2.5td coolant level rising

[Adrian D]

Hey everyone.

Today I noticed something funny, the coolant overflow bottle was almost full and the top radiator hose harder than normal. Nothing else is changed. Water temperature is normal, heating works normal, oil temperature normal, oil color normal, no contamination of the coolant.

I've been through 2 head failures and helped a friend fix his. On all 3 cases the thin hose going from the heads to the overflow bottle would push out bubbles / thick foam. Not mine, this time it runs clear coolant.

The heating valve (which closes when I shut down the interior ventilation) leaked both times when I had head failures but this time it's dry, so no pressure in that part of the system I guess.

While squeezing the top radiator hose with the engine off the water level came back to normal. However, the radiator end tanks sounded like coolant was slushing there, just as if there were air pockets ?

Went for a drive after the coolant level dropped back, mid-way everything was fine (top radiator hose was ok, coolant level ok) and when I got back home the overflow bottle was full again.

Sorry for being long-winded but this is ridiculously weird and happened all of the sudden. Is it safe to say my thermostat is acting up and it's time for a new one ?

[layback40]

Sounds like you may have an air lock in there.
When ever I have interfered with the cooling system I run with the cap loose for a while keeping an eye on the level. I have had that small hose from the head manifold block a few times in the fitting on the manifold. That causes a buildup of any air to form a pocket.

[Adrian D]

That's what I thought at first.

The top hose is definitely not blocked.

After the engine cooled off I could open the radiator fill plug without having coolant pour out. Weird...

I'll try a new thermostat.

[SeaComms]

Sounds like one of three possibilities. Air bubble in the system with the air heating up and expanding pushing the water out into the over flow bottle, or, a blown head gasket leaking compression into the cooling system pressurising it again with air and forcing the water to the over flow bottle, or, stuffed radiator cap allowing the system to suck air in as it cools but still pushing water out into the overflow as it heats.

Run motor with the cap off for 10 to 15 mins and watch for a couple of large bubbles (air trapped) or lots of little bubbles (blown head gasket). If you see just a few larger bubbles that stop after a while, top up the radiator and stick the lid back on.

If no bubbles are seen at all, buy a new cap.

[Deezelweazel]

Adrian,

get a new cap for the coolant overflow bottle first. It has a two way valve in it which may be defect.

Check also the little hose from the water bridge on top of the heads and its little banjo bolt. Mine was also blocked by contaminants - make sure it is open!

[Adrian D]

Are the overflow bottle caps available at parts stores or are they a dealer-only item ?

Coolant flows ok through the thin water bridge hose.

[Mudmonster]

i havent been able to find any aftermarket
but Cap part number 52028256 (thaks to Merv)