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Hi folks,
I am 90% sure I have a bad gasket, but I wanted to get some advice from more knowledgeable RDX owners.
Back Story: Owned the car for about a year, now with 205K miles, I did a compression test when I first got it, about 155-160 on all four holes. Never has it shown signs of a bad HG, and never burned coolant or oil. It's been a very solid engine for me. Running fine the other day and parked it.
Symptoms: I started the car, and it had a rough idle. Then, I noticed thick white smoke showing behind the car. (Dread sets in)
Troubleshooting: I checked the coolant, and it was full(over flow tank was at the full line). I proceeded to pull the intercooler and spark plugs. All the plugs were dry and looked the same (if that matters). I did another compression check with a semi-warm engine. Again, it was 155-160 across the board. I would imagine if I was down a hole it would show on that test. Right?
while testing the first cylinder I noticed a good amount of mist shoot out of cylinder 3. Not sure if it was coolant or maybe unburnt gas. I threw everything back together, started the car and it suddenly did not smoke at all. Still had noticeably rough idle, but that was it. I took the car for a spin, and everything seemed fine. I knew the real test would be letting it sit overnight and starting it in the morning. To my surprise, not a single puff of white smoke. So I am unsure if it really is a bad HG.
Is it possible there is coolant somehow getting into the intake manifold? Maybe from the turbo?
Any further advice or troubleshooting steps to help narrow this down would be appreciated.
So there are cooling lines in the turbo and exhaust manifold - any of those gaskets could eventually leak. Turbo may also leak internally at some point. The rough idle concerns me more - if it is related to the coolant leak then it indicates you're getting it into your combustion chamber at some point. That would rule out it leaking directly into the manifold. I'm not 100% certain on where the cooling lines run on the turbo, but if there is a way for it to leak internally to the inlet side then you could see it end up inside the cylinders.
Question - did the white smoke eventually stop and/or the rough idle even out as it warmed up, or were they both permanent as long as the car was running?
Question - did the white smoke eventually stop and/or the rough idle even out as it warmed up, or were they both permanent as long as the car was running?
When I started it for the first time and noticed the smoke I let it run for less than 5 minutes. In that time it appeared to clear up a little (Smoke and idle) but I did not let it get to full operating temp.
The subsequent start-ups showed zero signs of smoke from the exhaust. Literally none. Hence my confusion...
If you can get a cheap inspection camera on Amazon then use that and take a look at the pistons. A clean piston is a tell tale sign of a bad head gasket. There are different levels of compromise. For example, I had a car with rough starts but smooth running after warmup. Little to no smoke out of exhaust and I didn’t really see bubbles. No coolant mixes either. Inspection camera showed a clean piston and the remainder were dirty which meant that coolant made its way into that cylinder.
The mist coming out of cylinder three is what I would pay attention to. This is either coolant or gas from erratic ignition in that cylinder or a leaky injector. More likely coolant but do you recall if there was either gas or coolant smell when the mist happened? Other signs of a bad head gasket are an exhaust vapor smell in the coolant overflow tank and/or a still pressurized top radiator hose after the engine has cooled. You can also purchase a test kit to check for exhaust vapors in the coolant tank, which indicates a bad HG. If you drive the car more it may become more apparent what the problem actually is, if HG or other internal coolant leak I would expect the coolant level to go down.
If you can get a cheap inspection camera on Amazon then use that and take a look at the pistons. A clean piston is a tell tale sign of a bad head gasket.
I ordered a simple borescope to check it out. It's probably a good tool to have anyway.
The mist coming out of cylinder three is what I would pay attention to. This is either coolant or gas from erratic ignition in that cylinder or a leaky injector. More likely coolant but do you recall if there was either gas or coolant smell when the mist happened? Other signs of a bad head gasket are an exhaust vapor smell in the coolant overflow tank and/or a still pressurized top radiator hose after the engine has cooled. You can also purchase a test kit to check for exhaust vapors in the coolant tank, which indicates a bad HG. If you drive the car more it may become more apparent what the problem actually is, if HG or other internal coolant leak I would expect the coolant level to go down.
I don't recall what it smelled like because I was paying attention to the comp tester, and I don't recall it smelling like anything. If I get this borescope and I don't find any evidence of clean pistons, I will invest in a coolant tester. Thanks for the advice.
you also don't need to purchase, your local parts stores should have them readily available for free loan: call around and ask for a "combustion leak detector"
I don't recall what it smelled like because I was paying attention to the comp tester, and I don't recall it smelling like anything. If I get this borescope and I don't find any evidence of clean pistons, I will invest in a coolant tester. Thanks for the advice.
Keep in mind if the problem just started you may not be able to see to detect any problems with the borescope. I repaired a bad head gasket problem that had gone on for some time and the piston wasn't any cleaner than the other ones, if anything it had more deposits and so did the valves and spark plug, especially the spark plug, see photo. I attached a few photos of the piston and head where the head gasket failure and coolant leakage into the cylinder occurred. Chevy Mailbu V6 engine with head gasket failure. The head gasket failure also kept blowing apart the coolant overflow tank, too much pressure for the tank to handle even with the pressure relief of the cap.
Left cylinder had head gasket failure
Top piston was area of head gasket failure Head gasket failure top piston head gasket failure
I did some research and found a couple of sources that describe the water-cooled exhaust manifold having an internal crack and allowing coolant into the hot side of the turbo. If this is the case with my car, I wonder if the O2 sensors are getting thrown off causing the rough idle.
06-04-2024, 09:16 AM
