Hi Experts .Have been loosing a little coolant for a while enough to bring low coolant light on but plenty still in expansion tank and no overheating problems at all and have checked everywhere but cant find any leaks from hoses or radiator and have replaced coolant outlet and had aluminum thermostat and of course new chains and water pump .The car runs perfectly although we have noticed a very slight miss on start when cold but slight blip of accelerator and idles and runs beautifully and would think it is perfect. A few drops come out the overflow when fill it up expansion tank with coolant but not enough for this to be the source of leak and have captured the overflow to check but will further monitor this .The car has only done 10300kms/63000miles .My mechanic today is suggesting that there maybe a leak in the cylinder heads which scares me a little. It is winter but not that cold here in Adelaide and when started cold after being outside over night there was white smoke coming out of the two exhausts but thought just condensation .Also my mechanic says there was a little blue smoke but the car does not seem to use any oil at all none since last serviced 3000kms/16000 miles ago . The oil is perfectly clean and no sign of water or anything else in the oil and under oil filler cap absolutely clean .
Would love some advice could it even be the inlet manifold which I have had on another car but maybe just hopeful on this .
Regards
Nigel Adelaide

 

A pressure test of the cooling system is needed. I'm surprised your mechanic has not done this already.

I don't know what year you have, but the early V8 has a head gasket problem, and replacement with 4.2 gaskets is a fix. The fact that you see white smoke on start up doesn't mean much, especially if you can't smell antifreeze.

It's more likely a leak of the octopus or heater hoses, which can be hard to find as the coolant often evaporates if it's a small leak.

 

Thanks RJ
My car was built very late 1999 and has 5 digits at the end of the Vin number rather than the 6 of the earlier cars . I am just investigating the problem and just took it to my mechanic to change the expansion tank and top hose outlet with the sensor in it think he is a little scared of the Jag and happier with a Chev .The system holds pressure for at least a couple of hours after the car is turned off so have to wait along time to check the coolant level so there is lots of pressure in the system have sprayed coolant a couple of times when trying to check the coolant level . My car is a 3.2l and was only aware of the 4.0l alternative and didnt know later cars were 4.2 but then they are too expensive for me . Will keep looking for leaks around all hoses and under the expansion tank with the heater hoses not sure what you mean by the octopus so if you could guide me there it would be great.
Would love to find a little leak and you are probably right about white smoke on a cold morning not significant but will stick my nose in it to see if I can smell coolant this morning .
Nigel

 

Have just been for a 160 km/100 mile run in the country with no sign of low coolant light coming on and car running perfectly. A couple of times when we stopped the cooling fan came on for about 20- 30 seconds and is a cool day . The container I put under the overflow line from the expansion tank had about 250ml of coolant in it so this is where the coolant is coming out and not the exhaust which pleased me. .What is causing it to come out overflow the hand book says fill the expansion tank to the top. My ideas .1. Too much pressure in system and maybe thermostat not fully opening but temp gauge gets quickly to half way and stays there .2. Don't need to fill to top as up you don't with most cars and the low coolant light a bit sensitive did also make sure float was moving freely before trip and cleaned the level sensor and its electrical connection. 3. There is compression from engine getting in to the cooling system which I hope is not true .
When started this morning there was no white smoke out the rear exhaust but this time car was in locked garage and no smell of coolant at exhaust
Feel a bit more positive after our drive as know where coolant is going but would appreciate any comments or ideas .
Nigel

 

sounds like an overfill, change the t-stat.

 

These engines can be hard to bleed for the uninitiated.

It often takes several repeated attempts.

 

Thanks Plum and Sean will change the thermostat as I have a new one . My mechanic said bleeding was tricky and may have to top up a couple of times but the coolant is coming out the overflow outlet and the lines into the expansion tank are crossed over and are in correct positions thanks to the Forum. I have just put my spare radiator cap on as I am grabbing at straws. Do people have trouble with the caps ? So pleased I have you guys to ask for help .

 

The caps can be a problem, but I don't quite understand what you observed. You said you collected coolant overflowing from the expansion tank. I assume you mean the tank that has the pressure cap.
The coolant should go from there to the atmospheric recovery tank in the fender well, and then be drawn back into the expansion tank when the engine cools. Do you not have a recovery tank?

 

Thanks RJ237. I feel so stupid as just thought that overflow went to ground and pulled that line out and put into a container to check where coolant was going as had seen a few drops under the car but thanks to you I now how the system works and I now understand the atmospheric tank is in the bottom of the LH front guard the line goes into a round clear plastic horizontal grommet with the hole in the middle for the line from the expansion tank to go into and therefore syphon the coolant back up to expansion tank when car cools.I do have an expansion tank up the top near tool kit with the cap and I now know I have the extra tank low down in the mudguard . Where the line goes into the atmospheric tank should it be a water tight fit or just a loose fit which it has been all the time I have had the car and could have been original problem as always lost a little coolant . So pleased and glad you replied as this may solve my problem although there maybe a leak in this atmospheric tank as there was a few drops of coolant on the ground under this tank but could have been due to the loose fit of the line into the tank. Can jack car up and inspect .
Have two radiator caps and both look good and the o rings unmarked on them so can try each of them . Have just put in a new Thermostat today but that may have been just for practice now I understand things.
Cheers
Nigel

 

It's possible that the tank or the line could be leaking, but I think the line should be loose to prevent pressurization.
If the pressure cap did not seal correctly or the line had a crack, the overflow coolant would not be completely drawn back when the engine cooled. Adding more coolant to make up the difference would eventually cause the atmospheric tank to overflow.

 

Thank you again . Will check the line thoroughly for cracks and my first cap I feared did not seal correctly and use to hear a slight hiss form it when car was off but hot and my new cap does not do that . Checking the tank and its location seems unlikely that it is damaged and could have been overfilled when kept topping up and will keep tank not sealed so as not to pressurize it. Sadly I broke the line from expansion tank to radiator changing the thermostat so wont be able to try until I get a new line tomorrow. Will report back. Have just checked the line to recovery tank and there are no cracks in it so hope that is eliminated.
Regards
Nigel

 

Well have fitted a new coolant pipe from expansion tank to radiator. Sovereign Motors who sold me pipe cheaper than on eBay explained how the system works like Rj237 did above and also explained how there is a small valve in the top of the expansion tank cap that opens up when cool to allow the expansion tank to syphon up coolant from the atmospheric recovery tank in the the LH front fender/guard. .Needed to check if this valve is open on a cold cap when off . Now just have make sure i have all air out of system and all is fine and seems no cylinder head problem .So pleased I understand how the cooling system works thanks to the Forum and Sovereign.

 

Also, be absolutely sure those overflow tubes -- from the radiator and the expansion tank -- are correctly fitted; they cross over each other and are often misrouted causing blowing fluid. I guess you learned not to lean on them?

 

Hi Jim yes you are correct the first lesson I learnt was to make sure the outlets are crossed when I bought car they were in the wrong place so poor old guy could not drive far but forum taught me the lesson .The next lesson was not to lean on them but have replaced the one I broke and continue to learn .Problem is I dont think the coolant is being syphoned up from recovery tank in the LH fender . My question is does anyone know for sure if the joint where the line from expansion tank goes into the recovery tank should be a loose fit or should it be/ water tight /sealed? RJ237 feels it should loose .The line seems to be in good order with no cracks the other possibility is the expansion tank cap .I have two caps and on close examination they seem both the same with little valve inside the top slightly open recessed when cold to allow coolant to come back up to expansion tank from recovery tank .
Cheers
Nigel

 

I will let one of the pros correct me (please): I believe it is a watertight fit at the radiator and reservoir; and loose fit at overflow, but tight at the reservoir. Clearly, tight fit at both ends of the TST tower and reservoir line.

RJ and your tech have explained it correctly.

 

Jim you are all correct just went to my friend Geoff at Sovereign Motors here in Adelaide and he agrees with you 100% just have to make sure the pipe goes to the bottom of the reservoir in the fender .He also had a special little test for radiator cap . It is OK if you cant blow but can suck on the bottom so he said mine passed this test as was fine . He was very pleased when I told him I changed the top hose plastic outlet with the o rings and sensor as it is a very common failure and the top hose blows off just like with the old plastic thermostat housing .
Nigel

 

Hi Jim becoming fairly certain that I have a leak in the Atmospheric Recovery tank in the LH fender . Can you or anyone tell me the best way to remove the tank to check it .Do I go from underneath the front of the car or through the wheel arch don't want to pull bits apart I don't need to .
Cheers
Nigel

 

Download the JTIS repair manual from the stickies. I have never had a problem with this part of the coolant system.

 

Nigel to remove the tank you'll have to remove the front undertray from the front bumper, which is held on with torx bolts and spring clips (I'd replace with s.s. nuts bolts and washers as these rust solid over time) The tank itself is held on with 3 x13mm? bolts I think, you'll need an extention to reach them from underneath, I don't think its possible from the wheel well. All the Best.