I stopped major activities with my XJS until spring time. I only start the car in the garage every week or so, and occasionally take it around the block when weather allows, to keep the juices flowing. Did not expect anything bad to happen...

Well, something did happen. Today it was sunny outside. So, I decided to take the cat around the neighborhood. On my entry back into garage, I noticed a trail of liquid. Looked like greenish -- coolant, I assumed.

I raised the front of the car and saw coolant streaming (literally streaming) down from the area somewhere between bell housing and transmission pan. It is streaming only when the engine is running. When I shut down the engine, the leak stops.

I could not see clearly exactly where it was coming from. neither from the bottom nor from the top. Though I took pictures

Given how persistent the stream was, I assume some hose might have broken? But what hose exactly? What coolant related hoses are this far in the back?

 

My first thought is "heater hoses". If one of them sprung a leak it would flow down the firewall/bellhousing vicinity

Another thought is the heater core blew, emptying coolant in the HVAC case....which then flows out the little drain tubes. The tube poke through the floor of the car just aft of where the engine and transmission butt together. However, if a heater ore, you'd hear/feel/see/smell something inside the cabin

Cheers
DD

 

Thanks, Doug. I did not (and do not) smell anything unusual inside the cabin. I did not suspect anything was amiss until I got out of the car and saw the coolant trail.

So, this means it is likely one of 'heater hoses" that broke? How to access and troubleshoot them?

 

They're pretty well buried under a bunch of 'stuff' at the firewall. If you remove the balance tube...which itself is a bit of a chore.... you can get a pretty good look at them. And, if you've gone that far, you might well replace them regardless, unless you know they've already been replaced in the last few years.

Cheers
DD

 

The heater tap would be a smart thing to replace, "while you in that deep".

 

Jaguar was intelligent, there is *Just Enough* room in there to get a socket driver in and a smallish hand to pull off the old hoses and push on the new hoses. Not a millimetre extra space, but it is possible without major disassembly.

 

Ok, thanks, all. Wasn’t planning doing all that, but I guess I have no choice...

first thing first. Where is the balance tube and how do I remove it?

 

Balance tube is at the back of the engine, it joins both intake manifolds to provide air flow between them. Metal tube with rubber sections at each end held on with hoseclamps. Be aware that the rubber can be fossilized from heat. Mine broke up when I tried to remove them, I simply went to the junkyard and found something similar in shape in a radiator hose that was the right diameter and cut out the length I needed.

 

The rubber sections at each end of the balance tube is 1". Mine are 55mm long.

 

Ok, took a look at the back of the engine and figured out where the balance tube is. It is the thickest thing in the middle of the picture below.

I will start removing things from there, including the balance tube. Looks like I might need to remove a few additional things, such as blue/white and a few other things.

Strangely, I don't see anything amiss when examining the area from the top. Maybe it will become clearer once I start taking things apart?

Is it ok to start the car after removing the balance tube? I think I will need the engine running to pin point the location of the leak.

 

Or start the car and see if you can see the pinhole from the top. I quickly saw where I had a pinhole in my hose.

 

The heater hoses are gone; there are three, one from the A bank water manifold to the tap, and one from the tap to the heater inlet, and one down the B bank side from the heater outlet to the return. I would advise against starting the engine, what will it prove? You know you have to change all three hoses to be safe, as one has failed. The hard part is getting the old hoses off their spigots, and the copper pipes leading into the heater matrix are not that strong. I suggest a sharp rigid knife and cut them off their spigots starting at the open end and cutting along the spigot to its end inside the hose. All three can be changed engine in situ, it was one of the first ever jobs I did on my car 20 years ago, for exactly the same reason as you.
The attached pic shows two of the three hoses. They are, as you look at the photo, just to the right of aircon valve, one above the other. The lower of the two goes to the heater valve (not in the photo as removed, but sited in the middle of the firewall just below the bonnet closure line) and the higher you can see goes to a solid tube running down the RHS chassis rail. The hose from the A bank water manifold to the heater valve is easy to trace if you start at the valve and work back.

 

Great pictures! Thank you for sharing!

gives me idea of where to focus when clearing the area at the back.

Will make next attempt over the weekend

 

Quick update. Finally had time to look for the leak this weekend (as last weekend was lost.)

I found the leak. It was not easy to see initially. But I let the engine run longer (while placing an oil collector pan under the car to collect streaming coolant.) As the engine was warming up, I started seeing smog, which led me to the leak.

Folks were correct: it is one of the heater hoses.

I suspect that I likely disturbed it when replacing oil pressure sender couple of months ago. But it was likely already very old and on the way out anyway. So, will start clearing the area in the back and replace the hoses.