It's not a bad idea to let the engine tick over for a couple of minutes after a hard run, just to let it settle down and adjust its knickers.
Had a turbo Subaru Legacy a while ago and there was a little sign on the driver's door saying to do that. Obviously the sign didn't mention knickers.
I work on fast ferries running 4 x V20 twin turbo diesels and we never, ever go from full chat to tickover immediately, we always 'take the tops off' before the final slow down and it eases the temperature stresses enormously.

 

G'day All, I just flushed my radiator on my 1977 XJS 5.3L and followed the workshop manual to fill correctly to get rid of air bubbles. The correct Thermostat according to the manual has the little toggle hole at top of Thermostat to allow fill up properly. Open Filler cap, Open bleed valve at top left corner of radiator and fill slowly until full. Leave sit a while and recheck level and top up. Run motor at high idle and let heat up and recheck all again.Close bleed valve and replace filler cap. This worked for me and Temp is below or at N. If anyone knows if this is correct or not please let me know.

Cheers,

Kev

 

If it worked for you and you're sure all air pockets are gone, it's the correct method

Did you get a very strong, steady stream of coolant from the bleed valve....enough to make a real mess out of your driveway? That's what you want (the strong stream, not the mess).

Elevating the front of the car is an old trick that often helps, as the air pockets want to travel upward.

You didn't mention selecting heat on your climate control so the heater valve would open, though. (Or simply remove the vacuum hose from the valve). You might have an air pocket in the heater core....it's fairly common.


Cheers
DD

 

Doug,


Where is the vacuum hose from the heater valve? I have a very small unconnected hose coming from the lower drivers side of the engine(below fuel rails) that leads out to the front of the expansion tank. It looks like it may connect to a valve that is attached to a hose near the radiator/expansion tank. The hose does have vacuum when the engine is running and I am tempted to attach it to the valve. Maybe it came loose or is it supposed to be left unattached? Thanks.

 

It's over on the RH side of the firewall....along with about 73 other vacuum hoses



I'm not sure what that hose is but it doesn't sound like the hose for the heater valve. There are so many vacuum operated devices on a V12 you really need the manuals to sort everything out. But if it has vacuum whenever the engine is running I can assure it was not intended to be left disconnected.

Cheers
DD

 

I will leave the hose disconnected... I thought maybe I knocked it off of something while replacing the thermo switch. You are right that there are a LOT of hoses on this car. LOL. Thanks Doug.

 

No, don't. At least plug it off.

I edited my earlier post to read ".....not intended to be left disconnected".

Best bet, though, is to find out where it should go and what it does. It might be important. These old V12 had umpteen vacuum devices. You really can't just arbitrarily disconnect them. Selectively, yes. Arbitrarily, no.

Cheers
DD

 

Bought an 82 switch from faster jags. Arrived in a day. Going to clean radiator, flush, throw in this switch, and see how goes. Will update you.

 

I have a XJS repair operation manual and will try and find out where the loose hose goes. Thanks.


Update... I am pretty sure it is a vacuum hose that goes to possibly a vacuum dump valve?.... That is what it looks like in the repair manual and the hose reaches just far enough to go on the end of the valve.

 

Did full flush. Not much sediment or sludge in drainage at all. Refilled, bled (but get low coolant light for about 30 seconds when I start engine, think I need to just top up a big).

Replaced aux fan fuse (was blown) and added 82 degree thermo switch. Running just a tad cooler already. Great stuff. Thanks for the help.

 

Congrats!

 

From a really cold start, the low coolant light is on for a good... 10-15 seconds, then turns off. No signs of leakage. Assuming I just need to top up a bit when cold at this point?

 

Sounds like you need to add some coolant...

 

Did your light stay off?

 

Jag is in the garage in NYC. And its raining today (so no way i'm taking it out.. there's no rust on the car anywhere and i'd like to keep it that way). The light does go off after 10-15 seconds. I haven't topped up yet. Will probably do it while cold on Friday afternoon before I take it out. Will let you guys know!

 

Update. Did flush. Topped and bled. Blew out radiator. Changed thermostatic switch lower temperature switch. Also took out cats, mid resonators, and have quick cat intakes.

Result - fun, fast, loud at high revs - and best of all cool. Runs below N almost all the time now (except in NYC traffic, at the N).

 

As we are speaking of temperatures...


It's summer, and getting somewhat hot here in Colorado. It's been teasing 90's lately, and I'm sure that we'll be closer to the 100's sooner rather than later.


Morris runs fine, stays around the "N" as long as it's not just sitting in non-moving traffic (then it hovers above the "N") and I have the air conditioning off. The problem is that when it's this hot, this is when I WANT to use the air conditioning. THEN, whether I'm moving or not, the temp goes way up. Yesterday was 89 degrees, and the needle got to about 3/4 high with little/no traffic, speeding along on the highway. However, it never boiled over, though the bonnet itself was pretty hot (whether from the sun, engine heat, or both, I can't say). It stayed the same once I entered the city and I hit traffic. It started to go down once I turned the air conditioning off. I'm afraid this might be overheating, but other vehicles I've owned also tended to get this hot with the air conditioning running and it was still in the "normal" range (at the top of it, but still in range).


Thoughts on this?

 

Not sure, I should have maybe posted this on this page, but I had an issue a couple of weeks ago where the clutch disk on my AC condensor decided to remove itself while I was travelling at 70 MPH on a North Bound highway. It blasted parts through the radiator (now leaking like a seive) as well as dislodged the belt that drives the water pump.

I am my own mechanic of sorts (Shade Tree type??) and am HOPING all that is wrong is the radiator. I am trying to remove the stupid thing and cannot find or figure out what is holding it in at the bottom.... Mind you. No lift, no pit. Nothing to get the car in the air to see what in the hell is holding the bottom end of the thing in.

Tried looking on You Tube, but I find one video and 5000 others dealing with Hondas, Dodges, old Le Car's and the like.... Anyone have any leads as to HOW to remove the radiator out of a 1989 XJS V-12?? PLEASE HELP....

 

If all the pipes and hoses, and the flat metal piece across the top are removed there shouldn't be anything (like bolts) left holding it in, the radiator is just located on the bottom by two pins that go into rubber grommets ... but, the foam around the sides and bottom, and the grommets are probably pretty well bonded to the radiator and body of the car, and the radiator itself is fairly heavy. I don't remember exactly what I had to do other than lift and pull, maybe try to rock it from side to side also. I did put sheets of cardboard on both sides of the rad before removing, to try to protect it since, as you noticed, it's very crowded in there. Also some moving pads/blankets on top of the engine.

I was able to get mine out by myself, but it would probably be easier with someone on each side of the car.

Hope this helps! Eric

 

It is unusual for the temp gauge to go up well above the N even if the aircon is on. In those sort of temps my car has never been this hot. It suggests the cooling is marginally OK until the aircon condenser radiator has to do some cooling and thus is passing extra-warmed air into the coolant radiator. Definitely I would investigate in your position.

My suggestions would be, as a start (all this is well covered in the Great Palm's book):

• remove the coolant rad and clean out the fins as they get seriously bunged up, with debris you cannot see, in the gap between the oil cooler and aircon condenser rad stack, and the coolant rad
• If the coolant rad has never been renewed, have it recored
• clean out the oil cooler and aircon condenser fins
• check the engine driven fan is working correctly. It has a heat sensitive hub that is meant to freewheel when the engine is cool and 'go solid' when hot and thus drive the fan fully. If this hub piece is faulty (frequently they are) the main fan will not be pulling enough air to cool the rads.
• check the water pump belt, and the belt driving the fan, are properly tight
• check the small electric fan is coming on with the aircon (some do OEM, some do not, also OEM) if yours either is not working at all, or is not coming on all the time the aircon is on, rewire it to do so. The forum will explain how and it is not hard to do. The OEM fan is very inefficient, swapping it for a modern aftermarket fan is a very good plan, in any event.

good luck
Greg