John Rogers wrote:
>
> I recently sent my oil press. / water temp. gauge for a rebuild (I
> managed to use the starter solenoid to weld the sending tube shut.
> Isn't that what the solenoid is really for :-( ?) At any rate.. I
> assumed that the temperature guage would be correct when I got it back.
>
snip
> Previous to this saga, I installed a coolant recovery tank that should
> theoretically keep the expansion tank on top of the radiator full. Does
> this do any good or is it just a waste of time?
>
> If the guage is wrong maybe I should just not be so nervous.
Yes recovery tanks are a good idea.
The way I used to check them "on the car": I would drain, undo the bulb
at the front of the head, boil a small pan of water on a pot plate and
carry it to the car. I would then use my propane torch to re-boil the
water while the bulb was sitting in it and see what the gauge read. If
they did not read 100/212, I would either send the gauge in, give the
customer the "correction factor" or (sometimes) remove the ring/glass
for access and reposition the needle (pull off with pliers and push back
on - do NOT twist) If you just got it back from a rebuild/recharge, SEND
IT BACK, there's no excuse for them not calibrating it properly.
Just as a speedo is best set to be correct at around 60 MPH with
progressive errors either side of that speed a temp gauge is calibrated
at boiling. Since 185-190 (85-90 C.) is the preferred operating temp,
gauges are usually set to be correct at or near boiling since any error
at the low end of the scale is not important.
There's a small, curved, hollow, brass bellows inside the gauge. As the
ether in the bulb, tube and bellows expands while it warms, the bellows
tries to straighten. A link to the needle moves it to give the reading.
If the bellows is damaged due to extreme overheating (steam at 240?) or
ham-handed repair, the readings will have an error at one or the other
end of the scale.
One of those mechanics Ulix dislikes so much
|