Massive Coolant Loss- What To Do?

[erikv11]

... -How did I not overheat and have damage when I lost all that coolant when the heater core failed, and I drove almost 5 minutes after the low coolant light went on ?- ...

Given the choice between magic or physics, I give the edge to physics.

That is, I wouldn't consider the fact that the car didn't overheat as evidence of some miracle, but of the simplest explanation: there was enough coolant in there to protect it.

The light first comes on when the coolant level approaches the bottom of the reservoir, not when the system is empty. Obviously, the light coming on doesn't mean the same thing in every case. So, it doesn't mean the system emptied catastrophically for you, just that at that moment it was low. Maybe it started as a slow leak, and got much worse about when or after you stopped the car. The heater core likely continued to leak while you were walking to the station and back, and over the 40 minutes of miscellaneous filling. You added liquid into a hot engine, it emptied to the carpets, you put in more.

I wouldn't advocate anyone drive 5 miles with a sudden onset low coolant light, but it seems to have worked out for you. Three cheers!

[greg850r]

I'm considering that when I install a new heater core this fall, I might do what others have done, and just run long hoses from the block, through the fire wall, to the old tubes cut short, into the core. Q: what do people use at the fire wall to fill the passage hole, or do they?

-How did I not overheat and have damage when I lost all that coolant when the heater core failed, and I drove almost 5 minutes after the low coolant light went on ?- -Any other thoughts, I'd be glad if you let me know.

The black plastic part at the firewall usually breaks where the lone torx retaining screw goes in to it to hold it to the front metal plate on when you take it apart. The new one isn't cheap and is something of an unnecessary intermediate part that does not help the system function, it just lets you snap the lines in easily both inside and under the hood. Getting rid of it gets rid of 4 sets of o rings and 4 plastic clips that get hard over time and break.

When I eliminated it on mine I cut the front half off the two aluminum tubes behind it halfway down, slipping heater hoses over the half still attached to the heater core and secured with hose clamps. Exactly where to cut is optional. I cut mine so the ends were located in a spot that made tightening the hose clamps easiest. I found leaving one a little longer so the clamps were not on top of each other to be a benefit. I reused what was left of the black 2 hole plastic part, opening the holes up to slip fit around the hose. I forget exactly what tools I did it with, but I believe I wrapped the hoses with something where they went through for a tight fit with no air leakage from under the hood to the interior. I do remember I had to go back and re-tighten the hoses under the dash because the ends of the pipes you cut then lack an enlarged end to help the clamp achieve a leak free grip.

The low fluid light is telling you the reservoir tank is empty. If it holds at that level you can literally drive it forever with the light on. At that point it's still full and circulating because the tank is the highest point in the system, so as I said, if it leaked out slowly you were ok for the short distance you kept driving. Erik's point about adding cold fluid to a hot motor is spot on, that could have been the biggest threat to the health of your motor.

[erikv11]

That's a good description on the coupler delete. Here's a good writeup and includes some pics from when I did the elimination back in 2011 (viewtopic.php?t=44948). You'll want to seal around the hoses or you will get whiffs of exhaust in the cabin.

I am now mixed on which is better, to keep or eliminate the coupler. If eliminated, the hoses directly from the engine will move a lot and may stress the connection at the heater core over time. Replacing the coupler that is currently my preferred method, but it is more expensive.

[MoVolvos]

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Hope you guys don't mind my 2 cents into this. I took the new one out I think 3 times before I got it right.
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