Club 80-90 Forums

Help Please. Van been off road over winter and been starting it once in a while with no probs. Started it last weekend and expansion tank boiled up and started steaming. Its a 1985 Dg and i changed coolent last year and run it up and down country without problems. Read Haynes and some of the threads on here (thanks) but more confused and wanted seek advice before trying to fix. Was going to change thermostat, fan belt, check and change water pump if needed but been reading about air locks etc and now don't know where to start? Read Wiki and some threads but more worried now. Thanks, nick.

Two questions...did the system pressurize? as in, the hoses became hard with pressure. It is vital that the system is sealed and can pressurize to raise the boiling point of the coolant.
Secondly: The main header tanks pressure cap can fail leaving the coolant to boil at 100C instead of around 115C under pressure. Effectionately called the 'Darlek cap' on later systems, they often fail.

Did the thermo switch for the rad fan kick in? most fans are staged and the first speed should kick in when the temp gauge needle rises to approx 2/3rds the way.

Martin

Hi Martin, I think it presurised. There are two large pipes coming out of the header tank one above eachother. The top one was red hot and the other was cold. I do not think that the fan came on. If you put the dalek cap on with the threads screwed and it leaked would this same thing happen? I believe that i may have left air in the system last year when i changed the coolent. nick.

Yeah....basically that darlek cap is supposed to seal the system and allow the coolant to pressurize.
You could certainly try bleeding the system. I'm not sure of the exact specs but usually this kind of pressure/expansion cap works in two ways, one to allow the system to pressurize, opening at around 12-14PSI where any excess coolant goes in to the top up tank and two: to allow for fluid to sucked back into the main header tank as the system cools and retracts.

Of course your main worry is that this could be head gasket failure.
Coolant pressure test or cylinder leak test to diagnose.
Can also be diagnosed with a coolant sniffer (Very technical lol) to check hydrocarbons in the coolant (bubbles or rising of the coolant level due to head gasket leak)
Martin