[x300] Coolant Leak Mystery

[AttyDallas (Paul L.)]

@Dave_Harvey

Sorry I’m late to join this thread. I usually just lurk.

I too had the slow coolant loss on my 98 XJR with some coolant odor and
no puddles under the car. Turns out that the heater hose that connects
to the backside of the water manifold had a tiny leak right at the hose
clamp. Finally found it by pressurizing the cooling system with a test
kit I bought from HF. Although the leak was at the front of the engine,
most of the coolant ran down the valley and dripped off of the back of
the engine.

I changed the right-hand heater hose this past weekend. It is possible
to do this WITHOUT removing the supercharger. If anyone is interested,
here’s how I did it (with assistance and sage guidance from The Wife).
Requires two people (three to remove and reinstall the hood).

1. Remove hood.
2. Remove radiator fan assembly. This is necessary to get access to the
   belt tensioner.
3. Remove supercharger belt from top pulley ( no need to remove it from
   crank pulley).
4. Remove water manifold (with thermostat housing intact) by first
   disconnecting the temp sensor connector & four hoses.
5. Remove air intake tube (between air cleaner & throttle body).
6. Remove throttle body by first disconnecting coolant tank air bleed
   hose (the one closest to the throttle body), cruise control vacuum hose,
   throttle cable, three electrical connectors and two coolant hoses.
7. Block off the supercharger intake passage to prevent ingress of
   foreign matter using a clean rag, duct tape, etc.
8. Disconnect the plastic brake booster vacuum pipe from the
   supercharger inlet manifold by pressing the collar toward the manifold
   and gently tugging on the pipe. On mine, the collar wanted to fall out,
   so I set it aside in a safe place.
9. Release the clamp at the rear end of the heater hose. I clamped
   long-nose vise grip pliers onto the hose clamp because my hose clamp
   pliers were too bulky to fit into the tight space.
10. Lubricate the joint where the hose goes over the steel pipe with
    WD-40. Using a long screwdriver, long-nosed pliers or other long tool,
    work the hose loose.
11. Have your assistant pull the hose out thru the front of the car.
    Take note of the passage from which the hose emerges. Prolific cursing
    on the part of all involved is appropriate at this point in the proceedings.
12. Here’s the tricky part: feed an electrician’s “fish tape” thru the
    new hose from front to back. Make sure the tape has no burrs or sharp
    edges that could damage the hose. Note the shape of the hose,
    particularly the slight S-bend in the middle. Feed the end of the tape
    into the hose passage from the front of the car. Make sure that the
    tape runs inboard of the knock sensor and emerges from under the
    supercharger near the steel pipe to which the hose will eventually
    join. It is not necessary for the tape to enter the steel pipe.
13. Lubricate the outside of the hose (I used vegetable oil) to help it
    slide through the tight spaces.
14. Pushing from the front of the engine, work the hose down the tape,
    under the supercharger and it will eventually emerge at the back of the
    supercharger, near the steel pipe.
15. Carefully withdraw the electrician’s tape.
16. I could not figure out how Jaguar ever installed the spring clamp
    over the heater hose at the back end, because the small steel tube and
    the bracket are in the way. I punted and used a screw clamp. I’m not a
    fan of screw clamps, but in my mind it was the best option here.
    Install the clamp over the end of the hose with the screw outboard, and
    slide it forward, out of the way.
17. Using a long screwdriver, long-nosed pliers or other long tool,
    position the end of the hose at the end of the steel pipe. Lubricate the
    steel tube and use long-nose pliers to slide the hose over the tube.
    It’s all downhill from here.
18. Install the clamp over the hose and cinch down. Make sure the screw
    is oriented so it can be tightened if necessary without removing the
    throttle body.
19. Reinstall the water manifold on the front of the engine, using new
    O-rings. I used a screw clamp here too on the heater hose.
20. Reinstall the plastic brake booster vacuum pipe onto the
    supercharger inlet manifold by pressing it into the collar (first
    replace the collar if you removed it).
21. Reinstall the throttle body, using a new gasket (I got lucky and
    mine was intact from a recent removal for other reasons).
22. Reconnect all electrical connectors and hoses. Install the click-on
    bleeder hoses last because they are fragile and tend to get in the way
    of other things.
23. Reinstall the air intake tube.
24. Reinstall the supercharger belt.
25. Refill the coolant. Follow the usual bleed procedure.
26. I started up the engine, did a leak check and completed the bleed
    process before I reinstalled the fans and hood.
27. Reinstall fan assembly.
28. Reinstall hood.

– Dave in L.A.

OMG … 28 steps just to r/r a heater hose? I have heard horror stories about what’s needed to replace just a hose on an XJR b/c of the 'charger being in the way, and this one just about tops all those. I’ll NEVER own an XJR (or an XKR, if it has the same issue) …