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This is one of those technical detective stories that I am sharing because it might prevent someone else experiencing what I am currently dealing with as a result of an act by a previous owner that was either foolish or sloppy.

A few weeks ago, I bought my '52 Packard 200 Deluxe from a man who is bright and very talented as a machinist. The car is to act as my daily driver while I get my temporarily stalled SLURP project back on track (needs body work and paint at a time when my job is in serious jeopardy), and then is to become my next serious project, but only once the SLURP truck is back on the road.

I knew when I bought the Packard that it has a number of ?issues?, as the previous owner had serious health and other problems that interfered with his ability to keep the car properly up to snuff, but I figured me and my pro mechanic / restorer friend Randy could get those repaired in a sensible timeframe.

Looking back now at some of the things that happened, or that I noticed, over the past few weeks, I realize now that they were ?clues? that I should have grasped, that there was a problem lurking that COULD have been prevented, but that now has occurred.

The clues were ?masked? by other simultaneous distractions that grabbed my attention with their higher apparent immediacy, but here they are isolated and grouped:

- The heater coil, which on a Packard is under the front seat, had a leak in it, and so had been isolated from the engine coolant by the previous owner. He confessed this after Randy crawled under the car during our pre-purchase inspection, and noted that there was very little corrosion under there EXCEPT in the floor in front of the seat

- The coolant hose to the heater coil was not only shut off in the engine compartment via the factory shutoff, it was in addition CLAMPED off, with the previous owner mentioning that the shutoff had not in fact properly stopped ALL flow

- The coolant expansion tank has consistently had no fluid in it, despite 100 degree daily temperatures and 60 to 75 mph driving

- The top radiator tank has exhibited signs of weeping coolant at its lower seam

The other day, when I came out of a store, I noticed there was a small puddle of coolant under the car, and a small but steady drip. Popping the hood, I found the source of the drip ? that lower seam on the upper radiator tank.

There was NO fluid in the coolant overflow tank. I looked closely at the radiator cap, and noted that it was marked 16 psi. Oh-oh.

To understand fully what happened here, you need to know a bit about automotive engine cooling.

A typical car engine is atrociously inefficient in extracting usable mechanical energy out of gasoline. It actually only gets maybe 15 to 20% of the energy in the fuel to the ground as power to move the car. The rest gets converted into heat.

The engine coolant, a mix of anti-freeze and water, grabs much of that heat via the cooling passageways in the engine, and the water pump circulates the heated coolant out of the engine, through a thermostat that only allows it to flow OUT of the engine once it hits a certain temperature (i.e. after the engine has ?warmed up?). The pump forces the coolant through the radiator, where the coolant hopefully gives up much of its excess heat to air that is flowing through the radiator. That air is forced to flow through the radiator by either forward motion of the car at a speed of at least 30 mph, OR it is forced through the radiator by a mechanical or electric fan (mechanical in the case of the Packard). Once the coolant has flowed through the radiator, it is pumped back into the engine to repeat the cycle.

Since only 15 to 20% of the energy content of the fuel is converted into car motion, the amount f heat being radiated by the radiator is huge. In fact, it is enough at highway speed to heat a house in Minnesota in the winter. So, long ago, car designers came up with the clever idea of routing just a small portion of the engine coolant through a heat exchanger inside the engine compartment. That heat exchanger is called the car heater or more technically, the ?heater core?! This is why we have two hoses from the engine cooling system that penetrate the firewall. One delivers the hot coolant to the car heater, and the other brings it back to the engine cooling system.

This idea of using hot engine coolant to heat the car interior was brilliant, because there is so much heat available in that coolant, that it heats the interior rather quickly and effectively, even in subzero climates. There is also a serious downside: if the heater core develops a leak, you put hot coolant right into the floor of the vehicle. Oh, and by the way, the hot coolant is VERY corrosive. Since almost every vehicle has either carpeting or rubber mats and insulation backing, you TRAP and HOLD that corrosive coolant under this flooring, and right against the steel floor. Over time, if a leak develops and is not fixed quickly, you get corrosion of the floorboards.

The engine coolant also has two other interesting properties that are relevant.

One property is that as the coolant gets hot, it expands in volume. This means that you need either an ?air gap? in the system somewhere AND the ability to relieve excess pressure via a blowoff valve, or you need a coolant overflow tank. Most cars and trucks use a coolant overflow tank, as it is a more efficient and safer way to handle this volume increase as temperature rises. The radiator cap has a spring in it that allows the excess coolant to flow past it into a coolant tank separate from the radiator.

The other property of interest is that if you can pressurize the coolant versus letting it operate at atmospheric pressure, you can raise its boiling point. In fact, for every 1 psi of pressure you run, you gain about 3 degrees of temperature. So, if you can pressurize the entire cooling system to say 10 psi, you can raise the boiling point of the coolant about 30 degrees, which means you can have the engine get much hotter before it ?boils over?. You ?pressurize? the cooling system by making its components capable of withstanding MORE than whatever operating pressure you specify, and you provide a radiator cap that is set to release at a preset OPERATING maximum pressure LOWER than the design temperature of the components.

I was told by a NAPA parts store owner that most modern cars run their cooling systems at about 15 or 16 psi, in order to gain this extra working temperature range before boilover. However, the Packard service manual for my straight 8 engine built in 1952, not today, clearly specifies a 7 psi radiator cap as the intended pressure relief device. Oops.

Here is what I figure happened on my Packard:

At some point during the prior owner's use of the car, he replaced the radiator cap. In doing so, he replaced a 7 psi cap with a 16 psi cap. There are two reasons why he might have made this change in radiator cap rating. One is that he wanted ?the extra protection? of another 9 psi x 3 = 27 degrees of hotter coolant before it would boil. If this is what he intended, then he was foolish, because of course it is unlikely that ALL the components in the factory cooling system could take MORE THAN DOUBLE the pressurization that the system was intended to run at. The second reason he might have done this is simply because no 7 psi cap happened to be available to him. The NAPA man told me that 7 psi caps are not exactly common these days, since most contemporary cars and trucks run higher pressures. But, if he did this, he SHOULD have replaced it with a 7 psi cap at the first opportunity to do so. By not doing so, he was sloppy. And a price was about to be paid for his sloppiness.

The NAPA man told me that given the above scenario, the first component that he would expect to fail is the heater core inside the passenger compartment, since it is typically the weakest link. Guess what. It did. That's why the floor is corroded under the seat area.

Next, he would expect that the shutoff valve that would stop the coolant flow to the heater core might be unable to seal against the 16 psi pressure. Right again. THAT is why the clamp was put in the circuit by the prior owner.

The NAPA man also confirmed that you would expect the coolant expansion tank to run dry under these conditions, as the coolant tank is not accessible to the hot coolant until the radiator cap releases. Since the heater core failed first, the excess coolant got pumped into the car instead of into the coolant expansion tank. You literally couldn't get ANY fluid into the coolant expansion tank unless the system pressure exceeded 16 psi, which is WAY beyond the 7 psi design operating pressure.

This explains too why the top tank on the radiator started to weep from its bottom seam. The pressure, while still less than 16 psi, would not force open the radiator cap release, but was sufficient to exceed the capability of the tank seam. Hence the weeping.

On the day that I saw actual coolant drippage from the seam, the pressure had evidently gotten higher yet, but still not high enough to release via the 16 psi radiator cap, so it forced coolant through the tank seam. In the process, it probably permanently damaged that seam to the point where it will now leak, versus merely weep, when the engine gets hot again.

This of course necessitates a repair or replacement of the radiator to restore system integrity.

New old stock (NOS) Packard radiators are of course not found on every street corner, and even if they were, their integrity would be suspect now after over 50 years of storage. So, we are looking at a repair or re-coring of the current radiator. This is not an earth-shattering expense, particularly since removal and replacement of a Packard radiator is fairly easy (plenty of room unlike in modern vehicles), but the cost is nevertheless measured in moderate 3 digits. With my job security deteriorating literally each week (we lost 3 more people last week or so via layoff from the team), I am pissed that the prior owner's foolish or sloppy actions have now wiped out the heater core, rusted the floor of the car, destroyed the heater shutoff valve, ruined the integrity of the radiator, made my daily driver car temporarily unreliable, and will cause me to spend a LOT of money to correct all the created problems, right when I have much more important things to tend to. It is particularly frustrating that the correct 7 psi cap cost me only $4.50 including tax at the NAPA store and was in stock right on the shelf. The prior owner's foolishness or sloppiness will literally cost me hundred of dollars in remedial repairs, all because he made a very bad $4.50 technical decision.

My friend David Horner at Restoration Specialties, who sees a LOT of antique cars in his daily business, tells me that it could have been much worse. IF the radiator tank seam had not failed, his guess for next most likely point of failure on the loooooong straight 8 engine cooling system is the head gasket. THAT would have been really fun.

So, a word of warning: pay close attention to the details of what you or someone else working on your car or truck does. A foolish or sloppy action or decision can have consequential results that are pretty irritating and potentially very costly.

Jim G

You have to look at it this way: that 16lb cap just found what would eventually be a major problem when it failed, and probably at the most in-opportune time. I did the same thing on my '56, put a 16lb cap on it. I ended up replacing the radiator, and the heater core on the firewall because of this. It found all the weak points in the system for me, that's for sure!

BTW, the heater that's under the seat is for the rear seat passengers. You should have one on the passenger side firewall. If you don't, then someone removed it.

This is a great story. I was going to say that a 7 pound cap is available from the NAPA Dealer for $4.00 or $5.00.

Along these same lines a story of my own. I got my 51 from a friend who couldn't keep it running so left it parked for 10 or so years. He told me He quit driving the car because every time he went out in the car it would overheat. He replaced the radiator and the water pump. Still overheated. He even went so far as to tell me he checked with a friend of his who owns two Packards and was told " Yea all those 51's over heat that's just the way they are." Sure enough when I started driving the car on almost any day I would loose coolant over the side. There is no overflow tank on a 51. One day I started the car after topping of the radiator coolant level and was messing with something else and noticed water running out the overflow pipe. The engine was just started and had not even warmed up yet. I found that at some time he had changed the radiator cap with the wrong one. The cap said 7 pounds all right but was designed for a radiator with about a 3/4" drop. The packard filler neck has a 1" drop. The rubber seal on the cap was 1/4" above the seat in the bottom of the filler neck. He might as well have left it off all together. Again the NAPA dealer came through and had the correct 7 pound cap with a 1" drop in stock.
BTW ever try to buy simple things like a radiator cap or spark plugs from Kragen Auto? I get aggravated every time I drive by a Kragens. Lately has anybody said " Yes but who makes Packard, Ford or General Motors?

Out of curiosity, had your radiator been redone? They didn't have overflow tanks originally and I remember some time back in one of the forums someone had problems finding the proper 7# cap because the more modern cap necks are a bit shorter & wouldn't seal properly.

EDIT Bob47 just answered my question. Napa must be one of few carrying different lengths and Kragen/Autozone/PepBoys kinda a waste if you don't have Ford/Chevy--at least down here.

HH56: You are very sharp.

First, yes, the radiator was repaired and rejuvenated in August of 2007 while owned by the previous owner - i.e. 11 months ago. I know this from the excellent provenance that came with the car.

In addition, I checked that new cap, and found that underneath it, within the radiator "spout", there is a machined spacer. Evidently, the purpose of that machined spacer is to enable use of the shorter more modern radiator pressure caps in the Packard radiator. Either the prior owner, or someone before him, had installed that spacer, which by the way, is completely removable, thus enabling use of EITHER the longer Packard cap or the shorter modern cap.

I wonder if the car had been running that 16 psi cap since that radiator overhaul 11 months ago.

TurboPackMan: I don't regard this process as "finding the weak points". ANY system run at over twice its intended pressure is going to fail somewhere. At 7 psi, it might have been, and probably would have been, just fine. This is like pumping up a tire rated for 40 psi to 90 psi and then saying we "found the weak point" when it blows. That's not a valid test of the tire's integrity.

Jim G

Quote:

Well, it worked, didn't it? LOL!