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2004 Dodge Stratus R/T sedan, 2.7 liter V6, 140k miles
So the car overheated and I found my coolant overflow tank to be completely full. Diagnosis determined combustion gas in the cooling system. No other symptoms. No smoke, no drivability concerns, compression is good even when the engine is warm. So at least one cylinder is leaking pressure into the cooling system, overpressurizing the cooling system, causing the radiator cap to vent excess pressure/coolant into the overflow tank. The car only become susceptible to overheating once too much coolant is lost to the overflow tank, leaving too much air in the cooling system.
So my question is what are the likely causes of this combustion gas leak? This obviously isn’t a classic case of a completely blown head gasket. What am I looking for? Cracked block, cracked or warped head, some other gasket issue?
Unfortunately, being a V6, there are two heads, and I don’t know which one is the problem. I am not optimistic that a leak down test will definitively tell me. The leak must be very small, and might be non-existent when the motor is cold.
Here’s the link to the thread for the diagnosis in case anyone is interested:
https://www.ericthecarguy.com/kunena/8-Service-and-Repair-Questions-Answered-Here/64081-why-would-car-overheat-randomly-one-time?limitstart=0
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have you done a compression test… uselly they fail the compression test because it is a leak???
it is comman for a head gasket to allow vapers to go in the coolent…. have you had it check and known that is the issue or are you guessing… I just want more clrification… look at scanner danner on youtube and he did a gas alalisys on the coolent tank for gas vapers to check for a head gasket leak… it can also be a cracked head or block… thats why I would check the compression both dry and wet more closlyI did a compression test on the motor while it was still hot. Compression is good (192-206 on all cylinders).
I added a link in my original post to the thread where I talked about the diagnosis. I did the gas analysis that you mention after a simple sniff test revealed the smell of combustion gas in my cooling system.
[quote=”crypkilla” post=172386]I did a compression test on the motor while it was still hot. Compression is good (192-206 on all cylinders).
I added a link in my original post to the thread where I talked about the diagnosis. I did the gas analysis that you mention after a simple sniff test revealed the smell of combustion gas in my cooling system.[/quote]
how did the sparkplugs look anyone more dirty with black or white dirt on it???what you can also look at when you take the spark plugs out look in the cylinder at the pistons and see if any of them look steamed cleaned…. other then that only thing I can sugest is taking both heads in and have them do a pressure test on each one… and check for leaks and check for warpage….
if anyone else have any other test to try to deteman wich head it is or where it is comeing fromHere’s a pic of the plugs. You tell me how they look. The two things that stand out to me are the discoloration on #2, and the deposits on the rest of them (conspicuously absent from #2). Whether that’s from steam-cleaning or not, I don’t know. These plugs have 67k miles on them. I think the maintenance interval is 100k.
I might take a look at the tops of the front three cylinders (no way I could see the back three), but I don’t expect to see much. The amount of any coolant that has burnt off is likely very, very small. Also, the car hasn’t had many miles on it since the problem began. So I would expect any steam cleaning action to be negligible.
Similarly, because the physical size of the leak is likely so small, and really only present as it warms up, I don’t expect to find anything with a leak down test (and I don’t wanna keep pulling the plugs out of a hot aluminum head).
looks like your to rich on all the plugs to me….. did you notice any liquid on any of the plugs? like they where wet
I have heard those engines had a lot of problems?
Do a search on it, you might be better off selling or trading in the car and get a different car?[quote=”Rob781″ post=172446]looks like your to rich on all the plugs to me….. did you notice any liquid on any of the plugs? like they where wet[/quote]
Scan tool shows the long-term fuel trims are within plus or minus 5% which I belive is fine. Fuel economy is unchanged and same as it’s supposed to be. There was no liquid on the plugs.
[quote=”451Mopar” post=172454]I have heard those engines had a lot of problems?
Do a search on it, you might be better off selling or trading in the car and get a different car?[/quote]I’m pretty sure the most common problem is sludged up oil passages. I change the oil regularly.
If I sell it now, as is, I can’t (in good conscience) get more than a few hundred bucks for it. If I fix it, it’s worth a lot more, and then I can think about selling it.
A leak down test in each cylinder, at proper pressure should narrow down the issue.
But it is still a guess as to a faulty head gasket, warped or cracked head or warped or cracked block is the cause.
That will involve a tear down and inspection of all those components.There is no silver bullet here, it’s going to take some elbow grease to pin down the cause.
It’s possible that there might be a crack in an exhaust port which is sending exhaust gasses into the coolant. Compression and leak down tests will never discover this type of failure.
Also, your engine has an aluminum block with cast iron cylinder liners. I’m assuming these are wet liners, meaning that the liners’ outer surface forms part of the water jacket. If there was a crack in one of the liners, say, near the bottom of the piston travel, it’d be possible that combustion gasses would get into the coolant jacket when the piston uncovers the crack. Again, compression and leak down tests wouldn’t detect this. Having said that, I think that this scenario is somewhat remote. Firstly, I’d still expect some oil/coolant mixing, and that doesn’t seem to be the case here. Secondly, short of defective manufacturing, there’s no good reason for a liner to fail at the bottom of the bore. It isn’t a highly stressed area.
I’d say the cracked exhaust port theory is far more likely.
Well thank you for all the info so far folks.
First I intend to do a leak down test. While doing that, I might also add to my chances of finding the leak by doing the following:
- stop the crank from spinning by propping a breaker bar from the crank pulley bolt to the ground
- attach a rented cooling system pressure gauge
- apply 150 psi to each cylinder at TDC to see if I can raise the pressure in the cooling system I would just look for bubble, but the pressure container setup on this car makes that tricky)
I am skeptical that either test will narrow down the leak, given that (a) it is likely very small, and (b) it could be lower in the sleeve (less likely), or in the exhaust port (possible).
After the test, I will simply tear it all apart and have a look. Joy.
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