Heater Core Bubbling (1 Viewer)

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May 28, 2017
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Northern California
1997 LX 450 with 214k miles. The problem is a bubbling sound behind the dashboard when I switch the heater on after driving for a while with the AC. Earlier, the gurgling sound would occur first thing in the morning as I pull of the driveway. But since then, I replaced all the heater hoses, radiator cap (OEM), overflow reservoir cap/hose, and 2 weeks ago, the heater valve because the plastic connectors (nipples) were worn out and pitted. This improved the situation and I don't have the early-morning gurgling any more, especially if I park overnight with the heater set to the ON position.

So now, the only time I hear gurgling is if I drive for a while with the AC on, then on an incline and under load switch on the heater.

It seems that air is seeping into the system when the car's hot and the heater valve is closed.

I do not lose coolant. It remains rock-steady over periods of months and thousands of miles. I did a chemical test for combustion gases in the coolant and got negative results.

I do have traces of oil seeping into the coolant and accumulating on the radiator cap and in the coolant reservoir. Engine runs great and compression is from 179-195. Does anyone have any pointers or advice where to look (besides replacing the head-gasket to solve the oil issue)?
 
With oil in the coolant there is a good chance that the oil cooler located on the block underneath the exhaust manifold is leaking. Search on oil cooler and you should find more info. The bubbling sound is air trapped in the cooling system and may need burping. Again search on burping, there should be a number of threads for more info.
 
Yes check out oil cooler sounds like your issue with oil getting into the coolant, the gurgling is air , might get a pressure pump and test the cooling system see if you find any leaks maybe
 
The oil cooler gaskets were replaced a few months ago. When I was in there, I saw traces of oil lining the inside of the cover and in the crevices. Cleaned everything out as best as I could and flushed the coolant system with cascade dishwasher soap. But oil is still appearing on the radiator cap and a little is accumulating in the reservoir. Maybe it will just take a bit of time for everything to flush out, but I have no idea of time frames. A few weeks? Months? Years?

As far as the air in the heater core: I'll continue trying to burp the system. But sometimes it gets better, sometimes it gets worse... Will keep trying to figure it out.
 
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