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)

[BLU-125]

Off topic.

[Adrian D]

I owe ya one Mudmonster. As luck has it, I found an brand new one in Germany, for the grand price of 13 euros shipped. WOOT :D

[Adrian D]

Well, no result with a new thermostat and overflow bottle cap. The coolant level still rises and it's not a happening by any rule. Stopping after a 30km drive I notice steam from the engine compartment. Coolant was coming out of the bottle. The engine cooled down, I added some coolant back and on the drive back no funny behavior. The top radiator hose wasn't getting hard (sign of a cracked head).

What's interesting is that I hear burbling from under the bonnet after I shut the engine off. So I imagine it's some air pocket forming...

I sure hope it's the small coolant return hose at fault :(

[Adrian D]

The return hose is not clogged...

Another thing I noticed is that after I opened the coolant overflow bottle there was very little water in the top water manifold.

I'm stupified, I do several trips around town, everything is ok, then I drive an easy 30 miles and coolant overflows. Another 30 miles but this time off-road through snow and mud and it's again ok. No sign of overheating, no sign of anything else. Stupified.


I ********ing hate these weird problems and I REALLY hope it's not a cracked head.

[The Smiths]

sounds like a bit of air lock - most likely is in th eheater matrix - fill it with a hose pipe ad the shove the pipes back o

[Adrian D]

More testing today: The return hose from the radiator to the overflow bottle is not clogged. I've let the engine run for 15 minutes at operating temperature, with the overflow bottle open and it began to fill it up. Very little water coming to the overflow bottle through the small return hose.

Bottom radiator hose was warm, top radiator hose was cold (?!?!?), heater hoses were luke-warm. The heater blows hot air.

I'm going to remove the water bridge tomorrow and start the engine like that, to see if any of the heads bubble and if not, I will try on the old water pump (slightly leaky but still working).

I remember clearly that during summer I could open the overflow bottle with the engine warm and it would not overflow and I could see plenty of coolant coming through the small return hose. I can't open it now, it overflows.

Still stupified.

[Adrian D]

Head nr 2 is cracked.

A very wise person told me back in 2009 when I had another head failure that I should save up for new heads. Wise words...

Looks like I have several options:
1. Buy 4 new heads from VM and be done with it for ~150.000 km (about 10 years considering how much I drive)
2. Buy 4 new heads from Apaz Madrid, who claim to have improved the design quite a lot, although they are in the market only since 2008-2009. A bit cheaper than new heads from VM.
3. If a VW TDI swap is accepted as road-legal, buy a used head, replace it and use the VM until the TDI swap is complete (130hp, more torque and the possibility of close to 200 hp reliably with the appropriate mods). Less taxes due to smaller displacement and slightly better fuel consumption.

[Adrian D]

Apaz Madrid heads are payed for and they should arrive in about a week. $800 shipped vs close to $1500 for stock ones from the dealer. And so far everybody who used them reported lower temperatures in the same conditions compared to the stock ones.

http://i52.photobucket.com/albums/g8/DAdrianD/BUJIAVERTICALDOSESPARRAGOS.jpg