I've got a real weird one on my hands and am asking for advice.
92 Caprice with 310,000 miles on original 305 engine.
For the last 3 years or so I have not been able to just flush/fill and
put a stock thermostat in the car and have it work properly.
The heater core, all hoses, radiator and several different brands of
thermostats, new cap (3x) (195 degree, but I tried 190 as well) have
all been changed. The water pump is about 4 years old but shows no
signs of trouble.
Here is what happens:
1. Raise front of car on ramps and fill the system leaving the
radiator cap off. Run engine until thermostat opens and then top off
the coolant with 50/50 mix.
2. Let car cool down and do the same thing again until level in
radiator stays the same all the time, at the top of the neck. Fill up
coolant overflow jug half way. Put on cap and test drive car.
3. Temperature gauge (cold car) will start to rise slowly then go way
up almost until redline, sit there for a few seconds and then the
gauge will drop like a rock down to normal. However, the gauge will
still swing more than it should after this point although it will
NEVER go back near the red.
4. Drilling a small hole in the edge of the thermostat fixes the
problem and the car runs fine.
1. I do not lose any coolant.
2. I DO see some bubbling in the radiator, but nothing that I would
attribute to anything other than the coolant sloshing around.
So far it has been suggested that I have a head gasket problem, but I
doubt that because like I said I have been driving for 3 years like
this (hole in thermostat of course). I put A LOT of miles on this
otherwise perfectly running car. Oil is clear, coolant is clear and
exhaust gas doesn't smell sweet of anything. I just changed plugs and
they looked fine as well.
Water pump cavitation problem?
Air trapped in the system? I have left it overnight on the ramps with
the cap off and still have the same troubles.
Should I get a new thermostat housing and put a bleeder valve on it?
Any other ideas?