Sudden & violent loss of coolant

[jimthack180]

I have a 1988 V12, only done 80000, last serviced at 76500, when parked in town yesterday ( very hot weather ), with the engine switched off, I was suddenly aware of steam coming out of the gap between the nearside front door and the wing. By the time I had got out and walked round to have a look, it was like Niagra falls. All the coolant was escaping onto the road, dripping down under the nearside front wing, just behind the wheel arch. I've only had the car a few weeks, it's my first Jag, & I've done about 800 miles with no problems. It also sailed through the MOT the other day, absolutly fine. Had to call the RAC, who suggested it might be the heater & relayed me back home. The last owner apparantly only did 260 miles in 4 years and the car was in his barn most of the time. Any suggestions ??

[dhdove]

Jim
Don't know about the V12's but the 3.6's header tank overflows and backfeeds into and from a "holding tank" (plastic), held in the OFFSIDE wing behind the front wheel. If this splits water pours out between the front of the door and the wing join on the sill.....sounds familiar?
I've never really worked out what this second "header" tank was supposed to do.
When mine went on the 3.6 some time ago I just kept a careful eye on the coolant level in the header tank and didn't allow it to get too HIGH thus filling up the tank in the wing.
Oh, I remember what it's there for now, to fill your sills up with corrosive anti-freeze solution.
Don't give up on the old girl. After being stood it's probably not her fault.
The #1 Question is how much coolant have you actually lost? If not a huge amount then hopefully you can proceed as above in the meantime.
Otherwise you may have other problems...ouch
Sorry you missed out on Cadwell Park as a result, it was great and HOT (see elsewhere)
Best Wishes
DH Dove

[Mark_B]

Common problem I understand with the v12 is debris such as leaves accumulating between the radiator and aircon condensor blocking airflow. Quite often the temperature gauge is a liar too. If an engine is almost about to boil over but doesn't quite, it generally does so less than a minute after shut down, as the heat flowing from the hot cylinder head exceeds that of the heat loss from the radiator.

Fortunately there's a lot of very good advice about v12 cooling around especially from the usa, I think the Kirby Palm -edited and produced compilation of newsgroup postings from xj-s owners: 'xj-s, the book' has gathered everything that's worth knowing about v12 cooling together in one place.

[poprivet]

the 3.6's header tank overflows and backfeeds into and from a "holding tank" (plastic), held in the OFFSIDE wing behind the front wheel......
I've never really worked out what this second "header" tank was supposed to do.
Someone once suggested that during a dealer service, the metal tank was topped up to overflowing. During the first couple of heat cycles the excess water expanded into the plastic tank leaving a cooling system without air-locks and at the correct maximum fill.
The plastic tank merely stopped the excess water dripping on the floor which would have worried its owner.
Any other theories?
Pop

[Brakebuster]

the plastic ' header tank/overflow bottle ' located in the wing ( or to be more accurate ' atmospheric recovery bottle ) is indeed for overflow, however , it also has another function,

as the engine coolant cools it creates a vacume and pulls some of the overflow liquid back into the proper header tank of the cooling system,
thus keeping it topped up

this ' recovery bottle' should be filled to about half way if being serviced, allowing fluid and not air to be recovered if required

BB

[gjeffrey]

The UK V12 of that era has a plastic coolant overflow bottle 'inside' the wing. There is an aluminium panel that forms part of the wheelarch on the passenger side - the bottle is inside there. This device catches overflow coolant from the header tank. The plastic bottle has it own drain pipe too - which emerges at the bottom of the passenger side wing.

If the coolant gushed from this area check this 'overflow' bottle. I recommend you read Kirby Palms free book.

If the coolant was hitting the passenger side exhaust pipe - likely it is a leak from the pipes that enter the heater matrix or even the vacuum valve that controls heat to the cabin via these pipes. The vacuum valve is a common item to need replacing every 7 years or so as they simply rot away. Replacements can be bought at suppliers like SNG Barrett for a reasonable price. Fitting is a bit tricky but do-able. On a V12 you HAVE to make sure the coolant system is FULLY operational - don't drive the car unless it is - otherwise it can cost you an engine - read Kirby Palms book.