2012 Jaguar XJL Supercharged (AJ133) – Looking for input from anyone who has dealt with a leaking charge cooler/intercooler brick on a 5.0 Supercharged AJ133.

The car previously suffered a head gasket failure and was repaired. During the repair, a used donor supercharger/manifold assembly was installed. The donor blower still had junkyard markings on it and has a worn coupler that will be serviced soon. Since the rebuild, I've been chasing a coolant loss issue that is becoming increasingly difficult to explain.

Current Symptoms:
- Gradual coolant loss with no visible external leaks
- Sweet coolant smell from the exhaust, especially after sitting (with 200 kpa cap)
- Startup hesitation/misfire after a heat soak (200kpa stick cap)
- Persistent mild misfire at idle and light load
- Under heavy load the engine smooths out and makes full power
- Symptoms are worse after sitting 20+ minutes- Coolant level slowly drops over time
- Long highway trips are no problem (recently completed a 600+ mile trip)
-No coolant contamination in the oil
- No overheating what so ever
-Passes leak down test and head gasket coolant bottle test

What Has Already Been Done: - Head gasket repair completed
- Injectors swapped/tested
- Oil changed 7+ times since rebuild and remains clean
- Coolant reservoir replaced
-I use only 93 octane with 3 periods of bg44k treatment
- Thermostat housing replaced (Aluminum) with a brand-new unit already installed
- Cooling pipes upgraded to aluminum
- Multiple cooling system leaks repaired
- Compression tested
-Pcv hoses changed
-Bypass hose changed(old *** brittle)
-All new spark plugs
-Only use OAT orange coolant
-Replaced both hpfp

Compression Results:
- Cylinder 1: 149 psi
- Cylinder 2: 149 psi
- Cylinder 4: 142 psi
- Cylinder 6: 145 psi
- Cylinder 8: 143 psi

Interesting Observation:

The car originally ran a 110 kPa cap and would slowly consume coolant but generally started fine Everytime unless it was 44° F outside or less After installing a 200 kPa cap, startup hesitation, coolant smell, and smoke became much more noticeable.

Which lead me to replace thermostat housing as there was a spraying leak. Which lead to last leak. Again the mechanic shop with the one we put the 110 kPa cap on which was far out of spec probably to hide the leak.

I've now switched to a 140 kPa cap from an xf. The symptoms seem reduced but have not disappeared completely. Also, when the thermostat housing leak existed, relieving pressure at the reservoir would immediately stop the coolant from spraying. This has me wondering whether a higher-pressure cap is forcing coolant through a small internal leak path elsewhere in the system.

At this point, I'm beginning to suspect one of the intercooler/charge cooler bricks inside the donor supercharger assembly may be leaking coolant into the intake runners. And I already plan on removing the supercharger because the coupler is bad. And I'd like to change the oil in the supercharger. I'm no stranger to tear down as I'm on my second 4.0 XJR rebuilding the whole engine.

Questions:
1. Has anyone here confirmed a leaking intercooler brick on an AJ133?2. What symptoms did you experience?
3. Did you have startup smoke, coolant smell, coolant loss, or misfires that were bank specific?
4.Did your symptoms improve when cooling system pressure was reduced?
5. Has anyone successfully pressure-tested the intercooler bricks?
6. Does anyone have a good used intercooler manifold assembly, intercooler bricks, or a supercharger lid/manifold available for sale?

Any confirmed experiences or photos would be greatly appreciated.

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And before anyone ask yes I have check fuel pressure is there all with inspect My mother has the same 5.0 SC. Rail hits 2100 psi on start up and drops to desired, but the engine commands different pulses for the injectors on the banks. Injectors aren't leaking

Some pictures for reference

 

I have not seen one leak but anything is possible. It's not that bad to pull the lid, I would yank it off of there and pressure test them. Each side just goes to the 2 hoses on the front, would be easy enough to rig up a small pressure test setup and hit them with 150kpa while full of water and see if they leak.

 

You're back!
I was wondering how you've progressed with your XJ.
I can't help with any SC- related input since ours is NA.
I don't recall if your previous posts said, but when you did the head gaskets did you have the heads and/or block checked for flatness and resurfaced?

 

Hey, nice to see you again! I've been busy finishing up my spring semester and working on a couple of cars and electronics for people so haven't had much time to theorize here😭

Yes, the heads were sent to a machine shop and checked during the head gasket repair, so I'm confident that part was done correctly. Where I now believe the issue may have originated is with the supercharger assembly. If you remember my previous posts, the shop replaced the original supercharger with a used blower and intake manifold assembly. Both components had junkyard markings and written part numbers on them. They kept my original unit as a core. After I left an honest review regarding the experience, they refused to return my original blower unless I paid an additional $300-$400 for it, despite already charging me $1,000 for the used replacement. Over the last year I've gone through virtually everything else on the car while continuing to daily drive it and changing the oil every 1k-3k miles.

Despite the issue, I've still enjoyed the car and put plenty of miles on it, even put new shock absorbers, control arms and got the 2017 headlights.

The engine has passed a leak-down test, compression test, and combustion gas test. There are no external coolant leaks remaining. I've replaced the HPFP, checked fuel pressures, and verified that most values are within specification. The only value that seems slightly off is rail pressure, which I've wondered could be related to the ECU compensating for a cylinder intermittently affected by coolant ingestion. About four weeks ago I discovered that the coolant cap installed on the car was only a 110 kPa cap. When I replaced the expansion tank, the new tank came with a 200 kPa cap, and after checking other AJ133 vehicles, including my mother's Range Rover, I confirmed that 200 kPa appears to be the correct specification. (Before giving it to the mechanic shop I confirmed my cap was actually 200kpa, they changed it)

Once I installed the 200 kPa cap, I immediately found another weak point in the cooling system. After a spirited drive, the thermostat housing began spraying coolant onto the driver's side headlight connector. I replaced that with an aluminum housing, which should have eliminated the last known external leak point. What caught my attention was what happened next. With the system now operating at the proper pressure, the car began developing a hot-soak startup issue. If it sat for 20-30 minutes after reaching operating temperature, it would occasionally struggle to start and sometimes produce a brief puff of sweet-smelling white smoke for 10-15 seconds before returning to its normal behavior. Releasing pressure before shutdown noticeably reduced the symptom, and switching to a 140 kPa cap reduced its severity compared to the 200 kPa cap. Having previously owned an Audi A7 that suffered from a leaking supercharger intercooler core, the similarities started looking very familiar. That led me to wonder if the used blower/manifold assembly installed during the repair may have a damaged intercooler brick or developed a small crack at some point in its life.

At this stage I'm mainly trying to determine whether anyone else has experienced similar symptoms from a leaking intercooler brick on an AJ133, and whether anyone knows of a good source for replacement cores, bricks, or manifolds if I end up pulling the supercharger apart to investigate. 😄



Before I changed it to the aluminum after running the 200kpa cap the first time

 

Try running with the coolant cap loose. You will have no pressure in the system. Does it still leak?
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Yes. It will still have the slight idle misfire while running, but if I relieve the pressure before shutdown, the hard start is basically gone.When the system stays pressurized after a hot soak, that's when I get the hesitation on restart and brief coolant-smelling exhaust. That's what's making me suspect the intercooler

 

Could pull the plugs and borescope the cylinders after a hot soak, see if there's coolant in the cylinders. I still think pull the lid and check them, it's not that bad to do.

 

True, I'm planning to remove the lid. Currently the xj is my long distance driver for certain client relations activities so I have to do this on a day I have 2 days of down time since my motorcycle is back on the jack so I can swap the tires🫠.

When I do the test on the bricks I'll update the form.