Dismantled Oil Cooler-FYI

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    Now here is something you don’t see daily. This is a dismantled oil cooler on my 836. Pretty straight forward except there are 4 (second item from top left corner, not counting bolts, washers and nuts) gaskets, one on the inside and one on the outside of each of the 2 side covers.

    Only serviceable parts appear to be the above gaskets and side cover gaskets. Check the honeycomb for leaks. I think you could solder if any are found.


    Dont run it. It WILL fail and wipe out your main bearings. Cislak makes a bolt on bypass kit…….not sure if he still has any in stock. I have seen them fail by often, I tried to run one on my car and I gave up after 4 failures in less than one year.


    What causes the failures? Were they necessary in the first place?



    Good to know. I will check with John. What fails?




    I am assuming that water gets in the oil and water is a very poor engine bearing lubricant. It looks to me like the 2 gaskets inside the side covers could be a easy point of failure as the core is a fixed length and the side covers have some variation due to the cover and line gaskets. If the gasket thicknesses are not perfect, I can see where water could get in the oil there. Also, as everything expands and contracts, over a heating cycle, there are parts that could loosen.



    The “Oil Temperature Regulator” as it was called came with the introduction of the 1933 models and their hydraulic valve lifters. Keep in mind, in 1933, oil technology was not anywhere near what it is today. They did not have modern multi-viscosity motor oils with all of today’s additive packages, and certainly did not have synthetic motor oils. To try and keep the oil viscosity more uniform, Pierce-Arrow designed the small heat exchanger to mount on the side of the engine to actually help warm the oil when the oil and the large sump of oil in a Pierce-Arrow engine is cold, but probably more to help remove heat from the oil when the engine is running hot. The whole idea was to have a more uniform oil temperature and oil viscosity to support the hydraulic valve lifters. It basically damped down the large oil temperature extremes and narrowed the range of the oil temperature.

    The heat exchanger core is like a small hot water heater core. With time, corrosion, and vibration, the core itself can form stress cracks or pin hole leaks. Remember when you got that “sweet” smell in the interior of your 10-20 year old modern car, maybe some residue on the inside surface of the windshield where the defroster vents were, or the yellow/green ethylene glycol drops on the floor of the car? These are all signs of a leaking heater core. In the case of the Pierce-Arrow oil temperature regulator , Ed is right, it allows water to mix with the crankcase oil……as was stated before, water is a poor lubricant in an internal combustion engine.

    A telltale sign is if you open the radiator cap (on a cool engine) and you see oily rainbows in the coolant water. This is an indication of oil in the water….which could also mean that there is water in the oil.

    If you want to run the oil temperature regulator, 1 solution is to have a radiator shop make you a small custom heater core. Another answer is just to run a straight piece of pipe through the regulator body. Since we now have the benefit of modern motor oils, you could block off the oil and water passages and not run either fluid through the regulator and just have the housing their for show.

    Happy Motoring,



    The core in the oil cooler failed on my ’36 many years ago. My clue was that the coolant in the radiator looked like chocolate milk. A radiator shop pressure tested the core, the leak was there. They solder repaired it, and it remained working until John Cislak did they engine. At that time he put in a bypass, and everything is fine without the cooler..


    A few thoughts on the oil cooler: If the core develops a pin hole while in use, or the gaskets leak, the first result will be oil in the water, since the oil is under 20 to 50 pounds pressure, and the water is at zero psi. So if you check the water regularly, there will be no danger of wiping out your bearings. Just fix the core when your finger comes out brown. The real danger is if a car is left sitting with a full radiator and a leaky oil cooler – the water is at a slight pressure due to the height of the radiator, and the oil lines have drained, allowing the water to get into the oil lines.


    The first Pierce that I restored was a wonderful original 1934 840 sedan. I wish I had it to do over again, the gray body paint was so nice that, when I put the unrestored body back on the restored chassis, people asked why the primer was so shiny….but in the 70’s and 80’s, you had to restore them.

    Point is, I knew nothing of Pierce cars, but when I took the oil cooler apart I sensed a problem coming. I fabricated an oil line to fit exactly where the “cooler” would be, and installed…and the car was a fantastic running car with no hint of any oil problems….



    Spoken like a true mechanical engineer . I gather from the comments that the oil cooler was important, but the oil technology has improved to the point where the cooler’s original intent is now moot. I hate to bring this up in an existing thread, but should we be using zinc rich oil in these cars?


    I have seen a cooler failure where a seem split and the oil and water mixed in the crank case. I can’t remember if it was a factory oil line, pressure regulator, and oil filter set up. Maybe it was due to modifications of the system? Or did the oil drain back and let the water into the lower end when parked for a long length of time. There are two style oil cooler cores. Honeycomb and fluted. If the amount of water / coolent in the lower end is a small, the engine operating temperature will boil it off without much problem. I think all agree with modern oil the cooler is not necessary. And can only turn into a problem down the road. It sure will make a mess of your cooling system, and if you push the oil and water out the over flow, it will take weeks to clean the car up.


    I discussed the requirement for Zinc Dithiophosphate (ZDDP) with petroleum engineers at one of the major engine oil companies. Their conclusion – the relatively low RPM Pierce-Arrow engines do not require ZDDP. The most likely cause of failure of camshaft bearings in an engine is the failure to use a proper lubricant for the bearings during engine assembly.


    I am not sure how ZDDP got into this discussion, but here it is.

    If you run a Diesel Grade oil there is not problem (higher in ZDDP).

    Also, the ZDDP controversy relates to more modern “Classic” cars, those that run pushrods / flat tappets and not roller cam tappets as on Pierce-Arrow motorcars.

    By more modern “Classics”I mean 50s & 60s American Iron, particularly high output vehicles like the Mustang and Chevelle.

    This topic has been beaten to death more than a few times.

    Run a good grade of Diesel Grade (CJ4) oil, like Shell Rotella or Castrol GTX and you will be fine, but I repeat myself.

    Paul is correct in his comments, but others worry and CCA profits from their unnecessary concern.

    However, if you must, you can spend extra money and run the CCCA motor oil or you can buy a ZDDP additive at your local auto parts store for $10+.

    Even if you do run the “high priced spread” it is short change considering the general cost of owning and maintaining a Pierce-Arrow motorcar, and we all get to squander our money how we wish. If we didn’t have that freedom, we would all drive soulless Toyota Corolla cars.


    Hey now, Corollas are about as reliable as your refrigerator – and just about as exciting.


    The temperature regulator was installed on more cars than Pierce, senior Packards among them. I have the SAE technical paper by the engineer who originally developed it. Indeed, its purpose was to warm the oil up in winter and cool it on hot days – maintaining within a closer range of temperature.

    My first one leaked, my second one has been fine for 30 years – maybe. Years ago I put peak temperature indicators on the goes-in pipe and goes-out pipe on a 400 mile 65 mph 90 degree+ summer drive down I-80 and I-5. The max temperature in was the same as the temp out – in other words the oil temp was pretty much the same as the water temp and water wasn’t doing much to cool the oil. Multi-vis oil solves the cold start/run issue, so seems prudent to bypass it.

    Reminds me of another 1930’s SAE paper I have somewhere with some interesting tests and analysis of oil cooling and other means to cool the bearings. Its been a few decades and mean to dig it out again but the conclusions were somewhat non-intuitive with some interesting insight on bearing failures with high speed driving.


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