Overheating problem 5KT - 1981, type 43

[Jim Jordan]

Hi,

I've exhausted all alternatives open to me short of getting a newer car
which I'm investigating.

My car started overheating some months ago, not badly, just some.  At first,
I linked it to the coolant temperature gauge, for I had removed the
instrument cluster to make some bulbs work and thought I may have disturbed
a connector contact, etc.  Several reworks and rechecks could find no
problems.

I tested the coolant temp gauge by connecting a 60 ohm resistor and a 450
ohm resistor in series with the sensor wire to ground, simulating the VW
tester recommended by the Bentley.  Gauge reads properly with each
installed.  I changed the TCA700Y voltage reference device to a known good
one.

I used a digital thermocouple pressed against the head next to the temp
sensor and measured the outside surface temp to be ~210 F before replacing
the radiator with a cleaned one.

I've changed the thermostat, fan switch(3X), temp sensor(3X), most of the
hoses(irrelevant), installed a freshly leak tested, boiled out, rodded out
radiator(a pita), changed the coolant at least 3 times, used a cooling
system cleaner followed by flush and renewed coolant.

Most of the cowling is still good and in place although patched with
flashing and pop rivets.

The temp gauge still reads high although the engine runs fine albeit at
higher temperature, maybe.  Oil is relatively fresh, topped off, and oil
temperature reads in normal range.

Could the water pump fail while the timing belt is still operating properly?


Any other ideas that come to mind that might solve this problem?

Thanks in advance.

Cheers!

Jim Jordan