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2004 XK8 - Coolant leak on top of t-stat housing at connector

XK8 / XKR ( X100 ) 1996 - 2006

2004 XK8 - Coolant leak on top of t-stat housing at connector

 
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Old 05-20-2019, 07:56 PM
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Default 2004 XK8 - Coolant leak on top of t-stat housing at connector

I had a squealing belt when cold. Removed the engine cover and found a small leak at this connector on the t-stat housing.

Is there a seal in there I can replace or do I have to replace the whole housing? Seems like there ought to be a seal.



Seems like it has been doing it for a while but I haven't noticed any smell.



I cleaned the area and ran the car up to full temp. Seeping commenced once there was pressure.



Hoping for some guidance before I start ordering parts.
 
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Old 05-21-2019, 06:55 AM
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You need to replace the entire coolant outlet duct (part no. AJ89486). These plastic assemblies eventually warp, crack, break down, and leak. Get a new manifold front seal as well (part no. AJ87991). The job is considerably easier if you remove that front manifold plate at the top front of the engine to open up some working room to get to the two rear bolts (Torx T-30 for the 4.2 engine) that hold the coolant outlet duct in place. Once removed, you will see that the manifold front seal is cooked, so be sure to install a new one as part of the job. The two front bolts on the coolant outlet duct (again, Torx T-30 for the 4.2 engine) are easy to get to. Also, putting the hood into the vertical service position makes this job so much easier. Pump out the coolant expansion reservoir, remove the heater core hose connection and pump it out, then remove the two large radiator hoses and pump them out. You will then have pumped out enough coolant so you will not make a big mess during removal of your coolant outlet duct....

I did this job on my wife's 2006 XK8 in late November 2014 at 85,500 miles. I paid $115 for the new coolant outlet duct (it came with a new thermostat) and less than $5 for the manifold front seal. I believe my exploits back then are described in a thread that I entitled "Slight Coolant Loss". There are quite a few other threads pertaining to this job as well. Note that the 4.0 engines have an aftermarket aluminum coolant outlet duct assembly available to them. Unfortunately, our 4.2 engines do not. So if you keep your car long enough, you will probably have to replace these plastic coolant outlet ducts multiple times since they all eventually break down as the years and heat cycles add up....

Good luck and keep us posted on your repair....
 

Last edited by Jon89; 05-21-2019 at 07:11 AM.
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Old 05-21-2019, 08:25 AM
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^^ This is spot on. I did the same. Other thing is that this assembly comes with a new water temp sensor, already threaded and sealed, in addition to a new thermostat and all required o-rings. No brainer, really. Last, consider replacing this multi-section line from the top to the overflow tank. It will likely be very brittle, and snap in half just for looking at it.

Obviously, being coolant-related on an aging car, you can easily slip into "what else" scenarios, especially with the coolant already drained. Here it is:
  • That hose you see in the back, taking a hard 90 deg bend downwards is one of the 2 valley hoses. Squeeze it and assess whatever life is left in it. Mine was so soft and deformed I am surprised it did not burst.
  • The water pump is right there below. Cheap, easy job.
  • If you do the water pump, do the belt.
  • How old are the upper/lower radiator hoses? Have you seen them collapse?
  • How about a new overflow tank cap to help with the bleeding?
  • While the coolant is out, how about a cooling system cleanup? My cabin heat saw a MAJOR improvement after a core flush and detergent/radiator cleanup. I now have (some) heat in the cabin a half mile from driving off.
Best of luck, keep us posted.
 
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Old 05-21-2019, 08:28 AM
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The squeal is most likely due to coolant on the serpentine belt. Replace the belt when you fix the leak.
 
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Old 05-21-2019, 08:42 AM
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If you have a scanner that will read engine temp. check it after the swap. My engine was running cold after replacement (180-185 F) so I returned the housing for another. Now I see 199-201 F which is good. The readings were confirmed by the infrared thermometer.
 
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Old 05-22-2019, 01:23 PM
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Thanks for all the advice guys.

I will be replacing the housing, seal, water pump, idler/tensioner pulleys and belt. I agree it is best to do it all while I am in there.
 
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Old 05-22-2019, 10:55 PM
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I see where the shop manual says to replace the 3 bolts that attach the pulley to the water pump.

Did any of you do that - or just reuse the existing ones?
 
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Old 05-23-2019, 06:13 AM
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I checked on that when I did mine, consensus was reuse.
 
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Old 05-29-2019, 08:57 PM
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Well this is a real pisser. The new thermostat housing leaks worse than the original one.

I get to do it again after I make the dealer give me another one. Yay.

This new one was leaking before I ever started the engine. Just filling it back up with coolant was enough to get it trickling out. Running and under pressure from the water pump it leaks massively.

So the next one I will fill with water and see if it leaks before I install it.

 
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Old 05-30-2019, 07:57 AM
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Sorry you have to repeat the job. I wonder if your new coolant outlet duct was missing one of the rubber seals, or if a rubber seal did not seat properly for you during installation....
 
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Old 05-30-2019, 09:07 AM
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Originally Posted by Jon89 View Post
Sorry you have to repeat the job. I wonder if your new coolant outlet duct was missing one of the rubber seals, or if a rubber seal did not seat properly for you during installation....
The leaking elbow connection came preassembled and appears to be lacking a seal. It is not loose though. Under pressure it floods out of that connection.

Since I just replaced the two pieces I should be able to replace only the main housing and avoid R&R of the other piece that required removal of the intake cover plate. Will take less than an hour that way.

One thing for sure is that the system is getting a good flush now that I have to drain it down again.
 
 
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