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In a message dated 12/17/2002 11:32:16 PM US Eastern Standard Time,
geryvon@videotron.ca writes:
> Today I'm seeing some different characteristics in the water pressure
> readings. Used to be that after cooling down I could see 4 or 5 lbs
pressure
> for many days and I don't think increasing pressure after start up was tied
> to rpm. Now pressure drops instantly on shutdown and is closely tied to rpm
> to Max of 15lbs as the engine is revved up. This looks bad to me although
> temps in flight are fine. What do you think?
> Peter
>
I think you have succeeded in removing all of the air from your system. I
suggest that with hydraulic lock up, you get coolant pressure indication very
quickly after start up. As soon as you achieve operating pressure, your
relief cap starts dumping coolant to the make up tank. On shutdown, the
slightest reduction in temperature, any reduction in volume drops the
pressure to zero very quickly.
With no thermostat in place, the most effective restriction to flow is the
radiator core.
The pressure tap is reporting the high pressure between the pump output and
the restriction. The restriction is nearly constant but the pump output
varies with RPM, thus the pressure reading tracks RPM. All is normal. You
could remove the plug in the bypass hole and install a stock thermostat. That
would get you rapid warm-up and a restriction upstream from the pressure tap.
I assume that the minimum operating pressure you are seeing is the relief cap
setting? I have not recorded coolant pressure in the car but have done so on
the dyno. In piston engines with just the outer rim of the thermostat in
place, up to 40 PSI develops in the block. I use a radiator cap with the
pressure mechanism removed. The overflow hose goes to the bottom of a stock
RX-2 make up bottle. This bottle has the pressure cap on it. This is a Stant
lever cap 16 pound. The bottle acts as an accumulator (air spring) to
maintain a constant pressure without dumping coolant. The bottle is only 1/4
full of coolant. It works like a charm. It is the stock layout of the RX-2/3.
Lynn E. Hanover
CoolingSystemIII_WEB.jpg
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