Quote:
Originally Posted by bonneville Joe
I'm going to throw this one in here..
My car was cooling right at 160 all spring. Once the hot summer months hit it was running near 220. I replaced the thermostat with a new 195 as that is all the parts store had and it would warm up to 220 and not budge. I took the thermostat out completely and the car runs a notch under 160. Even sitting at a stop light in 95* summer heat it will barely get to 170 and then once I start moving it drops right back down again. Had the same issue with the '67 Bonneville I had last summer. That car didn't have a gauge but it would puke water everytime I parked it. Took the thermostat out and it ran fine, even when we had the week or so of 105* august days last summer.
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Hi Joe,
I took the plunge & REMOVED my thermostat last Friday --- and so far, so good.
I still haven't given it the "acid test" of extended highway driving, but that'll come, too...
I delved a little deeper into the official GM Shop Manual for my 1978 Trans Am, & came up with a couple of really "...quick & dirty" (but VERY easy & effective) checks that one can readily perform on a T/A, to ensure whether there might be a temperature reading fault with the guage, the sensor, or any of the associated wiring...
Specifically, locate the temperature sensor on the engine block, and then DISCONNECT the wire which attaches to it (i.e. create an open circuit) --- with the ignition "on", your guage should read as closely as it can go to the left side of the scale which indicates "maximum coolness" (in other words, whatever the lowest temperature might be indicated on the scale --- for our cars, it's shown to be 100F).
If the guage worked as indicated, you must next install one end of a temporary jumper wire from the wire lead which goes to the guage, and connect the other end of this jumper to ground, leaving the sensor dis-connected (i.e. create a short circuit) --- with the ignition "on", the guage should swing hard right, i.e. toward the "maximum hot" end of the scale. In the Firebird, this is indicated as being 260F.
If the guage reads properly after these two steps, then suspicion should rightfully fall upon the sender itself. If you did not achieve the readings indicated by the two tests, then suspect either the guage itself, or its associated wiring.
The GM shop maual goes on to say that the guage may also be checked by substituting a resistance source in place of the sender...specifically, the guage in the Trans Am should read 100F at 350-ohms, 220F at 68-ohms, and 260F at 46-ohms...but this may well be beyond the scope of what you're trying to achieve here, i.e. determining if it's the guage, or the sender, that's giving erroneous readings.
It's all very interesting, and NOT all that complicated, either...
Eddy
Ontario, CANADA