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Jaguar S type coolant pressurising possible EGR cooling Jacket failure need to bypass please help!!!


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Hi,I am new to forum, hope to get some help/advice regarding my 2006 S type diesel with a coolant problem. Bought cheap as a project with few faults, limp home mode had kicked in and owner wanted to get rid. OK , drove home , could maintain 70 mph on motorway, regular stops, no overheating, no clunks or rattles, just very slow! At start up brake vacuum build up slow but brakes ok after a few seconds idling, also one diesel injector seemed to be leaking due to fumes under bonnet one side. (these last two problems were resolved after discovery of a blocked DPF causing higher than normal pressure within engine, potentially catastrophic!)

Noticed coolant leak from expansion tank, pressurising, maybe lost 1 litre or so of coolant in 100 plus miles, also noticed Oil on dipstick black and up to high mark (first job changed Oil and filter). No sign of Head Gasket failure, no Mayo on Oil cap or dipstick and no oily residues in coolant, gas test did not show hg failure either, blue chemical did get lighter blue over time but never yellow/green, did test over exhaust pipe and it changed quickly from blue to yellow. My OBD2 reader revealed EGR and MAF faults, managed to resolve Limp mode by software upgrade, EGR, DPF delete,plus tuning to give about 250 BHP (EGR blanked off , DPF fitted so looks ok for MOT,I have found out these devices make next to no difference to emissions, make cars uneconomical,reduce power and potentially shorten life of your engine). Intend to use car for occasional track use, its performance is now up with my old straight 6 supercharged XJR, just cant believe its a diesel!

My problem now is that the coolant has been pressurising,(temp gauge stays in middle,not overheating?) fan not working, so removed it to find the sensor/control circuit board inside motor burnt in one place. Bought a second hand fan replacement but still did not work??? Replaced temp sensor, still fan not working , so replaced thermostat , water pump, no change. Replaced radiator, old one was scaled up/blocked and this did relieve the problem a little but still pressure in system. Tried running, idling with radiator cap off and a plastic Lucozade bottle with base cut off, neck of bottle screwed into expansion tank, an old trick that works if you need to "burp" system. Could not see any coolant leaks from usual suspect metal pipes underneath, its very tight space and hard to see. I changed to a new 16" Thermostatic fan (it works independent of ECU using a probe inserted in top radiator hose, it has adjustable temp switch kicking in when needed in traffic , they work ok on classic cars so why not?) and fitted fan within the cowl of original 18" fan and used Aluminium high temp metal tape to make a good seal around fan cowl to radiator.Also changed to Evans waterless coolant, expensive stuff but ideal for high performance use, even fitted aluminium 1.5mm sheets of metal around front condenser radiator to create a more efficient airdam through bumper, now car still pressurises coolant and loses a small teaspoonful through expansion cap after maybe 30 mins drive, accelerating hard/ at speed /in traffic. Evans coolant is good but can not fix a faulty cooling system. The condenser rad at front looked a bit dirty/old so cleaned with a jet of low pressure water and I removed the lower dozen or so rotten aluminium veins to allow better airflow, slight improvement.

I trawled internet and found a guy who had a similar problem with a Range Rover Sport Td V6, he eventually found out a failing EGR coolant jacket was allowing a trickle of exhaust gas into coolant causing similar symptoms of hg failure, pressurising the coolant, according to JLR fans the hg on these engines rarely fail?

I am hoping for some advice as to how to safely bypass cooling jacket of EGR, They are hard to get at for a start, I already blanked the EGRs myself (easy enough job fitting 4 metal blanking plates,removing a pair of pipes and a butterfly valve), I may have to leave EGRs in place and just join the in/out jacket coolant hoses?

Please if someone has measurements regarding internal width of in and out coolant pipes please let me know, also how to joint them? Maybe a plastic / metal connector that fits inside the pipes and clamped on? At moment I guess there is some exhaust gas heating up blanked off valves thus heating up the coolant passing through them and there must be an exhaust leak into coolant. No sign of white smoke or steam from exhaust, a small amount of coolant may be burned up but I am not losing much coolant?? The exhaust gases seem normal, very clean, no soot,  I had a scare on an initial test drive, black smoke and poor acceleration that turned out to be a loose intercooler pipe, easily fixed.

Also if I leave EGRs fitted, blanked off and coolant hoses bypassed, I guess they will just sit there doing nothing but getting hot? Ideally they should be removed and a blanking plate fitted to the exhaust manifold but due to location maybe near impossible to do?

I hope my story is of help to anyone having similar problems, trawling internet, many times these problems get misdiagnosed and owners spend £1000s trying to put them right, fitting new head gaskets with no improvement and finally scrapping car / fitting replacement engines at huge cost. I have done the work myself over several months on and off, not exactly spent a fortune but takes time ,hopefully bypassing EGR coolant jackets is the solution?

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Managed to buy cheap used egr waterjacket off fleabay, seller has cut off rubber pipes leaving rubber ends and clips on,it's complete with metal pipe that connects to exhaust manifold.I can study it closely and see how to make a coolant bypass.It may be best to remove EGRs completely,should not be too difficult to make a blanking plate to go on exhaust manifold,just a pain to fit.Knowing type/ size of bolts holding it on manifold would be helpful.If this works I will post a reply either way as would be useful info for others.

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