Long story short, my mother XK started to run hot so she turned on the heater and found a parking lot ASAP.

I Arrive, coolant tank is empty...... We let the car sit for a few hours, I go back top off the tank & start up the car to see what's going on. Once the engine was up to temp it stayed there, engine running fine. I gingerly drive home staring at the temp gauge. Almost home the low coolant warning comes on, temp is still fine as I pull into the garage.

After shutting down the engine, pop the hood (cover for coil packs was already off) I can hear a hissing sound coming from the #4 plug area (drivers side, rear by firewall in case my cylinder numbering is off). I'm thinking this is the pressure from the coolant system escaping somewhere. What is the most likely source in this general vicinity?

Few years ago I replaced the expansion tank and all hoses except those going to the heater core.

This weekend I'm going to rent a coolant pressure kit, I would like to have a rough idea of where I should be looking.

Any ideas?

I need to update my avatar, it's over 180k now.

 

No idea, but your Mom done good

 

The Norma connector between the engine and the octopus hose is famous for leaks but I have never heard one leaking so bad as to hiss. Big job changing that out. Some have cut the connector out and replaced with a piece of 5/8" heater hose and clamps.

Just because you replaced the reservoir doesn't mean that is not leaking now.

A pressure test kit is the way to go.

 

+1

The limitation with a pressure test is running it cold. This will find a leaking hose or connector but miss a pinhole or minor crack in the reservoir which only opens when the engine is hot. I spent weeks chasing down an intermittent leak from the base of the reservoir on my last XK8.

Plastic cooling system components are great for manufacturer's profit margins but they have a much higher failure rate than metal equivalents.

Good to hear your Mother's quick thinking prevented the kind of overheating damage we read of so often on the V8's.

Graham

 

My mother has been around exotic / sports cars since my father bought his first Corvette in 1960. She's well versed on what to do when certain things happen
This Jaguar is her all time favorite, purchased with 60k on the odo and every year talks about moving to something else or an XK with lower miles....this one just keeps chugging along. Against my better wishes the chain & tensioner have not been looked at since my parents purchased the car. Knock on wood.


I would be estatic if it were the expansion tank. I sort of ruled that out because last time the tank had a crack it would only loose enough coolant to empty the tank. This time it took 3/4+ of a gallon to fill it.

It was a 95 degree day and she had the A/C on.

I've never "heard" a coolant leak like this with the steam pressure escaping somehwere like that.

Worst case scenario is a head gasket - what are the typical signs with this engine other than oil / coolant mix? Anything else I should be aware of?

 

I think I found it.

Using a pressure tester on the expansion tank, it leaks out as fast as I can pump it in. The sound is coming from the front of the engine, looks like the gasket under the junction where all the hoses connect to....guessing that is the thermostat housing?

Looks simple enough, any gotchas with this gasket? Any "why you are in there" parts I should order?

All of the hoses are only a few years old

Should I buy a complete new housing like this kit contains?
http://www.rockauto.com/catalog/x,ca...ch%2Bfor%2BBGA

 

Thermostat Housing is a common failure. The preferred update is to replace with an aftermarket aluminium housing.

Here's the diagram and list from the Parts Manual:

JAGUAR XK8 - Thermostat & Water Outlet Pipe.pdf

Where exactly is it leaking from?

Graham

 

The hiss may be coolant leaking onto the hot exhaust or engine. I found a leak coming from the hoses at the bulkhead dripping down on to the exhaust. I've also had it leaking from the back of the vee under the manifold and from the thermostat tower base. A stain from the coolant may be a clue. Because of all the clutter at the back of the engine it's hard to trace. Over time i've replaced every hose under the vee and back of the engine and it's a fiddly job requiring removal of the throttle body to trace. Check the back of the vee on the left for dribbles especially when the engine is hot. A stethoscope can be helpful to localise it.

Regards
John

 

Just saw you localised to thermostat tower. Replace it with the alloy one but beware. I put a new gasket in and it still started to leak a year later so i took it off again and put two o rings on top of each other in the groove. It's been fine for a few years now.

Regards
John

 

Well, it's not the thermostat housing.

I topped off the system with water so I could see the leak.....this explain why the noise was so hard to pin-point since it's coming from a hose under the intake manifold.

In the first photo, the hose at the bottom of the picture is fine and I think I replaced it since the clamps on both ends looks new. It's the hose buried under the intake spraying down.

Anyone have the diagram for this hose? I cannot find the shop manual I ordered or my parts diagrams (recently moved, on a travel laptop).

Figures.....the one hose I did not replace. That's how it goes

Am I taking the intake manifold off to replace this one?

 

From your description, I believe you are talking the heater return hose, 1 of the 2 heater hoses that run under the intake manifold on your XK8.

The 1st hose, the heater feed hose (the one that you already replaced), connects to the coolant outlet pipe above the front of the engine & runs under the intake manifold where it then connects to the heater pipe at the rear of the engine. The 2nd hose, the heater return hose, also runs under the intake manifold. It runs from the back of the water pump housing (directly below the thermostat tower) to a connector at the rear of the engine.

You will have to remove the intake manifold to replace the heater return hose. I did this job replacing both hoses at once on my 97 last year & it was not too bad.

Attached is a PDF of TSB 303-48 which describes the procedure in detail. There are also a few diagrams showing the path of the hoses. Please note the parts list at the end as you will need to replace all 8 of the intake manifold inlet gaskets as well as the throttle body gasket.

The JTIS will also be invaluable to you, particularly the sections involving the throttle body & the throttle intake elbow.

I also took advantage of having the throttle body removed to thoroughly clean it & replace alot of the brittle vacuum hoses attaching to & surrounding it. You will see what I mean when you get it all apart.

I also have attached a pictorial that was done on an XJ that helped me a great deal when I did the job. This pictorial is not my work. Heater hose pictorial credit is as follows (with many thanks):

Heater hose replacement on X308 - 7/06/2005
Copyright 2005 jaguar@blackonxy.net

Best of luck to you!

 

Yup, that's the one.

Thank you for the links, will come in handy.

Back when my mother first bought this car I picked up a two volume set of 3-ring binders that was sime kind of shop manual. I have no idea where it is. I'm assuing it's the JTIS in paper form? I'm sure I also have it on a CD too....need to start digging.

The job doesn't look too bad, I can take the intake manifold off my 928 blindfolded I've done it so many times.

There is also a small oil leak at the front of the motor I wasn't aware of. Searcing around the foum looks like it might be the front oil cooler line, need to tackle that before it ruptures.

 

JTIS is available for download from FAQ's if you can't find your CD.

Graham

 

Found it, thanks!

Well, a whole pile of hoses ordered and a new aluminum thermostat housing.

 

Unless you have a set of Crow's Foot wrenches, you might want to check previous threads on swapping the Thermostat Housing. Most of us end up bending a wrench to access the rear bolts.

Graham

 

Even with the intake manifold removed?

I have crow's foot wrenches and a few bent up / welded wrenches from other projects.

 

Not many have the intake removed when tackling T'Stat replacement. At least that's one small benefit of having to replace the heater hose.

Graham