86 190E 16V with a 148k. Late spring I had all the fluids changed in the car, including the coolant. Over the summer, there did not appear to be any loss of coolant. Last week, the low coolant light came on while I was driving, then subsequently went off a few minutes later. Coincidentally, it was also the first time that the outside temp was in the high 40's, low 50's so the heater was on.When I checked the level, it was just above the sensor. I topped it off and began to check for any obvious leaks from hoses or connections. I did not find any, nor does it appear to be leaking from the heater core (no steaming of windows, no smell of antifreeze, no wet carpet.) I have looked at the exhaust and it is not white.

I have driven it since I topped off the fluid and it has not leaked since. I let it idle till the fan cycled on just to make sure it got into operating temps.

I plan to have the system pressure checked, but if anyone has any insights I would appreciate it.

Thanks.

Bob
86 190E 16V

Did you check the overflow tank? They sell a dye in NAPA that you can add to the coolant and will show any leaks with a "black" light.

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J.H.
'86 300E

If the monovalve has been closed all this time (unlikely), you could simply have air in the heater core.

That engine is notorious for not filling completely unless you work at it, so I'm not surprised you are low after running the heater some. Did you get gurgling sounds in the dash? If so, definitely air in the heater core working out.

I'd also replace the pressure cap if not done recently, they go bad and allow coolant to burp out into the overflow tank under the fender.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks for the tips. I'll check out the expansion tank as well as the cap.

Bob
86 16V