2004 XC70 Low Coolant, Radiator Replaced

[IlikemyXC70]

Hello. Last night I got a message saying to stop safely due to low coolant. When I checked under the hood, the coolant tank was low, but I also noticed the upper radiator hose was over pressurized. I opened the coolant tank (hot, just like you're not supposed to ), there was a gurgling, and then the coolant returned, and the radiator hose went back to normal. It's only been a day, but it seems to be back to normal.

Any idea what could have happened?

I replaced the radiator about two weeks ago, and I had the thermostat replaced back in February. When researching the radiator repair, I read that there are no special procedures for refilling there coolant, and there is no need to "burp" the system. Maybe I read some bad information?

[jonesg]

burp the system by squeezing the top hose, drive around the block and top the level up before it gets hot.
run the heat to make sure you're getting circulation.

At least get a torque android phone app so you can see what the actual coolant temp is.

I use this one, Its pretty slick for $10.
https://www.amazon.com/Generic-ViaBecs- ... 123&sr=8-3

[vtl]

Replace the expansion tank cap. FCP sells Gates 9445462, but I would go with genuine Volvo, as many of those aftermarket caps are known not to work.

If the new good cap will not help, you have a blown gasket or a crack in cylinder.

[IlikemyXC70]

If the new good cap will not help, you have a blown gasket or a crack in cylinder.

I sure hope it's not that :0 But, I think it was just an air bubble in the system. I didn't flush the cooling system after installing the radiator. Whenever I do cooling system work, I'll get the low coolant warning after driving a bit, so I stop to top it up. Thinking back, I believe there was a pocket of air trapped in the upper radiator hose, and, against recommendations, I think opening the recovery tank hot allowed the air bubble, which had risen to the physically highest point in the cooling system, to escape.

Regardless of what it was, or still is, we're driving fine. Might even get a carwash today before it rains lol

[jonesg]

If the new good cap will not help, you have a blown gasket or a crack in cylinder.

I sure hope it's not that :0 But, I think it was just an air bubble in the system. I didn't flush the cooling system after installing the radiator. Whenever I do cooling system work, I'll get the low coolant warning after driving a bit, so I stop to top it up. Thinking back, I believe there was a pocket of air trapped in the upper radiator hose, and, against recommendations, I think opening the recovery tank hot allowed the air bubble, which had risen to the physically highest point in the cooling system, to escape.

Regardless of what it was, or still is, we're driving fine. Might even get a carwash today before it rains lol

There a quick test for head gasket failure, with the engine stone cold in the morning, open the coolant cap, if its under pressure.... you have a problem. Further testing can quickly confirm.

I used a bottle of water, some clear hose and a spare coolant cap, drill a hole, insert tube through coolant cap and run the engine, if air (gas) bubbles increase and decrease with rpm the system is breached, probably gasket.

[IlikemyXC70]

Update: I checked the recovery tank for pressure, cold, yesterday morning, and there was some, but not as much coolant returned to the tank this time. I checked again this morning, cold, and no pressure at all.

I'm currently thinking I did not purge all the air from the cooling system after replacing the radiator, and I think that is what was causing my problems.

I have a new recovery tank cap on the way along with an oil change kit. The cap is about $7 from FCP, so I'll replace it just in case.