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'88 560 SEL
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Discussion Starter #1
I have an '88 560 SEL. Heat worked intermittently, then stopped working during the last cold snap. No coolant loss, so after searching the forums, I figured that it was monovalve. I replaced the monovalve yesterday. The old one had a tear, so that seemed to be it. It was an easy fix, or so I thought. When I started the car for the first time after the replacement and turned the heat on, there was a gurgling sound in the dash. Heat came on, drove it around for a bit, then the low coolant light came on. There was a sweet smell in the car, but no wet areas. Temp remained less than 80 degrees the whole time. I opened the hood, and yes, the reservoir was low but not empty. Couldn't see any leaks. Looked underneath, there was steam around where it dripped out onto the exhaust, which I think is where the overflow hose drains. I think this was caused by the car burping the excess air out, am I right on this?
So today I checked it, there was no fluid loss overnight. Filled it up to the cold line, drove it to work with the heat on full. No sweet smell in the cabin, no wet areas, light did not come on. I opened the hood and the coolant in the reservoir had dropped by about a half an inch! Checked with a flashlight, couldn't see anything wet under the hood, checked underneath, no steam or leaks. Since there was no coolant loss prior to the monovalve repair, I think it could be one of three things:
1. There's still air in the system and it's still working it's way out
2. The heater core is leaking(!)
3. There's a leak somewhere else that I'm not seeing

There are none of the typical symptoms of heater core leaks- no smells or wetness. Could I test for a heater core leak by shutting off the heat and refilling the reservoir, and seeing if it drops again? Would putting the old monovalve back in block the heater back up and prevent a leak?
As it's the holidays I'm short on cash and trying to avoid repairs for a few weeks. Thanks in advance!
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