Pressure testing radiator
Thread Starter
Race Director
Joined: Jan 2000
Posts: 10,059
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From: Slower than a speeding bullet................ Fort Lauderdale, FL
Pressure testing radiator
I have attached a pressure tester to my expansion tank, and within the
first 2 hours, I have lost about one pound. It seems like it will keep losing,
and I'm checking it about every hour. Car is cold (has not been run).
I see no leaks in the tank, and hear no air escaping when I pumped
the tester to 15 lbs.
I have a brand new DeWitt aluminum radiator, and temp gauge has shown
very hot (near 240) on a 92 degree day. I am going to change the temp sending unit also (which is probably incorrectly calibrated from what
I've been reading), but wonder if my problem is also related to loss
of pressure ? I am using a 15 lb. cap.
Any thoughts ?
Thanks
Team Owner
Joined: Oct 2000
Posts: 38,897
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From: Washington Michigan
Re: Pressure testing radiator (Mr. Wonderful)
System pressure has nothing to do with operating temperature - all it does is raise the boiling point of the coolant so it doesn't "puke" from the overflow during heat-soak after shutdown. A 50-50 anti-freeze/water mix with a 15# cap won't boil until it reaches 265*F.
Doesn't sound like you have any significant leakage. Suggest you get an I.R. gun "shot" of the upper radiator hose just above the thermostat housing, and compare that to the gauge reading at the same time so you know what the gauge is telling you; the gauge will probably read hotter than the I.R. gun reading. None of the replacement senders are calibrated the same as the original #1513221, but the Wells TU-5 ($5.00 at AutoZone) or Standard ST-6 are closer than the rest. Do the I.R. shot procedure again after installing the new replacement sender so you know how it's calibrated. Shoot the black hose, not the housing itself - smooth/glossy surfaces will give a much different reading than the true reading you'll get from the dull black hose.
Doesn't sound like you have any significant leakage. Suggest you get an I.R. gun "shot" of the upper radiator hose just above the thermostat housing, and compare that to the gauge reading at the same time so you know what the gauge is telling you; the gauge will probably read hotter than the I.R. gun reading. None of the replacement senders are calibrated the same as the original #1513221, but the Wells TU-5 ($5.00 at AutoZone) or Standard ST-6 are closer than the rest. Do the I.R. shot procedure again after installing the new replacement sender so you know how it's calibrated. Shoot the black hose, not the housing itself - smooth/glossy surfaces will give a much different reading than the true reading you'll get from the dull black hose.
Thread Starter
Race Director
Joined: Jan 2000
Posts: 10,059
Likes: 266
From: Slower than a speeding bullet................ Fort Lauderdale, FL
Re: Pressure testing radiator (JohnZ)
Thanks for your reply, John.
I have borrowed an IR gun, and am planning on testing it soon.
I will do the before and after test with the sending unit as suggested.
Just wanted to see if the tank was in good cond.
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
Re: Pressure testing radiator (LT1driver)
The TU-5's and ST-6's I've seen and used vary from correct to about 20* high, much better than other replacements (including AC's); I've never seen any replacement that reads low. Always check the calibration vs. the gauge with an I.R. gun after installing a new one. I have an older ST-6 in my '67, and it calibrates dead on.
