at 150k we're starting to get regular problems (more money out!). So, today, bowling along the motorway and MIL lamp comes on, MF display said something about excessive coolant, stop and check. I did just that, coolant level was fine, between min/max but it's black!. So, I'm thinking head gasket right?. Hmm, so I checked to see if there's excessive pressure on the expansion tank, nothing really say's I'm over pressured. I keep an eye on the coolant level while I continue to drive. It's normally sat on the next mark down from half way and other than warming up it's usually sat there, but as I'm driving it's going as high as mid way (never gone that high before) and then back to my normal tick mark. If I idle or reduce load of course I can get it to go lower, likewise if I crank up the cabin space heat with the window down. So, no cream on oil filler, no excessive pressure in expansion tank but the coolant is black. Could it be the recent EGR valve replacement, that would contaminate the coolant with exhaust gases being transferred when the EGR valve is open?? I've not lost any coolant but the mere fact it's been disturbed might be a problem.
Of course, to complicate matters, I recently bought a diagnostics tester, looking at the many values this thing can chuck out I've got a huge amount (than normal that is) of errors, CAN bus errors all sorts. I also noticed looking at the injector readings that 1&4 seem positive whereas 2&3 give negative readings. This diagnostics thing is quite new to me but it did seem strange, they are not huge values, maybe +/- 2-3 (I believe I was looking at injection volume rather than timings). So, another trip to the garage but you think there's a cheap solution, maybe a gas in coolant tester maybe or specific values on my tester that might hone my nose to the problem...