1.6 td coolant 'migrating'

[lentulus]

After an hour of driving at 66 mph on the motorway,during the hot weather last week, on came the 'low coolant' flashing red light. Coasted on to the hard shoulder immediately,engine off.The water temp needle was well over to the right.The dalek cap reservoir appeared empty,but the expansion tank behind the flap was almost totally full up!.I drained the expansion tank down to halfway between the max/min marks,and returned the excess to the dalek top tank. Checked the 8 year old dalek top, which passed the suck and blow test. Started the engine and bled as much air as I could out of the system,and now continued in limp home mode (50 mph). The water temp gauge adopted a new position indicating hotter than normal and I cautiously stopped at every service area and it was necessary again to drain one and refill the other tank.The radiator fan never kicked in, but then in my experience,it takes a mountain pass and ambient temp in the high 20's.

Starting the engine from cold this morning , fine , but it sounds slightly ragged , compared to usual , when warmed up. A lot of gurgling in the dalek top tank,and the level therein slowly reduced to about the halfway mark.No obvious signs of oil in water or vice versa.

No doubt someone has 'been here before', but I haven't , and would very much value your thoughts on this.

Cheers - steve.

[ajsimmo]

Sounds like coolant system over pressurising, most likely due to head gasket blowing into coolant, forcing contents of tank through cap into overflow.

[clift_d]

WHS ^

Get a garage to do a check for combustion products in your coolant. The test samples the gases from the radiator overflow through an indicator fluid. If the fluid changes colour then you've got combustion products in your coolant, which means that the head gasket is letting combustion gases leak into the coolant from the engine, and this gas is pressurising the coolant system forcing the main tank to empty into the overflow tank.

[lentulus]

Only now getting time to look in more detail; thanks for the replies,and I too was thinking head gasket.Took it to my local engine rebuilders for a sniif test of the coolant as suggested, but they were unable to do the test as all the coolant would gush from the header tank,and they could not see a way round it.......So thinking to have another go at trying to bleed it myself, and be sure it's not a tricky airlock,got the temperature up to radiator fan kicks in and then revved it some.Suddenly I could see the previously translucent (frothing) coolant turn dark. Engine off and allowed to cool. A film of black oil and some tiny black flakes on the surface of the water in the header tank. Would that clinch it do you think ?

cheers

Steve.

[ermie571]

No expert....but it don't sound good....

[ajsimmo]

Probably, yes. You've created circumstances the engine wouldn't normally experience - higher coolant temperature and lower coolant pressure. Therefore the pressure gradient across the compression seal of the gasket is greater, and the already failing part may have just failed big time.
Have the head gasket and cambelt changed, but don't skim the head - it's a Vw no-no! If the engine hasn't been cooked (yet) the head should be fine. Use new head bolts, and check if a retorque is needed afterwards. There's two different types of gasket material, both will fit, and the later metal one doesn't need the final retorque stage.

[lentulus]

A shame that it was not possible to do the sniff test, and I have now fouled up my own cooling system. Anyway,as you recommend, head off (plus timing belt)

and we'll see where we are......

Unless it happened at the original 'migration of coolant' incident,I am confidant it has not been cooked .This 1989 jx engine ,for which I have the full service and maintenance history ,has done 205,000 miles to date.The head gasket was previously renewed at 90,000 miles. It suffered a sudden loss of coolant at 136,000 miles when a hose failed,but there have been no overheating issues in the intervening 70,000 miles. Did have a leaking flange on the front of the cylinder head for about a year (two years ago). But that was fixed,and the coolant was always kept topped up in the meanwhile.

Thanks for your posts,

steve.