Hey everyone,
I'm trying to diagnose what's wrong with my coolant system. It started with me having an uneven idle, so I drained my coolant and cleaned out my IACV and that seemed to fix it. A few months later while driving I noticed my engine overheating at idle. Checked the coolant levels and the radiator was almost dry. I assumed that when I refilled the radiator I hadn't bled the system properly and I had an air pocket which caused the coolant to boil off from driving it around for a few months. I also noticed that my fans weren't coming on unless the A/C was on. I checked the thermostat and it was opening and closing as normal, but the thermoelectric fan switch had a high resistance so I replaced that and my fans started working again.
OK so I fill up my coolant system again, heater on full, engine hot enough for the fans to come on, both upper and lower radiator hoses around the same temperature, and I notice coolant bubbling out of the radiator when the engine is running. More when I rev the engine, like a sudden surge of pressure in the system (video here). Now, obvious first guess is a head gasket leak, so I do a combustion leak test but there's no combustion gases in the coolant system (or at least none making their way to the radiator cap). So I do a pressure test and notice there is a very slight drop in pressure over time - from about 16 psi to 14 psi over about 8 minutes. I do a vacuum bleed on the system but the overflowing coolant is still there. Pressure seems to jump when the engine is revved then drops back down but not completely (video here). Another clue - when I was doing the the vacuum coolant bleed, I wasn't able to build up vacuum in the coolant system. It didn't get much past -0.2 bar. When the engine was cold (thermostat closed) it was getting higher (around -0.8). One more clue - I've been noticing a high pitched whine sound when the engine is running which stays on for a second or 2 after the engine has stopped, which makes me think a vacuum leak. Also the idle still isn't perfect although it's hard to describe.
If I could know for sure that it was a head gasket leak I'd be happy to do it, but I don't want to go to all that effort only to find out it's something else. Is it possible that either the IACV or the water pump or some other component could be pushing air into the system?
I'm trying to diagnose what's wrong with my coolant system. It started with me having an uneven idle, so I drained my coolant and cleaned out my IACV and that seemed to fix it. A few months later while driving I noticed my engine overheating at idle. Checked the coolant levels and the radiator was almost dry. I assumed that when I refilled the radiator I hadn't bled the system properly and I had an air pocket which caused the coolant to boil off from driving it around for a few months. I also noticed that my fans weren't coming on unless the A/C was on. I checked the thermostat and it was opening and closing as normal, but the thermoelectric fan switch had a high resistance so I replaced that and my fans started working again.
OK so I fill up my coolant system again, heater on full, engine hot enough for the fans to come on, both upper and lower radiator hoses around the same temperature, and I notice coolant bubbling out of the radiator when the engine is running. More when I rev the engine, like a sudden surge of pressure in the system (video here). Now, obvious first guess is a head gasket leak, so I do a combustion leak test but there's no combustion gases in the coolant system (or at least none making their way to the radiator cap). So I do a pressure test and notice there is a very slight drop in pressure over time - from about 16 psi to 14 psi over about 8 minutes. I do a vacuum bleed on the system but the overflowing coolant is still there. Pressure seems to jump when the engine is revved then drops back down but not completely (video here). Another clue - when I was doing the the vacuum coolant bleed, I wasn't able to build up vacuum in the coolant system. It didn't get much past -0.2 bar. When the engine was cold (thermostat closed) it was getting higher (around -0.8). One more clue - I've been noticing a high pitched whine sound when the engine is running which stays on for a second or 2 after the engine has stopped, which makes me think a vacuum leak. Also the idle still isn't perfect although it's hard to describe.
If I could know for sure that it was a head gasket leak I'd be happy to do it, but I don't want to go to all that effort only to find out it's something else. Is it possible that either the IACV or the water pump or some other component could be pushing air into the system?
