Engine: 70: Head gasket leak? Crack in head/block? V70N, 2.4T, 2002

[berg07]

Background:
• Volvo V70N, 2.4T, AWD, 2002, 200 hp
• Motor code: B5244T3
• Driven 302 000 km
• Head changed 2017 (282 000 km) according to service history. Reason for this is not stated. Timing belt and spark plugs changed at the same time.
• Motor oil changed in October 2019.
• Cooling system bled several times lately due to suspected air pockets in the system (fluctuating heat in cabin).

Symptoms:
• Loosing coolant without signs of external leak. About two liters of coolant lost in four months. Car is driven at least 40 km daily.
• Cooling system stays pressurized over night. Radiator hoses are hard in the morning.
• When I open the expansion tank lid/cap in the morning (cold engine), air escapes and the coolant level rises a couple of centimeters.
• During longer drives the interior heat sometimes fluctuates. Suddenly it blows cold air. The heat comes back later. AC (climate control unit) set at auto.
• The temperature gauge stays in the middle when engine is heated up – keeping normal operating temperature while driving and at idle.
• The cooling fan seems to be working properly.
• The engine has not overheated during my ownership (since October 2019). I have no idea about the history before that.
• No signs of coolant in oil, on dipstick nor under the oil cap.
• No signs of oil in coolant.
• The engine sometimes runs on four (of five) cylinders at the first start in the morning. I once got a P0305 (cylinder 5 misfire detected) error code after a morning start. The engine runs normally otherwise.
• The thermostat opens – the upper radiator hose gets hot after the engine gets up to temperature.
• My first thought: the expansion tank has a bad cap, which does not open and release excessive pressure. I have changed the cap – no effect on the problem. Cooling system still stays pressurized although the engine is cold.

Tests:
• A chemical block test showed signs of exhaust gases in the cooling system. The fluid turned from blue to yellow after a while. This is an indication of carbon dioxide in the cooling system.
• A compression test showed even compression between all five cylinders. Cylinder 1: 14,0 bar, Cylinder 2: 14,2 bar, Cylinder 3: 13,5 bar, Cylinder 4: 13,7 bar, Cylinder 5: 13,5 bar.

Suspicions:
• Leaking head gasket between coolant channel and cylinder (cylinder number 5 based on error code?)
• Crack in the block?
• Crack in the head?

What are your thoughts?

[skv70d5]

Were you able to locate the problem in the end? Going by your detailed description I would suspect that it was the head gasket.

[berg07]

Originally Posted by skv70d5

Were you able to locate the problem in the end? Going by your detailed description I would suspect that it was the head gasket.

No, I was not able determine the exact cause. I tried fixing it with a liquid gasket sealer that you pour into the coolant expansion tank. Since then, the symptoms went away: no exhaust gas in the cooling system, no pressure in cooling system overnight, no suddenly varying cabin temperature.

I still have some minor loss of coolant, but not nearly as much as before. I use the car daily.

[rogereld]

If you have no external signs of leaks and are losing coolant, you may need to look for leaks inside the car. The heater matrix has a couple of O rings on the rigid pipes that are a common source of leaks. Coolant water will gradually leak out and disappear beneath the carpets in the front left side footwell. This can happen gradually for a long time without anything obvious inside the car. Sometimes you can find some salty or green stains on the inside of the plastic trim in the footwell where coolant has been slowly leaking and evaporating. Poor demisting of the windows in cold or damp weather can also be an indicator. There are you tube videos that give a guide on how to fix the problem.