1998 xj8 V8 4,0 ....I have had a coolant leak/loss problem recently so new water pump put in , and then some head gasket seal because mechanic thought it may be head gasket trouble... The water was coming from the expansion tank underneath front bumper... I think it has stopped loosing water now but I am getting a restricted performance message on the dashboard and orange warning light , when I accelerate quickly car chugging like it can't get enough fuel ...car is running a bit rough when idling.. not as smooth as should be... Then after a time light and message disappear...car runs fine ... Any help would be appreciated ... Steam seems to be coming from one exhaust.... seems to happen more in traffic than on a good run... Thanks Trevor

 

Trevor, a couple of things, firstly if you don't have one buy one (an OBD reader) this you plug into your car, turn ignition on and read the trouble codes - there should be some with a warning light on.
Once you have the codes we can pin point the issue.
There is a common issue with crossed coolant pipes, if not connected correctly (crossed) then coolant can get forced into the expansion tank.
The other one is a failing fuel pump - very common now the cars have a few years on them, you can check the fuel pressure +/-40psi odd on the fuel injector rail there's a valve to plug a pressure tester in, failing that a quick press and see if you get a jet of fuel on ignition. It sounds fuel side related, possible old fuel filter also...but at this point it's guess work.
Post the codes when you are able to pull them for further help.

 

Hi Sean pipes are correct way round going to header tank...fuel pump replaced a couple of years ago ... Codes are attached and tiny bubbles are being produced in the header tank I notice.... So what do you think???

 

Hi Sean I have coded attached and pipes are correct going into header tank I notice little bubbles in the header tank and fuel pump replaced 2 year ago... what do you think?? Thanks for the advice gratefully received

 

Sure looks like head gasket. Note to mechanic: adding gasket seal can plug the heater core because it's low flow. There is a test kit to check exhaust gas in the coolant, surprised your mechanic isn't aware. Maybe you need a new mechanic.