Hello every body,

I have a Jaguar S type 2005 V8 which has a weird over heating problem, I've checked with many mechanics to find out what's wrong with it but no one can give me clear answer.

The problem is :
after I'm filling the car with coolant I can drive the car as much as I want without any problem but if I turn of the car for 10 minutes and then turn it on again after a few minutes the coolant starts spraying out from the expansion cab and car is getting over hit. then what I always do is to wait for the car to cool down then I add coolant again and the car is fine again.

for a while I used to turn on the auxiliary water pump manually and the car was completely fine but now the auxiliary water pump is broken.

Mechanic told me its from the cylinder head gasket but:
There is no oil in the coolant and there is no coolant in the oil, No white smoke no black smoke and if its from head gasket why when I turn on the auxiliary water pump the the car is fine?

I've changed the water pump, thermostat, expansion tank cab and serviced the radiator. The fan is working properly and there is no any sign of leakage.

Today I've noticed the pressure inside the water hoses is too high even if the car doesn't gets over heat.

Please help

Thanks
Payam

 

Sounds like you need to replace that pump.

 

Thank you but as I mentioned I did already. but just noticed the oil level is too low even much lower then minimum level and I didn't changed the oil filter for a long time ! can be the reason?

 

I meant the aux one that you said is broken.

Any oil loss needs very urgent investigation. Can you not find a competent car mechanic...

 

You could still have a head gasket leaking pressure from a cylinder into
the cooling system not involving any oil system compromise. Check your exhaust
for an antifreeze odor and or wetness as a sign. Have your cooling system tested for pressure with engine running when cold, there are tools for this.

Good Luck.

Regards,

 

ah the aux pump? it can be a temporary option because its an electric pump not designed to use all the time. also I should open the bonnet every time to turn on an off!

Today I changed oil an oil filter but still over hitting.

Thanks for your attention

 

Thank you will check it tomorrow but do you know how I should remove air from the cooling system properly? because all the time even if the car is over heated the radiator is completely cold, the lower and upper radiator hoses are very hot but the radiator is completely cold!!!!!

 

The aux pump should be on always when ignition is on. It needs to work.

 

Did you have a good look at the thermostat housing when you changed the thermostat?

They have a tendency to break at the lug that holds the thermostat into the cap, and damage the centre pipe, causing the coolant to recirc around the pump.
Affects the 4.2 V8 engines.

They, and indeed all engines do not like to get overheated, and if this continues you are more than likely going to be replacing cylinder head gaskets, if indeed you have not already reached this stage,......anyhow.

Pop the thermostat cover off three screws and have a look.
Photos attached.

Search for overheating on all boards, and it will throw up issues with other models XJ,XF etc all with the same 4.2 engine issues.

Good luck,

Bydand

 

it should be on!!!! I thought it's for heater system and it works only if heater is on!!! anyway thank you I'will try to find a replacement .

Thanks

 

The thermostat was fine. but there is two important point:

First: If the head gasket has a problem, why if I turn on the auxiliary electric water pump then the car is fine and no over heat any more!!!!

Two: when the car is over heating the Radiator is cold not even warm its cold. every thing is hot except radiator!!!

What do you think?
Thanks

 

If radiator doesn't get hot then there's a serious fault such as thermostat blocked or wrong type or badly installed. If aux pump not working that's at least part of the fault.

If this happens more than briefly you will probably cause serious engine damage to the point where it may need very very expensive work that may not be viable.

 

Can you confirm the Housing for the thermostat is good and NOT like the one in the photos I posted in the last post.

If the housing is damaged ,as shown, the water pump will just churn the coolant water around the radiator and NOT push it through the cylinder head. i.e recycling the cooling water, and producing no flow.

I guess when you run the aux water pump, it will flow a small amount of water through the cylinder head and cool it a little. Hence my request to just check the thermostat HOUSING

 

If your radiator is not getting hot have you checked that it's not blocked? Might need to take it out for a good flush or replacement if too bad.
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[QUOTE=Payam;1043671]ah the aux pump? it can be a temporary option because its an electric pump not designed to use all the time. also I should open the bonnet every time to turn on an off!


Correct me if I am wrong.

You say you have installed an aftermarket Aux water pump?

You must open bonnet to turn it on? Why not install a switch inside on dash?

Can you upload a photo of this? I would love to see it.

 

[QUOTE=MyBlackCat;1044320]Hi, no it was the original one but its broken now!


Today I removed it from the car completely. to see what happens!!

 

Hi, today I opened the thermostat again to see how is it? it is OK! picture are attached.

Also today I removed the auxiliary water pump from the car. then I drove about 30 minutes, didn't get any over heat yet but pressure in side water hoses seems very high even if I let the engine to cool down still pressure stays high.

 

Thank you but I did it already.

 

I still think bydand has your answer. Look farther back in that housing, it can break back there without failing exactly like his did. I have seen both types of failure. It causes coolant to mostly just recirculate back into the engine, rather than go through the thermostat.

Good luck!

 

To add my $0.02 here (not that this would be the cause of your issue) but doesn't this MY call for OAT coolant?

+2 on thermostat assembly. Also, check thermostat for proper operation. Finally, did you properly bleed the cooling system and what type of water pump did you use to replace? OEM or aftermarket.