Bubbling coolant
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Bubbling coolant
Hi! I have a XC90 with a 185bhp D5 engine. Seems like there is air in the coolant as it were bubbling when I came to a complete stop. Is this normal? Video below.
https://streamable.com/s94ipp
https://streamable.com/s94ipp
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From: Burlington, VT
Are you losing coolant or had any recent signs of overheating or service work on the system? Does the upper radiator hose feel rock hard when the car is warmed up? You may want to get a pressure reading on the coolant system as too much pressure can be a sign of a head gasket issue.
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No recent service work on the system, followed regular service intervals at Volvo. I have had problems with the car losing acceleration at times the last months. The car has been serviced at the Volvo dealer earlier this year and they told me that the swirl flap was defect, and it needed replacement. They applied a (quick fix?) and told me to drive the car until the car warns me again ("engine may need service"). A month later some oil seemed to have been leaking from the line/hose in the front of the car. I called the closest Volvo service center about this and they told me that the amount was insignificant and I could proceed to drive the car. After driving to the mountains I got a "low oil level" message in the car, and I went to the closest gas station to top off. The oil level has been fine after this, but the car seems to be losing power more frequently when accelerating (recently misfiring too). I went to the local service center again, and they did a compression test and the motor seems to lose pressure on the fifth cylinder. They told me that they had to take the top off to inspect, and it was expensive ($1700) and depending on what they find the repair cost could override the actual value of the car. I took the car back home to think about the alternatives. Some days later I went with the car on a short trip to a lake, and that was when I heard noises from the front of the car and decided to open the hood, and discovered that the coolant was bubbling. Coolant level is slightly above the min level. The coolant is clear, but has a light brown color to it (coolant is supposed to be blue?) Also, the engine bay had a burnt oil smell to it. The car has never warned me about the engine overheating (temp gauge never exceeds optimal operating temperature).
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From: Burlington, VT
the cooling system is a closed system - as the coolant warms it will expand - and flows into the overflow reservoir. as it cools it will contract and pull the excess back into the radiator. The only other considerations I can think of is 1) the cooling system was recently serviced and some trapped air may be working its way out or 2) you have a head gasket issue (there'd be other symptoms such as a rock hard upper radiator hose when warm). A shop can do a cooling system pressure test to measure if you are out of range. The other thought is you have a slow leak and something is introducing air back into the system. I'd monitor the coolant level to see if it drops below the low fill mark when cold.
As to your coolant color, coolant should be replaced every 5 years with a fresh water (distilled not tap) flush. The light brown color is probably rust from some of the internal components and not all that uncommon. What would be a concern is an oily film or sludge appearing in the overflow reservoir. Sounds like you are due for a radiator flush.
Regarding the low compression test result for #5 - Did the shop do both a wet and dry compression test or a leak down test? Engines can lose compression 1 of 3 ways: a) worn rings/piston wall issues. The wet compression test adds oil to the combustion chamber which will temporarily correct most piston/ring issues so say you measure 120 dry/180 wet... that points to the piston. b) a burnt or bent valve. Here the wet/dry test results wont differ. A leak down test can then be done which pushes compressed air into the cylinder and measures how quickly it leaks out (when the valves are closed). This will help confirm a valve issue. c) head gasked issue. similar to a valve issue, the wet/dry tests won't vary and something may show up on a leak down test. usually head gasket issues have other symptoms (like low compression in adjacent cylinders) and an inspection cam can be used to look for valve damage. As your tech noted, these test results will provide a a reason to tear into the engine (very costly) or not.
As to your coolant color, coolant should be replaced every 5 years with a fresh water (distilled not tap) flush. The light brown color is probably rust from some of the internal components and not all that uncommon. What would be a concern is an oily film or sludge appearing in the overflow reservoir. Sounds like you are due for a radiator flush.
Regarding the low compression test result for #5 - Did the shop do both a wet and dry compression test or a leak down test? Engines can lose compression 1 of 3 ways: a) worn rings/piston wall issues. The wet compression test adds oil to the combustion chamber which will temporarily correct most piston/ring issues so say you measure 120 dry/180 wet... that points to the piston. b) a burnt or bent valve. Here the wet/dry test results wont differ. A leak down test can then be done which pushes compressed air into the cylinder and measures how quickly it leaks out (when the valves are closed). This will help confirm a valve issue. c) head gasked issue. similar to a valve issue, the wet/dry tests won't vary and something may show up on a leak down test. usually head gasket issues have other symptoms (like low compression in adjacent cylinders) and an inspection cam can be used to look for valve damage. As your tech noted, these test results will provide a a reason to tear into the engine (very costly) or not.
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the cooling system is a closed system - as the coolant warms it will expand - and flows into the overflow reservoir. as it cools it will contract and pull the excess back into the radiator. The only other considerations I can think of is 1) the cooling system was recently serviced and some trapped air may be working its way out or 2) you have a head gasket issue (there'd be other symptoms such as a rock hard upper radiator hose when warm). A shop can do a cooling system pressure test to measure if you are out of range. The other thought is you have a slow leak and something is introducing air back into the system. I'd monitor the coolant level to see if it drops below the low fill mark when cold.
As to your coolant color, coolant should be replaced every 5 years with a fresh water (distilled not tap) flush. The light brown color is probably rust from some of the internal components and not all that uncommon. What would be a concern is an oily film or sludge appearing in the overflow reservoir. Sounds like you are due for a radiator flush.
Regarding the low compression test result for #5 - Did the shop do both a wet and dry compression test or a leak down test? Engines can lose compression 1 of 3 ways: a) worn rings/piston wall issues. The wet compression test adds oil to the combustion chamber which will temporarily correct most piston/ring issues so say you measure 120 dry/180 wet... that points to the piston. b) a burnt or bent valve. Here the wet/dry test results wont differ. A leak down test can then be done which pushes compressed air into the cylinder and measures how quickly it leaks out (when the valves are closed). This will help confirm a valve issue. c) head gasked issue. similar to a valve issue, the wet/dry tests won't vary and something may show up on a leak down test. usually head gasket issues have other symptoms (like low compression in adjacent cylinders) and an inspection cam can be used to look for valve damage. As your tech noted, these test results will provide a a reason to tear into the engine (very costly) or not.
As to your coolant color, coolant should be replaced every 5 years with a fresh water (distilled not tap) flush. The light brown color is probably rust from some of the internal components and not all that uncommon. What would be a concern is an oily film or sludge appearing in the overflow reservoir. Sounds like you are due for a radiator flush.
Regarding the low compression test result for #5 - Did the shop do both a wet and dry compression test or a leak down test? Engines can lose compression 1 of 3 ways: a) worn rings/piston wall issues. The wet compression test adds oil to the combustion chamber which will temporarily correct most piston/ring issues so say you measure 120 dry/180 wet... that points to the piston. b) a burnt or bent valve. Here the wet/dry test results wont differ. A leak down test can then be done which pushes compressed air into the cylinder and measures how quickly it leaks out (when the valves are closed). This will help confirm a valve issue. c) head gasked issue. similar to a valve issue, the wet/dry tests won't vary and something may show up on a leak down test. usually head gasket issues have other symptoms (like low compression in adjacent cylinders) and an inspection cam can be used to look for valve damage. As your tech noted, these test results will provide a a reason to tear into the engine (very costly) or not.
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