As discussed last time, we have been working on some of the many electrical issues created by the Lucas electrical system found in a customer’s 1970 MGB. This customer had recently noticed his heater was not producing warm air, and we discovered the coolant had changed color and the temperature gauge vibrated as you revved the engine up.
We found a few issues upon further investigation. First, the thermostat was stuck in the open position, therefore not allowing the coolant to warm up enough to get heat inside the car. Second, the heater core was nearly plugged internally with gunk. The coolant smelled acidic and actually stained the concrete floor a light brown color. The bouncing temperature gauge needle was from the temperature sender unit which had a loose electrical connector, and vibrated with the engine speed.
To get all the old fluid out of the engine block, we removed a drain plug on the side of the block. The sediment was so deep and compact, that nothing came out when we removed the drain plug (see below).
First we used a 5/16-inch drill bit:
Next, we jerry-rigged an old flexible speedometer cable to a drill:
Then we roto-rooted the hole until the nasty, vintage 1970 sediment came gushing out:
To clean a system in this acidic condition we used a cleaning product that actually neutralized the acidity. We removed the thermostat for full flow, filled the engine with water and cleaner, and let her run. Flush, flush, flush…until we saw clear water. We used a garden hose and 60 psi of city water pressure to flush out the heater core. It was a happy heater when we were done.
The cooling system turned out well. We ended up with plenty of heat for the heater and plenty of cool for the engine. The little gauge needle even smoothed out with a new sending unit. The new coolant is nice and green compared to the old brown acid, and it smells great (see below).
On regular everyday cars, at New Concept Auto Service, we use a suction/pressure flush machine which exchanges nearly 100 percent of the old coolant for new. We use a new, high-tech antifreeze which lasts about three years under normal conditions. So long as you follow this formula, your chances of having any cooling system issues will be minimal, whether you drive vintage or new.