Been chasing a persistent little leak from the front, somewhere around the S/C cooling/cabin heating pumps.
Finally it escalated to more than a slight drip and I could see a constant spray from a hose that connects to the S/C radiator (I think). I removed the clamp, then realized that removing the hose is likely a major job, so I rotated the hose, put the clamp back on and all seemed well. Two days of test driving and no issues.
The next night, the coolant low message appears in the middle of town, the temp goes up then down when stationary/moving. I had to drive 0.8 miles to get out of traffic, was thinking it was just the little dribble back, down a little in volume in the reservoir again. Popped the hood, and this time the wetness was not at the front, but more toward the suspension turrets. The expansion tank looked empty.

Rats, I thought, must be the valley hose, at last.
I had some water in the car, so added a little in and sure enough, it comes spitting out from under the supercharger, and could be seen dripping on the ground from the rear of the engine.
AAA got me home, and the next day I started ordering parts.

Big thanks to Dsetter and all the others that have gone before me on this.

At the weekend, I started stripping the car down, everything seemed to be fighting me, from the wiper blades onward.
What I did discover is that it is not the valley hose that went, but AJ811638 that runs from the thermostat housing back down into the valley, a big hose, maybe 1&3/4" or so.
With all the parts ordered, and a need to sort a vacuum leak too, I might as well plow forward on doing the valley hose too. I imagine I will also need to look much more closely at the S/C cooling pump, radiator and hoses.
Do we have a good location for identifying and/or purchasing hoses?
These are the ones I have ordered so far,
Part Number Part Name Price

AJ89746 Hose-Heater $19.75

AJ83445 Gasket $17.94

C2C11477010 Seal-Water Outlet $4.04

AJ83292 Gasket $10.87

AJ88507 Inlet Hose $14.27

C2C18160 Inlet Hose $46.91

AJ88559 Tube Gasket $4.68

AJ88560 Valve Gasket $4.68

AJ811638 Hose $9.97

C2C18161 Upper Return Hose $61.22
along with $30 water pump and both v-belts.

These are on today's shopping list,
C2C32836 Upper hose, radiator to thermostat housing $39.89

C2C10866 Lower hose, radiator to thermostat housing $74.29

C2C10872 return tube, probably expansion tank to thermo housing $40.18

AJ811771 vent hose, expansion tank $40.83
and I did C2C19596 drain hose a couple of years ago when I did the cabin heater pump.

I think the only other one I am missing, is from the lower passenger side of the aluminium thermostat housing that goes to the aluminium pipe that then runs down the chassis leg from the front of the engine to the rear to feed the cabin heater, any ideas on a part number?

The hose that connects the S/C electric pump to the radiator seems to be no longer serviced. I need to check mine carefully and evaluate alternatives.

Also vacuum pipes? What diameter should I be looking for there? I saw 3 mm mentioned, but that seems small? Are all pipes the same internal diameter?

 

If you are all the way in you might consider the heater hoses as well. Just had a set fail at 127k miles.

 

Which ones, the ones that go through the bulkhead?

And why is the top radiator hose so expensive? $100+ for a hose with no apparent special feature to it?

 

Might as well change both knock sensors while the s/c is off.

 

That is correct. I found some Dayco hoses that I cut to match at a local AutoZone. I have a recent thread about it. The lower one blew the outer sheath. Best of luck to your endeavor.

 

I got it the last of it apart at the weekend, fiddly little job!
Knock sensors are on their way and I am on a mission to change every hose I can.
Access to the ones attached to the S/C radiator is a bit of a pain.

The Valley hose was not holed, but had expanded and felt like the inner layer was gone, I doubt it would have lasted much longer. As I pulled it off, it actually split at the join of the larger to small diameter hoses.
The throttle body is pretty black too, best I get some of that off there before it goes back.

 

Well, I am going to call this one finished, although the car has only distilled water in the system as testing continues. Will add a gallon of orange coolant this weekend and replace the plastic undertrays.
It turned into quite a marathon as once I got her back together the first time, the radiator failed on the third drive afterwards. The pipe that the top hose fits to broke off from the plastic header tank and so a new radiator was needed and a pile more dismantling.
Observations - despite the details in the online parts catalogues, mine runs two identical knock sensors, (the more expensive versions) not two different versions as suggested. (the noticeable difference is in the electrical connector - the wrong knock sensor had a much larger connector. So the car has one new and one original sensor now (conditions in the valley were nice and clean and dry and the sensors are mounted an inch or so off the valley floor and looked clean and dry so not expecting they were drowned or anything.
The EGR gasket (pipe to manifold) was physically too large so the original went back in there too. (sorry at work now and do not have part numbers available - ask me if you want them).
The curly pipe from the electrical pump for the supercharger coolers to the radiator burst when trying to remove it the third time and a replacement was located by searching the stores at the local autozone. Part number used was B88395 (cost was $13.49), trimmed an inch off each end and it seems to fit quite well, but it has been less than a week so far. The connector on the supercharger intercooler radiator seemed to be more rectangular in shape than round and the constant pressure clamp had difficulty getting the original or replacement hose to seal, so a worm drive clamp was used there.
Opening the expansion tank bleed screw did aid air escape, but most of the work was done by using the two electrical pumps to fill the system before actually starting the engine. Ran it on distilled water only during all tests.
Other than that it is just a lot of hard to get to nuts and pipes. The proper tools for the spring clamps made things a lot easier, but I used only two versions, one that was like pliers and one that was like a flexible claw grabber for the hard to reach clamps. There was a fair amount of swearing, and some blood was sacrificed, but the car runs nicely again and hopefully will need no attention to the cooling system, belts, pulleys, etc for a long time.

 

You can get the top rad hose for the SC car for £14.99 on ebay UK c2c10865 is the part no. I bought one and it is new old stock.

 

On this side of the pond, C2C16212 superseded C2C10865, no idea if they are identical in shape and size though.
C2C16212 is the one I bought. I trimmed an inch off of it to make it a more comfortable fit and it seems to be holding fine.

Car is good right now, added the coolant and the weekend and nothing else broke or started leaking.

Transmission fluid and filter are next (second time for this task) to ensure levels are restored after some small loss on changing the radiator.

 

When you do the transmission work you might take the time to ensure the wiring harness seal is good (or just replace). I did not replace the first time and it leaked on an inclined driveway. Second time, replaced and now dry as a bone. I also replaced the rubber seals on the valve body to transmission interface. There are 4 tube like rubber seals and one double-square that fail on older cars. Mine had 125k miles and the square one was a bit dodgy. There are youtube videos on how to do all of it and is not so bad if you are patient and mechanically inclined.
I used Mercon SP transmission fluid and it seems to be working fine.

Best of luck.

 

My hose just started leaking at the throttle body. Dealer quoted $1011 to replace. I cut the curved section off hose; and spending $18 (1ft fuel line, 1 metal hose to hose connector, 2 worm clamps, and $5 toy for my daughter), got it fixed in about an hour. I know it's not a long-term fix but take off the intake and all associated hardware to replace a small hose???

Total dealer quote was $7463 including upper and lower control arms, etc. Beautiful car I've had for 10 years but I can't take it anymore.

 

Gotta pay the fiddler if you want to dance to his music.