2005 xc70 seems to be sipping coolant

[CallaoCrusher]

Mrscullini - did you ever find the leak/fix anything? I have a slow one and looking for answers.

[Pittsjock]

Have you replaced the PCV system?

If not, the vent hose could be leaking coolant. My wife's car (2007 XC70, 188k) recently started "sipping" coolant as well. Out of the blue she got a "low coolant" message late last year. I could not find any evidence of leakage. We had done a PCV cleaning around 130k, but only replaced the breather box and its direct hoses - not the vent hose that goes back to the turbo and has coolant running through it.

As there was also evidence that the crankcase was being pressurized (oil leaking from dipstick & cap), I went back into the PCV system. FWIW, the idle circuit was functioning (passed the glove test), so I suspected a problem with the high speed PCV circuit. The breather box and return passages in the motor were clean, but there was evidence of "water" inside of the breather box - milky oil residue in the return hoses. The oil in the engine sump showed no evidence of any water/coolant which gave me comfort that I did not have a crack in the head/block.

My best conclusion is that the hose was leaking slightly and allowing some coolant into the PCV system. That hose is rubber, plastic and aluminum and is subject to some fairly intense heat stresses. Some of the coolant was being burned (making the car run a tad bit rougher), and the rest was mixing with the oil and finding its way back into the engine via the breather box. Apparently this did not go on long enough, or with enough volume to show up visibly in the oil in the sump.

I replaced the PCV vent hose and the problems have all gone away.

[zanzabar]

Pittsjock, which hose are you referring to? Can you tell us a part number? Is it one of the ones from this kit?:
https://www.fcpeuro.com/products/volvo- ... urbopcvkit

I'm having trouble picturing a hose that runs from PCV system to turbo and is carrying water/coolant?

[Pittsjock]

Zanzabar:

PCV Vent Hose VOL-30731068 (in the listings on the page you link to from FCPEuro)

This is the metal & rubber hose. One end connects to the thermostat housing and the other, through a "banjo" bolt back into the water jacket of the engine.

The other banjo bolt connects the PCV breather box to the intake manifold through a 1/4 inch (or so) tube. This banjo bolt has a "check valve" in it and regulates the idle circuit/high speed circuit.

I haven't taken the hose apart, but the aluminum hose encases the coolant line (which is there, I guess to aid in condensation?) and a vacuum/intake line to the turbo which is the "high speed" circuit that draws the engine pressure/vapor through the turbo once it is kicked in.

Hope that helps!

Patrick

[rburner]

I took mine apart with the same Sipping Coolant situation on my 2005 XC70 2.5. I took it apart to replace the oil trap which was mostly clogged and found the plastic line on the Banjo bolt (with 2 brass brake line washers) was broken in half, brittle and totally clogged with oil like the oil trap was. The Banjo bolt at one end, goes into the bottom of the Intake manifold for vaccume I assume - and the other end Tees into the rubber hose on top front of the Oil Trap / Flame Trap box, I assume to draw vapor from the Crankcase ( Volvo PCV Breather System Kit Turbo Models (S60 V70 S80 XC70 XC90 Part #: KIT-S60TURBOPCVKIT). In the kit, it is the 3/4" line mostly aluminum which has a hidden 3/8 smaller line inside the larger line. The Larger line is a breather line from the Oil Trap box to the Turbo. The Smaller hidden line inside is a Coolant line from the Thermostat housing to the Turbo, which runs close to $200.00. I am replacing the broken Banjo line with a oil resistant neoprene type line tomorrow with 2 clamps since it is for vapors/vaccume use only. I have not found the coolant escape route yet. We will see how it goes tomorrow.