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Discussion Starter · #1 ·
Okay, so over the weekend, I dropped my car off to have the HG replaced.

Rather than accepting it as the HG, my friend(Volvo tech) who would be doing the change, looked into things further and found small cracks on the bottom of the reservoir. It looked to him like that was where the leak was. Cool, reservoir was replaced.


Now, it's my understanding that this is a closed system, correct? Any given morning, I've seen the coolant level low, but opening the reservoir to fill, the system "pops" and the level rises. From what I've read, that would be normal in a closed system? As the engine cools, the coolant system creates a vacuum, drawing the coolant down into the block. Upon opening it, the vacuum is released and the coolant is able to expand to normal levels.

Is that all accurate? This morning(~35ish degrees F), my coolant level was BELOW the min mark. As a test, I started the engine. I had no warning light(possible the sensor is messed up, but it IS brand new and plugged in)

I shut the car back off and opened the reservoir. The system popped, and the coolant rose to about the halfway mark.

So, I guess one of my main questions is, when checking in the winter, do you "pop" the system to check the level? And the other main question: Is the sensor accurate enough to "include" the vacuum/pressure? My understanding of the system was that the level will start low, rise as the engine warms, and then settle back down as it pressurizes.
 

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I have a coolant leak (or worse) and have been topping the reservoir off every couple of weeks for months. My car behaves exactly as you describe, the level rises once the cap is removed, being cold does not matter.

The idiot light does not consider vacuum. The way I know to add coolant is that the low coolant message come on when the car is cold. If I am at work I just drive it anyway and it goes off after 30 seconds to a min. as the coolant heats up and expands.
 

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Discussion Starter · #4 ·
I just checked my coolant on a coffee break...

This was it when I looked at it initially:



And this was it after I cracked open the reservoir:



Air pocket? I mean, that second picture is where I'd imagine you want the coolant level to be, right?
 

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when it heats up it becomes pressurized to keep the water from basically evaporating out of the system. I always thought it was normal and never thought much of it.

maybe its just the difference in volume for the coolant being pressurized in the radiator hoses and such.
 

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Funny you posted this. I am having the same issue except mine gets low after driving for a few days. My reservoir was cracked too but at the seems int he middle and its been doing it since the new reservoir was swapped in so Im wondering if the system is just working out air bubbles etc or if theres a leak. Most likely I have a feeling there is a leak somewhere.
 

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Be careful on waiting until the low coolant light comes on; I did so and now have a bypass in my head gasket - oil leaking into coolant. The car never ran hot by monitoring the temp gauge. If you have a coolant leak get it fixed ASAP even if it means stomaching dealer costs.
 

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So, I guess one of my main questions is, when checking in the winter, do you "pop" the system to check the level? And the other main question: Is the sensor accurate enough to "include" the vacuum/pressure? My understanding of the system was that the level will start low, rise as the engine warms, and then settle back down as it pressurizes.
Correct. I would put a mark with a marker when you check the level in the morning. Be cautious as the level will be influenced by the outside temperature therefore park in the garage.
 

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Or put in dye and start checking around...
 

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Discussion Starter · #11 ·
Funny thing about that, no one seems to have coolant dye. It's all either refrigerant or fuel dye.
 

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Your Bertone' says fix me!
 

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Discussion Starter · #15 ·
It certainly does. Really wish I had it road worthy, though I'd rather not put the poor thing through a New England winter.
 

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Well, it was a lot lower this morning. I guess I should still get that HG replaced.
Can you drain 1/4- 1/2 of oil and see how it looks like? Water/coolant is heavier than oil and should stay on the bottom of the pan. Probably can do the same with transmission fluid. You can also send the samples for analysis to make sure before going into this HG adventure.But I would imagine that with a major leak you would be able to see the coolant presence.
 

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Discussion Starter · #17 ·
It's a stick, so the transmission's fine. I'm going to pull the plugs tomorrow and take a look at them.

I suppose I could drain a little bit of the oil, but there's nothing on the dipstick and I have 0 driveability issues.
 
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