JD 2650, Pressure in Radiator when cold

[Water Wheel]

Have I got a problem and if so what is the likely cause?

The 2650 blows coolant out when I top it up ( over fill it ?) but only down to the level plate in the radiator, including running out of a small hole in the bottom of the water pump.

There is a fair bit of pressure in the radiator after just a couple of minutes running while still cold, is this normal ?

Oil looks clear and filler cap/ pipe are clean not milky.

Basic tractor with no expansion tank

 

[DrWazzock]

Head gasket failure

At a guess the water has run low at some point due to leakage at the water pump seal. Low water level has caused overheating of the cylinder head and head gasket failure which leads to combustion gases getting into the cooling system overpressurising the system and blowing water out.

Or the head gasket has simply failed anyway, blowing water out the cap and water pump seal.

Rev it , cold with the cap off, well topped up, and watch for bubbles in the radiator header. Or fit a combustion gas detector where the cap goes on. Usually a tenner off eBay. Chemical solution changes colour if combustion gas present. But make sure it’s suitable for diesels.

If you are really unlucky it’s maybe a cracked head or worse cracked cylinder but hopefully it’s just the gasket.
Head off, send for refurb including skim and pressure test. New head gasket, new water pump., new thermostat, rad and block flush. Jobs a good un.

 

[Water Wheel]

Thanks .
Wont put a like as I don't like it, but makes sense.
For light work wouldn't know there was a problem.
Its been indestructable for a lot of years.

 

[DrWazzock]

For light work you could maybe leave the cap loose or even off to vent the air off and it might not blow so much water out. Did that for a couple of years with the DB780 in my beet harvester until I got round to fixing it properly. Careful you don’t get water in a cylinder when stood for a while then bend a con rod on start up because the trapped water won’t compress. Just dab the starter switch to see if she will turn over before going for a proper start. Don’t let the water run low or it might end up with a cracked head or block, seized piston etc, as you know.

 

[Wisconsonian]

Every old tractor with no expansion tank will blow coolant off if filled to the top cold. The pressure building right away may just mean the cap is holding pressure. if it's not bubbling when running, then keep running it and watching the temp gauge, or fit an expansion tank and a lower pressure cap so it's easier to watch the level.