Packard Forum Index » V-8 (1955-56)

Bobby, it is not a new radiator. My friends, who were helping me during the restoration, took the radiator to a radiator shop after I told them the car ran hot. I assume at the shop, they did whatever was needed to insure the radiator was fine. There was no word that it was not okay.

I don't know about the cap. You mentioned I might have the wrong cap or a bad cap. Assuming I change the cap, if there is such a thing as the "right" cap, which cap do I need? 56 Clipper Sedan.

The coolant was new when I left the shop. Can't say if it was overfilled or not, since I did not fill it. After I broke down, I noticed coolant came out. I assume it wasn't overfilled because my friends know a bit about cars more than me, but I would not rule it out.

All radiator caps are not the same! You need a 12 psi one. Less psi rating would cause it to leak out when in fact it isn't overheating. This is a cheap and easy fix.

I'd call the shop and ask them what they did to your radiator. If it's the original one, it should be recored. I'd doubt that a 'Power flush' would be effective, by now the actual core has begun to disintegrate. This could easily account for your symptoms.

If you open the cap when the car is COLD (make sure it's cold!), the coolant should be just above the honeycombs, about an inch or two from from the actual top of the radiator. If it's there, regardless of what might have seeped out, you're OK, just keep an eye on it. If not, then my guess it's the radiator itself.

Finally, my thermometer arrived. I got the temp of the car up and measured.

Top of radiator is showing about 220 F at its highest. 209 seemed to be a common number around the top. Around the middle it will be in the 170's - 180's.

What does this mean in terms of whether I am running hot or not? Over 200 sounds hot to me.

I haven't made lots of measurements on lots of vehicles but it seems hot to me. Both my Packards measure about 5 degrees or a bit less over the thermostat rating in the radiator top tank.

For what it's worth, on my 56 using a super duper high quality Harbor Freight precision laser thermometer.

Am reading about 195-205 at center of top tank right in front of inlet -- straight on from front. Appears to be about 10 degrees lower side to side. The angle and distance the laser takes the reading seems to make a big difference with this HF special. Tried to keep these at 12" distance. Hard to get a good core shot so don't trust the center reading. It's taken at a steep angle thru the fan blades but is running 160-180. Bottom tank taken from under car straight on is about 10 degrees lower than top tank.

Not totally real world conditions as car didn't leave the garage. This is after the car was idling for about 15 minutes with AC on and the gauge at dead center.

I got the cheapy, too. $20 model made by Rosehill.

So, everyone says get the thermometer. Now is the advice, ".... but you can't trust it?" LOL!!!!

What do you recommend I do to confirm whether I am running too hot or the gauge is not right?

Boil water on the stove and then measure it. Should read around 212f plus or minus depending on your local altitude.

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I don't have a lab quality thermometer like O_D but following along Kev's suggestion I did compare my coolant temp using an ordinary kitchen thermometer and the infrared. At 6" they matched within a couple of degrees but at distance there was significant difference.

Upon actually checking my operating instructions, found a recommendation to try to measure non reflective surfaces and also a distance chart this mfg included.

The area of sensing seems to be the variable. On this brand, at 8" the area sensed is 1" diameter. At 16" it is 2" diameter and at 24", 3". Not sure how they handle it but if there is a wide variation between temps in that sensed area, expect they would be averaged and that would be the displayed temp.

Just FYI, after sitting for approx 30 min after the laser temp reading, coolant was 185 in top tank. Garage temp is about 80.