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

"Hot" or "higher" is forcing more heat out, so in effect it's a good thing, up until it effects the lubrication and other aspects like fuel delivery, etc. So if it's just a few degrees higher in the hot weather, idling, I'd not worry unless you want a perfect running original. The seven psi cap will take around 215-220F. It's counter intuitive but DO NOT use a lower temp. thermostat.
The real issue is are one or more local areas "really hot" due to restrictions. A thermal scan may indicate that. Nothing less than "boiling out" the block would accomplish "factory" heat transfer performance.
If you aggressively try to clean the water jacket, you open up the possibility of leaks, etc. I'd just repeat the drain and system flush a few more times and take what I got. The issue is not to transfer junk from the motor to the radiator where the passages are smaller, so disconnect the hoses/separate. These motors are hard to flush and reversing the flow can't hurt. I stuck a hose nozzle down the thermostat hole as Owen suggests and reverse flushed mine.
Is the hood/bonnet up during this time? It's designed to take air in the front through the radiator and opening the hood can short circuit the fan.
If it doesn't cool down after it's moving then I'd go further with disassembly. A fan shroud might help increasing air flow at idle. They didn't come about until later. These motors turn rather slow at idle compared to most so a low speed open fan is not an effective air mover to begin with. Is it idling too fast? After I got it running, my 2365 would idle in the drive at 400 rpm almost indefinitely and not heat up.
Double check the water pump is functioning correctly, etc.
Also what oil are you using? Some put higher viscosity modern oils in older motors and they weren't designed for that. That increases viscous "friction" which means heat.
Another more exotic solution may be to use one of these new high heat transfer radiator liquids, but no experience in these motors, but have used elsewhere.

Fish'n Jim wow!, quite a primer on heat, heating and heat transfer. The wealth of information in your post gives me a basic knowledge of the "inner" workings of different parts of the cooling system and the why and wherefore that a radiator cap is more than just a cap....And, seeing the bigger picture of a closed or open hood while the engine is hot and forcing more air through the radiator with the closed hood!!! These points are the result of seeing the bigger picture and the inner workings of all the "units" needing to work together, and properly, to cool our toys. Thankyou for expressing your post so well. I never leave this website w/o learning something new.

Regards,
Steve

Just to add my two cents worth. I have bought thermostats that were bad out of the box. once or my 52 deluxe and once for the desoto. make sure it is a good one . With thermometer and boiling pan , makes sure it opens. or try running it without for a test .

Over heating straight 8's has got to be one of the top 10 (or higher) topics - very common and as noted has very many culprits to work through.

This was my input on another "overheating" post:

>> After replacing the water pump with a rebuilt one, having the radiator checked and cleaned, setting the timing "by the book" (6 degrees past TDC), checked for good-strong firing from the distributor, pulled and cleaned the distribution tube and cavity, removed the freeze plugs and pressure washed the inside the cooling jacket best I could, replaced the timing chain (while I was there), none of which resolved the problem completely. It still ran hot but didn't boil over. Temp gage would get up to "H" and stay there, and only slightly come down with higher RPMs.

The remedy I finally discovered was to set the timing "by ear" - which ended up (with my engine) 12 degrees. Seems strange, but it starts fine and runs and idles at normal temp. <<

Good luck - and enjoy resolving the problem. It will be very rewarding when you get it - I promise!

Interesting comment SamS....I have read in past posts that book specs are for the cars in the first part of their life...the older the car the less reliable the specs become and at their current age I read to use the factory specs to start from then use trial and error...especially with timing....to fine tune so the car runs optimally. Though doing this is counter intuitive your solution works. I'm glad you found a solution to your overheating problem.

Thank you. These are great inputs!
Actually, the engine runs hotter at idle with the hood on then when it is off.
That is why I am thinking it is a circulation problem.

I was planning to go to a 140 degree thermostat. I have a 160 in there now. I realize that it is not smart to remove the thermostat completely since you need heat in the engine to remove impurities from the oil, etc.

I already had the radiator cleaned well so I appreciate your comments on not doing the forced aggressive flush but instead using the acid flush a few more times.

I like the idea of a fan shroud. Do I have to make that custom? Or do you think I can buy one from a later model?

Before you go to any "extra" efforts (i.e. more than what was done by the factory in 1949~50) don't overlook the timing. Adjust the timing by ear (without the light). On top of the age of the engine, there's several other modern factors that could skew the book's setting requirement of -6deg BTDC (different gas & oils, global warming? [just kidding], etc..).

Timing was such an easy fix for me I just hate to see anyone going through the same headaches as I did. Would of saved me alot of sleep!

You can install an after market 6-bladed flex fan. My 47 Custom Clipper was fitted with one of these after market fans, and it worked great. These fans move a lot of air at idle and low speeds and the blades flex so as not to impede air flow at higher speeds. They are available at auto parts stores and can be bought online from speed shops (Speedway, Summit, JEGS, etc.). The fan can be spaced out with thick washers should your water pump shaft be larger than the center hole of the fan. These fans have the mounting bolt holes in a fan shape to accommodate different bolt patterns. Spacers were needed on my Custom Clipper installation. It was smooth, quiet, and in balance.

Another fan option would be one off of a 356 engine. It is odd looking in that it is 5-bladed with the 5th blade not evenly spaced between the other four. Never mind the appearance, they are efficient, smooth, and quiet. Rare and expensive.

(o{}o)

I agree thoroughly with SamS; changes thru the years in compression ratio (head milling mostly), fuels, etc. I always do my final timing "by ear" though I'll often use a timing light to get in the ballpark.

Sam S,

The timing definitely helped! We advanced it and then backed it off just like you said.

Now doing oxylic acid flush and trying to improve on it.

Checked the radiator fluid for exhaust gases and found none. So head gasket seems to be good

Definitely going in the right direction!