Coolant disappearing / Check engine light blinking

Asked by TBuick1998 Jan 15, 2020 at 05:09 PM about the 1998 Buick LeSabre Custom Sedan FWD

Question type: Maintenance & Repair

My check engine light was on for quite awhile but the only code read was
coolant temperature. Then, the car broke down and the intake manifold was
replaced. Immediately after, the check engine light came back on reading the
same code. The mechanic claimed it was a sensor issue and the car should be
fine. About a year later, the check engine light began to blink indicating a
misfire. The codes that read now are PO171 and PO303. The coolant
disappears quickly but there are never puddles or wet spots under or around
the car. The car will not start again if I drive for more than 10 miles and
immediately try to start the engine. It will start if it has been sitting for more
than 3 hours or so. The oil pressure and battery gauges fluctuate after the car
is running for awhile as well. I am just wondering where the coolant is going
and why the engine has trouble starting. Any help is greatly appreciated.

1 Answer

735

First, pull your dipstick and make sure the oil does not look milky. Then when the engine is cold open your radiator and make sure you do not see any oil in the coolant. When coolant disappears it often indicates a blown head gasket. A blown head gasket can allow the coolant to get into the cylinders and get blown out the exhaust pipe. Your PO303 indicates misfire on cylinder 3. I would expect that is where the headgasket may be blown. A car may continue to run fairly well with a small blowout in the head gasket between the cylinder and a coolant port. It will cause a drop in power and gas mileage which you may or may not notice. But over time it can really mess up the catalytic converter(s). You can do a compression test on the cylinders for confirmation. Most of the big name auto parts stores let your borrow compression testing equipment.

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