Packard Forum Index » Post-War (1946-54)

1951 300, 327, Ultramatic.
I have a "new" style thermostat in my car. 160*
I have noticed that on uphill grades or speeds above 60 mph that my temp gauge will climb to the high side of the M. Once i flatten out, or slow down to 60 or lower, it goes back to the "center" (between E and M).
Its never boiled over. Radiator is a fresh recore, new water pump last year, block flushed, cooling tube pulled and cleaned.
Car runs much cooler with recore radiator ! Money well spent !

Was wondering about flow rate between old (bellows) style thermostat and newer style.
Is the newer style thermostat more restrictive. The opening in that thing isn't that large compared to hose and housing sizes around it.
Did the "bellows" style have a larger opening in it ? did it flow more coolant and work better in the lower pressure system (8 # cap) than the newer ones ?

Or ???

Thanks.

I don't think the bellows style thermostats are meant for use in a pressurized system. As for the size of the opening, most all thermostats are much more restricted than the hoses and other fittings in the cooling system. I have read that a pressurized system will prevent the bellows type thermostat from opening as it should, since the system pressure will work directly against internal pressure in the bellows that is trying to open it.

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That is correct and Packard stopped using the bellows type in 54 and even retrofitted some earlier models when the higher psi radiator caps became more the norm instead of the older 7 psi caps. There is an article on the use of the two types starting on page 39 in the May 54 service counselor.

I asked a pretty similar question on this about two years ago here and got some great feedback. You can view that conversation here:packardinfo.com/xoops/html/modules/newbb ... php?post_id=262470&keywords=Bellows

I will say that I ended up purchasing a Duralast Gold thermostat that claims to have a "larger than OEM opening." So if you're looking for something with a little more flow, the part number is 15356DLG. It's been working well for me so far!

I will say, it sounds like your engine is doing normal Packard stuff, and so long as it doesn't keep climbing you're probably good. It's pretty well documented on here that at this age, the gauges aren't always altogether accurate. I grabbed an infrared thermometer and took some readings at various markings on the gauge so I have a better sense of what my gauge is actually telling me (and if I'm really ever getting to a danger zone. There's another post like, two topics down from this with a service bulletin that mentions that 227° as the boiling point in your car.

So yeah, always worth keeping an eye on I think, but sounds like you're in good shape.

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If you check the owner's manual (not even service manual) this is indicated as fairly normal behavior. I'm a bit surprised on the high speed, but not for hill climbing.

That behavior is pretty normal for my car as well. '54 327. Most of the time it's around center of the gauge, but uphill and in warmer weather it will creep up and sometimes hit the high side of the M. I'm running a 7lbs cap right now and it's been fine except for one time. That day was over 100 degrees and I was coming up a long grade at 50mph. Afterwards the radiator was puking coolant out the overflow. Temps with an infrared gun showed I was about 210 or so.

Modern cars with heavily damped temperature output hide this fluctuation since its disconcerting to the customer, but all cars swing up and down just as much as the old ones did.

Most water pumps are only pushing a nominal flow of 10-20 GPM in normal low RPM town driving and perhaps 50-75 at max RPM, not a huge flow of fluid and the pressure drop from slight differences in thermostat opening would be insignificant compared to the total loss caused by the radiator and engine passages.

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This is true. Hook up a scanner to your modern vehicle and watch the temps. On my 2005 Tundra the temperature gauge stays right at the middle from a temperature range of 184 degrees all the way up to 221 degrees. Zero movement in that range. Once it goes to 222 the needle moves up quickly. The temps on the truck will vary widely depending on load, speed, and incline. I was so conditioned to never seeing the temp gauge move in modern vehicles that I thought there was a problem when the temp gauge moved in my '54. It's all normal.