A few days ago my S1 4.2 XJ6 threw its Fan Belt. The steering got very heavy as I lost power steering but I had not long left home and decided to turn around and head back.

The temperature had started to climb but was just beyond the 'L' in normal when I pulled into the drive. I was still a bit worried so I got some thin rope and looped it around the Water Pump pulley. I then used a cordless drill with the rope wrapped around the chuck to turn the pump.

I replaced the Fan Belt the next day and refilled the cooling system but, there is now intermittent gurgling sounds and steam coming from the Expansion Tank overflow pipe?

Could I have an air lock or do I need to flush the system?

 

OOPS.

"L" is pretty hot from memory, and Jag gauges are not super accurate.

Was it boiling, gurgling when yo got home????.

Maybe an airlock, not common on S1 6cyl cars from memory.

Is the engine running OK??.

You may have a sad thermostat from that heat episode, I would change it anyway as a precaution.

 

Might as well give it a flush, new thermostat and new coolant. I did mine this weekend and only took a bit over an hour, after I fixed the broken housing bolt the last owner kindly left for me.

As for burping, I just ran it without the caps until warm, had it on ramps as well so the front of the car was higher, replaced the cap on the thermostat cover, car came up to temp and put the one back on the oveflow. It did burp and fart a little and am pretty sure all the air is out.

 

hi Woz, you can try to bleed air from the cooling system?

rotate the coolant recovery tank or radiator cap to the second, unlocked/unpressurized position,

warm up car by idling around 1,500 rpm, until thermostat has gone thru at least 3 open/close cycles and Temperature stays at more or less Normal,

turn Heater ON and TEMP knob all the way to MAX once engine is hot, let engine idle,

you should see coolant being expelled from the radiator or recovery tank as air bubbles are bled out when thermostat opens.

turn off engine, wait a few minutes, remove cap with a rag, add coolant as needed,

repeat by revving engine around 1,500-1,800 rpms. System should not be pressurized while doing this, the radiator cap or coolant recovery tank cap should be in the unlocked position to allow air and coolant out.

when engine has fully cooled, add more coolant if needed.

 

The XK engine does not like being overheated, even for a short time as the head gasket may fail. If the cylinder head does not have a 'stake-down kit' fitted to the exhaust tappets, a tappet may come loose as well and rise up far enough to be struck by the camshaft.

Grant is correct about the Jaguar temperature gauge and the sense of humour with the green area!

If you decide to change out the thermostat, be careful when removing the three bolts holding the thermostat housing in place as they typically corrode and may break. Replacing them with stainless steel bolts will make their removal easier in the future.

I have personally found using an 82 C thermostat rather than the 88 C one used in later versions of smogged XJ6s will help the engine run in a more suitable temperature range for its design.

To assist with bleeding the cooling system, remember to turn on the heater as well so there are no trapped pockets of air.

 

I learned the temp guage and low water light lesson, the hard way!
My car is now lumped.

Expensive lesson, but it is on the road and better than ever with it's LT1 power and OD transmission.

 

Thanks for the replies guys! I hope I haven't done any permanent damage?

I'll flush, change the thermostat, new coolant and bleed. If I'm still having issues it might be something more sinister.

Time will tell?.....

 

I didn't have the time or resources to get a new thermostat but, I did replace it a month ago. Anywho, I pulled the drain plugs disconnected the top and bottom radiator hoses and flushed the system with cold running water.

With all the plugs refitted and the system refilled with quality anti-freeze, I started the engine and let any residual air bleed out of the system. Once the engine started to warm I fully fitted the expansion tank cap and the engine rose to the 'N' in normal and stayed there!

I haven't been for a test drive yet, so I'm not going to sign off on a job well done just yet but, it's looking good so far.

Thanks for all the help along the way.

 

Once you have driven for about 100km, recheck the system when it's cold to see if there is any coolant loss. If there is, you should have the cooling system pressure tested to find the source of the leak.

 

I've driven to work this morning and temp has been good but, there is coolant leaking from the Header Tank. I've just replaced the gasket and think its coming from the cap itself? I've heard that there is a 'screw on' version that replaces the standard type, can anyone confirm?

 

AHA, you are referring to the cap on the top of the thermostat housing, which is usually a blank cap??.

A blank CPC cap part #2001 is still available if you hunt it out.

JagDaim in Melbourne used to have the screw on conversion you mentioned, but that was many years ago that I got one.

 

Grant, yes the thermostat housing cap. I've checked the Jagdaim website and they do list one. I had to call for a price and although you can't see in their pictures, it's made of solid gold. It must be at $140!!!!!

I'll make my own for a little bit less than that....

I noticed that the lip on the filler neck was a bit deformed and was able to straighten it out so the cap has a fighting chance of sealing. Idle checks are good, test drive to follow.

 

Yep, good old supply and demand, but I do agree that is a tall price in anyones book.

That lip is the weak link, and some careful reshaping, as you have done, will give the correct results. I have done that many times.

Only got one of those other units, and I reckon it was up there in price at the time, but did the job admirably, and the OE style was nil stock at that time, so you do what you got to do.

A new blank cap with a nice soft seal will also help heaps.

 

The test drive has been completed and all appears to be well but, I'm going to have a crack at making up my own screw cap and filler neck as it will be one less thing to worry about.

I had a bit of ticking before the this issue cropped up and already have a stake down kit and LH Cam Cover Gasket ready to go, so I'll pop the cover off and take a look.

 

I disagree based on my experience. I have driven a 4.2 engine for over 22 years now, my '84 XJ-6.

...one hot night years ago, (no, it had nothing to do with a girl), I'm driving home happily and all of a sudden I felt a THUNK !

Temp starts rising (so the TEMP gauge was working), as soon as traffic let me I stopped at a level parking lot, opened the hood, heard the coolant gurgling (boiling) among other hissing sounds. Waited a few minutes with engine shut and started to release the pressure in the cooling system by turning the radiator cap slowly; At first I though it was a radiator hose but there was no leaking until I saw a section of the belt hanging.

Ok, no spare belt, have to get home, I am not calling a tow truck, I'm going.

I waited until traffic thinned. I removed the radiator cap, and drove it home with the Heater in MAX about 15 miles away, coolant boiling out, and as soon as I got home I inserted the garden hose in the reservoir tank to cool the darned thing.

Next few days I replaced all the belts, flushed the radiator and block, drained and refilled with new coolant, and from then until today, there was no head gasket damage.

so my point is: these engines run hot to begin with, they DO enjoy heat, and there is some "built-in" tolerance to extreme heat.

yes I was lucky, or was I ?

 

You are EXTREMELY lucky! When the XK 4.2 litre overheats, the head gasket typically fails since the aluminium head has different heat absorption characteristics than the cast iron block. The other two failures I have noticed are valve tappets rising up out of the head, especially on the exhaust side and dropped valve seats. The dropped valve seat usually causes the valve to break and go through the piston crown.

Hopefully you will not have any of these experiences.

 

yes I was lucky, but so far no head gasket failure! Other than the passenger side tank leaking, (twice replaced), I've had no issues with this car.