About two days ago I used the happy pedal and went for it in sports mode (a rare occasion). Seconds after instigating the manouvre the red "warning low engine coolant" message displayed. Slowing, up promptly allowed the car to recover to normal operation cancelling the fault. So instead of checking the coolant I left it to cool over night (opening the cap is a no-no when hot due to pressure loss and eventual cavitation when warm again). I topped up the next day (less than half a litre) only to get the red light again further down the road. I had a leak.

After much rummaging and crawling around under the car the leak was passenger side dripping from gearbox bell housing. Figured it was heater plumbing related, no. It was apparently coming from the back of the "vee".

To cut a long storey short I think I've traced the leak to near the front of the vee where the plastic housing mates to the centre of the engine (just below inlet manifold intake) havn't confirmed it is fractured plastic pipe yet though. The throttle body coolant hose connects here with an amazing length of pipe (over a foot long) despite being within inches of the connection point! I had to get the inlet manifold off to get to the hose connection in the top of the engine block only now I can't get the manifold off due to the fuel rail connection on the right appearing to be permanently attached to the rail. Is this the case? can it be detatched? I could remove the rail from the manifold but don't want to risk disturbing the injectors. It is a polished silver ring with spring clip over. Removing the clip does nothing. I also want to remove the manifold completely to get a good go at cleaning the mating surfaces up and inspect for further leaks.

Help and tips please for the rebuild! PS, never seen such brittle wiring harness and plastic tubing, treading carefully......EGR pipe routing between the vee to the front of the inlet manifold has taken care of a few of these plastic/rubber connections.

 

For any others interested, can safely say the 4.2 V8 NA is alot easier to deal with than the supercharged. Most parts easy to reach, just have to be careful moving the wiring harness about to gain access (old and brittle). I removed the 4 bolts holding the inlet throttle assembly, 4 bolts holding the inlet plenum to inlet manifold, 3 bolts holding the wiring harness at the back of the engine then the 10 bolts securing the inlet manifold to the engine.

The failed pipe was the larger diameter item about 2-3 inches long that connects to the top of the engine underneath the intake manifold. Would say that this was misaligned at manufacture or replaced wrong during a service and subsequently after many more miles had split.

Things to watch out for were sensor attachment (possibly inlet temp) and vaccuum pipe attached to the back of the inlet manifold at the rear. The vaccuum pipe detatches from a connector visible in the engine bay at the back at the right hand side (drivers side in uk). I didn't detatch the fuel rail feed line, just swung the whole assembly up and away towards the passenger side all still connected (photo). Oh and re-route the knock sensors cables to the front of the engine on the passenger side. Reassembly: do a dry run first to check nothing is in the way under there (sould not rock !). I re-used the old metal gaskets as I need the car for work tomorrow, with a very very liberal amount of sealant both sides (do not do this if at all possible, get the replacements). I used a tightening sequence spiral from centre outwards. I guess back to front could also be used. Will re-torque again after a few miles.

The car has done over 100kmiles and looked reasonably good on inlets, some oil residue from pull-over, nothing major. Reassembly was alot quicker. There was one spare connector on the driver side with cylinder 7? nearest driver? Guess it must be diagnostic port? It did hesitate when restarted and sounded like it was knocking , possibly readapting as I fixed a few other manifold vaccuum leaks I found. Cured itself after a few seconds -RESULT! PHEW!

 

Congrats, and great job on your repair effort. Thanks for posting....