What did I do wrong? Rad/Block flush

First coolent renewal and engine block and rad flush on our 300tdi I followed haynes manual to the letter.

But when I came to refilling the system with BLUE 50/50 concentrate coolent mix, I found that the system filled to the top BEFORE it should have. Also I was p**sed off to find some GREEN watery coolent in the expansion tank ( which I had drained along with the block and radiator ).

I can only sumize that I did not drain all the old stuff out, and the minutes of hose pipe flushing with water did not flush all the old stuff out.

I removed all the hoses that haynes said to, and the drainage plug in the side of the engine block.

We have since suffered a cyl head gasket failure so I'm trawling my memory of things I noticed before she blew.

Also now, 50 miles after cyl head gasket repair has been done, temp gauge rockets into red zone after 10 minutes of driving, whilst coolent in expansion tank stays cool/cold to touch.

I wondering if before gasket blew, was there a coolent circulation blockage which caused overheat / gasket fail. OR did I cause some sort of an airlock which caused it to overheat.

My worry now is that an airlock / blockage caused the cyl head gasket to blow, and that that blockage is STILL present after repair.

I know that these temp gauges senders have their earthing issues, but I still have this memory of the problem when I renewed the coolent.

Anyone had a story like mine?
thanks,
steve.

check rad is hot all the way across they often dont and only part of rad is cooling, biggest cause of over heating ,when refilling remove rad bung and thermostat housing bung fill till rad over flows refit bung fill till thermostar housing and expansion tank overflows fit both excess will blow out of expansion cap run engine with heater fully open then recheck level in expansion tank doesnt mean engine is full check level with thermostat housing bung easier if you fit brass replacement rad not cooling over entire surface is common over lr vehicles but easy to check with your hand with engine hot and switched off

thanks james. I havent done the check on the rad as you describe, but I will do. How does the bit sound to you about my drain and flush not removing al the old coolent? Are there trapped pockets like this on 300tdi's ? or does it sound like operator error? ( i hear that last phrase alot in work! ahah )

i wouldnt worry abou it its very hard to remove all old coolant but since you put 50/50 back more than enough to work properly also check top hose when hot to make sure thermostats opening you can feel hose heat up after stats open , if you fill as i described you will fill all pockets

thats a simple way of checking the thermostat opens, thanks. I've just been out in the landy and i'm pretty sure the temp gauge going to red zone is an electrical gremlin, as you can put it into the red and bring it out again just by switching lights/wipers/demister on or off.

latest observation.
after a 15 minute drive gauge was in red zone, thermostat housing to hot to touch, top hose to rad hot. coolent in expansion tank cold.

Is your thermostat working?

and rad hot all across

top hose hot thermostat working

Hmmm my mate had similer prob when he bought the 300.
Head gasket had already gone coz after about 10 miles it chucked out steam n looked like a train.
Had new HG put on and head skimmed.
Would expect a little bit o steam in the exhaust system but temp go's to half when warm
then all of a sudden shoots up to the red in about 5 to 10 sec's,turn it of n turn ignition back on an temp says half.
Putting it down to a bad earth or wiring prob somewhere....
How fast do the temp needle go up from half to full steviefd..? if its very quick i would say it may be electical.
Also expansion tank dont get very hot as i dont think that they were disigned to have water running through them, thay are only used to allow for any air in the system to be replaced by water and to allow for water expansion when water gets hot...
but maybe im wrong i have been in the past.
hope this helps.