Hi I'm a newbie jaguar owner and poster, I have a 2000 S-Type 4.0 L with 160,000km it is in very nice shape inside and out but I bought it with some existing engine trouble of overheating and a pats alarm code 16 causing the car to be immobilized, I think I have fixed the alarm code 16 by making sure the battery is fully charged and the code goes away then the engine will start but the main problem is overheating. The water pump has been replaced nothing seemed to be wrong with the old after removing it and the thermostat was replaced as well,
still overheats... I properly bleed the air out of the system and it seems to be fine at idle but when I take it out on the road and give it a little test it seems as soon as I step on it a bit the temp gauge goes from proper half way operation right up to the red very quickly and it blows coolant out the lid of the reservoir tank, I pull over right away let the engine cool (it is hot) and when I take the fill/bleeder cap off the little tower on the engine just above the thermostat it's full of air again and again, this happens every time. I think it's filling up with air or exhaust gas which causes the thermostat to close and the engine quickly overheats... How can the coolant system keep filling up with air over and over 6 times so far for me, is the head gasket blown and causing this...

Thanks for your reply
Dave

 

Hi Dave, it does sound like a blown head gasket, but have you had the header tank and the exhaust fumes analysed?

 

Also check whether the timing chain has slipped, probably due to the tensioners having failed. Note that you need the new metal-bodied tensioners.

 

I haven't had the header tank or exhaust analyzed, not sure what the header tank is ?

 

It seems to run ok jagv8 except has a low and sort of erratic idle could a slipper timing chain cause the air that keeps showing up in the coolant system though.

 

Er slipped*

 

The header tank is the part of the cooling system where you fill and or check the coolant level.

 

Check the thermostat housing - the OEM plastic housing is crap - there could be many hairline cracks within the housing assembly - same goes for the plastic cap that is on top of the thermostat housing.

If your testing rules out a blown head gasket - I would highly recommend upgrading the thermostat housing to the aluminum version... I did so last year and what a difference!

 

Okay.... I am just amazed.... after weeks of trying and replacing things like the water pump, thermostat... I had started to convince myself that it was turning out to be a head gasket... A very expensive job...

I can't believe I have fixed it.... It was the cheapest part you can buy... A coolant tank cap... Yes just the cap.. The cap was blowing out, the system was de pressurizing then then water around the engine would boil causing the thermostat to close, the boiling steam in the system then caused the thermostat to stay closed because that area was now full of air ... I can't believe it...I was ready to take the engine apart to try and save on the monster repair bill of head gasket repair... in the first post I didn't know that the lid was blowing coolant before it overheated, I thought it had overheated first and then blew coolant out the cap... Thank you all for helping and if you have an over heating issue try the $7 cap first lol

Thanks guys cheers

 

Please don't forget the timing chain tensioners. They will bite you hard. Maybe they have been replaced??

Keep an eye on the top tank because they are very prone to cracking and leaking. Your old cap was not allowing pressure to build and you have now fixed that so the cooling system is under full pressure.
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Well it was fixed and fine idling in the lane way.... The new cap definitely helped with that, but I spoke too soon a road test proved it to be overheating again...

I have found a new problem that may be part of the solution, the aux water pump is not working due to a bad connection from the brown blue wire at FC3-2
That leads to relay #5 , the aux water pump relay.

I will get this fixed and let you know.

 

You may have an airlock in the cooling system. These engines are difficult to bleed. Look up some past threads for the recommended procedures.

 

I strung a new wire from FC3-2 (brown blue wire) to relay #5 and cut the old one, aux water pump works now and I was able to properly bleed air out of the coolant system. So far staying cool on a long idle and a short test run, fingers crossed

I will post results after further road testing.

 

It still overheats, I have the aux water pump working now so I can stop the engine from overheating by turning on the interior heat and the engine stays at normal half way on the temp gauge but if I turn the heat off the engine temp quickly climbs and it overheats. Air constantly gets in the thermostat housing and the top radiator hose and the reservoir tank fills itself with coolant until I turn the interior heat on and it seems to blow the air out of the thermostat housing and top radiator hose area into the reservoir tank (lots of bubbling) and then the coolant in the reservoir drops back down to normal level and the engine immediately cools back down. I pulled the thermostat out because the radiator pipe on the other side of the thermostat (leading to the bottom of the radiator) was cool when the engine was overheating and I put the thermostat on the kitchen stove in a pot of boiling water and it opened up ok but
It does not seem to open in time when the engine gets hot. Is the air getting in the thermostat housing area from the coolant boiling? Why does it push coolant into the reservoir tank? I have the aluminum thermostat housing and the system is pressurizing ( pipes are very hard). I can't keep the engine cool without running the interior heater.

 

Hi there Dave, sounds like it could be one or more of the following:

1. Water pump not working;

2. Faulty thermostat;

3. Airlock in the coolant circuit;

4. Blow head gasket(s)

etc etc


If it were me I would bleed the system first to remove any airlocks then remove the thermostat and check what happens, overheat wise.

 

To add to thebiglad - first item to rule out is the air lock - get JTIS and follow those bleed instructions to the letter. You must bleed the coolant system from the bleed hose tucked between the master cylinder and coolant tank.

You will more than likely need to do this process more than once and let the engine cool off in between "bleeding sessions".

Once you rule out the "air lock" is not the cause of your issue, then look at #1 and #2 carefully in that order.

Regarding #1 - if you have the original plastic impeller water pump - some of the plastic fins may be broken off - there is a water pump "upgrade" that employs metal fins w/ aluminum gasket vs. plastic fins/O-Rings (use hylomar for aluminum gasket) - there are skeptics here on the forum on these metal impeller replacement pumps vs. OEM plastic - but my $0.02 here is I'd rather have metal vs. cheap plastic.

Regarding #2 - in relation to cheap plastic - if you have the plastic thermostat housing - check the cap and O-Ring on top of the housing - that has to be tightened to only 8Nm w/ a 10mm hex wrench I believe (6.7 ft lbs) - tightening that cap anymore can render the O-Ring/Cap useless and could be the cause of your issues. They make aluminum thermostat housings - I installed one w/ success - Finally, check that thermostat housing cap for hairline cracks - again, cheap plastic w/ all the heat abuse will fail down the line...

 

I have bleed the system many times according to the jtis and the water pump has been replaced with the metal fin one, the old one had intact plastic blades, the thermostat housing has been upgraded to the aluminum one vs the original plastic one, I have replaced and re checked the thermostat on the kitchen stove.

It is the head gasket then I guess

 

My car, 2000 4.0 S-Type with only 34,000 original miles began overheating within the first mile after start up. If I stop and resume driving, the temp. gauge goes from all the way from the right back to normal, and the car drives perfectly until I restart it. Has been to the dealership 3 times. They call it a real mystery. Two weeks and $5050.00 later the car is still not fixed.

Help, please

elizabethe

 

Elizabethe-

Is the coolant actually reaching 'boilover' temp or is it just an indication issue? Did you try the bleeding methods described above?

What did your dealer do for $5K?

 

Do not asume it's the head gasket. You can test it to prove it one way or the other.
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