any suggestions?

    3. Wich hose you mean ?

  2. Sorry if this is the wrong board. I had the check engine light, I was getting a P0508 code. Replaced the thermostat, Did the drive cycle. Check engine light went away... Check enging back on, same code P0508. Coolant level is good, car runs great, Temp is perfect. Idles at 600 rpm with no variation and does not raise and fall. Do I need to change my Engine Coolant Temp Sensor? Can you point it out where it is? Thanks for the photo walk through on the above job. Kelly Fontes 2006 XJL 38,000 miles. Las Vegas, NV.

  3. Thanks for posting this info. I just want to let you know that I just check out your site and I find it very interesting and informative. I can't wait to read lots of your posts. Best Programmable Thermostat 2017

  4. what are the torque specs for the bolts when tightening?

  5. still it will be savvy for you to look at the cost of the thermostats previously making the arrangement. jim here

  6. I just replaced the thermostat housing now I find a leak on bottom what looks like plug .? Does that have threads or it’s part of plastic unit ?( 2004 Jaguar XJ 4.2

  7. High engine heat comes on
    Squeeze hose and the antifreeze goes up and down in the reservoir engine is hot
    Is the thermostat good if this occurs?
    Any help you can give

  8. Just installed a new water pump in my 2007 xj8. Old wp had plastic impeller. New one is metal. Why go cheap on a part like this on a $70,000 dollar auto?

  9. Hi. I just replaced the thermostat housing and there was a yellow plastic piece that holds the two pieces together. Does that yellow piece need to put back on? If so can you please tell me how what tool I need. Thanks

  10. Hi the fuel regualater, new i pit in, now the pipes, two of them that laid,
    under the fuel ragulreater, i have the numbers of it were sweling up and burst, i replase with athe pipes, now they are very hard, i think on the one curf that what gous tru these pipes, the bends is not right, and wroung, i did write the numbers off the two pipes, googel it, not working, i cannot drove the jaguar s type v8 4.2l 2005 , it can only go for 5 km , then it is hot, i have to wait, that the motor cool off, i have some photos , od the engen it is not easy to see this pipes, if you can please sent me an coppy e-mail to look what whent wroung , i hope we understand another regards Petrus Botha. e-mail asddress is.