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· Registered
4,630 Posts
Discussion Starter · #1 ·
Hello All,

In addition to the "Ice" light mentioned in another thread,
my car is in the habit of telling me that I have "Low Coolant"
when I do not. This is not as consistent as the "Ice" light,
but it happens fairly often.

Every time I have checked in the past, and that's probably
been at least on 10 different occasions, the expansion tank
atop the radiator has been full, whether the car was warm
or dead cold.

Today, I decided to do a precautionary check when shortly
after driving several miles and the car had warmed up some.
The cap on the expansion tank was more difficult than usual
to remove, and the tank was full, as usual.

I took the car out again for another test run of several
miles, running at highway speeds, and when I arrived home
and stopped in the driveway I noticed afterward that there
was a bright green puddle, and a trail from that into the
garage. When I began poking around underneath, there
was a relatively steady stream coming out of the overflow
hose from the expansion tank. This has never happened
(that I've noticed, and I think I would have) in the past year
and it concerns me.

There was absolutely no indication of overheating on
the gauge or via the "Engine Overheat" light.

Any insights into reasons that sudden overflow like
this might occur would be appreciated.


· Registered
4,630 Posts
Discussion Starter · #2 ·
Just wanted to follow-up my own posting with some very useful information that was offered to my by Jon Waples on the RROC forums with regard to how the "Low Coolant" checking works:
Your low coolant light can be the result of a loose or intermittent connection somewhere. The coolant probe in the header tank consists of two stiff wires that are ordinarily submerged in coolant. This completes the circuit. If the coolant goes too low, the circuit is broken and the light comes on. Breaking the circuit elsewhere does the same thing. Check that the little itty bitty nuts that make the wire connection at the header tank are clean and snug.

The wiring on mine that runs from the tank is not in the best of shape. I tried restripping the ends and putting on new crimp connectors, but that didn't help. Given what I found of the condition of the insulation near the ends of the wires, I would not be at all surprised if I've got a broken wire somewhere along the lines.

I hear a "neeeeeext" being called on my "to do" list.

· Registered
18 Posts
If the system keeps pushing coolant out of the overflow you may also have a pressure problem. When the system loses pressure it will push coolant out. Check the pressure switch on top of the expansion tank (not sure if it’s serviceable) and also check the expansion tank cap. If it was dropped at some stage the sealing edge may be damaged.



· Registered
4,630 Posts
Discussion Starter · #4 ·

Thanks for your response. I do believe that the original problem was a pressure problem that I accidentally induced by not sufficiently tightening the cap. Once I refilled the expansion tank and put the cap back on tightly, I have had no problems with the coolant levels.

In fact, SRH33576 made it all the way from Virginia to Utah and back as part of the RROC fall tour. [I only wish she hadn't also had an all too intimate encounter with a mule deer during that same tour!!]

· Registered
16 Posts
I had the same problem on my 1973 Silver Shadow SRH15075.
The solution was very easy:
The car before been sold to me remained parked for a very long time (about 3-4 years).
In the right side of the expansion reservoir is located an over-pressure valve, it proveed purge out the water and the pressure in excess to prevent mechanical faults.
The valve is fixed with a rubber gasket with a particular pre-formed shape to be able to allow the valve. If the car remain unused, the rubber become dry and crack and when engine runs its sufficent a minimal pressure to loose also a great quantity of coolant immediately indicated by the warning light in the car.
Practically in 99% of situations is not the valve to be faulty but simply the rubber around.
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