I was getting ready to say that crud in block , at least in theory would not prevent heat from getting to water. Where else can it go? Crud or not. Crud is wet . Water still boils at 212 plus. Even if in crud.if it boils there it carries the heat away, as steam , then immediately condenses back to water — point is heat is carried? If it did boil locally it would push crud off ? I have trouble with it causes the overheat ( in block) as then block metal gets hot and water does not = not our problem . Heat concentration around cylinders kind of low too, compared with say exhaust port . The Water when “ cooling fails” is in fact very hot. Too hot . Block too .
But restricted flow you mention is another whole game . That stops radiator from rejecting the heat . And “cleaning out block “ cleans out the head openings . So experience quoted is 100% correct , and correct advice .
Excellent post, great info ;
only way for water to carry heat is to move . And move fast . Only way out of block for hot water after pumping into the block front is through the heads via those small holes . They added more of them in motor home head. ( hmmmm) So if head entry water passages are restricted at at all at gasket surface, by a “crust” or deposits it is the same thing as a thermostat not opening fully . Restricted flow.
So we have some new info? New to me that it does this. Has to be a good radiator —AND the water has to move fast and free . What rodding radiator does , also.
Old posts about a year or two back also got somewhat into incorrect 440 pumps given to you at parts counter as 413 replacement, “for all B block” , there was some kind of impeller depth change and a metal water distribution plate behind impeller in some early B blocks . If wrong combination causes overheat ,due to gap or fit behind or around impeller , does not move water fast enough . I am still not clear on this myself , re: what years , but for sure is out there.
Pump and housing will interchange together , cannot mix up . Then And add in AC pump vs regular pump . Possibly 4 pumps? The parts number guys might look into this .. or we look for the steel plate inside next time open, start a data base . How far in impeller goes from gasket face?!
different pump number means what ?oddly AC pump has fewer vanes I think . Yet must be more gpm.
Too bad there is not some way to measure or judge gpm or flow when any of this happens . Compare two hot cars at neck at 1500 rpm?
See if radiator same temp top to bottom ( = fast flow, best total cooling) In the meantime those holes must be clear.
Sent from my iPhone
I wil second Andy’s comments. I bought my G coupe almost 18 yrs ago. It had been parked for approximately 20 years prior to my ownership. It ran when I got it, but I changed oil, plugs, etc…. As soon as I did a garden hose flush, I started fighting overheating issues. I had the radiator rodded out, recored, change thermostat, hoses, re-flushed…. all to no avail. At this point I knew there had to be something wrong internally. As soon as I pulled a cylinder head, this was confirmed. The water passages had barely 1/8” hole due to crusty junk being built up in what should be probably a 1/2” diameter water passage.
In my circumstance, the engine rebuilder could not get the passages cleaned out with the normal Hot Tank process. They ended up sending my block and heads to Redistrip, the place where they dip entire car bodies to strip away paint and rust. This worked. I rebuilt the engine to stock specs (as far as the cooling system is concerned) and have had no issues. This includes driving across country and back, including through the Mojave dessert at 113F degrees.
This issue is what prompted the entire restoration of that car. I have probably put 40,000+ miles since on the car and have had no cooling issues (other than freeze plugs, which is another story).
I agree with Keith. These cars worked when new as designed and still will. In my case I battled overheating in my G for years. A new radiator or a proper rodding-out would work for a while. Ultimately it ended when I took my engine to George Riehl for rebuild. He wouldn't just have blocks hot-tanked, but he took them to a place for a shot-peen type process. The block came back looking like a fresh casting. No heating problems since. Point being, you can throw all the fancy radiators you want at your car, but if there's 40-50 years of rust and gunk in the block cooling passages then it won't help. And a radiator shop or garden hose "flush" isn't going to do it.
I have no technical words of advice to offer, but I will be a cheerleader.
I recall a trip of 200 miles I took in my C in the summer of 2016 when the temperature was over 95, the sun was blazing, the humidity was in the 90s, and I got caught in construction traffic jambs. I had put in a recored radiator (of unknown composition) in 2011, I have the factory fan shroud, and everything else in the cooling system is factory except for a temp-controlled fan clutch. I ran my A/C with its big ole RV-2 compressor full-bore that day, but the temp gauge hardly budged over center.
All I'm saying is keep working at it, and stay with the factory setup. Those engineers were pretty good at their craft. Get all of it right and to spec and you will eventually win.
Posted by: John Grady <jkg@xxxxxxxxxxxxxxxxx>
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