D5 163 Chucking coolant out

[Sebastienclement]

Hi all,

I've got a problem with my 163 D5 in an XC70 that I have been trying to investigate today. The car has been losing coolant rapidly and the low coolant warning has been coming on. This happens rapidly - certainly within 30 miles (my commuting distance) when the coolant has been at Max before setting off.

Things I have observed today...

• Top and bottom hoses both get hot
• Heater blows hot (although it gets hotter when revved)
• When running with the coolant cap off, the water level drops slightly when revved (I've read this is an indicator that the water pump is good).
• I couldn't get the fan to kick in at all, despite holding the revs at a sustained level for 30 minutes - the fan kicks in immediately if I unplug the coolant temp sensor - so I assume the car is not overheating, and the coolant system is coping just fine.
• No steam from the exhaust
• No exhaust / diesely smells from the coolant

The main issue that I have, is when the car is up to temperature, and then put under load the coolant level rises to the top of the tank and will begin to flow out through the coolant cap. Once the revs drop, so does the level and gets a bit lower each time eventually resulting in the low coolant warning illuminating. Could this be as simple as a faulty pressure cap?

I can't see anything pointing to head gasket, but I can't also see any obvious reasons why the level would rise so much (from the max mark to overflowing) when revved.

Any ideas?

[Clan]

Originally Posted by Sebastienclement

Hi all,

I've got a problem with my 163 D5 in an XC70 that I have been trying to investigate today. The car has been losing coolant rapidly and the low coolant warning has been coming on. This happens rapidly - certainly within 30 miles (my commuting distance) when the coolant has been at Max before setting off.

Things I have observed today...

• Top and bottom hoses both get hot
• Heater blows hot (although it gets hotter when revved)
• When running with the coolant cap off, the water level drops slightly when revved (I've read this is an indicator that the water pump is good).
• I couldn't get the fan to kick in at all, despite holding the revs at a sustained level for 30 minutes - the fan kicks in immediately if I unplug the coolant temp sensor - so I assume the car is not overheating, and the coolant system is coping just fine.
• No steam from the exhaust
• No exhaust / diesely smells from the coolant

The main issue that I have, is when the car is up to temperature, and then put under load the coolant level rises to the top of the tank and will begin to flow out through the coolant cap. Once the revs drop, so does the level and gets a bit lower each time eventually resulting in the low coolant warning illuminating. Could this be as simple as a faulty pressure cap?

I can't see anything pointing to head gasket, but I can't also see any obvious reasons why the level would rise so much (from the max mark to overflowing) when revved.

Any ideas?

cracked cylinder liner ? Head gasket is a multi layer stainless steel device so doesnt "blow" unless the head or block are damaged .

[Sebastienclement]

Originally Posted by Clan

cracked cylinder liner ? Head gasket is a multi layer stainless steel device so doesnt "blow" unless the head or block are damaged .

I can't see it to be honest... No oil and water mixing, no fumes smell in the coolant, no power loss, starts easily, no smoke or steam...

[cheshired5]

Flip the seal inside the expansion tank cap and and see if that helps.

[damageandy]

Originally Posted by cheshired5

Flip the seal inside the expansion tank cap and and see if that helps.

Agree.

A dodgy cap can give all sorts of 'headgasket' associated symptoms.

[Sebastienclement]

Okay, I've had some time to look at this today. I'm still a bit baffled.

I've replaced the coolant cap with a brand new one - this has made a significant difference. Before when removing the coolant cap, there was never pressure in the system. There is now!

Took the car out for a run, and 8 miles in I got the low coolant warning again. I stopped, undid the cap and the coolant rose slightly, topped it back up, ran the engine at fast idle until the level settled, cap on and off we went. I haven't had the low coolant warning since this.

Once back home on the drive & idling, the coolant level would suddenly begin to lower and take around 20 seconds to go from max to min. I topped up again and it hasn't dropped since then - perhaps a significant airlock that I've finally shifted?

One concerning thing is there is a 'stream' of something, whether it's small bubbles or I can just see coolant flowing, from the hose at the bottom of the expansion tank (power steering reservoir moved out of the way). It seem to rise up to the top of the tank - this concerns me as Google tells me that's head gasket...

[Sebastienclement]

Here's a link to a video of what I'm talking about...

https://photos.app.goo.gl/AQfP3bTQhsyhNrt6A

[Clan]

Originally Posted by Sebastienclement

Okay, I've had some time to look at this today. I'm still a bit baffled.

I've replaced the coolant cap with a brand new one - this has made a significant difference. Before when removing the coolant cap, there was never pressure in the system. There is now!

Took the car out for a run, and 8 miles in I got the low coolant warning again. I stopped, undid the cap and the coolant rose slightly, topped it back up, ran the engine at fast idle until the level settled, cap on and off we went. I haven't had the low coolant warning since this.

Once back home on the drive & idling, the coolant level would suddenly begin to lower and take around 20 seconds to go from max to min. I topped up again and it hasn't dropped since then - perhaps a significant airlock that I've finally shifted?

One concerning thing is there is a 'stream' of something, whether it's small bubbles or I can just see coolant flowing, from the hose at the bottom of the expansion tank (power steering reservoir moved out of the way). It seem to rise up to the top of the tank - this concerns me as Google tells me that's head gasket...

there should be coolant flow from that thin bleed pipe on the bottle oy is from to top of the radiator , bubbles in that do mean a combustion gas leak in the engine somewhere ..

[Clan]

Originally Posted by Sebastienclement

Here's a link to a video of what I'm talking about...

https://photos.app.goo.gl/AQfP3bTQhsyhNrt6A

looks like bubbles to me , what do you think as you are actually there ?

[damageandy]

Sniffer test to confirm, you can get the for about a fiver.