Originally, I was going to post about my loss of coolant. I was going to just add the one picture that shows fluid across an area of the engine, and ask if that could possibly be coolant, and if so, what's broken...

Then I broke a hose (a very fragile one it turns out), and I'm wondering A) Could it be that this was already partly broken and the cause of losing coolant, and B) What exactly is it that I broke?

I have about every PDF imaginable for this car, including the Workshop manual, but I'm having trouble specifically identifying the hose that I broke. It appears that it is indeed a part of the cooling system, but I'd like to know if it's low or high pressure, and if this might be a common area for leaks. Also, is it possible that fluid only goes through this hose in certain cases (like when the heater is on or when the AC is on)?

Any help is greatly appreciated.

 

I figured it out. Part-load engine breather tube. Temporary fix with duct tape. Will replace after I'm home.

 

Yep, the part load breather tube. But the more important question is where are you loosing coolant ?
These engines DO NOT like being OVERHEATED.
As it is a normally aspirated engine, my 1st place to look would be the plastic thermostat housing.
2nd place I would check is the heater hoses that run under the inlet manifold.
You do know the temp gauge tells lies, and normally shows about the middle until its a bit too late ?
A good reason to enter the RealGauge prize draw if not already done so.

 

Thanks Andrew for the ideas of where to check. Yes, I'm aware of the lies that the temp gauge tells, so I've been checking it at least every other day and also do not see any other signs of overheating...mostly smoke or steam...I don't see any of that. 95% of the time, I drive short distances (15 minutes).

It never seemed to have a problem before, but now, every once in awhile, I do smell coolant after I stop the vehicle, but I never see any leaks.

I'll mention the following at the risk of public lashings, but maybe it will help:
I had the common problem of the expansion tank coolant level sensor float not floating and therefore causing my coolant level indicator to always come on - though I clearly had plenty of coolant. After lots of reading in these forums, I was able to "fix" the problem with a float-helper (foam ring). That resolved the issue for close to a year, though I still checked the level quite frequently. It then slowly started failing, probably due to the float getting "water-logged" (yes, I was still checking the actual level). Recently, I was about to go on a rare trip (3 - 4 hours) and I really didn't want to have the constant red light indicator on my display the whole time, so I jumpered a wire, bypassing the float detector. Everything was fine and the level was good every time I checked it (this was about a month ago). Then I was about to go on another trip (2 hours), and checked the expansion tank, only to find it completely empty. I added coolant and then checked it again just before I was to head back home, and it was empty again. I filled it back up, watched for leaks, etc. and then headed back home.

Before the first trip, I recharged my AC (it was low). AC was fine the whole trip, but I decided to check it again prior to the second trip, and hardly had any pressure, but plenty of cold air. While I was charging the second time, it started out with pressure and then seemed to lose pressure - the odd thing was that I had just topped up the coolant reservoir and, while I was injecting the AC fluid, it appeared that the coolant level was fluctuating and perhaps even a bubble in sync with what I was doing with the AC.

As far as I know, the AC lines and the coolant lines are separate systems, but if not, maybe that gives an indicator as to what's going wrong? I continue to get very cold air from the AC and good heat from the heater...

 

The AC refrigerant (gas) lines, as you rightly stated are not inter connected. I also had intermittent lose of coolant ( about 1/2 pint ) but only if, and this is the weird bit, if I went to my local motor factors, exactly 1 mile away, and drove back again
had feint smell of antifreeze but no visible drips.
I could drive to my aunts in wales, 200 odd miles each way, and no loss of coolant or whiff of antifreeze, then 1 day I noticed a bit of damp at the back of the engine / bell housing area. Knew what that was, the dreaded heater hose pipes ! If I was you I would be looking for whitish/ blueish calcium like stains from the back of the engine/ bell housing area, a bit like limescale stains.
Small leaks evaporate with the heat of the engine before they can turn to drips. You may even be able to look down the valley under the inlet manifold with a small extending mirror , impossible on mine as the supercharger is in the way, and see an escape of steam, or at the least a fogged up mirror. I know its been a bit of a long winded reply, but hopefully helpful .

 

Start a collection of plastic lines for the coolant etc. Not very expensive. Coventry West near Atlanta will sell you all the heater and coolant hoses for about $400. Worth every penny. Much cheaper than an engine.

 

The heater or "octopus" hose is probably where your leak is as Andrew says. It is difficult to see, but that is where I had some recent leaks on my XJR. Not so fun to change by the way, but there are many here who have done it and documented how they did it. Good Luck!