I drive a 1982 XJ6 in CA that have get overheat several times (around 5 or 6 times) up to 90° C ~ 120° C (according to the themperature gage), I already change water pump, replace fan clutch (installed another used one), cleaned thermostat housing (thermostat is missing since I bought the car) and I will install a new hose kit and thermostat. The car rides like normally from 60° C ~ 70° C but when starting an ascent even if is short (.5 mi) my car begins to warm up. Do someone knows what could be wrong?

 

With a new thermostat you should be running at least 82ēC to 88ēC, depending on what thermo you bought. I suspect your new one is stuck open.

But, as far as overheating goes.....

-Your used fan clutch might be weak. After a good drive to get the coolant hot turn off the engine and spin the fan by hand. It should only spin 1-1.5 revolutions. More than that is suspicious. If it freewheels, it's outright bad.

-Remove the radiator. I can all but promise that it's clogged with leaves and debris. You can clean this yourself but as long as the radiator is out you might as well have it cleaned professionally at a radiator shop. It might well be clogged internally

-Make sure your aux electric fan is working. It should come on at 94ēC. If it doesn't, post back.

There's nothing exotic about the cooling system on the Ser IIIs. All the usual checks and fixes apply.

Cheers
DD

 

Hi Doug, thank you so much! your advice was very helpful.

I think the fan clutch is working ok, it goes from .75 up to 1.5 turn when spinning by hand.

Actually my XJ6 doesn't has a thermostat yet, I'll install it this Saturday. It is a 71ēC. I'll take your advice of removing the radiator for cleaning same time.

I was thinking that the small fan in the front of the condenser was for A/C system but anyway I realize that it isn't working when my car is over the 94ēC (even when A/C is ON) but it does work when applying DC power from the battery.

Any advice?

Regards
Marshall Ro

 

Cooling fan:

It's probably the red relay (left of radiator, up high) but here's a checklist that might help:

http://www.jag-lovers.org/xjlovers/x...nchecklist.htm

Thermostat:

I advise against a 71ēC thermo. You should use an 82ēC or 88ēC. The fuel injection system is still providing "cold running enrichment" until about 80ēC so you want to run at least that hot to save fuel.

Make sure to get a thermo with the steam relief hole in the mounting flange. If not, drill a 1/8" hole at the 12:00 o'clock position.
Cheers
DD

 

For what it's worth - I had overheating, but not too bad (its England after all, with cold and wet summers!!) and had the radiator re-cored, which was possible because it was copper with brass fittings, as I think yours is. I had no more problems except when it got REALLY hot, as in Waterford, Ireland, in a traffic jam when the fuel vaporised in the fuel rail.

As I remember from my 1980 XJ6, the thermostat has an extension that closes off the bypass passage as it opens. With no thermostat at all, your coolant could well be finding an easier way back via the bypass to the waterpump than the radiator.

 

Good point, Fraser, and a good reason to be careful about generic thermostats!

Cheers
DD

 

Hi Fraser/Doug, I have another issue:

cooling water is going to the engine probably because it warmed up several times and gaskets may be damaged. I would like to know which parts do I need to repair and gaskets sets that should I buy.

Cooper block weld could help ( CRC 05371 Copper Block Weld Permanent Block & Radiator | eBay ) ??

Thank you in advance.

Regards
Marshall Ro

 

Those cooling system sealants sometimes work, sometimes not....and even if they do you can't be sure for how long or if they'll clog your cooling system. But if you need a band-aid until you can replace the head gasket it might be worth a try.


Presuming the diagnosis is confirmed you need a "head gasket kit" which any Jag outfit can provide.

You might need lots of other parts as well depending on your mood and pocketbook. It makes a lot of sense to replace hoses, belts, fuel injector hoses, etc etc while the cylinder head is off.

Have you ever done a head gasket job before?

Cheers
DD

 

No, I have never do a head gasket job before but, I already have contact professionals shop for that. This professionals are very close friends to me but, they haven't worked that deep with this kind of car so, that's why we want to know a close list of parts I'll need to buy before starting the job.

I already identified the head gasket set that I'll need.
What I have changed is fuel injector hoses on 12/2010.
Cooling system hoses on 04/2011.
Rotor, cap, fuel and air filter, sparkplugs and wires set on 03/2011.
What do you think about replace timing chain?

Regards!

 

The timing chains very rarely fail. I wouldn't worry about it.

Cheers
DD

 

Hi Marshall03

The timing chains on these engines are pretty long-lived, but eventually they wear out. What sort of mile is your engine at ? The top chain is easy to replace with the head off, but not the bottom one which needs quite a lot of dismantling to replace. I am assume you would be replacing with chains without split links. I would never want to use a split link in timing chain, maybe I am old fahioned as |I believe a lot of people do this. It is, of course, a duplex chain top and bottom, so maybe its OK.

I'm not sure what you mean by

If it is what I think it is, (from personal experience with my 1980 4.2 way back in 1990 !), you have cracks between the cylinder bores due to VERY poor construction method in the engine. The blocks with the long studs, (7L and 8L blocks) had castingS with siamesed bores, (1-2-3, 4-5-6). So as first cast, coolant could not cross the block between the bores. So Jaguar engineers put water passages in by machining a horizantal slot between the bores that broke into the coolant jacket either side, the cutting tool accessing for cutting via the bores !! So now you had bores that look like a 2-stroke engine !! So to cover these holes, thin-wall liners were pressed in. The trouble was that the machined coolant passage was only about 1" below the block top, and about there is only about 1/4" between each bore, so over time this bridge of metal would crack through from the coolant jacket towards the top of the block. Once this happens the bridge strength has gone, and the block sinks here, taking the clamping load off the cylinder head gasket.

The cracks now allow combustion chamber gas at high pressure into the coolant jacket, which forces out the coolant, result - overheating. I had this with my car and it wasn't until I went to a chap to buy a 2nd hand bootlid that I found out the truth. (Jaguar never said a dicky bird about this problem, shame on them, they just took the money in exchange engines).

I bought an uncracked block off this chap and rebuilt my engine around it. According to him 7 out of 10 7L blocks crack and 8 out of 10 8L blocks. Jaguar eventually gave up this horizontal water passage slot, and cut a narrow slot vertically between each bore, and omitted the liners. This meant no cracks, but the head gaskets do still fail, albeit after a much longer interval.

When you get the head off your engine you will know the situation; look for cracking between bores 1-2, 2-3, and 4-5 and 5-6. The only cure is to dismantle the engine completely, then with the bare block, machine out the liners, machine a recess around the bore top and insert "tophat" liners. These liners have a lip such that when pressed in, the two lips almost touch the lip on the next liner, thus covering the crack, and giving the headgasket fire ring something to seal on. The block with front timing cover attached, is then faced off ready to assemble. Timing cover must be machined at the same time as the top of it forms part of the engine top for the head gasket to seat.

Alternative to the above is to find a later engine with the vertical coolant passages in the block, not the horizantal ones. These are easily visible on the block top once the head is off. I dont know what engine number the change was made.

You may, of course be lucky and have the vertical slots, so it will be just a case of head off and change the gasket.

 

Well, my XJ6 stop overheating when replaced fan clutch, thermostat, hoses and the red fan relay.

Now I can ride it and it does not overheat but, I know that coolan is mixing with engine oil because I can see water residues inside the oil cap.

It is not the the vertical coolant passages type. I upload some pictures of the engine, the condition I bought it on 02/2010:

Jaguar Forums - Jaguar Enthusiasts Forum - marshall083's Album: marshall083

Regards!

 

Apart from cracking between the bores, (and I am afraid this looks likely in your case, unless you have had the head off and seen no cracks), there is another path which allows coolant to enter the oil.

The timing chain cover forms the back of the water pump, and there is a passage through from the pump into the block. Over time and neglect of previous owners failing to replace antifreeze, the corrosion inhibitors in the antifreeze eventually disappear by molecular breakdown, so corrosion can start on the cast iron block and the aluminium head, and front timing cover. There is a wall about 3/16" thick around the timing cover passage for the coolant into the block, but casting technology means this can vary so only 1/8" could be the thickness in places. Over time this wall can corrode away allowing coolant to enter the timing chain chest from where it enters the engine oil. I have seen one timing cover almost gone with about 1/32" wall thickness left in place !! My own engine was pretty bad, so I cheated and used some Araldite to make up the wall thickness. It must have worked as I had no more problems. OK, I had an uncracked block too.

I said "over time" and in most automobiles, you would never expect to get to this state of things before the car is scrapped, but your car is a survivor at 29 years old !!

If you want to really get stuck in and fix it, they are a lovely engine to work on.

 

I know that antifreeze replacing was an issue. As judge by the pictures you can see expansion tank was damaged and the color of the coolant leaked is like brown, so I replaced expansion tank.

Sure I will continue working on the car. One day it will be like new, step by step.

Thanks Doug and Fraser. I will start working on it later this month so, probably I will more questions by that days.

Regards

 

Ferel free to ask, as I have "been there" as they say, although I have to say it was a long time ago, like 1990. I rebuilt my 4.2 engine round an uncracked block and before that did a 2.4 that was in my Mark 2. The 2.4 was a lovely engine, but it did struggle a bit to push a Mark 2 along. It must have been all that body lead in the shell !

 

Hi again. I took the jaguar to the shop last week. Yesterday I when to see and the process was in taking separating the head but, my surprise is that the mechanics can't separate the head of the block. It seems that is very stuck and this becoming difficult to retire it of the block.

Any advise?

 

There's a fairly substantial "ledge" on the underside of the head alowing a bottle jack on each side to push the head off.

Apply pressure, come back in a few hours, apply more pressure, repeat, repeat. Eventually it'll come loose. Last one I did took 2-3 days under pressure to eventually come free.

OR......

Remove the studs. Removing the studs really speeds the job along but you run a risk of breaking a stud inside the block....which sorta ruins your day :-)

Cheers
DD

 

My heart is with you on your engine, as I have been to Hell and back for an XK engine !!

If you feel tempted to take the head studs out, be very cautious, they are about 12" long and pass through the coolant passage in the block and can corrode badly. So if going down this route, you need to take out the core plugs in the block, each one being next to a stud, so you can see how corroded each one is, and also observe what happens when you try to extract it. If the top moves but not the bottom leave it alone.

 

The bottle jack on each side worked from the night to the morning. The head studs are in good condition, 4 of them was already taken off for cleaning and looked OK.

Thank you very much!

 

Do you recommend iridium spark plug for this Jag?