Changing Thermostat Housing Assy AJ811793 - Tips?
 

Hey, 2006 XJ8 here. I was told awhile back that my Thermostat needing changing (I get code P050B) but that I could save a bundle of money doing it myself. Sure enough, I saved ~$130 just on the part itself.

But the thing freakin' looks like a heart valve transplant, I mean holy cow...

https://www.jaguarforums.com/forum/a...ine=1395789613

Anyone done this repair before and have any tips?

Also, I found this a few days ago:

https://www.jaguarforums.com/forum/a...ine=1395789613

My VIN falls in this range...any way I can tell if this repair was done to my car? I think so, because of the Feb. '06 date, but would like to be sure...don't want to go digging under the hood for nothing!

Thanks!

Thermostat and Housing R/R
 

Hello fellow Jaguar owner,
Having changed the housing and thermostat on my 350 last fall, I thought I could pass on a few words of encouragement.
Firstly, don't let the design intimidate you. If you remove the yellow clip it is possible to slip off the nozzle which attaches to the head assembly. The yellow clip is only used to keep the pieces together until installation. The various other nozzles and such hold the device together after install.
This piece with the four bolt holes is the hardest piece to remove due to the proximity of the throttle body. Which brings me to what I think is key to making this project as painless as possible. That is, remove the throttle body. I know there are those who are much more experienced than I who might tell you it's unnecessary to do this, but, it was the only solution I found to reach the back two fasteners from the flange. It made the process so much easier, I can't believe it's done any other way. Be cautious when removing the TB Assembly so as to not damage the gasket, otherwise a trip to the parts supplier will be necessary.
Other than the obvious issues such as draining the coolant below the level of the assembly, and care when removing electrical connections, I would only suggest one other thing. Take pictures with your cell as you go. You might never need them but it's good insurance.
As for codes, mine wasn't throwing codes. I experienced the fans going into warp speed while pulling into the garage one evening.
It turns out the housing was falling apart internally.


Good luck! It's not as bad as you might think. And very profitable.
Also, nobody will treat your cat with more care than you!

Going to attempt this repair this weekend, lots of nerves but many thanks for the advice!

I need to change my thermostat also but I have the super V8 and it doesnt look the same as the one in the picture. Mine is right up front and on top. I thought, wow how easy is this going to be! Wrong! I can not get a torque bit in on the bottom where the water outlet bends down. Does anyone have a tip or trick to get at this bottom bolt? I dont want to break any of that pretty cast aluminum. Anyone?

Just be very careful when you are undoing the bolts, if the car has never been apart then the bolts could be seized, and they aren't exactly the strongest bolts i've ever seen.

https://www.jaguarforums.com/forum/x...warned-105468/

The torx bolt on the bottom of the thermostat housing is the one where the head twisted straight off with the body of the bolt still in the housing.

If I had to do it again on a "new" vehicle i'd take the whole housing off, not just open the thermostat housing, because of that bottom bolt that broke...

I'm having enormous difficulty getting any of the hoses off. Is there some trick to this? It feels like I'm trying to pry apart rocks.

I'm totally stalled right now, I can't get the throttle body off either because those 2 hoses won't come off either. There must be an easier way than grunt and brute force.

I usually get a thin flat-tip screw driver & push it between the hose & the spigot, this helps to "break" the seal of the hose onto the spigot.. It is a PITA, but don't get frustrated & just start pulling, you can damage the hoses by putting too much strain on them. Good luck.

The bane of my existence isn't just those hoses, but those F#@%ING CLAMPS, they're a NIGHTMARE to deal with. It's like they were designed by Satan and installed by his minions, facing the tabs downwards so it's hugely difficult to get the pliers on them, and then it takes the strength of Hercules to hold them open while trying to maneuver them down the tube. 1 hose took me 3 hours of fighting yesterday..I ran off to Pepboys this morning to get a special tool ($25, no returns thank you very much), and it's still not easy.

Here's a picture of the tool (one end wrapped in masking tape for some cushion) and a hose, I've got the clamp off the nozzle but the hose is still stuck on.

https://www.jaguarforums.com/forum/a...ine=1397513403

The Pepboys attendant said he hates dealing with those clamps and changes them to screw types every chance he gets...I'm thinking of doing the same. Only thing is I don't know whether those would apply the right amount of force...these f#@%ers are TOUGH...

Quick update: I've removed the front part of the thermostat housing to try to attack the hose from another angle, it turns out my housing was also failing internally, albeit in a less crucial spot:

https://www.jaguarforums.com/forum/a...ine=1397517158

https://www.jaguarforums.com/forum/a...ine=1397517158

Glad to see you're making progress on this.

Please be sure to come back and add detail so we can add FAQ / RESOLVED to this to help others in future

I had to travel for 2 days, so I had to leave the Jag in pieces...

I've gotten all the hoses off finally (there was much rejoicing), and I've removed all the forward facing screws on the thermostat housing. I've now gotten to the part Rrd623 advised about, removing the Throttle Body Assy, and I can see pretty plainly what he's talking about, there's just no way to reach those 4 screws on the back otherwise.

However, when I read his reply, it didn't click that I'd have to remove the whole shebang, I thought it'd be just the valve part...is there any precautions or extra steps I should be aware of, other than simply removing the 4 bolts? Is there an 'official' process to do this, in the handbook or wherever?

My slow progress kinda belies my inexperience at this kind of work.

Hi a4500435,

I've been following your thread with interest since I'll no doubt need to do the same work on our '04 this summer.

The full X350 service manual is available in the download section of the "HOW TO" thread of this forum. Go to the link below and scroll down to "Special Thanks to those Workshop Files provided by DB6":

https://www.jaguarforums.com/forum/x...k-links-20085/

For service related to the thermostat, you need the Powertrain section:

http://www.mediafire.com/download/9b...Powertrain.pdf

For replacing the thermostat only, the non-supercharged instructions begin on pg. 1213. The supercharged instructions begin on pg. 1218.

Removing and installing the thermostat housing is described in several sections related to other operations - with a quick search I didn't find a self-contained unit. The first mention of removing the thermostat housing is on pg. 310, and you might need to go back a few steps to disconnect or remove other items before you get to the steps on that page.

You can search the pdf file by holding Cntrl or Cmd plus the "F" key. A small search window will appear (near the top of the screen on my version of Adobe Acrobat Reader). Type in a search term such as thermostat housing and click the right arrow to find the next occurrence of that term, click the left arrow to find the previous occurrence. This section of the manual is 3,594 pages, so searches can take a little time, depending on your computer speed and other programs you may have running.

Please keep us informed!

Cheers,

Don

I've been going through the handbook for weeks, I wouldn't have attempted this otherwise!

I haven't taken off the Throttle Body Assy yet, for a couple of reasons: 1. I can't find any official procedure or even the part name; 2. There's a whole host of hoses and connections I don't want to fight again.

https://www.jaguarforums.com/forum/a...ine=1397773415

Instead, I've twisted off the main part of the thermostat housing; the interior tabs are broken, I don't know if they were before I took the part off, but the plastic seems weakened anyhow.

https://www.jaguarforums.com/forum/a...ine=1397773415

The work area:

https://www.jaguarforums.com/forum/a...ine=1397773415

Right now, I could just take apart my new housing and twist it onto the old pipe, but that seems lame after going this far. The only way I can see to remove the old pipe is as Rrd623 said, to remove the Throttle Body Assy completely. I can reach 3 of the 4 hex bolts with a socket wrench, the top left one (in blue) I can only get a hand wrench on.

https://www.jaguarforums.com/forum/a...ine=1397773415

https://www.jaguarforums.com/forum/a...ine=1397773415

I'd really like to know what exactly I should expect in taking off the whole TB Assy...this is not something I've really planned for.

Ok, I need help: I've removed the 4 hex bolts, and 2 others I found on the side that connected the TB Assy to a metal pipe...however I can't get the TB Assy out.

HOW DO I REMOVE THESE 2 CONNECTIONS?

https://www.jaguarforums.com/forum/a...ine=1397778833

It seems XF has the same crappy plastic thermostat assembly module. Would be nice to hear any tips from those who did the replacement. My topic -
https://www.jaguarforums.com/forum/x...eating-118038/

Try a heat gun---and for reattaching too.

GL

R&I thermostat Housing / outlet pipe assembly
 

A big tTHANK YOU to all on this thread for sound and detailed advice: from diagnostics to remove & replace. my 2006 XJ 4.2L had an unusual overheating issue - temp gauge stayed right in the middle all the time on the highway, but when I stopped and drove below 35 MPH, temp gauge would steadily climb. originally tried replacing the thermostat, but to no avail.
I read on this thread of 2 other members with very similar situations - they recommended replacement of Oultlet pipe assembly and recommended Jagbits.com for parts. All great advice and 2006Jag had a great photo depiction of his effort - helped tremendously and I'm proud to say we completed the repair over the past 2 nights and we're back on the road today.

thanks again to this great group for all your advice.

Is the yellow clip not needed? I just did new water pump, and serpentine belt & ordered the entire thermostat assembly! I left the OLD black pipe that connect to the thermostat housing under the TB to the block on there and am only installing the new housing! My question, the yellow clip is a pain to install back unless I take off TB it seems?? Do I even need it (yellow clip)???? Any help would be appreciated! Thinking of just installing with out yellow clip seems it should be held in place with the bolts and oring to not leak???
Thanks for your time, apprecitated!

03 Stype 4.2

The yellow clip is not needed at all. It is only used to hold the two pieces together at the factory, for shipping and for installing so the two parts do not slip apart. I removed it before installing the entire thermostat assembly and had no problem with installation with the two half's wanting to separate at all, they are pressed together rather tightly as there is a rubber ring the seals them together. The yellow clip is a throw away item.

Housing,
Just re-read all the post and here's my two cents.

The only reason to remove the TB is to get at the two rear bolts on the piece that is shown on the left side of the picture in post #1. You'll note it has 4 bolt holes. The yellow clip looks like it is there just to hold this piece to the main housing. Mine came without this clip. Don't know why it's there. That piece won't come off unless someone pulls it off. It is held in the main housing by an "O" ring.

Remove this part by just holding the main housing and twist, it will pull out.

Remove all the bolts that are holding the main housing to the engine and just twist it back and forth until it comes loose from this part--leaving the old one in place.
When your ready to replace the new housing, remove the new "O" ring off the new piece, and after you take the "O" ring off the old down spout (still attached to the engine) grease up the new "O" ring and slip it on this part that was left on the engine.

When replacing the new T housing, wiggle the new housing onto this and be sure the "new O" ring is well seated into the new housing.

I've replaced the new housing on both my cars and did each this way with excellent results.

PROS: You do not have to remove the Throttle Body and disturb its seal to the engine or remove any of it's hoses.

CONS: None really. You just have to be sure the new "O" ring that you put on the old part seats in the new housing. You may have to work the new housing around some what, but the "O" ring will go into the new housing. Use some Lithum (sp?)Grease.

Note: Use a very small about of this grease on the "O" rings on the housing that butt up against the engine and on all hose connection tubes on the new housing. Remember, just wet the tubes for the hoses. You don't need to over do it. Makes putting the hoses back on a snap........

Cheers

Thanks no leaks job came out good!!!! Cheers

does anyone have a step by step procedure documented (instead of searching for thermostat housing in the service manual)? I hate to admit it, but I replaced all of the cooling related stuff when I get our current jag about three years ago. Looks like the thermostat housing is leaking again so I'm replacing it. I thought I documented it, but can't find anything and now don't remember how. Want to do it tomorrow, so if anyone has anything, that would be great.

Thanks,

Gordon

To anyone who did it before....
1- How much time did it take you?
2- what is a reasonable Independent shop will charge?
3-My car also needs new plugs; are they easier to reach with the thermostat off?

I just saw this thread, and felt bad that I didn't see it sooner. I too have replaced the thermostat housing twice on my car. Both times I left the riser under the throttle body in place and didn't attempt to get at the four bolts that are so difficult to get to. That part is only a riser and if it fails then I will be forced to go the full way with removing it. Until then, (165,000+ miles), I will just continue to replace the housing without removing the riser. Chuck's recommendation on greasing the O ring is what I did. Same for the hoses.

1.) I did my thermostat within the past month - took me about one hour from start to finish. I'm getting good at this job which is something I wish I didn't have to say.

2.) Have no clue - but more than what I paid for a thermostat housing on EBay.

3,) No, they are not affected by the thermostat. I have changed all of my plugs even the back two, without removing anything under the hood. With the right extension(s) and u-joint connection all plugs can be extracted without taking anything else off under the hood.

Sorry to resurrect an old thread, but wanted to post some additional info for anyone that finds this in the future. Changing just the crossover pipe and leaving the neck that connects to the block may have been a quicker repair back when the original was only 5-6 years old, but this plastic will not hold up over the long term.

My first coolant housing was replaced under warranty around 57k miles. Right on schedule the thermostat portion failed again at 130k miles (engine was not getting up to normal temperature). Pulled the old housing off and found that the dealer took the shortcut of only replacing the pipe section and not the neck. The date code on the original crumbling neck is 2006, on the latter pieces 2012.

In my opinion there's not much savings in leaving the neck assembly in place. If you've already removed the throttle body, there's only 6 more bolts (2 on the EGR and 4 on the plenum) and the plenum comes right off. Then the neck can be replaced.

#Sarchasm so glad Jag decided to take a page from BMW's book and use plastic that is coolant-soluble for the critical system!

https://cimg1.ibsrv.net/gimg/www.jag...feb6c1e4f2.jpg
https://cimg2.ibsrv.net/gimg/www.jag...292bccc9df.jpg

Totally agree with you mhamilton. Don't bother just replacing the individual parts when you can get the whole thermostat housing including temp sensor and thermostat for cheaper than buying the individual parts. And as you say you might as well change the whole lot when you are in there anyway. Totally a waste of time just replacing the individual parts. I recently did this with mine as my housing was leaking badly and I also did the water pump and belt at the same time.

Have changed the thermostat with housing on both the 04, & 07.

Of course i changed the Neck portion on both.

The big difference in the two was, the 04's was assembled with regular bolts.

The whole assembly had regular bolts

Not the torx headed ones on the 07.

HUGE difference in the effort, & time to remove.

Replaced them all on the 07, with regular type bolts.

Just in case it ever needs changed again.

For the torx bolts on my car, I used a T30 bit in a 1/4" 6-point socket, with a 3" extension on a 1/4" drive ratchet. Removed them with no problem. Used a little tape to keep the torx bit from falling out of the socket.

Got mine out as well, but bolts with regular heads are easier.:icon_shrug:

I did swap the housing, but I failed to do the "neck". ( So I replaced the gasket on the neck and left the old plastic in place.)
Which screws did I miss to get to these neck-screws out ?

https://cimg3.ibsrv.net/gimg/www.jag...563275d8d8.jpg
https://cimg8.ibsrv.net/gimg/www.jag...7562565a9c.jpg